Future Planetary Exploration

A Programming Note

2012-01-31T21:37:00.000-08:00

For the last several weeks, my days have been consumed writing a paper describing my current research, and my energy for writing for the blog has been limited. With the paper done (at least until the reviewers get their say!), I want to return the blog for a couple of lengthy mission descriptions for the Insight Mars Discovery proposal (see the last post before this one) and the Bepi-Colombo mission. If I can find sufficient material, I'll also describe the Comet Hopper Discovery proposal to round out the current Discovery missions in competition (I've covered the third mission in the Discovery competition, the TiME Titan lake probe, previously).

You’ll also see that the blog has a new look (and my apologies to the three readers who were on the blog when I tried out several different color schemes in rapid succession). A couple of readers said that the previous colors made the blog difficult to read. If you have any problems with the new colors, please let me know in the comments.

Mars Insight Mission Proposal: Part 1

2012-01-31T21:30:00.000-08:00

The one-slide justification for a geophysical pathfinder mission to Mars. While a sequence of missions have given us detailed information on the Martian surface ("What y'all got"), geophysicists have a much poorer understanding of the interior of Mars ("What we got"). From a presentation by the Insight proposal PI Bruce Banerdt at JPL to the Mars Exploration Analysis Group (MEPAG). Dr. Banerdt has spent twenty years working to get a seismometer on Mars (with some interesting detours along the way, such as being the

Mars Exploration Rover (MER) project scientist).

At its core, the Mars Insight mission (previously called the Geophysical Monitoring Station (GEMS) mission) is pretty simple: Duplicate the Phoenix lander, deploy a seismometer and heat flow instrument, maintain a radio link with Earth, and then passively record data for the next two (one Martian) years, With this post and the next, I’ll explore the justification for this mission and place it within the context of the long line of proposed Mars geophysical missions. In today’s post, I’ll address two questions:

1) Why a geophysical mission?

2) How does the Insight proposal compare to previous proposals?

and then in the next post I’ll address two additional questions:

3) What can be done with a single station?

4) How would the Insight mission conduct its studies?

Why a geophysical mission?

Because we live on the surface of our planet, it's often easy to forget that the vast bulk of our planet lies beneath our feet. The interior of our world is the product of the processes that formed and evolved the Earth and the other terrestrial planets. In turn, the processes that operate inside the Earth have shaped the surface of our planet and contributed gases to our atmosphere. The decades of research into the Earth's interior have been essential to understanding our planet's history and current state.

All the reasons for studying the Earth's interior also apply to Mars -- we cannot understand that planet without understanding its interior. However a geophysical mission to Mars may give us more than just a deeper understanding of that world. We continue to explore the Martian surface because it retains records of conditions from the earliest history of the terrestrial planets (including perhaps the conditions that led to life).

The Earth's interior retains considerable heat that causes vigorous mantle convection that has erased the record of Earth's earliest interior structure and composition. Mars is much smaller than the Earth and appears to have lost much of its internal heat early in its history. As a result, Mars may preserve the internal structure and composition from its early history. Understanding the interior of Mars may help us understand what the interior of the early Earth was like and serve to constrain our models of how our world evolved.

The 2011 Decadal Survey reports listed the key questions for a geophysics mission:

"What is the interior structure of Mars? How are core separation and differentiation processes related to the initiation and/or failure of plate tectonic processes on Mars?
"When did these major interior events occur, and how did they affect the magnetic field and internal structure? What is the history of the Martian dynamo? What were the major heat flow mechanisms that operated on Early Mars?
"What is Mars’s tectonic, seismic, and volcanic activity today? How, when, and why did the crustal dichotomy form? What is the present lithospheric structure? What are the Martian bulk, mantle and core compositions? How has Mars’s internal structure affected its magmatism, atmosphere, and habitability?"

The 2002 Decadal Survey listed three recommended Mars missions -- the Mars Science Laboratory (on its way to Mars), an upper atmospheric mission (the MAVEN mission in development), and a network of geophysical stations. Subsequent reviews of Mars priorities continued to rank a geophysical mission highly, but none has gotten beyond the proposal stage. The 2011 Decadal Survey did not prioritize a geophysical mission because of, "its lower scientific priority relative to the initiation of the Mars sample return campaign," but noted that, "potential Discovery missions to Mars include a 1-node geophysical pathfinder station." Conducting the first flagship scale mission in a series to return samples from Mars would consume enough of NASA’s planetary science budget that the members of the Decadal Survey could not justify prioritizing a second Mars mission. They left open the possibility of a limited geophysical mission that might fit within the budget of a Discovery mission. Insight is a proposal for such a 1-node geophysical station.

How does the Insight proposal compare to previous proposals?

There has been a long history of proposed Mars geophysical missions extending back into the late 1970s at least. Perhaps only the Mars sample return mission has had as many serious proposals and near-starts without actual approval as a geophysical mission.

Proposals for geophysical missions often are called network missions because the measurements ideally would be done from a network of stations across the surface. In these posts, I will focus on geophysical goals, however, meteorologists also would like to place a network of stations on Mars. While meteorologists and geophysicists would propose different types of networks (meteorologists would like many relatively simple stations distributed across the globe while geophysicists would be delighted with regional cluster of three stations and a fourth on the opposite side of the globe), most network mission proposals have included sets of instruments for both disciplines. (However, the Pascal Discovery proposal in the early 2000's would have landed 18-24 simple meteorological stations on Mars.).

Two geophysical proposals proceeded almost to approval before budgetary issues forced their cancellation. The French Netlander mission would have landed four stations. The Humboldtstation, on the other hand would have landed with the European ExoMars rover and made measurements from a single location.

The following table compares the proposed instruments of Insight with those proposed for the Netlander and Humboldt stations:

Two observations stand out from this table. First, there are a wide range of measurements that geophysicists would like to conduct from a geophysical station (and none of these proposals included some additional priority instruments such as electromagnetic sounders that, like the ground penetrating radars, would probe the local subsurface to considerable depths). Second, the Insight mission has far fewer instruments than either of its predecessor proposals. To fit within a Discovery budget, this mission would carry the barebones instrument compliment. There's not even a panoramic camera, although there would be a camera on the arm that deploys the instruments to pick out locations to deploy them. (I suspect that after instrument deployment, the camera arm might be used to look around at the surrounding scenery.)

ExoMars and Budgets Update

2012-01-19T20:42:00.000-08:00

Space News today had an article on the evolving politics of the ExoMars mission from the European side. According the the article, "CNES [the French space agency] President Yannick d’Escatha said both the ExoMars program and the space station budget will be on the table for European ministers when they meet in November to set multiyear space budget and program priorities." The article reports that European nations have committed only 850M euros of the 1B euros required for the European portion of this joint mission with NASA. One idea to lower the European costs, dropping the demonstration lander, was proposed by France but rejected by Italy. The article suggests that France as well as other nations may be wavering in their support for the ExoMars mission.

There has been no news on NASA's commitment to the ExoMars mission, pending the release of the President's FY13 budget proposal next month. That budget will also determine how funding for the Webb Space Telescope will impact NASA's planetary program.

Several recent articles have discussed how difficult it will be to fund new flagship missions. While the emphasis is on astronomy missions, the same issues likely will apply to flagship planetary missions. I recommend Big science in an era of tight budgets.

Editorial Thoughts: The impacts of the continuing financial downturn are still being felt. NASA's budget proposal to be released next month will be the first to follow the release of the Decadal Survey and the commitment to the higher funding needed to complete the James Webb Space Telescope. If the Decadal Survey laid out a vision, then the next budget will be the administration's response to that vision and the other competing priorities for NASA in an era of budget cutting. The administration has promised to include its decision on NASA's participation in the ExoMars as part of that budget release. I plan to release an analysis of the budget proposal the day it is released.

From the Space News article, it appears that the next opportunity to revisit ESA's commitments will come at the ministerial meeting next November.

Cassini - An Example Extended Mission

2012-01-13T22:05:00.000-08:00

"You didn't say things about existing missions. Rumor says that Cassini's going to have a 50% cut to science. At some point it's below the threshold of viability and it will destroy science... Planetary science is on the verge here, and it's not just future missions, it's present missions too."

Statement by a planetary scientist at EPSC/DPS conference last fall as reported by Emily Lakdawalla in her Planetary Society Blog

In my last blog post, I talked about the Senior Reviews that NASA will be holding early this year to decide funding for continuing science missions. Continued operation of missions past their initially funded prime mission incurs considerable costs. I've seen quotes of $5M per year to $60M per year depending on the complexity of the spacecraft, the mission activity, and the size of the science team. To ensure that sufficient funding remains to fly new missions, NASA sets a budget for continuing missions and then periodically appoints a Senior Review panel to recommend the mix of continuing missions to maximize the science return from that budget. Rumors, as noted in the opening quote, suggest that the budget for continuing missions is likely to be tight and good missions may suffer significant cuts. We don't yet know what the budget will be for the Senior Review, and may not know until the release of the FY13 budget in approximately a month. So these are rumors, possibly correct, possibly not. However, the community is worried.

While this blog has primarily focused on new missions, today I'd like to examine what continued funding for missions can enable using the Cassini mission as an example. First, though, I'd like to make it clear that I'm not stating a preference for which missions should be continued. A good case can be made for all the missions up for review (see the list in my previous post), and I certainly don't have the information to make an informed recommendation. Rather, the Cassini mission nicely illustrates the wide range of what continuing missions as a group can achieve because it is exploring an entire system rather than a single world. (Well, okay, I'll admit to really liking the Cassini mission, but I have other favorites, too.)

The Cassini mission currently is in its second extended mission scheduled to last -- pending funding decisions based on the Senior Review recommendations -- until 2017. From a news article, it appears that each year of continued operation costs around $60M a year. That funding level, if continued, would pay for about three-quarters of a Discovery mission or about a fifth of a small Flagship mission to Europa. Emily Lakdawalla reports in the same post quoted above that three-quarters of the Cassini budget (~$45M/year) is required to continue operations of the spacecraft at the minimum safe level, and the remainder pays for scientific analysis of the returned data.

So, what is the Cassini spacecraft doing in its extended mission? The spacecraft is in its second extended mission, frequently called the Solstice mission. When Cassini arrived at Saturn in 2004, it was winter in the northern hemispheres of Saturn and Titan, equivalent to January on Earth. In the first extended mission, spring arrived. When the mission is currently scheduled to end, summer will have begun, equivalent to June on Earth. Saturn orbits the sun much more slowly than Earth, so the total mission from arrival to end will have been 17 Earth years long.

The many planned encounters of the Cassini prime and two extended missions. In addition to encounter science, the spacecraft will conduct on-going studies of the rings, Saturn's atmosphere, and the magnetosphere.

The science being conducted can be broken down into three types of investigations. In the first, the spacecraft is examining the Saturn system for changes in time, particularly those brought on by the changing seasons. In the past year, these observations saw the birth of the Great Northern Storm on Saturn and the spring deluge on Titan that created extensive changes on the surface over an area equal to the states of Arizona and Utah.

A second set of observations extend measurements previously made. For example, new observations with the cosmic dust analyzer and ultraviolet spectrometer found that the larger grains of ice deep within the plumes of Enceladus are salt-rich, strengthening the case for a subterranean ocean inside that world. This discovery was made from the close flybys of Enceladus done in the first extended mission. Similarly, the Cassini spacecraft continues to image new areas of Titan in higher resolutions, explore the composition of the rings, and conduct additional flybys of the other moons.

A third set of observations come under the heading of entirely new exploration. In all the orbits of Saturn so far, the Cassini spacecraft has been kept well away from the major rings. At the end of the Solstice mission, Cassini will dip its closest approach to just outside the F ring for 20 orbits. Then the periapsis will be lowered to fly through the ~3,000 km clear region between the inner edge of the D ring and the top of Saturn's atmosphere for another 22 orbits before finally plunging into Saturn to terminate the mission. With these orbits, the Cassini spacecraft will conduct science at Saturn similar to that the Juno spacecraft will do with its close-hugging orbits of Jupiter.

Cassini's proximal orbits from this presentation.

In this final mission phase, new higher resolution studies of the gravity field and magnetic field will allow scientists to better model the deep interior and rotation rate of Saturn. The close orbits will enable better estimates of the mass of the rings to estimate the age of the rings. New portions of the magnetosphere and its trapped plasmas will be directly sampled. (Alas, no one in the 1990s when the mission was planned thought to put a microwave instrument on Cassini like the one on Juno to enable deep probing of Saturn's atmospheric structure and composition. :> On the other hand, Juno won't have an extensive ring system to explore up close.)

Cassini provides in a single extended mission examples of the science that extended missions can produce: long term observations of variability and change, continuation of measurements to fill in gaps, and entirely new studies. Each of the missions in contention for continued funding through the Senior Review would extend our knowledge of the solar system. The members of the Senior Review will have to choose among an embarrassment of riches.

I'll close with this link to the top 10 discoveries from the Cassini mission in the past year enabled by its continuing missions. You can also look through this presentation to learn more about the science goals of the Solstice mission (also called the XXM mission.) This post describes how the Solstice mission was designed.

I'll also reproduce the statement from the Outer Planets Analysis Group on why it believes that the final close flybys of the rings and Saturn deserve continued funding:

OPAG Statement On The Cassini Mission’s Proximal Orbits: Critical Data for Giant Planet & Solar System Origins

Completion of the Cassini mission’s Proximal Orbits is critical to multiple high-priority planetary science objectives. Cassini is poised to perform these orbits near the end of its Solstice Mission, making measurements not possible from previous orbits. These measurements will be a key component of a broad multi-mission data set needed to reveal giant planet and solar system formation and evolution processes from comparisons of the gas giants Jupiter and Saturn, followed by future comparisons of the gas giants to the ice giants Uranus and Neptune. This knowledge is critical to understanding the veritable zoo of different planetary systems now being found around other stars.

Comparative planetology of gas giants is a high priority objective for research into giant planet and solar system formation and evolution [1,2]. Fundamental aspects of these areas are currently unknown, including processes and materials that deliver volatiles such as water and organics to giant planets and terrestrial planets, and time scales for planetary formation and protoplanetary disk evolution. Comparisons among giant planets, beginning with comparisons of Jupiter and Saturn, are a tool for examining the results of these processes and thus the processes themselves. A meaningful comparison of Jupiter and Saturn requires knowledge of elemental and isotope composition in the well--‐mixed atmospheres of both planets, and knowledge of gross interior structure to provide context for the compositional information [3,4].

The data set needed to provide this knowledge is being assembled using data from multiple past, present, and future NASA Flagship and New Frontiers missions. The Galileo Probe provided the elemental and isotope composition measurements at Jupiter, except for oxygen. NASA’s Juno mission, part of the New Frontiers Program, is en route to Jupiter to make the interior structure measurements needed there. This objective, together with composition measurements (ammonia, and the water the Galileo Probe missed), comprises a significant part of the Juno mission’s science and the mission budget, and completes the comparison data set for Jupiter. The recently completed Planetary Science Decadal Survey recommends a NASA New Frontiers Program mission, a Saturn atmospheric entry probe mission, to make the elemental and isotope composition measurements needed at Saturn [1]. Interior structure measurements at Saturn, equivalent in science value to that of Juno’s interior structure measurements at Jupiter, would round out the data set. Without these, the comparisons would be inadequate for unambiguous models of planet formation.

It is precisely these Saturn interior structure measurements the Cassini Proximal Orbits would provide. The cost of acquiring the data with Cassini is a relatively small fraction of the Solstice Mission budget. If Cassini does not acquire that data set, the task of acquiring it would fall to a new, future Saturn orbiter mission. Such a future mission is not within NASA’s planning horizon, so it would be decades in the future. This would delay understanding fundamental giant planet and planetary system formation processes in our own solar system, and notably in other planetary systems now coming to light as a result of NASA--‐funded exoplanet search programs.

REFERENCES

[1] Prepublication release of “Vision & Voyages for Planetary Science in the Decade 2013--‐2022,” National Academies Press, Mar. 7, 2011; Available at http://www.nap.edu/catalog.php?record_id=13117 .

[2] Entry Probe Missions to the Giant Planets, D.H. Atkinson, T.R. Spilker, S.K. Atreya, & 53 others; white paper submitted to the NRC 2012 Planetary Science Decadal Survey, available at http://www.archive.org/details/EntryProbeMissionstotheGiantPlanets .

[3] Saturn Exploration Beyond Cassini--‐Huygens, T. Guillot, S. K. Atreya, S. Charnoz, M. Dougherty, & P. Read, in Saturn From Cassini-Huygens (M. K. Dougherty et al., eds.), Chapter 23, pp 745--‐761, 2009, DOI 10.1007/978--‐1--‐4020--‐9217--‐6_23, Springer Dordrecht, Heidelberg--‐London--‐New York.

[4] Coupled Chemistry and Clouds of the Giant Planets, S.K. Atreya, A.S. Wong, A chapter in The Outer Planets and their Moons (T. Encrenaz, R. Kallenbach, T. C. Owen, C. Sotin, eds.), pp 121--‐136, Springer, Berlin--‐New York--‐Heidelberg, 2005. Also in Space Sci. Rev., 116, Nos. 1--‐2, pp 121--‐136, 2005.

Planetary Missions Up For Review

2011-12-28T23:38:00.000-08:00

You may never have heard of the upcoming NASA Senior Review, but it may have as big an impact on planetary exploration in the coming decade as any mission selection except possibly the approval of a Flagship mission to Mars or Europa.

First, though, some background. When a mission is first approved, its budget includes funds for operating the spacecraft in flight and initial analysis of the scientific data. The period of flight covered by this budget is known as the prime mission. Once the spacecraft completes the prime mission, there's usually years of life left in it to go to new targets (such as the flights of the Deep Impact and Stardust spacecraft to second comets) or to continue collecting science at the prime target (such as the rover Opportunity at Mars or Cassini at Saturn). These mission continuations are called extended missions.

NASA has to budget substantial funds to operate its many planetary and other science missions in their extended missions. Generally the costs of these extended missions aren't well publicized (likely because NASA and the press reasonably assume few people in the public care). However, we know that the Cassini mission in its current extended mission costs about $60M per year (probably near the high end) and the EPOXI (formerly the Deep Impact) mission costs about $5M per year (probably near the low end). Cassini could operate through 2017, so the rest of its extended mission will cost ~$300M (assuming flat budgets). The EPOXI mission will cost around $45M if its fuel holds out for a 2020 asteroid flyby. Compare these costs to the $425M dollar cost of a new Discovery mission.

Then consider the list of missions that are in or will enter extended missions in the next two years:

Cassini (Saturn)
EPOXI (possible 2020 asteroid flyby)
GRAIL (lunar orbiters)
Kepler* (planet finding space telescope)
Lunar Reconnaissance Orbiter
Mars Odyssey Orbiter
Mars Reconnaissance Orbiter
Opportunity Mars Rover
MESSENGER** (Mercury orbiter)
*Kepler is an Astrophysics Division mission, but it, too, will be up for review
**MESSENGER's extended mission was recently approved in a special Senior Review

To decide whether or not to continue funding an extended mission NASA holds Senior Reviews. These panels evaluate the potential scientific return of the extended mission against its costs. The panel can recommend continued funding as planned, enhanced funding, reduced funding, or mission termination. As I understand it, NASA provides a budget for of its science divisions for extended missions. The panel needs to recommend the mix of missions and their funding to fit within the budget.

Early in 2012, a series of Senior Reviews will be held that appears to cover all NASA's planetary, astrophysics, and heliophysics missions that are in or will enter extended missions by 2014. (I don't know if the Earth science missions will be included in this senior review.) As backdrop to this review, remember that each of these divisions are projected to face flat or declining budgets in the next several years. In addition, NASA will need to find funds in its declining budget from these programs to help fund the completion of the James Webb Space Telescope, the over budget successor to the Hubble Space Telescope.

The review panels have a tough job. Each of these missions continue to gather data for which there will not be a chance to gather again for many years or even decades. How do you rank, for example, the science that will be enabled by the next 1%* of Mars imaged at 0.3 m resolution by the Mars Reconnaissance Orbiter against the next 40+ planned Titan flybys by the Cassini spacecraft? (*In it's first four years of operation, the MRO's HiRISE camera imaged about 1% of Mars at this resolution.)

While NASA is still waiting to hear (or be able to publicly talk about) its future planetary program budget, the indications are that the budget for extended missions will be tight. Dollars reserved for extended missions will not be available to fly and build new missions.

In my next post, I'll look at what is at stake for one extended mission, the Cassini mission at Saturn.

Process for the Planetary Science Division's (PSD) Senior Review from here

Most recent PSD update from here

Appendix

My Google searches failed to find the website for the Planetary Science Division's Senior Review. (Either poor searching, or it's posting may have been delayed because the planetary budget appears to be in particular flux.) If you are interested, however, you can read the guidance for the Astrophysics programs' Senior Review along with results from past reviews.

Each extended mission team has to write a proposal to support its request for continued funding. The call for proposals includes this description of the process for the reviews:

Instructions to the Senior Review Committee (SRC):

In the following descriptions, “project” denotes a full mission or project in the traditional sense or U.S. participation on a mission led by an international partner. NASA HQ will instruct the Senior Review panel to:

(1) Rank the scientific merit of each project on a “science per dollar” basis (based upon expected returns during 2013 and 2014) in the context of science goals, objectives and research focus areas described in the SMD Science and Strategic Plans.
(2) Assess the cost efficiency, technology development and dissemination, data collection, archiving and distribution, and education/outreach as secondary evaluation criteria, after science merit/usefulness.

(3) Based on (1) through (2), provide findings to assist with an implementation strategy for Astrophysics Division missions in extended operations for 2013 and 2014, including an appropriate mix of:

Projects continued as currently baselined;
Projects continued with either enhancements or reductions to the current baseline;
Project terminations.

Titan on the Installment Plan

2011-12-14T21:37:00.000-08:00

From AVIATR presentation

Without planning it, almost all my posts for the last several weeks have looked at options for modest Flagship-scale missions, whether from NASA (Europa), ESA (Ganymede), or both jointly (Mars). That's largely by default -- there's little news for either small or medium-cost missions. For lower cost missions (<$500M), NASA will not select its next Discovery mission for several months and the next competition is likely two years away, ESA's next selection for a medium class science mission (roughly equivalent to a NASA Discovery mission) is years away, and Japan, India, and China continue developing their next missions. For medium scale missions(~$1B), I've not heard a date for the next NASA New Frontiers competition, and I believe that the agency is waiting to see the budget projections from the FY13 budget proposal before deciding when to select the next medium scale mission.

That leaves the modest cost ($1.2-1.5B) Flagship missions as the current topic of news. Scientists have identified three high priority worlds for future intensive investigations: Mars, Europa, and Titan. Fulfilling the identified high priority science goals for each will not come cheaply: $8.5B for a Mars sample return mission, $3-4B for Europa, and ~$4B for Titan (per Decadal Survey estimates). To help make these costs more manageable, engineers have found ways to explore Mars and Europa on what would be essentially the installment plan.

The Mars sample return program would be split across four missions and the Europa program would be split across three missions (including an eventual lander(s)). The four Mars missions would be a 2016 orbiter that provides a communications relay, the 2018 rover that would collect samples, a mission to retrieve and launch the samples into Martian orbit, and a mission to collect the samples from orbit and return them to Earth.

The Europa missions would be a multiple-flyby spacecraft that would collect high volume remote sensing data, an orbiter that would carry the minimum instrument set for measurements that could only be done from orbit, and eventually one or more landers.

So could Titan be explored in a series of smaller missions? The Titan Saturn System Mission Flagship proposal called for a highly sophisticated orbiter, a balloon platform for aerial surveys, and a probe to sample the atmosphere and a northern lake. As many of you already know, mission teams have already taken advantage of this natural division to propose three low cost missions.

Before looking into those missions, it’s useful to look at the advantages and disadvantages of Titan from a mission designer’s point of view (it’s scientific and exploration advantages are well known to readers of this blog). On the plus side, Titan poses a thick atmosphere that makes entry, flight, and landing easier than on any world except possibly our own. It is frigidly cold, but for either a short-lived probe or a long-lived probe with a nuclear power supply, that is likely not a problem. (In fact, the AVIATR plane depends on constant movement to bring cool air past its power units to keep from overheating.) Unlike Europa, there are no harsh radiation belts to fry electronics at Titan. And there are no Richter-scale technology developments needed to continue exploring Titan as would eventually be needed for a Mars sample return to launch the samples from the surface and retrieve them in Martian orbit.

On the negative side, Titan is far from Earth. This results in long cruises, typically around seven years, with mission operations costing $7-10M a year during cruise. On a $425M Discovery mission budget, that’s a significant piece of change.

Perhaps more difficult is that at those distances, data rates either must be low if a small antenna that could be carried by a probe or plane is used, or the spacecraft must have the power supply to sustain high bandwidth communications to Earth. It is for this reason that an attempt to define a lower cost Titan orbiter in 2007 determined that the lowest practical cost for an orbiter would be ~$1.5B. A less expensive spacecraft couldn’t support the data rate to return a high resolution map of Titan.

Despite these challenges, teams have proposed two Discovery class missions and one that fits between the Discovery and New Frontiers ($1B) mission classes. The inherent tradeoff for all these missions is that they accept low data rates to fit within allowable mission budgets among other tradeoffs that include smaller instrument compliments.

For the TiME Discovery proposal, which would land a long-lived probe on a Titan lake, the low data rate probably does not incur significant science tradeoffs. Its composition and physical properties instruments are inherently low data rate. The probe will carry a camera, but the number of pictures would likely be limited. (I also suspect that the view from the middle of an arctic lake under a hazy sky far from the sun is likely to be low contrast, which should enable efficient data compression of images.)

The following list compares quoted data return (some calculated on the back of an envelope from data in published documents, so all assumptions may not be the same) for one year of operation for different mission proposals. I’ve included a Martian orbiter for comparison.

AVIATR Titan airplane (~$700M) - ~1 Gbyte

JET Saturn orbiter with multiple Titan and Enceladus flybys ($425M) – 120 Gbytes

2007 Titan orbiter concept (~$425M)– ~300Gbytes

2009 Titan Saturn System Flagship Titan orbiter (several $Bs)- ~600Gbytes

Mars Reconnaissance Orbiter (MRO) ($720M) - ~1,000Gbytes

In one sense, these numbers may be misleading. The AVIATR mission, for example, would employ elaborate procedures to allow scientists to determine which data to return. Each of its bits may be 10X to 100X as impactful as a bit from the Mars Reconnaissance Orbiter. However, the high data rates of MRO have allowed extensive coverage of terrain types and monitoring that the 1GB of the AVIATR mission would not allow.

The message is that mission costs can be reduced, but there are few magic bullets. Reductions in cost come at the expense of capabilities, with the amount of data returned a key tradeoff. Since these missions are justified by the data they collect, this is a significant tradeoff.

If data rates are a challenge for Titan exploration, the relatively benign environment allows for missions to fly at cheaper incremental rates than for Mars sample return or Europa. For approximately $1.5B (if the proposer’s cost estimates are correct), NASA or another space agency could fly three missions to Titan. That is approximately NASA’s contribution for the 2016 and 2018 Mars missions or one of the new lower cost proposed Europa spacecraft. There would probably be some cost savings if one or more of the Titan missions were combined. The AVIATR plane mission would be greatly enhanced if it flew with an orbiter such as JET that could relay data back to Earth. The amount of high resolution imaging from the plane would increase many times over.

Two important caveats must be considered before getting too excited by visions of Titan missions. First, we haven’t seen independent cost reviews for these missions, and proposers have been known to be too optimistic. Second, we don’t know how these missions would rank scientifically in a mission selection competition. Would 1Gbyte of high resolution imaging from a Titan plane provide better return on the dollar than a sample return from a comet or a lunar geophysical network, for example?

NASA currently is committed to supporting the priorities of the Decadal Survey, which after funding the Discovery and New Frontiers programs, prioritizes the 2016 and 2018 Mars missions and if they cannot be flown, a Europa mission, and as third priority a Uranus orbiter. However, we are seeing a new level of creativity from NASA and the planetary science community in finding ways to continue exploration of the Solar System’s highest priorities. With the proposals on the table, Titan is in play as a target, either through individual missions or through a relatively inexpensive program for several low cost missions.

Retreat From Mars?

2011-11-28T22:31:00.000-08:00

"Without more funding and a firm, renewed commitment to Mars from NASA, "MSL will be the last thing we put down on the ground and MAVEN will be the last orbiter we do unless it comes from the Discovery program," said Jim Green, director of NASA's planetary science division."
Will NASA retreat from Mars after string of successes?
- Spaceflight Now

As I write this, the latest news on the Phobos-Grunt spacecraft is that it remains in orbit, apparently operational, but has not communicated with Earth in the last several days. In the meantime, the Curiosity Mars Science Laboratory launched successfully and its flight so far has been boringly good.

My hopes are with the Russian engineers and scientists as they attempt to re-establish control of the spacecraft and find another target, potentially an asteroid, now that that mission's window to begin the flight to Mars apparently has closed.

Looking to future missions, the news is also mixed. The only committed and funded mission to follow Curiosity to Mars currently is MAVEN, which is a Discovery-class orbiter to study the Martian upper atmosphere. (MAVEN was the last mission in the now defunct Mars Scout program which also flew the Phoenix lander.) The European Space Agency (ESA) and NASA both have hopes of flying a joint orbiter for 2016 and a joint rover for 2018. Neither has the money currently committed to do the missions alone and neither currently has the committed funding to implement their planned portions.

However, there are encouraging signs of progress.

First a brief recap on the 2016 and 2018 proposals. The 2016 mission would fly an orbiter that would carry instruments to study the Martian atmosphere and continue high resolution imaging of the surface. Most critically, this orbiter would also be in place to act as a communications relay for a proposed 2018 rover. The rover would carry a highly sophisticated ESA instrument suite to examine Mars for signs of life and habitability and NASA equipment to collect and cache samples for eventual return to Earth. The 2016 mission would also carry an ESA demonstration lander that would function for up to four days on the surface.

A new option is on the table now, that could be an exciting enhancement to the joint program. When NASA was unable to commit a launch vehicle for the 2016 orbiter, ESA asked Russia to contribute a launcher in return to having its instruments also fly. The initial reaction reportedly was, nyet!, but recent news sounds more encouraging. Scientists at Russia's Space Research Institute, IKI, have put together proposals for a minimum and maximum level of participation. For the minimum proposal, Russia would contribute unspecified instruments for the orbiter that have previously flown on other Russian Earth and planetary missions. The maximum proposal would add two to four Russian landers to replace the currently planned ESA demonstration lander. At least one version each of two different landers would fly, and if technical issues could be worked out, two copies of each version might fly. The first version would be a penetrator that would carry a weather station, and would be similar to the landers jointly developed with the Finns. The second would be a soft lander that would open up, petal style once on the surface. The proposed instrument is a French seismometer (which I believe is also the seismometer planned for the Mars GEMS lander in the current NASA Discovery competition). Power sources aren't mentioned in the news articles, but the implication is that both landers would be long-lived. Russia reportedly has at least one flight ready copy of each lander left as spares from its Mars-96 mission that experienced a launch failure.

There is no mentioned whether or not the Russian orbiter instruments would be in addition to the currently planned instruments (most supplied by NASA and one supplied by ESA) or would replace one or more of the planned instruments.

Russian scientists are currently in discussions both with ESA and with the Russian political system to secure approval and funding.

On the European front, ESA currently has 850M of the 1B Euros committed from its member nations that it needs to conduct its portion of the currently planned 2016 and 2018 missions. In the meantime, European financial problems are causing ESA to plan to reduce costs and Europe to debate whether to reduce funding for its flagship Earth observation program (GMES). I believe that GMES is a European Union program, rather than an ESA program. Either way, the news speaks to a tightening of budgets for space programs by European governments. Dropping the ESA lander from the 2016 mission would help reduce the gap between committed Euros for the Mars program and what is needed.

Then there is the American side, which is possibly the most confusing. At the moment, the President's Office of Management and Budget (OMB) is refusing to allow NASA to commit funds from future budgets to ESA to support the Mars program. At the same same time, Congress has just passed NASA's Fiscal Year 2012 budget with full funding for the Mars program and a rather pointed requirement that NASA implement the recently completed Decadal Survey that included the Mars program as its highest priority planetary Flagship mission. (If this seems crazy, welcome to our system of separate powers in government. Congress can set direction only for the current year's budget; commitments for spending from future budgets (eventually to be ratified or modified by Congress one year at a time) must be approved by OMB.)

The good news is that NASA has funding to support the development of its instruments for the 2016 orbiter and the 2018 mission remains a priority -- for the remainder of FY12. OMB has promised to make clear its position on NASA's ability to make future commitments to enable ESA to continue to count on NASA for 2016 and 2018 in its FY13 budget to be revealed in February. Reportedly, the responsible OMB official has stated that a key concern is that going forward with the 2018 mission is just the down payment on a program of missions to return samples that could cost $8.5B.

Editorial ThoughtsE: The 2016 and 2018 missions are both excellent missions, and I hope to see them fly. Even without NASA's equipment to collect and cache samples, the 2018 rover mission should fly. All of this political maneuvering is frustrating as hell, and my hat is off to the NASA officials who are handling this situation as the professionals that they are.

The addition of Russian instruments and landers would only make the 2016 mission more exciting assuming all the technical and managerial issues can be worked out without unacceptable additions to technical, schedule, or budget risk.

I can understand, however, OMB's position. It is looking at a suite of programs for human spaceflight and the over budget James Webb Space Telescope that it and Congress have agreed are NASA's top priorities and for which the current NASA funding likely is insufficient. The American budget problems are likely to reduce NASA's funding or at very best keep it flat. Commitments made in haste may be undone later.

I have come to wonder whether the American political process will approve the start of a Mars sample return program without the discovery of strong signs of life or at least habitability on Mars. If Curiosity or another mission (such as the 2018 rover) finds complex hydrocarbons consistent with life, for example, I think support for the sample return will be strong. Without it, it has proven difficult over the past twenty years to convince the political process that bringing back "a bunch of rocks" justifies the expense of many billions of dollars.

So, to address the question in the title of this post, I don't yet know if this will be a retreat from Mars. The fact that Congress held a hearing on NASA's Mars program budget impasse and required continued spending on it for this year is an encouraging sign. The scientific community remains committed to supporting the program. In normal times, I would be optimistic that these problems would be worked out. Given the budget problems and politics in the US, Europe, and Russia, I am only hopeful that they will be.

Resources:

Russia's proposals for the 2016 mission article at Russian Space Web and a shortened version at the BBC website.

Aviation Week article on NASA budget situation regarding its Mars program, U.S., Europe, Russia To Talk Mars Mission

"...land at Thera, and you might be able to taste Europa's ocean!"

2011-11-18T23:16:00.000-08:00

Artist's conception of a lake beneath a chaos region on Europa but above the global ocean.

Courtesy of University of Texas at Austin

"So for all of you people who were secretly hoping the thin-icers would win the argument because you are hoping to see humans send a probe onto Europa's surface and maybe even drill through the ice to its ocean, you have a consolation prize... land at Thera [Macula], and you might be able to taste Europa's ocean!"

Emily Lakdawalla,

Is Europa's ice thin or thick? At chaos terrain, it's both!,

The Planetary Society Blog

As many of you probably know by now, a paper to be published in the journal Nature next week postulates a new theory for the chaos terrain on Europa. As the nomenclature implies, 'chaos terrains' are jumbled areas on the surface of Europa that appear to be huge blocks of ice scattered across the surface with rifts between them. This new theory suggests that these areas are caused by the formation of large subsurface lakes beneath the surface. Initially, the formation of the lake reduces volume beneath the surface (water fills less volume than ice), causing the surface to crack and collapse. When the lake eventually refreezes, the volume expands pushing the shattered surface up into a dome. The surface of a chaos region, then, is a mixture of surface ice and water that upwelled from the subterranean lake. Current imaging suggests that up to 50% of Europa's surface represents chaos terrains ranging from fresh to old. One area that looks to represent chaos terrain with an active lake with greater volume than all the great lakes of North America combined is Thera Macula.

These chaos regions appear to represent the best locations to sample the ocean that underlies the surface of ice at Europa. Beneath that ocean lies a rocky core, which is tidally flexed and heated by the gravitational pull of Jupiter. That puts the ocean in contact with minerals and energy (think of the hot vent plumes beneath the Earth's oceans) that could provide the mixture needed to support life. In this respect, Europa may be unique among the icy worlds believed to have subterranean oceans. On Ganymede and Titan, by contrast, the oceans would be sandwiched between layers of ice, removing the oceans from the minerals and heat needed to support life. (A lively debate continues as to whether or not Enceladus' plumes come from an ocean in contact with the rocky core.)

The NASA press site has a summary of the findings and nice illustrations. I recommend reading Emily's write up even if you've read this or other press accounts. She does a nice job expanding on the press release.

Fortuitously, NASA has also asked a team of scientists and engineers to develop the concept for a minimalistic Europa lander mission. This follows the definition of minimalistic mission concepts for an Europa orbiter and a multi-flyby mission (see my post, Europa - New Options) that would each cost approximately $1.5B (not including launch). The hope is that the lander mission will also cost ~$1.5B, but that's not a requirement.

Since the team has yet to formulate it's plan, all details are subject to change. However, I'll summarize the presentations giving the current thinking captured in the kick off meeting (presentations posted here).

Europa's surface roughness presents a landing challenge.

Except as noted, all illustrations are from the Europa Lander Forum presentations posted at http://www.lpi.usra.edu/opag/Oct2011/lander_forum_presentations/

The surface of Europa at all scales at which it has been imaged (the best images come from the Galileo mission) looks forbidding to land on. Jumbled surfaces of ice appear everywhere, especially in the now high priority chaos regions. For this reason, the current concept includes two landers in the hope that one would make it to the surface intact. The landers would descend under rocket power, much like the Mars Phoenix lander. An instrument (lidar) would scan the surface to find the location with the smoothest surface, and the lander would steer itself to land there.

Radiation levels on the trailing side of Europa. The red line shows the boundary between the high radiation trailing hemisphere (left) and the low radiation leading hemisphere (right).

The jagged surface presents one problem. The radiation at Europa presents another problem. A radiation field surrounds Jupiter that becomes more intense closer to the planet. Europa lies fairly deep within this field and an unshielded spacecraft either would have a short life (~1 month) or would require expensive radiation hardened electronics and a price tag well above $1.5B. Here, the current concept proposes to use Europa itself as a radiation shield.

Cumulative radiation dose for a spacecraft in orbit around Europa (blue line) and a lander on the leading hemisphere of Europa (red line)

The major moons of Jupiter and its radiation field both rotate counter clockwise when viewed from above Jupiter's north pole. The radiation field is trapped within Jupiter's magnetic field and so rotates at the same speed as the planet, every 9.9 hours. Europa, however, orbits at the more leisurely pace once every three and a half Earth days. As a result, the radiation field slams into the trailing hemisphere of Europa full on, but not its leading side. (Remember that Europa is tidally locked with Jupiter and keeps the same face to the planet throughout its orbit as our own moon does with the Earth. As a result, the same face of the moon is always the leading hemisphere, and the opposite face the trailing hemisphere.) On the other hand, the leading hemisphere experiences just a fraction of the radiation of the radiation hitting the trailing hemisphere. (Thera Marcula lies near the edge between the two hemispheres just on the leading hemisphere side. )

Concept for the orbiter and two lander stack

The landers would be carried into Europa orbit by a carrier spacecraft. After entering Jupiter orbit, the combined spacecraft would perform sixteen Ganymede and Callisto flybys before entering Europa orbit. (The presentation doesn't specify how many Europa flybys would be performed, although the goal would be to get into Europa orbit as quickly as possible to minimize time in the high radiation fields.) After a few orbits around Europa, the first lander would be released with the second lander released at the same time or a few orbits later. Once on the surface, the landers might either communicate directly with Earth or use the orbiting carrier craft for data relay.

Concept for the lander

Many details of the mission are still to be worked out. For example the landers might either be battery powered if they are to last just a few days or carry nuclear ASRG power sources to enable life for several weeks until radiation kills the electronics. The concept images in the presentation show ASRG's on the carrier spacecraft and on each lander.

The minimum instrument compliment for the landers is one of the decisions to be made by the lander concept team. The slides suggest that the minimum might a mass spectrometer to measure the surface composition, a seismometer to examine the subsurface structure, and a suite of physical state instruments to measure temperature, radiation, light levels, and acceleration (presumably from surface flexing). An enhanced instrument suite might have more comprehensive chemistry and geophysical instruments as well as cameras. A likely key decision for the concept team would be how the samples would be acquired for composition measurements -- arm and scoop, drill, ?

Artist's concept of landing within a chaos region on Europa

Editorial Thoughts: Given the recent study suggesting ideal landing spots on Europa -- fresh chaos regions -- the idea of a landed mission as our next Europa mission becomes very attractive; hell, it is exciting. To temper that excitement, however, remember that a simple orbiter with a few instruments or a simple multi-flyby spacecraft with a few instruments would each cost ~$1.5B. This mission would require an orbiter plus two landers that each would have the approximate sophistication of the Mars Phoenix lander. That feels tight for a $1.5B budget.

There is also the practical problem that most of Europa has not been imaged or spectrally mapped to determine surface composition at high resolution. When we had a similar situation with Mars and the MER rovers, we selected a landing site for Spirit that looked at moderate resolution to be a lake bed but turned out to be a lava flow bed. (Fortunately, Spirit reached hills above the lava flow that retained clear evidence for past watery environments.) Unfortunately, our highest resolution imaging of Europa is on the trailing hemisphere, leaving the highly desirable low radiation leading hemisphere terra fuzzy.

So, should the carrier spacecraft include a high resolution camera and spectrometer to image Europa during flybys prior to orbit insertion to select the best landing locations? Orbital mechanics plays a dirty trick on us here. Galileo imaged the trailing hemisphere at highest resolution because the natural location to encounter Europa at around the 3 o'clock position (again, looking down from above the northern hemisphere of the Jovian system). At that position, the trailing hemisphere is fully illuminated and the desirable leading hemisphere is in darkness. A mission that tries to get into Europa orbit as quickly as possible would face a similar problem. Gravity assists can be used to walk the location of Europa encounters around the clock (so to speak) but at the cost of a longer mission and higher operation costs.

Once the carrier craft is in orbit, should it carry any instruments? For a truly minimalistic mission, the simple answer is no. However, much of the cost of the orbital science is getting to Europa and orbiting for a few days to a few weeks. The orbiter's radio system would allow gravity mapping, a high priority measurement to study the interior of the moon. I suspect that the temptation to carry at least a camera and a magnetometer (which enables inferences about the subsurface ocean through magnetic induction) would be strong. (The orbit would dip to just five kilometers above the surface to deploy the probes where a simple camera's resolution might be ~5 m.) The laser altimeter to measure the flexing of the surface to estimate ice thickness and the Langmuir probe to measure the particle and fields environment (and isolate their impact on the magnetometer measurements) might be too much. I think a camera to document the terrain of the landing sites both to pick safer spot and to put the surface measurements in context would be strongly desired.

I would not be surprised to learn that the final cost estimates for this mission with any carrier craft instruments deemed necessary or minimal added cost will be above $1.5B. Given that NASA's projected budgets cannot afford even a $1.5B mission, selling the political system on a, say, $2B orbiter plus two landers is probably not much harder than selling them on a $1.5B orbiter or multiflyby mission.

I'm hoping for good news out of this task force.

JUICE – Jupiter Ganymede Orbiter Revised Proposal

2011-11-13T09:09:00.000-08:00

Current concepts for the JUICE spacecraft. All illustrations are from the JUICE presentation at the recent OPAG meeting.

This time last year, both NASA and ESA were considering a joint mission to the Jovian system, with the former to concentrate on Europa and the latter on Ganymede. Today, NASA’s budget outlook has caused it to abandon its plans for the Jupiter Europa Orbiter (although it is looking at ways to reduce costs to enable a Europa mission should budgets become increase). ESA, however, is still considering its Jupiter-Ganymede orbiter as part of a competition to select is next large science mission. The new moniker for the mission is JUICE for JUpiter ICy moon Explorer.

At the recent Outer Planets Analysis Group (OPAG) meeting, two members of the JUICE proposal team provided an update on their proposal. Ganymede remains the focus of the mission, with the spacecraft studying it from orbit about the moon for the better part of a year with the final orbits just 200 kilometers from the surface. The original mission also included a number of Callisto flybys that have been retained in modified form in the latest proposal.

The focus of the JUICE mission remains the study of Ganymede from orbit around that moon

In the last few months, the JUICE team has looked at whether the mission could be enhanced to more thoroughly study the rest of the Jovian system, including Europa. From the point of view of celestial mechanics, adding Europa flybys to the mission would be relatively straightforward. Unfortunately Europa orbits Jupiter deep within that planet’s radiation belts. Targeting Europa requires enhancing the radiation hardening of the spacecraft and instruments, increasing mass and costs.

In the end, the team is recommending just two flybys of Europa as a compromise. The team looked at two options for those flybys. One would have the spacecraft make its closest approach to Europa at different faces of the moon to maximize geophysical measurements of the gravity (mass distribution) and interaction of the subsurface ocean with Jupiter’s magnetosphere. The second option would have the spacecraft fly over the same hemisphere and would focus on remote sensing surface composition measurements of high priority areas. The team has chosen the latter approach both because detailed composition measurements of Europa from the Galileo mission were limited and to simplify the spacecraft design. The proposal team recognizes that two flybys capture just a tiny fraction of the science that NASA Europa orbiter would have. However, the team estimates that as many as 50 - 100 flybys would be needed to fully replace a dedicated Europa orbiter, which would require radiation hardening not feasible within the mission’s budget but which would also result in the loss of the rest of the science objectives of the mission, that of Ganymede and Jupiter system science.

Example ground tracks and focus areas for remote sensing during the two Europa flybys.

The team also looked for ways to enhance studies of Jupiter’s atmosphere and magnetosphere. For both sets of studies, scientists would like to move the spacecraft out of Jupiter’s equatorial plane. By doing so, the instruments can view the atmosphere at higher latitudes and get a better understanding of the three dimensional structure of Jupiter’s magnetic field and plasma fields.

The team proposes to incline the spacecraft’s orbit around Jupiter by 29 degrees by using the Callisto flybys to first pump up and then pump down the inclination. There will be a price to pay for these orbital maneuvers. The previous mission plan had the closest approaches to Callisto well distributed around the moon’s surface. The new plan fixes the approach geometry so that the spacecraft follows nearly the same ground track for each flyby. As a result, the instruments will see the same portion of the surface and sense the same area of the gravity field as a measure of internal structure for each flyby.

Inclined Jovian orbits to study the Jupiter atmosphere and magnetosphere at higher latitudes

In the new plan, the JUICE spacecraft would follow nearly the same ground track for each Callisto flyby (left) instead of distributing the ground tracks around the moon as previously planned (right)

Unfortunately, Io remains too deep in Jupiter’s radiation field for the mission to flyby it. Future studies of this moon will depend on the success of the proposers of the Io missions in future NASA New Frontiers and Discovery mission selections.

Currently three missions, JUICE and two astrophysics missions, are in contention for the single funding slot for the next ESA large science mission. In February, ESA plans to select either its final choice or to eliminate one of the three with a final winner selected after further study. If JUICE is selected, it would launch in 2020, with a backup launch opportunity in 2022. Approximately six years later, the spacecraft would reach orbit. Another two and a half years would be spent exploring the Jovian system and preparing to enter Ganymede orbit for ten months of orbital science observations before the mission ends.

Editorial Thoughts: The budget for ESA’s next large science mission is capped, and major changes to the original Jupiter Ganymede Orbiter proposal are not possible. The proposal team has done a nice job of enhancing the proposal with limited additional studies of Europa, Jupiter’s atmosphere, and the magnetosphere.

The other two missions in competition for selection by ESA are exciting astrophysics missions in their own right. The competition is likely to be tough. Barring a significant budget increase for NASA, however, JUICE appears to be our only option for exploring the icy moons of Jupiter in the next two decades.

My thanks to Michele Dougherty, Professor of Space Physics at Imperial College and Lead of the JUICE Science Study Team, for reviewing a draft of this post.

Return to Venus

2011-11-05T21:22:00.000-07:00

Portion of Venera 14 landing image. Ted Stryk's website has the nicest versions of these images I've seen.

A bit over a year ago, I wrote that a return mission to Venus would be compelling because "We live on a terrestrial planet, and one on which we are undertaking a grand experiment to see what happens when we dramatically increase the proportion of greenhouse gases in the atmosphere. As a result, I think that furthering our understanding of Venus as a terrestrial planet and a greenhouse atmosphere carried to extremes is a compelling target for exploration in the next decade."

While NASA has taken a pass on Venus for now, Europe has no missions in the offering, and Japan's Akatsuki mission is struggling to reach orbit, Russia has a mission planned for 2018.

Russia's Venera-D mission has gone through several iterations. At one time, Russia had hoped that international cooperation might lead to a truly ambitious flotilla consisting of advanced orbiters, multiple balloons, and multiple landers. The new plan appears to be a Russia-only mission, but one that is still ambitious with a capable orbiter and lander. It is really three missions in one, with significant capabilities for studying the atmospheric structure and composition, the plasma environment enveloping the planet, the surface geology.

The orbiter will carry a number of spectrometers that will measure the structure and composition of the atmosphere from its top to the planetary surface. One of its instruments, the interferometer spectrometer, will replace the Planetary Fourier Spectrometer that failed on the Venus Express mission that would have measured the atmospheric structure below the cloud tops.

A second suite of instruments on the main orbiter and a small sub-satellite will extend our studies of the plasma environment. A key problem with studying plasmas environments is that they are dynamic, and it is hard to separate local conditions surrounding a single spacecraft from more global conditions. The sub-satellite will provide a second point of measurement to compare results.

The atmospheric and plasma experiments will continue, and significantly extend, studies that have been made by previous missions extending as far back as the Pioneer Venus orbiter in the late 1970s and continuing today with the Venus Express mission and hopefully continuing with the Akatsuki mission if it can reach orbit.

For me, though, the key contribution of the Venera D mission will be a return to the surface. The lander will explore a different terrain than previous landers, which landed either on the basaltic plains that cover most of the planet or on the fringes of the highlands. Venera D will be targeted to explore the tessera highlands of Venus that rise, like continents, above the surrounding lowlands.

NASA studied a tessera lander as part of its recent Decadal Survey. The authors of the report on the mission concept summarized the importance of a mission to these highlands: "The key science driver... is to measure the mineralogy and major elemental composition of tessera terrain, which is distinct from the plains and is yet unsampled... Tesseara terrains appears.. as the oldest material on a planet where the average surface age is ~500 million years. Thus, the tessera proved the best chance to access rocks that are derived from teh first 80% of the history of the planet, an era for which we currently have no information."

While the probe is called a lander, it is just as importantly, an atmospheric probe. The NASA report continued, [Previous] "compositional measurements of the atmosphere constrain atmospheric evolution, but to date, very little compositional or physical information has been garnered [below 16 km altitude], which is key to understand both atmospheric evolution and the surface-atmospheric interactions."

In many ways, the lander portion of Venera D is similar to the twice proposed New Frontiers SAGE Venus lander. A comparison of their instrument lists shows that both missions would have similar capabilities. In its most recent incarnation, the SAGE lander was targeted toward an area that Venus Express scientists believe may have been covered with recent lava flows. Should both missions fly, we will have sampled the dominant younger (<500 M years old) plains of Venus with the older Venera landers, possibly the much older surface on a tessera, and possibly the some of the youngest surface with SAGE.

Location of previous Venera landing sites from the Wikipedia article on the Venera landers.

Editorial Thoughts: Venera D is an exciting mission. I don't know whether it is a fully approved mission, or whether it is still a mission concept that needs to be formally approved by the Russian government. (If any of you have insight into its status, please post a comment.) A recent conference abstract (link below) says the mission is in Phase A, which is the earliest phase of a mission's conceptual definition and design. This would be normal for a mission still six years from launch.

Resources:

You can read Ted Stryk's summary of the Venera D mission (which provided essential background for this post) at http://planetary.org/blog/article/00003210/. He also posted a photograph of a poster on the mission from a recent conference.

A Russian space agency website on the mission can be found at http://www.venera-d.cosmos.ru/. While the website is in Russian, Google Translate produces a reasonable English translation, and likely does well for other languages. A recent conference abstract on the mission can be found at http://meetingorganizer.copernicus.org/EPSC-DPS2011/EPSC-DPS2011-1334.pdf. My thanks to colin_wilson at the Unmanned Spaceflight Forum for these two links.

I wrote a post on NASA's tessra lander concept, which you can read at http://futureplanets.blogspot.com/2010/06/venus-tessera-lander-concept.html.You can read NASA report on its tessera mission concept at http://ia600505.us.archive.org/30/items/VenusIntrepidTesseraLanderConceptStudy/03_Venus_Intrepid_Tessera_Lander.pdf

There is a summary of the SAGE mission proposal at http://lasp.colorado.edu/sage/archives/PDF/SAGE%20Fact%20Sheet-p6_for%20print_April-21-2010.pdf

I wrote a post on previous concepts for international Venus missions that would have been more capable than the current concept for Venera D: http://futureplanets.blogspot.com/2010/01/russian-and-european-venus-ambitions.html

Whither NASA's Planetary Program?

2011-10-27T22:13:00.000-07:00

"Word has leaked out that in its new budget, the Obama administration intends to terminate NASA’s planetary exploration program. The Mars Science Lab Curiosity, being readied on the pad, will be launched, as will the nearly completed small MAVEN orbiter scheduled for 2013, but that will be it. No further missions to anywhere are planned."

Obama readies to blast NASA, Washington Times

- Robert Zubrin

"Rumors of the death of NASA’s planetary science program are greatly exaggerated, according to the head of the agency division responsible for that activity...'“It is not true the planetary program is being killed' [said James Green].

- Planetary Science Lives, NASA Official Says, Space News

"...this is the most challenging budgetary time of my entire 33 year career."

- Dr. James Green, Director of Planetary Science at NASA Headquarters http://solarsystem.nasa.gov/news/column-view.cfm?CLID=101

"In 1980, the Director of the Office of Management and Budget (OMB) and the NASA Administrator made the decision to shut down planetary exploration in NASA in order to free up funds for the development of the Space Shuttle.... The administration leaders told us, face-to-face, that the planets could wait because soon the cost of access to space would be so cheap that we could fly any missions about which we could dream.

"We fought back, and they didn’t shut down planetary exploration. However, they did cut it deeply, resulting in a dark decade with no launches to and no data coming back from from other worlds.

"Imagine a NASA that for ten years (say, 2015 to 2025) ceases to explore the solar system and stops looking deep into the universe. We’re in a similar situation today. "

Is OMB wiping out planetary exploration? The Space Review

- Dr. Louis Friedman (former Executive Director of The Planetary Society)

I know that discussions of budgets are not the favorite topic of some of my readers, nor mine. However, the recent news and commentary on budgets has been dire enough that returning to this topic seems appropriate. Without funding, all the great ideas for NASA missions are no more than the paper or webpages they are printed on. And so, I am publishing one of my few opinion pieces. Please feel free to agree or disagree in the comments.

Four pieces of bad news, not including the unnamed sources cited by Zubrin, have triggered the concerns:

The President's budget request for FY12 projected severe declines in out year budgets for the planetary program. These cuts, if enacted in future years, essentially end NASA's ability to carry out Flagship scale planetary missions on its own for the foreseeable future.
The President's Office of Management and Budget (OMB) has refused to allow NASA to commit the approximately $1.5B needed for its proposed joint Mars program with ESA. No public reason has been given (but I have speculations, see below).
The James Webb Space Telescope (JWST) is severely over budget, and NASA has proposed to OMB that it cover the additional costs by in part transferring funds from other science programs, including, presumably, the planetary program. No figures have been given, but my back of the envelope calculations suggest that the transfers, if approved by OMB and ratified by Congress, might cost the planetary program a Discovery mission.
Current American law will require automatic cuts to all discretionary Federal programs, including NASA, if the two political parties are unable to overcome their differences on identifying future substantial budget cuts. A figure published by the journal Nature suggests the automatic cuts could be ~11% for programs like NASA. Again, that could cost the planetary program a Discovery or New Frontiers mission.

On top of this, NASA's human spaceflight program has been given an ambitious set of tasks that many don't believe it will have funds to fulfill without transferring funds from other programs (which has happened before and resulted in cuts to NASA's science programs).

I have been a manager at a major high technology firm, and I understand the challenges of budget crunches and trying to scramble to keep programs going and recraft roadmaps. Dr. Green and his colleagues have my admiration for what they are doing and their honest assessments of the situation.

I also applaud the efforts of the planetary science community, Dr. Friedman, and The Planetary Society for advocating for a strong planetary program. The political process, which will decide the level of funding, responds to strong community commitment.

With the information I have, however, I don't believe that OMB is necesarrily the bogey man preventing the planetary program from pursuing a great program. NASA's two biggest programs, human spaceflight and JWST, are under funded. Major new budget cuts to all of NASA are a real possibility. If OMB approves the Mars funding, can it meet the commitments made to the Europeans in the out years without gutting the rest of the planetary program? In addition, what America buys through the investment in the joint Mars program is the first mission in three needed to return samples from Mars. Another ~$6B (Decadal Survey estimate) would be needed to complete the program. If OMB doesn't believe the rest of the program can be afforded or has the necessary political support within Congress, then is the first payment a wise move?

As a strong supporter of planetary exploration, I favor the investment in the joint program because it also enables the Mars Trace Gas Orbiter and the European ExoMars rover, which would be a great mission in its own right. However, spending American taxpayer dollars to fly European rover instruments to Mars probably do not make a strong sell within OMB.

The total cost for building the JWST and the three missions needed for the Mars sample return would be about $8B each. European investments in a joint program might reduce the U.S. cost for the sample return by $2-3B. OMB has the option to support JWST and build on the $3B already spent and the option to begin investment in a Mars sample return program now and save $2-3B through cooperative investments by the European Space Agency.

Dr. Green points out that the astronomical community has done a great job of making the case for the science of JWST and building political support. My guess is that the real issue here is that the planetary science community has not made the political sale for the Mars sample return program, and as a result, OMB is reluctant to make the down payment.

I remember the 1980 budget disaster mentioned by Dr. Friedman in the quote above well. It led me to publish one of my first articles. In those days, the seriously proposed planetary missions were Flagship-class. A few people called for flying small, focused, and relatively inexpensive missions, some of which I profiled in that article. Eventually these ideas would lead to the highly successful Discovery and New Frontiers mission programs that do great science at less than Flagship prices. Check out the Messenger Mercury, Dawn Vesta and Ceres, and the Juno Jupiter missions for examples of what can be done.

Ultimately, the President's office and Congress will have to sort out priorities. Is the James Webb Space Telescope's science higher priority than the joint Mars program with ESA and an eventual Mars sample return? Is reducing the Federal budget deficit so important that NASA and many, many other programs should be cut? (Funding for my research comes from some of the programs facing cuts, so I have skin in this game.)

I believe that NASA's top science priority should be to understand the changes occuring to the Earth's biosphere on which we all depend. I personally prioritize planetary science over astronomical science, but believe both are important. Making the JWST's science NASA's top science priority after Earth Science is in no way a stupid call, but not the one I would make. My major concern with JWST is that a single launch failure or design flaw could make several billion dollars in future investment a waste. By moving forward with JWST, NASA is betting the bulk of its science program for the coming decade on a single mission.

In 1980, the only missions being proposed seriously were Flagship-scale missions. Today, NASA has strong Discovery and New Frontiers mission programs that fly missions for much less than Flagship prices. If the coming decade were to have the OSIRIS-REx asteroid sample return and each of the three Discovery missions that are current finalists (the Titan Mare Explorer, the Comet Hopper, and the Mars GEM geopysical mission) or equivalently good mission in their turn, it would be a good but not great decade.

At the last Outer Planets Analysis Group (OPAG) meeting that I listened to, it was said that the last Discovery mission selection included three outer planet missions that would fit into the Discovery mission budget cap. This is a new development and a major achievement for NASA and planetary science community. The Discovery and New Frontiers programs can advance planetary exploration across most of the solar system.

NASA also is not only game in town. Europe has two planetary missions in competition for selection, Russia has a Phobos mission ready for launch and lunar and Venus missions in development, Japan has another asteroid sample return mission in development, and India and China are building their programs of planetary exploration.

As for Zubrin's claim, the quick denial by a NASA manager known for being straightforward leaves me doubtful of his claim. There have been no other hints of this radical of a move by the administration. Congress has supported NASA's science programs, and a sudden change like this requires conccurance of the administration and Congress. Sometimes Chicken Little is right, but extraordinary claims require more evidence than a single uncited source.

I'll close with some words from a second article from Dr. Freedman that resonated with me: "As I have said many times, it makes no difference to Mars when it is explored or by whom, but it makes a huge difference to us, the people who own the program and carry it out. Just as when, nearly 20 years ago, the US abandoned the Superconducting Supercollider effort, it is one more piece of evidence of a great country ceding its greatness and reducing its hopes and investments for the future... For those who like to think short-term only, it also reduces jobs and national capability. Universities and companies around the country have motivated academic achievement and inspirational jobs with Mars and other planetary exploration."

Europa - New Options

2011-10-22T18:18:00.000-07:00

Click on the slide or here to go to the site with the presentation of the Europa mission study team

At this week's meeting of the Outer Planets Analysis Group (OPAG), NASA unveiled new options for exploring Europa as a possible abode of life (and with a third option still to come). The results are a work in progress, with completion of the studies to come next year. However, the results so far present entirely new options to finally moving on with the study of Europa.

The new mission proposals come after the sticker shock from the previous proposal, the Jupiter Europa Orbiter (JEO). When JEO was defined, NASA's budget outlook seemed robust and multi-billion dollar missions possible. At NASA management's request, its engineers designed a mission that hit the science "sweet spot." After many months of exploring the Jupiter system, JEO would have carried an extensive suite of instruments into Europa orbit. In what would have been an engineering tour de force, the spacecraft would have been designed to survive the hellish radiation fields around Europa for a full 90 days (and likely even longer).

Unfortunately, the independent cost estimate for JEO from the Decadal Survey's review pegged JEO's cost at close to $5 billion. Even for a robust planetary budget, the Survey's members concluded that the price tag was too high and asked NASA to explore cheaper alternatives.

The two mission concepts presented at the OPAG meeting are NASA's response to that request. To understand how the team arrived at its proposal, it's useful to compare the JEO approach to the Mars exploration strategy. In the former, a single mission would be flown that would have addressed all high priority goals for Europa exploration except for those that that required a lander. In comparison, the Mars program has depended on a series of relatively inexpensive missions that each address a subset of questions. For less than a billion dollars a mission, NASA flew Mars Pathfinder, Mars Odyssey, the Spirit and Opportunity rovers, the Mars Reconnaissance Orbiter, and the Phoenix lander. Only the soon-to-launch Mars Science Laboratory Curiosity broke the billion dollar mark (and rather substantially). Looking forward, the Mars program has (or perhaps given the new budget realities, perhaps its more correct to say, 'had') planned to break up the multi-billion dollar Mars sample return into three separate missions to reduced peak funding costs.

The question for the Europa mission study team was how to divide the JEO mission goals into manageable chunks. The job of the Europa mission study team was helped by the fact that the next steps in Europa exploration naturally divide into multiple goals:

The ocean goal would measure the extent of the ocean beneath Europa's icy shell and determine its connection to the rocky core of Europa. This is also, because of the nature of the measurements required, is the only goal that requires orbiting Europa.
The other three goals -- measure the vertical structure and depth of the ice shell, measure the composition of trace materials on the surface to understand the composition of the ocean and whether it might harbor life, and image the surface to understand the processes acting on the ice shell -- would ideally be done from orbit but could be done from a multitude (>30) Europa flybys.

Two key factors had driven JEO's costs upward. First, to meet JEO's goals from Europa orbit, the spacecraft needed to survive for 90 days or more in the harsh radiation field around Europa. This required extensive shielding and exotic technologies for both the spacecraft electronics and for the instruments. Second, collecting and returning all the data in just 90 days required high communications rates and as result high power rates.

Comparison of the two proposed spacecraft with the JEO proposed spacecraft

The ocean measurements that had to be done from Europa orbit required relatively small instruments, low to modest data rates, and only 30 days in orbit. By focusing the orbiter only on those required measurements, the radiation hardening, data rate, and power requirements dropped substantially.

The remaining measurements still required substantial instruments and high data rates. The team chose to place these instruments on a flyby spacecraft that would orbit Jupiter and encounter Europa 30+ times over the course of the mission. (The spacecraft also would encounter Ganymede a number of times, but those flybys were planned for gravity assists and were not science drivers for the mission.) By going to a multi-flyby strategy, the spacecraft spends only a little time each orbit in the highest radiation fields. There are also days each orbit to return the data, dropping the requirement for peak data rates and power.

Proposed instruments

The study team estimates that the orbiter and flyby mission each would cost around $1.5B, not including the costs of the launch vehicles. The assumption is that for budgetary reasons the missions would not launch together, and their launches might actually be years or many years apart. Assuming that funding can be found, this would place the science community in the difficult predicament of deciding which to fly first, knowing that the second mission might never fly. Is ocean science more important or is the combination of icy shell, composition, and high resolution mapping science more important?

Proposed flyby (top) and orbiter (bottom) spacecraft

Representatives from NASA's headquarters stated their delight in having new, much lower cost mission options to present to Congress for funding. They are so delighted that they have asked to have the same focused approach applied to a possible Europa lander mission. Presumably, once the studies for the three possible missions are complete, NASA will ask the science community to prioritize them. Then NASA will begin the job of securing funding to fly the highest priority mission. NASA's representatives emphasized that there is no money in the current budget plan to fly any of these missions. The President's office (OMB) and Congress will have to increase NASA's planetary budget for any Europa mission to begin development.

Note: A previous post, A Pragmatic Approach to Investigating Europa's Habitability provides additional background on the new approach.

Editorial Thoughts: It's exciting to have new Europa options on the table in a cost range that I can imagine one of them eventually being funded. However, looked at another way, the studies demonstrate again that exploring Europa is a multi-billion dollar proposition. Add the cost of the orbiter and flyby with their launch vehicles together, and you are approaching $4B, not too far from the estimated cost of JEO.

Which mission would I chose? As currently defined, I can't decide. The eventual goal would be to get a lander on the surface of Europa, which requires picking a location that is safe (high resolution imaging) and has interesting surface chemistry (imaging spectroscopy). This would argue for the flyby mission as the higher priority. That mission, however, would image only small portions of the surface at higher resolution than the orbiter mission would. (The orbiter would produce a 100 m global stereo map in three colors.) The flyby craft would carry a sophisticated mapping spectrometer (think of a camera that takes images in hundreds of colors) that would be too large and data hungry for the orbiter. If a simple spectrometer (for those of you familiar with these instruments, a profiling instrument) could be added or if the imager could image in more colors to get at spectral information, I would favor the orbiter. I certainly have no special insights into these issues, and included this thought experiment only to suggest the tough choices the planetary community will face if funding becomes available.

Updates

2011-10-06T03:38:00.000-07:00

ESA has announced the selection of its next two science missions. The Solar Orbiter, which will be a partnership with NASA, will study the sun from as close at 42 million kilometers from its surface. (NASA's Solar Probe Plus, which is in the definition phase (Phase A), will approach the sun as close as 3.7 million kilometers.) The Euclid mission will launch a space telescope to study dark energy and dark matter in the universe. (BBC article)

To follow up on my previous post, the heads of NASA and ESA met to discuss the redefinition of their joint Mars program without success. Unless NASA's budget problems can be resolved fairly quickly, this will leave NASA with no means to collect and cache samples for an eventual Mars sample return mission. As I understand ESA's budget, this also leaves ESA without sufficient funds to fly it's ExoMars rover. ESA apparently will seek new partners to share the financial burden and enable the mission (Russia has been mentioned). (Aviation Week and Space Technology article)

To highlight NASA's budget problems, the agency apparently is considering ending the Cassini mission at Saturn without completing it's current mission planned to end in 2017. This tidbit comes from the meeting announcement for the next Outer Planets Analysis Group (OPAG) meeting: "NASA has entered an era of strong fiscal constraints, and is struggling to maintain its commitments to missions in development and in flight. Community input will be vital in preserving robust Outer Planets Exploration. This OPAG meeting accordingly will focus on threats to the Cassini Solstice mission, implementation of the Planetary Science Decadal Survey, an update on European plans, and studies of potential missions to Europa." (http://planetarynews.org/)

Mars Program Troubles

2011-10-01T09:01:00.000-07:00

For the last week and half, I've been travelling and away from the internet. I have briefly reconnected to check on family (fine) and the planetary program (not so fine). Three articles (see below) break the news that NASA will not be able to contribute a launcher, as planned, for the joint ESA-NASA 2016 orbiter. It appears that ESA will be unable to continue with this mission unless it can convince Russia to provide the launch.

To briefly recap the previous plan, ESA and NASA had planned a 2016 orbiter that would provide atmospheric composition studies to settle the question of methane in the atmosphere and to act as a communications relay for future missions. A joint 2018 rover mission would collect samples for a possible return mission while carrying out a sophisticated in situ search for life, present or past.

According to the news reports, ESA and NASA are still considering the 2018 rover mission with a simplified communications orbiter.

Aviation Week summarizes the reaction among U.S. scientists with this quote: “The European Space Agency is willing to put €850 million [$1.16 billion] to collaborate with us. But for reasons unknown, somewhere in the administration somebody is refusing to release the letter that would allow the head of ESA to collaborate with NASA Administrator Charles Bolden,” Hubbard says. “Why on Earth would you refuse to allow over $1 billion of funding? It borders on the irresponsible.”

Editorial thoughts: Budget politics in the United States are, to put it in terms that avoid stronger four letter words, a mess. The two political parties have opposing views on future spending, and seem to have lost the ability to compromise. At the same time, NASA reportedly has prioritized the James Webb Space Telescope as its must do science mission, which may reduce funds available for planetary missions. Between these two rocks, the planetary program is navigating uncertain budgetary waters and may not be able commit to a large project. It may take one or two more election cycles before the planetary budget has a firm course, and that may be at a much lower level than today.

Articles covering this story:

Aviation Week and Space Technology

Space News (most in depth article)

Universe Today

Notes: I will still be traveling for the next two weeks, so posts will be infrequent for a while.

Quick Update

2011-09-18T16:15:00.000-07:00

There's been little news to report lately, hence the lack of posts.

NASA's budget for FY2012 (which starts October 1) continues to wind it's way through Congress. The committees responsible for NASA's budget in the House and Senate both have completed their recommended budgets. They have recommended funding at $1.5B, just $40M less than the President's request. While the House committee recommended cancelling the James Webb Space Telescope (JWST), the Senate recommended a substantial increase in this program's budget (with the increase coming from other parts of NASA's budget than the planetary program).

These actions are good leading indicators for the planetary program. However, this is likely to be an unusual budget year. Current law requires substantial cuts to the federal budget that will be either automatic across the board cuts or will follow the recommendations of a super committee that will attempt to draft recommendations for targeted cuts. Any cuts to the planetary program would likely be applied to future mission planning and development (which is why I follow the budget in this blog -- budget politics certainly are not where my interests lie!).

I will be traveling the next few weeks, so future posts may be erratic for a bit. However, I may finally find time on airplanes to write a couple of posts I've been wanting to write.

Budget Fight

2011-09-09T22:39:00.000-07:00

As I'm sure most readers of this blog know, NASA's James Webb Space Telescope (JWST) -- the successor to the Hubble Telescope -- is seriously over budget. The latest estimate puts the cost to complete the telescope at $8B, with only $3.5B of that already spent. Based on the budget proposed for JWST for next year, it would take almost a decade to complete development. (You may see a JWST budget estimate of $8.7B, which includes $0.7B to operate the telescope after launch.)

NASA has proposed to the White House (specifically, the Office of Management and Budget) that it 'tax' it's other programs, both science and manned spaceflight, to increase the budget for JWST and launch it around 2018. There's no news, so far as I know, publicly available about the White House's reaction. The House of Representatives voted to kill JWST.

A number of leading planetary scientists have just published a strongly worded editorial stating, "We individually and together reject the premise that JWST must be restored at all costs... Without additional funds to NASA, JWST should not be restored unless and until an open science community assessment is made of the value of what will be gained and what will be lost across the entire NASA science portfolio."

A less strongly worded letter from Dr. David Alexander, Chair, American Astronomical Society, Solar Physics Division (SPD), echoes some of the same concerns, "The SPD fully supports the science goals of the JWST and the priorities of our colleagues in astronomy and astrophysics; however, it is extremely worrisome that the proposed solution to the problem will further reduce the ability of the other divisions within the NASA Science Mission Directorate to accomplish their own nationally sanctioned scientific programs."

The journal Nature's News Blog has some additional analysis of these letters and their motivation.

Editorial Thoughts: The problems in JWST's funding comes at the same time as NASA's manned spaceflight program faces it's own budget challenges. The programs on NASA's plate simply appear to be more expensive than it's current budget can pay for. I don't know what the least wrong solution is, but the following thoughts may suggest how difficult the choices may be.

JWST promises to continue Hubble's revolution in the understanding of the universe. Here's a list of the JWST program's major science programs, copied from the its website:

The End of the Dark Ages: First Light and Reionization seeks to identify the first bright objects that formed in the early Universe, and follow the ionization history.
Assembly of Galaxies will determine how galaxies and dark matter, including gas, stars, metals, physical structures (like spiral arms) and active nuclei evolved to the present day.
The Birth of Stars and Protoplanetary Systems focuses on the birth and early development of stars and the formation of planets.
Planetary Systems and the Origins of Life studies the physical and chemical properties of solar systems (including our own) and where the building blocks of life may be present.

What might be lost from the planetary program if it's budget is cut? The planetary Decadal Survey prioritized its programs as:

Research funding
Discovery missions (4-5 in this decade)
New Frontiers missions (3 in this decade)
U.S contribution to the NASA/ESA 2018 rover

If NASA were to cut starting the planetary program starting with the lowest priority, it would appear that the 2018 rover would be the first to be cut. That mission would place a second rover (after the soon to be launched Mars Science Laboratory) with a highly capable analytical laboratory on Mars. The mission also would collect and cache samples for possible return to Earth.

JWST and the 2018 Mars rover both would be great missions. How would you make the decision? If you are an American citizen, you might want to share your choice with your senators and congressman.

Venus: Forgotten Planet?

2011-09-04T00:09:00.000-07:00

For the last several years, I've followed every meeting of the several Analysis Groups that provide NASA with feedback on it's planetary exploration plans. There's a group for Mars (MEPAG), the outer planets (OPAG), small bodies (SBAG), and Venus (VEXAG). When there's no major issues in the area of focus, the meetings can be status updates that might provide tidbits of news. When there's a hot issue, the meetings can provide first looks at those issues with meaty presentations.

The just completed VEXAG meeting had a focus I'd not seen before, that appeared to be asking NASA to explain the lack of missions planned for Venus:

NASA SMD [Science Mission Directorate] View/Outlook for Venus
SMD Competed Missions - NF & Discovery
Discovery Program

These presentations haven't been posted yet, but the journal Nature has provided a summary of the concerns behind asking NASA to discuss these topics. According to the article, the Venus science community perceives, "an agency bias against Venus, a planet that hasn't seen a US mission since the Magellan probe radar-mapped its shrouded surface in the early 1990s, and which won't see one any time soon, after NASA this year rejected a bumper crop of Venus proposals."

The community has tried to get a mission prioritized by describing why Venus is worthy of exploration and listing priority investigations (for example, Venus Exploration Goals and Objectives). The SAGE Venus lander was proposed for the last New Frontiers competition, but was passed over and the OSIRIS-REx asteroid sample return mission was selected.

According to Nature, a quarter of the 28 Discovery proposals for the latest competition targeted Venus, but not one was selected as a finalist. Six of those received the lowest ranking, and only one that focused on atmospheric studies was judged competitive.

Nature reports that NASA's explanation for the low rankings is that, "Venus scientists need a clearer consensus on their goals and the measurements that they want to make." In the meantime, that community is seeing interest in Venus shrink among the larger planetary community as missions focus on other solar system targets.

Editorial Thoughts: I know from personal experience how tough proposal reviews are. The ones that hurt are those where the proposing team had a technical error (they should have caught those). Proposals for spacecraft missions also have to demonstrate that they can be developed with the program's mission cost cap. The Nature article doesn't mention any proposals rejected for technical or cost issues, but some may have been.

Usually, the bigger hurdle for proposers is developing a compelling scientific question to address. It's not enough to, for example, say that you will map x% of Venus' surface at 10x higher resolution than has been done before. You have to show what compelling question(s) will be answered. And your compelling questions have to be better than your competition's questions.

Given the low ranking for six of the Venus Discovery proposals, it appears that either the Venus community hasn't sharpened its priorities and questions sufficiently, or the best questions available for Venus that can be addressed within a Discovery budget aren't compelling compared to those for other solar system targets. It may be that previous missions have picked off the inexpensive low hanging fruit.

The European Venus science community has also proposed Venus missions to follow up on the Venus Express mission, but so far have had no luck. The Russians are defining a new mission, Venera-D, that would include a lander and possibly also an orbiter and balloon platforms. (I'm not sure that this is a formally approved mission or not. I'd appreciate it if any readers with a better understanding of this mission's status could leave a comment.) See this previous post on the European and Russian proposals: http://futureplanets.blogspot.com/2010/01/russian-and-european-venus-ambitions.html

Bonus: NASA generally doesn't reveal too much information on the Discovery mission proposals. The Nature article, though, gives the number of proposals by target for the competition in progress:

Venus - 7
Moon - 3
Mars and it's moons - 4
Asteroids - 8
Jupiter system - 1
Saturn system - 2
Comets - 3

The selected finalists were the Titan Mare Explorer (TiME), the GEMS Mars geophysical station, and the Comet Hopper.

CHANDRAYAAN-2

2011-08-26T10:25:00.000-07:00

News continues to be slow and my workload high, so I will post (with permission) another abstract from the recent Low Cost Planetary Mission conference. The entry of India and China into the group of planetary faring nations will expand the roster of missions we'll be seeing the next decades. Our moon is a complex world, and exploring a new region by this joint Indian-Russian mission of the surface along with orbital observations is likely to bring new discoveries.

CHANDRAYAAN-2 MISSION. J. N. Goswami1 and M. Annadurai2, 1Physical Research Laboratory, Ahmedabad-380009, India, 2ISRO Satellite Center, Bangalore-560017, India.

The first Indian planetary mission to moon, Chandrayaan-1 [1], with a suite of Indian and International payloads on board, collected very significant data over its mission duration of close to one year. The success of this mission provided the impetus to implement the second approved Indian mission to moon, Chandrayaan-2, with an Orbiter-Lander-Rover configuration [2]. This will be a collaborative mission between the Indian Space Research Organization (ISRO) and the Federal Space Agency of Russia. ISRO will be responsible for the Launch Vehicle, the Orbiter and the Rover while the Lander will be provided by Russia.

The orbiter for the Chandrayaan-2 mission is similar to that in Chandrayaan-1 from structural and propulsion aspects. The indigenously developed Geostationary Satellite Launch Vehicle, GSLV(Mk-II), will place the Orbiter-Lander-Rover in GTO (180km-36,000km), following which the Orbiter will boost the orbit to LTT. Separation of Orbiter and the Lander-Rover modules will take place in LTT and they will reach lunar polar orbit independently. The orbiter will be placed in an elliptical (5000km-200km) polar orbit prior to the descent of the Lander-Rover module to the lunar surface. Multiple communication links involving Rover-Lander-Orbiter-Earth, direct Lander-Earth and Rover-Orbiter will be implemented.

Althouh the exact landing location is yet to be finalized, a high latitude location is preferred from
scientific interest. The orbiter will be finally placed in a 200 km circular orbit and the instruments on board will have a close up view of the moon. The scientific payloads on the orbiter include a Terrain Mapping Camera (TMC-2), an Imaging Infra-red Spectrometer (IIRS), a Synthetic Aperture Radar (SAR), a Collimated Large Area Soft X-ray Spectrometer (CLASS), and a Neutral Mass Spectrometer (ChASE-2). TMC will provide 3D imaging and DEM, while the IIRS will cover the 0.8-5 micron region and collect information on mineralogy, detect OH and H2O on lunar surface and measure thermal emission from the moon. CLASS is an improved version of C1XS flown on Chandrayaan-1 for inferring chemical composition based on detection of X-rays emitted from lunar surface during solar flares. ChASE-2 is a modified version of ChASE on the Moon Impact Probe (MIP) on Chandrayaan-1 that provided hints for the presence of water molecule and CO2 in the lunar exosphere. The Synthetic Aperture Radar will include both L (1.25 GHz) and S (2-2.2 GHz) bands with selectable (few meter) resolution.

There will be two payloads on the Rover: an Alpha Particle induced X-ray Spectrometer (APXS) and Laser Induced Breakdown Spectroscopy (LIBS) for studies of chemical composition and volatiles present in lunar surface near the landing site. The Lander will have a suite of Russian instruments to study physical and chemical properties of the lunar surface and sub-surface material, lunar environment and siesmic activity [3]. The lander will have direct communication link to Earth Stations as well as via Orbiter and act as the hub for communication with the Rover. The design and development of the various mission elements as well as of the scientific payloads are currently in progress both in India and in Russia.

References: [1] Goswami J. N. & Annadurai M. (2009) Current Science 96, 486-491. [2] Goswami J. N. & Annadurai M. (2011) LPS 42 #2042,. [3] Mitrofanov I. G. et al. (2011) LPS 42, #1798.

TiME and Updates

2011-08-23T23:11:00.000-07:00

It's summer time, which means that news is slow and I'm spending over half my time doing field work for my research. Anticipating both a slowing of news and limits on my time, I've lined up a series of abstracts and news releases that either update or expand on a future mission proposal. If you assiduously scan the Internet for this type of news, I apologize for the repetition. Otherwise, I hope you find these posts informative. When news does occur, I will report it.

Updates

NASA continues to study options for missions for Europa with an update promised for this Fall. The proposals under consideration would use the Stirling-based ASRGs rather than the MMTGs that had been planned for the flagship mission. This probably both reflects the lack of a start of new plutonium production (ASRGs use approximately a quarter the plutonium of the MMTGs for the same power output) and the lower cost of the expected missions (NASA has been reluctant to commit a multi billion dollar mission to the still unflown ASRG technology).

The latest cost projections for the James Webb Space Telescope that will be the successor to the Hubble Telescope are $8B for the hardware and $700M for the first five years of operations after launch. The journal Nature reports that NASA has proposed taking half the money still needed from the science program and half from the rest of NASA's programs. Editorial Thoughts: In the last decade, NASA reduced science spending to fund the manned spaceflight program; if approved this proposal would tax the manned spaceflight program to support science. It's possible that the planetary program would also be reduced to help fund the Webb Telescope. This telescope promises to be a cornerstone mission to understanding the early history of the universe, and while I would hate to see a planetary mission not flown, I'd hate to see this telescope cancelled even more. (For a less optimistic view of NASA's budget problems, check out NASA Watch.)

The White House has ordered all federal agencies, including NASA, to prepare their FY13 budget proposals, which will be submitted to Congress next winter, assuming a 5% cut from this year and identifying an additional 5% cut that could be taken. Editorial Thoughts: I don't know what NASA's planetary budget will be two years from now, except that no further decline than already planned may be good news.

Titan Mare Explorer (TiME): A Discovery Mission to Titan’s Hydrocarbon Lakes

This mission to place a scientific probe to float in a Titan lake has been a popular one with readers (and myself). At the Low Cost Planetary Mission conference a couple of months ago, the current plans were presented. The abstract from that talk is republished with permission.

Abstract. The Titan Mare Explorer (TiME) will land on Ligeia Mare, one of three large methane seas discovered by Cassini in the northern hemisphere of Titan. The seas of Titan provide an opportunity to explore a planetary surface whose chemical constituents are radically different from Earth, with liquid hydrocarbons making up the lakes, rivers, seas, rain and clouds seen by Cassini-Huygens. The seas of Titan are also repositories of organic molecules, chemically generated in the atmosphere above the sea, altered in ways we do not yet know on the surface, then deposited in the polar seas. The seas provide chemical and isotopic clues to: the processes of organic chemical evolution that have gone on for billions of years on Titan; perhaps the original materials from which Titan formed; and a medium within which networks of organic reactions, different from those in the aqueous medium of Earth, proceed toward a threshold that could be considered as life.

The self-contained, ASRG-powered TiME capsule will enter directly into Titan’s atmosphere, to float on the Ligeia sea. It is designed to operate in an almost completely autonomous manner, floating with the wind and waves. The payload consists of just three instruments, focusing on organic chemistry, meteorology, seafloor topography, and sea characteristics. This short, simple, passive mission architecture is key to enabling Titan science within the Discovery program.

The next major step in understanding Titan will be achieved through the two goals of TiME: 1) Understand Titan’s methane cycle through study of a Titan sea, and 2) Investigate the history of Titan and explore the limits of life. The science objectives to support these goals focus on determining the key unknowns for Titan’s seas: their chemistry, meteorology at the sea surface, depth, and sea properties. TiME has a small, high-heritage payload of three instruments: a neutral mass spectrometer, a meteorology and physical properties package, and an imaging system.

The science objectives of TiME are highly responsive to NASA and Discovery program goals and the key themes and science questions in the NRC Decadal Survey for Planetary Science. TiME will directly measure the composition of one of the major organic inventories on Titan, responsive to the ‘Volatiles and Organics: The Stuff of Life’ theme. The noble gas and isotopic inventories to be measured by TiME are highly relevant to the cross-cutting theme of ‘Origin and Evolution of Habitable Worlds’, under ‘What planetary processes are responsible for generating and sustaining habitable worlds?’. TiME will examine the extent to which organic chemistry on Titan has progressed toward or even beyond the threshold of biochemistry, also relevant to the Decadal theme of ‘Origin and Evolution of Habitable Worlds’. The study of the first active liquid cycle on a planet other than Earth, and of Titan’s marine processes are directly relevant to ‘Processes: How Planetary Systems Work’.

TiME will reduce the risk and enhance the science return from future Flagship-class missions by exploring in situ a key component of Titan’s methane cycle, and pathfinding operations in Titan’s extraterrestrial marine environment. Future missions that arrive after Earth has set from view of Titan’s high northern latitudes would need to include a costly relay spacecraft or target the much smaller southern lakes. An opportunity such as that embodied in TiME will not occur again for almost 30 years. In situ exploration of a major sea is the essential next step for advancing our understanding of Titan, provides an unprecedented opportunity to engage the public, and will be a reminder of the excitement inherent in visiting an unexplored and exotic environment for the first time.

Editorial Thoughts: All three Discovery mission finalists (which also include a comet multi-lander and a Mars geophysical station) are compelling, and I hope that each gets to fly. TiME is the only mission, so far as I know, that must be selected in this competition to fly so that it lands when Titan's northern lakes are in view of Earth. Assuming that this mission survives the engineering and programmatic reviews over the next year, my guess is it has a high chance of selection.

Red Dragon to Mars?

2011-08-14T15:22:00.000-07:00

Click on the screen shot to read Space.com's article on Red Dragon

There's an interesting Discovery mission proposal in the works. It would use a commercial spacecraft in development to land what could be a very large payload on Mars within a price cap of $425M.

The spacecraft would be a derivative of the Dragon manned capsule under development by the Space Explorations Technologies (SpaceX) corporation. The capsule currently being developed would ferry crews and cargo to and from the International Space Station. While the current capsule is designed to splash down in the ocean, a future version is planned that would land using rockets.

The founder of SpaceX thinks big, and wants to develop technology that eventually will enable manned landings on Mars. As a result, the capsule is being developed with eventual use on Mars in mind.
Chris McKay at NASA's Ames research center is working with SpaceX to define a Discovery proposal that would use a version of the Dragon capsule -- nicknamed 'Red Dragon' -- to put a payload on Mars with a launch in 2018. The goals of the mission would be to drill down a meter or more below the surface in an area known to have ice just below the surface. (Two possible landing sites: Near the Phoenix lander or near the Viking 2 lander.) Samples would be brought into the capsule to be analyzed for molecules that would indicate life.

While the proposal in development is modest in its scope, the capsule would be capable of landing several tons of payload, more than all the payloads delivered to Mars to data.

Editorial Thoughts: What to make of this proposal? SpaceX is a credible company that has successfully developed the Falcon 9 booster and has orbited and returned a prototype Dragon capsule. It's recently won some big launch contracts, showing that the satellite industry is comfortable with its capabilities.
If the Red Dragon lander were to be developed, it might significantly drive down the cost of landing payloads on Mars since the technology would be based on a production line spacecraft instead of being a unique design. There's been a lively discussion at the Unmannedspaceflight forum discussing what might or might not be possible.

My take on this is that it's a clever idea, but many things have to happen before it could fly. SpaceX would have to complete development of its Falcon Heavy booster that would launch the mission. NASA requires several successful launches before it will commit a science mission to a new booster. The Dragon capsule would have to be enhanced to land on rockets. The entire entry, landing, and descent at Mars would have to be thoroughly tested. SpaceX might treat much of this development as internal R&D and not charge it to an individual Discovery mission. Even so, I wonder if the first flight can be kept within the Discovery mission cost cap. NASA would also have to pay for the Falcon Heavy launch in addition to the $425M for the lander and payload; I don't know how this launcher's costs would compare to launch costs for other Discovery proposals. A launch in 2018 given everything that must happen seems ambitious.

While the potential to land large payloads is enticing, larger payloads cost more to develop and test than smaller payloads, and fully utilizing a Red Dragon's capacity could exceed a Discovery mission budget. And the capsule itself might make it hard to deliver some types of payloads. For example, could a reasonably large rover be packaged inside and then safely exit the capsule?

There are also questions of whether this is the best choice of landers for the type of mission McKay envisions. Could the drill and instruments be flown on the proven Phoenix lander instead? (Note: McKay is a seasoned researcher, so he's undoubtedly already asked himself that question. Red Dragon may enable a key capability for this mission that the Phoenix lander doesn't within a $425 mission cap.)

Many questions, and for the moment few answers, which would be expected for a new idea and a spacecraft that is still under development. If these questions can be answered with clever engineering and within tight budget caps, then this would be an exciting development. I hope we hear more about Red Dragon in the future.

Resources:

Space.com article on Red Dragon

MSNBC interview with SpaceX CEO on his plans for Mars

Wikipedia background on SpaceX and the Dragon capsule

PriME/MASPEX and Updates

2011-08-06T21:17:00.000-07:00

I'll cover the updates first. Aviation Week and Space Technology (AWST) has had a series of good articles on planetary exploration and space science in the last two issues. (Unfortunately, most require a subscription.) Amy Svitak, formerly with Space News, now writes for AWST, and continues her excellent coverage of policy issues there.

In an article discussing issues with NASA and ESA joint missions across a breadth of disciplines, Svitak reports that, "ESA is considering modifying the proposed Ganymede orbiter to to incorporate some Europa science." Presumably, this would be science gathered in a series of Europa flybys. (Source: NASA's money woes thwart joint science missions with ESA)

In another article, Svitak reports that ESA is considering downsizing or eliminating its technology demonstration lander from the joint ESA-NASA 2016 mission so that more funding can be applied to the 2018 joint rover mission. (Source: Europe could downsize Mars 2016 mission)

In yet another article, (this time not by Svitak), AWST reports that the Russian Phobos-Grunt sample return mission that will be launched this year is on track.

PriME/MASPEX

Sometimes a good mission concept can enabled by a single instrument. When NASA announced it's list of candidate missions for its next Discovery mission (http://futureplanets.blogspot.com/2011/05/discovery-mission-candidates-announced.html), it also listed three missions that would be funded for technological development to enhance their ability to compete in future selections. One of these was the PriME mission, "Primitive Material Explorer (PriME), which would use an advanced mass spectrometer to provide high precision measurements of the the composition of a comet using a new, advanced mass spectrometer.

First some background on mass spectrometers, which are workhorse instruments in many laboratories and on many spacecraft. To over simplify what they do, mass spectrometers 'weigh' the chemical compounds found in a plasma or gas. (The composition of solids and liquids can be measured by heating them until they vaporize.) The weights of the different molecules form a mass spectra that can be interpreted to determine the compositon of the orginal material.

Two figures of merit are frequently quoted when comparing mass spectrometers. One is the range of masses they can measure, which are frequently expressed in atomic mass units (amu), which are approximately the mass of a single proton or neutron. The Cassini spacecraft's Ion and Neutral Mass Spectrometer (INMS) has a range of 1-99 amu, the Rosetta spacecraft has two mass spectrometers with ranges of 1-150 and 1-300 amu, and the Mars Science Laboratory's mass spectrometer has a range of 2-535 amu. The second figure of merit is the resolution of the measurements in terms of how finely different masses can be distinguished. (The websites for the different instruments either do not give the second figure or report it in different units.)

The PriME mission would fly a next generation space-borne mass spectrometer, MASPEX, with a range of 1-1000 amu. MSPEX's resolution and sensitivity would allow far more precise measurements of the composition of the gases released by a comet that has been possible with previous and current missions. MASPEX could help us work around a key limitation of any comet sample return launched this decade. We currently lack the technology to keep many of the cometary ices frozen throughout the long delivery back to Earth. As a result, we'd lose the ability to measure pristine samples. An instrument like MASPEX could enable more precise measurements at the comet of unaltered materials. It's not clear, however, that MASPEX would be flown on a sample return mission itself. A sample return mission is likely to sample the comet as far from the sun as possible to avoid its volatile outgassing and then head back as early as orbital mechanics allow. A spacecraft carrying MASPEX, however, would want to linger at the comet through out the periods of maximum outgassing closest to the sun. As a result, separate missions might be likely.

An enhanced mass spectrometer would be useful in missions to many types of destinations including Mars, Titan, and Enceladus.

We have no details on MASPEX's cost, mass, size, or power requirements compared to current generation mass spectrometers (which apparently can be among the heavier and more costly instruments for many missions). Hopefully, MASPEX will be competitive, and will provide a new level of capability for a wide range of missions. For some destinations, its improved capabilities would be enabling by itself, as with the PriME mission.

With the permission of the PriME mission's Principal Investigator, Dr. Anita Cochran, I'm reprinting an abstract on the PriME mission. I'm also reprinting a press release on the MASPEX mass spectrometer. I've read elsewhere that while this mission wasn't selected as a finalist for the current Discovery mission selection, the team plans to propose it again for the next selection.

The Primitive Material Explorer (PriME) Mission

Cochran, Anita L.; Weaver, H. A.; Science, PriME; Engineering Teams
American Astronomical Society, DPS meeting #42, #49.17; Bulletin of the American Astronomical Society, Vol. 42, p.1006
The Primitive Material Explorer (PriME) Mission is a proposed Discovery mission that will rendezvous with comet 46P/Wirtanen in 2021 in order to 1) clarify the roles played by comets in the formation and evolution of the Solar System and the origin of life; 2) ascertain the bulk physical properties, the surface geology, and the sources of activity in a fresh comet nucleus; and 3) investigate the compositional diversity of primitive material in the Solar System. PriME teams an experienced group of comet scientists (led by PI Anita Cochran and by DPI Harold Weaver) with university and industrial partners.

The PriME payload accomplishes the mission objectives with only three instruments. MASPEX (MAss Spectrometer for Planetary EXploration) has higher mass resolution and is more sensitive than any mass spectrometer ever flown. MASPEX will measure D/H in H2O, noble gases, isotopes of many species, and complex molecular compounds to test solar nebula models and the role comets played in delivering water and other biologically important materials throughout the Solar System. The VIS (Visible Imaging System), consisting of a Narrow Angle Camera (NAC) and Wide-Angle Camera (WAC), will constrain the conditions under which the building blocks of the outer Solar System were assembled by measuring key physical properties of the nucleus of 46P/Wirtanen. Using the radio antenna and close flybys of the nucleus, PriME will determine the mass of the nucleus to an accuracy of 1% and the bulk density and average porosity of the nucleus to better than 5%. All spacecraft subsystems have significant planetary flight heritage. The spacecraft is a high-heritage derivative of the Kepler and Deep Impact spacecrafts, compatible with the three launch vehicle families specified in the Discovery Announcement of Opportunity.

NASA selects SwRI mass spectrometer for technology development funding, possible future planetary mission

For immediate release

San Antonio — May 17, 2011 — NASA has selected Southwest Research Institute's MAss Spectrometer for Planetary EXploration (MASPEX) for technology development funding. Originally offered as part of the Primitive Material Explorer (PriME) mission proposal, the mass spectrometer was selected to further advance NASA's capability for evaluating the chemical composition of comets.

MASPEX is a highly sensitive ion and neutral mass spectrometer based on novel detection technologies under development by SwRI. Although similar to a spectrometer on the ESA Rosetta mission currently on course to reach comet 67P/Churyumov-Gerasimenko in 2014, MASPEX extends its resolution and sensitivity by one to two orders of magnitude. The spectrometer is designed to measure precisely the composition of volatile gases and plasmas found in planetary atmospheres as well as comets. Identification of isotopes in these extremely low-density populations is a particularly challenging target and an area where MASPEX is expected to excel. In addition to comets, the SwRI team is exploring a number of Earth-based spin-off applications of this novel technology.

Institute Scientist Dr. Hunter Waite and Program Director Dr. David Young, both of the SwRI Space Science and Engineering Division, serve as MASPEX co-principal investigators.

"With further development, MASPEX will have by far the highest sensitivity for identifying, measuring and sampling gases and plasmas of any mass spectrometer ever flown in space," says Waite.

"Measuring isotopic composition will yield for the first time quantitative clues to the origin of comets and other bodies in the solar system, and could provide valuable insights into the origin of life," Young adds.

To be considered for space flight, the SwRI team must demonstrate continued advancement of the technology in preparation for a future mission proposal. The spectrometer is one of three technology developments selected by NASA for further development.

Articles and a Blog

2011-08-01T14:02:00.000-07:00

A couple of good articles were published today on the Juno and Mars Science Laboratory missions.

Nature: Closing in on Jupiter's Past

NASA: Juno to show Jupiter's magnetic field in high-def

Aviation Week and Space Technology: NASA bets big rover on novel landing scheme

I also discovered a new blog that covers space exploration, including in-depth posts on planetary exploration. I'm not sure how I missed this blog for so long; perhaps because it's in Spanish and my search terms didn't translate well. (Google translate seems to do a pretty good job at providing readable English text.) I've added this blog to my blog list, and you can visit it at http://danielmarin.blogspot.com/.

Why an Enigma?

2011-07-30T11:30:00.000-07:00

Check out Ryan Anderson's description of Gale Crater at his blog, the Martian Chronicles. You can also download his scientific paper, Geologic mapping and characterization of Gale Crater and implications for its potential as a Mars Science Laboratory landing site

By now, probably most of you have read that NASA selected Gale Crater as the target for the Mars Science Laboratory that will land there next summer. Many news accounts repeated the story that all four landing site finalists would have made great sites, and that the science community wasn't able to come to a consensus about which one was a priority.

The journal Science has just published an article that gives the back story on the ultimate selection process. Unfortunately, a subscription is required, so anyone without a university library account is unlikely to be able to read the piece. So, I'll give a quick summary of the key points.

Gale Crater stands out for its geomorphic and compositional diversity. Unfortunately, no one knows how that big mountain in Gale Crater with all its layers formed. Wind blown dust? Volcanic ash? Impact debris? Science titled its story, "How an alluring geological enigma won the Mars rover sweepstakes." That term, enigma, Science reports, comes up a lot in discussions about Gale.

So, why did an enigma win? Here's what Science reports:

Mawrth has the most ancient materials (big plus), but as with Gale, no one knows how they formed. Also, the geology of Mawrth has been changed by a nearby impact, and the fear was that scientists wouldn't be able to tease out its history. As an additional problem, this site lacks geological diversity, and driving there might be like driving across the surface of Meridiani Planum, the Opportunity rover's site. (Fortunately, Opportunity has had craters to explore, but there's not a whole of diversity in between.)

Holden Crater lacks a delta to indicate that it ever had a lake, and the MSL mission is all about exploring sites modified by water.

Eberswalde Crater has a delta and eventually became the runner up site. While the layers in the delta would make an enticing target for exploration, this site lacked the diversity of Gale Crater.

In the end, the diversity of Gale Crater plus its abundance of water-altered strata won the day. As a bonus, the smooth plain where the rover will land may be a delta. For a mission of exploration, an enigma with diversity presents an opportunity.

Merging 2018 Rover Missions – Part 2

2011-07-26T21:24:00.000-07:00

This post will conclude a three part series on planning for the Mars 2018 rover mission that began with a look at the political and budgetary context for the mission and then the engineering building blocks available for constructing the mission. With this final post (until we have new news), I'll look at the science goals for the mission. (When I began, I didn't realize this would be a series, so the first entry is unnumbered.)

As with so much of this mission, the goals began as two separate set of goals. ESA looked to extend the science that the Mars Science Laboratory (MSL) will begin next year -- in-depth analysis of samples on the surface of Mars. The ExoMars rover has a larger suite of instruments than MSL, and unlike MSL which will collect its samples near the surface, MSL would drill up to two meters below the surface. NASA's rover, by contrast, would focus on collecting and caching samples from within a few centimeters of the surface. If the samples were eventually returned (requiring two follow on missions), the full sophistication of instruments on Earth would be used to unveil the secrets of the Red Planet

Now that ESA and NASA have decided to pool their resources to fly a joint 2018 rover, a science working group has begun defining the goals for the combined mission. The group shared it's early thinking at a joint European and American Mars Exploratory Analysis Group (MEPAG) meeting last month.

A number of presentations discussed the goals and implementation of the merged rover, with the focus of the discussion on the sample collection goals. This may reflect the relative maturity of the previous rover concepts. While NASA's rover was in early definition, the ExoMars rover was ready to cut metal and proceed towards launch prior to the merger of the two programs. However, what unites these two missions (other than the need to pool financial resources) is their goal to, "Search for evidence of past and present life on Mars."

Proposed science and sampling goals. From On-Mars measurements and strategies, summary

Mars may or may not prove to have signs of life (at least at the spots we explore), but it is unique in at least one respect. It retains a record of conditions on a world with a significant atmosphere and liquid water from when it and the solar system was young. While the first and mandatory goal is to search for signs of life or habitability, five mission goals focus on understanding the early formation of Earth-like worlds and the processes acting on their surface, especially those involving water. (Two goals relate to evaluating Mars for potential human exploration.)

The science goals lead to a list of required samples to cache. Highest priority goes to samples that have been exposed to water in the earliest epochs of Mars to look for signs of life and to better understand the role liquid water played in that planet's history. The next goal is to sample igneous rocks to determine the process of early planet formation. Rounding out the requirements would be samples of regolith (the dust, sand, and gravel on the surface) and the atmosphere.

The atmosphere can be sampled from any location, and regolith will be present almost anywhere. Studies from orbiters have revealed many locations altered by water and many with volcanic rocks. An early assessment of potential landing sites is showing that finding ancient water-altered material and volcanic rocks at the same site may prove difficult within reasonable roving distances. ESA and NASA plan to follow the same open process used to select the Mars Science Laboratory's landing site, and the science community has five to six years to find one or more sites that possess the right surface materials.

Resources: You can read the complete set of presentations at the MEPAG website: http://mepag.jpl.nasa.gov/meeting/jun-11/index.html

Editorial Thoughts: I am a strong supporter of the 2018 merged rover mission. Even if samples are never returned to Earth, the mission will continue the work of sophisticated analysis of samples at Mars that will begin next year with the landing of the Mars Science Laboratory (MSL). Presumably, this rover will go to a second site, but if MSL finds strong signs of possible life, it may follow up MSL's discoveries at Gale Crater. The investment of $1-1.5B by each space agency just for this goal seems to me to be a worthwhile investment.

The merged rover also offers the opportunity for a far more robust sample caching mission. NASA's original plan had been to collect samples from near the surface, where multiple forces can destroy organic material. ESA's deep drill offers the opportunity to collect samples from depths where more pristine samples are likely. There will have to be some engineering work done to enable the transfer from ESA's drill to NASA's sample cache system, so this is not a done deal, but it is a great opportunity.

Beyond the immediate great science that can be done on the surface of Mars by the rover, there is the hope that with samples collected and waiting on Mars, that governments will pony up the further investments needed to return those samples to Earth.

This mission still may face significant budgetary challenges -- it is a Flagship-scale mission in an era where budgets are tight on both sides of the Atlantic. I have my fingers crossed.

Thank you

2011-07-17T09:33:00.000-07:00

Sometime over the past twenty-four hours, this blog received its 100,000th visit. This probably vastly understates the actual number of posts read since many people use news readers to keep up with blogs. (I know that I do.)

Still, it is a nice milestone. This is a specialized blog that appeals to people not only interested in planetary exploration, but also interested in the twists and turns that missions follow from concept to launch.

Thanks to all of your for taking your time to read what I write; I do appreciate it.

"A Pragmatic Path to Investigating Europa’s Habitability"

2011-07-14T23:13:00.000-07:00

Surface of Europa's Icy Shell (NASA)

There's a new plan in the works to enable missions to Europa that bears a resemblance to a proposal first put forward in a European study and to a proposal put forward in a Decadal Survey White Paper.

Europa has proven to be such a hostile world to explore that it has wrecked a flotilla of proposed missions before any were approved for development. My library contains papers and reports on a dedicated mission to explore this moon and its ocean that date back at least fifteen years. Any mission is challenging -- deliver a spacecraft with a battery of high data rate instruments deep into Jupiter's gravity well and survive harsh radiation for weeks or months. Estimates of mission costs have run from ~$1B (a challenge goal, not met) to a behemoth that would have dwarfed any mission ever launched to the planets. The most recent was the Jupiter Europa Orbiter (JEO) that would have flown a highly capable spacecraft to orbit that moon for the better part of a year. Unfortunately, the estimated $4.7B price tag was politically unfeasible.

In an abstract ("A Pragmatic Path to Investigating Europa’s Habitability") for the upcoming (October) EPSC-DPS Conference, we are getting our first look at what a revised Europa program may look at. While the abstract is brief -- likely reflecting the limited time that has been available for analysis -- it's clear that a radical restructuring of the mission is being proposed. This work in progress comes from a NASA-chartered Europa Science Definition Team (ESDT). At the conference, they will "will report on the status of this evolving concept, and will solicit community feedback."

The mission they are considering would split the goals for Europa studies between two spacecraft. One would orbit Europa with a "very small" geophysics payload to perform those measurements that can "best carried out from Europa orbit." A second spacecraft would orbit Jupiter and carry out imaging and other remote sensing during multiple flybys. The abstract authors note that this minimizes the capabilities required by the Europa orbiter, lowering costs related to radiation hardening. The multi-flyby spacecraft would need far less radiation hardening, and would have substantial time between flybys to relay the large volumes of data that would be collected by the imaging and spectral instruments. The two spacecraft would be "phased in time", suggesting that they would be launched separately, perhaps years apart.

Editorial Thoughts: This new mission concept resembles the two spacecraft concept proposed by a European study. In that proposal, a small spacecraft would orbit Europa and use a second Jupiter-orbiting spacecraft to relay the Europa data and conduct independent Jovian studies. This approach both minimized the size of the spacecraft that needed to be hardened to withstand the radiation at Europa, and reduced the power and communications capabilities required by that spacecraft. While discussions about Europa missions often focus on the radiation (literally lethal to electronics), providing the power and communications systems to relay gigabytes of data in near real time during the short orbital life is equally a cost driver. Putting the high data rate instruments on a flyby spacecraft reduces the power and communications requirements because the data from each flyby can be sent in the days to weeks between encounters.

A Decadal Survey White Paper authored by David E. Smith of the Goddard Spaceflight Center also proposed splitting the JEO goals among multiple smaller orbiters. His proposal did not include a multi-flyby spacecraft for remote sensing.

While the abstract doesn't discuss which instruments would be on which spacecraft, I'll hazard some guesses based on the requirements set forth by the JEO science team:

Europa Orbiter

Laser altimeter to measure tides in the icy-surface
Ice penetrating radar to measure ice depth and look for liquid pockets within the ice
Radio science to measure mass distributions within Europa
Magnetometer to study magnetic fields induced by the ocean

Multi-flyby Spacecraft

Multi-color cameras
Visible-Infrared imaging spectrometers to measure surface composition

The idea of a multi-flyby spacecraft suggests some interesting possibilities. If ESA selects the Ganymede orbiter as its next large science mission, it could be tasked with the remote sensing flybys. The proposed mission already calls for a number of flybys of Callisto before orbiting Ganymede. A mission architect who has looked at Jovian moon missions has told me that it would not be difficult to add the additional radiation hardening needed to enable a number of Europa flybys.

If ESA doesn't select its Ganymede mission proposal, then NASA may revive its own similar proposal. Or the multi-flyby spacecraft could be kept as a Jupiter orbiter and used first for an Europa campaign and then for Ganymede and Callisto flyby campaigns. (Io flybys would require additional radiation hardening that might drive costs too high, although flybys at the end of mission might be conceivable.)

It will be interesting to see which mission the ESDT recommends for flight first. The Europa orbiter would return unique measurements that don't duplicate the limited data previously returned by the Galileo mission. On the other hand, the multi-flyby spacecraft would enrich our understanding of Europa and allow better planning for an orbital mission. It's also possible that the orbital mission might carry a camera for higher resolution, stereo imaging a few high priority sites identified by the multi-flyby spacecraft.

NASA will not be in a position to decide on its own mission(s) for at least a year or two at best. In the meantime, ESA will decide on its Ganymede orbiter, and NASA can make its decision in light of ESA's plans. There is no reason why the Europa orbiter could not be an international mission with contributions from two or more space agencies. Budgets are tight everywhere, and pooling resources makes sense.

Resources:

A Pragmatic Path to Investigating Europa’s Habitability (EPSC-DPS abstract)

System concepts and enabling technologies for an ESA low-cost mission to Jupiter/Europa (ESA study published 2005)

A budget phasing approach to Europa Jupiter System Mission Science (Decadal Survey White Paper)

Updates

2011-07-06T22:10:00.000-07:00

The candidates landing sites for the Curiosity Mars Science Laboratory have been winnowed to two: Gale Crater and Eberswalde Crater. Space.com is one of many sites carrying this news. Editorial Thought: Alas, my favorite, Mawrth is out of the running, apparently because the geology of the site was too difficult to figure out. The two remaining sites, however, are both exciting locations, and I look forward to learning about one of them in depth.

Space.com also has an article on the challenges facing scientists as they propose missions for the Discovery program in an era of constrained budgets.

In the first step towards enacting the FY12 NASA budget into law, the House has proposed a a bit less than a 10% cut to NASA's science program, including cancelling the James Web Space Telescope. Science.com is one of many sites summarizing this news. Editorial Thought: This is one of many steps in the dance that eventually results in final ratification of NASA's budget for next year. While this second step (the President's budget proposal was the first step and was largely good news for the science program) has bad news, there is still the Senate's take on the budget to come. And looming over the dance are the overall discussions to cut the growth in the budget substantially. Ultimately, the news for the science program may be neutral to bad (I don't see a scenario where the budget increases over the President's proposal), but we are unlikely to know the ultimate resolution for some time.

The journal Nature has an article on the shortage of senior scientists with experience as mission Principal Investigators for the next round of Discovery mission proposals. Editorial Thought: Most interesting to me was the statement that each Discovery proposal led to "proposals 'from the same guys'." This echoes statements from an abstract at the recent Low Cost Planetary Mission conference, "...as is the case with many regularly offered competitions, proposers often find that they must propose multiple times, improving their mission concepts based on review results and additional study, before a mission concept achieves sufficient quality for selection. This presents NASA with more mature, higher quality mission concepts from which to choose. However, over time, it can also stagnate the pool of proposed mission concepts as the selection pool NASA faces becomes filled with only those proposals that are continually resubmitted and strengthened. Diversity can suffer, and instead of a selection process in which the best, most exciting concepts rise to the top, instead an assembly line of steadily maturing mission concepts waiting their turn for selection is produced." (Opening up the Box: ASRG Missions in the Discovery Program, Curt Niebur). (NASA has at least partially broken this cycle by allowing ASRG plutonium power sources for at least the current Discovery competition.)

Merging 2018 Rover Missions – Part 1

2011-07-05T22:05:00.000-07:00

All images are from this presentation at http://mepag.jpl.nasa.gov/meeting/jun-11/31-2018_Objectives_V3_16jun11b.pdf. Click on any image for a larger view

Last week, I summarized the challenges facing ESA and NASA’s managers as they build the political and budgetary framework for their joint program of Mars exploration. In the meantime, scientists and engineers from both sides of the Atlantic have been defining the goals and exploring the implementation of the 2018 rover. Two weeks ago, a number of them met in the first international Mars Exploration Analysis Group (MEPAG) meeting to discuss those plans among other topics. Only brief mention in the presentation material was made to the budget by noting that, “The 2018 [rover] mission is very cost constrained.”

While it appears that the definition of the science goals is well advanced, the engineering analysis is in the early stages. As a result, the presentations in the meeting and their summary here are status reports for an on-going process. Details can and probably will change.

Previous objectives of the separate 2018 rovers

Until a few months ago, the 2018 mission was to be two rovers, delivered by a single lander, that would separately explore the same area. ESA’s rover would drill beneath the surface, hoping to find pristine samples to analyze with a sophisticated laboratory. NASA’s rover would examine materials at the surface with a less sophisticated set of instruments on a robotic arm and collect and cache a small number of them for possible return to Earth by future missions. While there were opportunities for collaborative exploration, each rover had distinct goals.

Budget realities for both space agencies have forced the decision to fly a single rover that will combine the goals of both agencies. Today, I’ll look at the scientific building blocks – the instruments – available to the combined mission. In the next post, I’ll discuss how scientists plan to make use of what would be the most sophisticated set of capabilities ever landed on another world.

To understand the challenges faced by the engineering teams, it helps to begin with some background on the types of measurements that can be done by a Mars surface mission:

Remote sensing instruments image the surroundings and use spectrometers to remotely characterize composition of surface materials. While providing important measurements in their own right, these instruments also allow scientists to select targets for in-depth measurements with other instruments or for possible return to Earth. The MER rovers had cameras and a thermal emission spectrometer; the MSL lander will have cameras and the ChemCam instrument that uses a laser to vaporize materials for spectral measurements. ESA’s ExoMars rover would have had cameras, an infrared spectrometer, and a ground penetrating radar as remote sensing measurements. Many images and measurements can be made in a day.
Contact instruments place are placed against the surface material to be measured. The MER rovers carried two contact spectrometers and a microscopic imager, while MSL would carry a single contact spectrometer and a microscopic imager. These instruments enable fairly rapid measurements (1-3 days per target) and the measurements can be repeated at as many targets as time permits.
Analytical laboratory instruments require samples to be brought inside the rover or lander but provide more sensitive measurements than the contact instruments. The sample material can also be manipulated in ways – such as wetting to induce chemical reactions or heating to vaporize materials – that are impossible with contact instruments. The downside to these instruments is that sample acquisition and measurements take longer (10-20 days), and some of the instruments have a limited number of experiment chambers. As a result, these instruments allow in-depth analysis of a fairly small number of samples. The MER rovers had no instruments in this category, the Phoenix lander had several analytical instruments within two instrument suites, the MSL lander will have two suites of analytical instruments, and the ExoMars rover would have had five suites.

(For simplicity, I have not included all instruments from each mission in the summary above.)

New goals for the single joint rover

The fundamental challenge for merging the rover missions previously planned by each space agency will be to accommodate their different suites of instruments. Both rover missions would have had remote sensing instruments. However, NASA’s MAX-C rover would have relied entirely on contact instruments and a surface drill located on an arm for its analysis and collection of surface materials, a strategy driven by that mission’s need to rapidly assess a number of potential materials to select the very few that would be collected for sample return. ESA’s Exo-Mars rover, on the other hand, would have forgone surface contact instruments to focus on a highly capable analytical laboratory suite. This mission would also have acquired samples only through a drill that could return material from as deep as two meters below the surface. (The goal is retrieve more pristine samples that have not been altered by the harsh conditions at and near the surface.)

The new rover retains the ExoMars goal to analyze samples collected

from depths below agents that are likely to destroy organic materials

The current vision for the new single rover would have it retain all the capabilities of NASA and ESA's rovers in a single rover.

The simplest implementation of the joint 2018 rover would keep the MAX-C and ExoMars heritage instruments distinct. In this option, samples for possible return are analyzed and collected by the rover’s arm and a surface sampling drill. Samples collected by the ESA deep drill could be analyzed only by ESA’s analytical instruments (and two ‘contact’ instruments that examine material along the bore hole). A potentially interesting surface sample found by the arm instruments could not be passed to the analytical instruments for a second opinion. Similarly, a really interesting sample brought up by the deep drill could not be passed to the arm to add to the sample cache for eventual return to Earth.

The science teams setting the goals for the joint rover recognized these limitations. Their members have assigned a very high priority to allowing samples collected by the deep drill for inclusion in the return cache. The ability to pass samples from the arm’s near surface drill to the analytical laboratory for analysis also would be valuable, but would be a lower priority.

Unfortunately, adding these requirements to trade samples between the surface and deep drill elements of the rover requires redesigns. For example, ESA’s analytical laboratory instruments have been largely designed. Moving them and the deep drill to a location in the rover where they could interact with the arm and sample cache hardware would require a redesign (degree of difficulty not discussed in the presentations).

Update: Building a Coalition for Mars

2011-06-30T20:40:00.000-07:00

In my last post, I talked about the challenges facing both ESA and NASA in building the political and budgetary framework for their joint Mars program. This week, NASA's challenges are highlighted. The U.S. agency was scheduled to deliver a letter of commitment to the program on June 28. Uncertainties in the NASA budget outlook has meant that the U.S. cannot make that commitment now. NASA hopes to be able to make that commitment by September 15 when it's budget outlook is clearer.

In the meantime, ESA has decided not to move forward on contracts for the 2016 orbiter and demonstration lander pending NASA's commitment. ESA's managers are looking to work with their industrial partners to continue work on the most time critical elements of the 2016 mission to allow it to launch on time if the funding commitment comes through.

Additional Reading:

Space News: ESA Forced To Defer Full-scale Work on 2016 Mars Orbiter
BBC: Mars missions in summer slow lane
AWST: NASA Funding Mired In Budget Politics

Editorial Thought: I have great respect for the managers of NASA's Planetary Science program. This budget uncertainty must be making what are already challenging jobs that much harder. I wish them the best as they work through these issues.

Building a Coalition for a Mars Program

2011-06-24T21:09:00.000-07:00

Space News has now published its third article this week on the problems that Europe is having creating a coalition behind the revamped Mars program. To briefly recap, the European Space Agency (ESA) and NASA have agreed to combine budgets to enable joint 2016 orbiter and a 2018 rover missions. (There will also be an ESA-only demonstration lander carried by the 2016 orbiter.) The orbiter must fly before the rover to ensure that their is a satellite to relay the rover's data to Earth. Budget pressures for both partners are requiring a major re-planning of the 2018 rover mission.

Originally France and now Britain (which are contributing 15% and 20%, respectively, of the costs for the European contribution to the missions) are asking for delays in proceeding with the 2016 mission until plans for the 2018 rover mission are firmed up. The governments of these two nations reportedly are concerned that the overall program remains under funded and may seek to descope the 2016 mission to shore up funds for the 2018 mission. Officials have raised concerns that the 2016 mission may experience cost overruns that would have to be met by taking funds from the 2018 mission.

Editorial Thoughts: Planetary missions require years to scope, design, build, test, and then finally launch. The plans for the 2016 mission have come together recently enough that it reportedly has a tight schedule. Delays now to resolve the 2018 mission apparently could threaten the ability to launch in 2016.

From the Space News articles and other sources, it appears that building a coalition among the European nations and NASA faces three challenges:

Total available funds. The 2016 orbiter and 2018 rover mission would be highly capable missions that are being combined with a budget (if I add figures together correctly) that is probably similar to the budget for the Mars Science Laboratory that will launch this year. ESA's demonstration lander also requires funding from the ESA portion of this pot. By reusing key pieces of NASA's Mars program technology such as the entry, descent, and landing system, there will be some key savings that will help reduce costs.

Merging goals: ESA and NASA came into this partnership with their own set of goals that need to be merged into flyable missions. Here are the goals that originally came from each agency:

2016 mission
NASA - data relay, comprehensive measurements of trace gases in the atmosphere, continued high resolution surface imaging
ESA - data relay, demonstration lander

2018 mission
NASA - select, collect, and cache samples from the surface for future return to Earth
ESA - collect samples using a drill from below the surface and analyze them with a suite of highly capable instruments

Now that ESA and NASA have merged their Mars programs and agreed that the ultimate goal is a sample return, these goals have started to blur, and scientists on both sides of the Atlantic would like to see the full set of capabilities fly. If budgets and schedules don't permit this, then the partners will have to find ways to agree on what to cut.

Internal politics: Both ESA and NASA get approval to start mission development and subsequent funding through political processes. Both systems seem to have pluses and minuses. ESA requires consent from its member nations that sometimes have conflicting goals based on their own scientific, technical, and industrial priorities. Once an agreement is reached, future funding appears to be relatively stable. NASA has a single government to respond to, but its budgets can fluctuate significantly from year to year as political moods at the White House and Congress change. While ESA's political discussions are being highlighted now, NASA will effectively need to have its contribution to the program ratified through the inclusion of funding for it in next year's budget. (The administration will propose the budget, but Congress can and probably will modify it. Right now, budget politics within the U.S. are particularly volatile.)

Politics and planning can be messy, and we may see more articles like the Space News stories. The nations within the partnership appear committed to a capable joint Mars program, so I expect that only the details that will be in doubt. In posts next week, I'll provide more information on the current status of plans for these missions.

Resources:

Follow these links to read the full Space News articles (listed in reverse chronological order):
France, Britain Reluctant To Recommit To Revised but ‘Risky’ ExoMars Mission, Despite French Objections, ESA Seeks To Press Ahead on ExoMars French Concerns Throw ExoMars Plan Into Doubt

MSL: Cool Videos

2011-06-24T15:46:00.000-07:00

JPL has just released a new, high-definition animation of NASA's Mars Science Laboratory (MSL) mission that "combines real scenes of Mars with spacecraft events such as landing on Mars and drilling into rocks." Check it out at: http://www.nasa.gov/multimedia/videogallery/index.html?media_id=97780842

The journal Nature's news site has an article stating the science team's recommendation for MSL's landing site will be Gale Crater. The article says that the expectation is that NASA headquarters is likely to ratify the selection. If Gale is the selected landing site, a video produced by Doug Ellison shows what the terrain at Gale looks like. The green lines are possible rover traverses. The video is at http://www.youtube.com/watch?v=rvXHu-U02UE

Latest Evidence for Enceladus Ocean

2011-06-22T11:22:00.000-07:00

A new paper in the journal Nature reports new evidence for an ocean within Enceladus. You can read a press release on the paper from NASA.

Enceladus Mission Options

2011-06-20T21:29:00.000-07:00

Enceladus' plumes. Credit Cassini Imaging Team, SSI, JPL, ESA, NASA

Enceladus is back in the news following a science conference dedicated to the latest results hosted by the Enceladus Focus Group at the end of last month. The journals Nature and Science (subscription or library access required) summarized latest findings presented at the conference.

Two results of the conference stand out: First, the evidence is mounting that Enceladus contains a liquid ocean beneath at least a portion of its icy crust, and second, that that ocean is in contact with the moon's rocky core. The combination of liquid water and minerals from rocks could provide the ingredients that are believed to be needed to enable the formation of life.

While the evidence is mounting (Science quotes scientists as believing the likelihood of a liquid ocean is, " 'pretty likely,' 'most likely,' or 'almost inescapable,'), it is still circumstantial in part because the Cassini spacecraft's instruments are not ideally suited to studying the composition of the plumes. After all, no one expected in the 1990s when the mission was designed to find a moon ejecting plumes of its interior into space. A return mission is needed to confirm these interpretations of Cassini's data and to examine whether the building blocks for life may have formed.

Several Enceladus mission concepts were considered by the Decadal Survey, and one was a runner up recommended for flight if more money than then planned became available for developing planetary missions. We now find ourselves in the opposite situation where less money than expected was planned. The $1.9 billion Enceladus orbiter described in the Survey's report now seems unlikely.

At the Focus Group's meeting, Nathan Strange, a mission architect at JPL, presented a history of investigations into Enceladus missions and options for a new mission to this moon. Since the discovery of the plumes, a number of teams have looked into follow-on missions:

2006 GSFC NASA Academy EAGLE Study
2006 NASA “Billion Dollar Box” Study
2007 NASA Enceladus Flagship Study
2007 ESA Titan and Enceladus Mission (TandEM)
2007 JPL Enceladus RMA Study
2008 NASA/ESA Titan Saturn System Mission (TSSM)
2010 PSDS Decadal Survey Enceladus Studies
2010 JPL “JET” Discovery Proposal (PI: Christophe Sotin)

The 2006 Billion Dollar Box study (goal: find compelling Enceladus or Titan missions at or less than $1B, it didn’t find any) and the Decadal Survey looked at the greatest number of options. One set of missions identified would have a spacecraft orbit Saturn and perform multiple flybys of Enceladus:

Multi-flyby missions where the spacecraft's orbit crosses the orbits of Titan and Enceladus, resulting in 10-20 encounters with both moons. At Enceladus, the encounters occur at the relatively high speed of 4 kilometers per second. (The Cassini spacecraft uses orbits of this type for its Enceladus encounters as would the proposed JET mission.) These are the cheapest missions, estimated in the neighborhood of $1.5B by both the Billion Dollar Box and Decadal Survey studies.
Early flybys of Titan followed by a leveraging tour in which many (20-50 of each moon) low-speed flybys of Rhea, Dione, and Tethys for gravity assists enable 50 or more Enceladus flybys per year at speeds ~1 km/s. These missions incur greater mission operations costs from both the longer mission time and the larger staff needed to manage the many encounters.
Plume sample returns in which icy particles are captured during plume and E-ring (composed of material from the plumes) flybys in a manner similar to the Stardust comet sample returns. These missions require technology to capture and preserve volatile material and to prevent release of the returned samples into Earth’s biosphere even in the event of a crash landing of the return vehicle. The authors of Decadal Survey report found these issues to be significant impediments to flying this mission.

At the next level of complexity are Enceladus orbiters. These missions would use the leveraging tour to lower the spacecraft's Saturn orbit to allow orbital insertion at Enceladus. Orbital missions incur the cost of the longer, more complex tour with the cost of larger fuel tanks for the insertion burn. Because Enceladus is a tiny gravity well deep in Saturn's much deeper gravity well, polar orbits would be unstable. As a result, polar orbits would be unstable, making the study of the plumes, which are found at the south pole, difficult. The plumes would either have to be studied in the low speed flybys prior to insertion or from brief excursions from stable orbits around Enceladus. An orbiter would allow detailed studies of the surface and interior of Enceladus up to latitudes of ~65 degrees, providing the opportunity to study the extent of any interior oceans and study the surface history of this moon. The Decadal Survey studies concluded that a simple orbiter would cost ~$1.9 billion, or about half again (with launch costs included) the costs of a New Frontiers mission.

Beyond these simpler missions would be an entire range of missions that include landers (hard to plan for with our current knowledge of the surface properties) and even missions in which the spacecraft would orbit both Titan and Enceladus.

Nathan Strange concluded his presentation with a list of the mission options that, in his opinion, might be possible to squeeze under the cost caps of the Discovery and New Frontiers programs:

Within the lower mission cost Discovery program:

Plume sample return
Titan-Enceladus flyby mission
Icy-moon leveraging tour (many moon flybys resulting in low speed Enceladus flybys)

Within the medium mission cost New Frontiers program:

Enceladus orbiter or orbilander (a spacecraft that first orbits and then lands on Enceladus)
Icy-moon leveraging tour
Plume sample return
Enceladus impactors

Strange emphasizes that these are ideas to explore and that these are concepts that might be "feasible with innovation and creativity." However, "Currently, there is no obvious solution for a low-cost mission above the science floor [minimum requirements]. We must innovate to both lower the cost and increase the science value of concepts."

Editorial Thoughts: If you are a regular reader of this blog, you've probably noticed that I've spent quite a bit of time exploring options, post Decadal Survey and lower projected budgets, relating ideas for continuing exploration of the icy-ocean moons. I believe that exploration of these moons should be a priority in the next decade if the science community and mission architects can develop feasible concepts. I wish Strange and his colleagues the best of luck in finding missions that thread that intersection between costs, feasibility, and compelling science that will enable one or more of these missions to launch in the next decade.

Additional Resources:

Nathan Strange’s presentation to a Decadal Survey meeting

The end of Nathan’s presentation has references for additional reading

Two Decadal Survey Enceladus mission concept study reports can be found here

NASA Enceladus Flagship Study Report, NASA Goddard Space Flight Center, 2007

Titan Saturn System Mission Final Report on the NASA Contribution to a Joint Mission with ESA, Jet Propulsion Laboratory, 2009.

A Preview of What OSIRIS-REx May Return

2011-06-16T23:11:00.000-07:00

Origin and Evolution of Prebiotic Organic Matter As Inferred from the Tagish Lake Meteorite Christopher D. K. Herd, et al. Science 332, 1304 (2011); DOI: 10.1126/science.1203290

Chance has provided us with a preview of the types of scientific analysis the samples returned by the just approved OSIRIS-REx asteroid sample return mission may provide. In early 2000, a fragment from a primitive asteroid entered the Earth's atmosphere. It is rare for scientists to be able to examine fairly pristine samples of these asteroids. In this case, the fragments landed on the frozen Tagish Lake in the Yukon region of Canada. A local resident spotted the samples lying on the ice, carefully retrieved them, and kept them frozen until they could be delivered to scientists. (Scientists also later retrieved additional samples in the spring before the ice had thawed.) (See http://en.wikipedia.org/wiki/Tagish_Lake_(meteorite) for more on this meteorite.)

Last week, a paper in the journal Science published the latest findings from this meteorite (see the press release below). The opening of the paper explains why carbonaceous chondrite samples -- the type of material in the Tagish Lake meteorite -- are so important to scientists wanting to understand the early solar system: these samples come from primitive asteroids that preserve the materials of the early solar nebula and results of the processes that occurred within those early building blocks.

The conditions for finding carbonaceous condrite meteorites in pristine condition are rare. Instead of waiting for a random sample to come to us, the OSIRIS-REx asteroid sample return mission will go to the asteroid to carefully select its samples to return to Earth.

Dante Lauretta, Deputy PI for the mission, has been kind enough to send me material on the mission over the past two years that have formed the basis for posts on this mission in this blog. I asked him if the the Tagish Lake samples are representative of the type of material they hope to return and whether baking by the sun might degrade the sample. He wrote back, "Tagish Lake is a good analog for the type of material that we are interested in. Our spectral analysis of 1999 RQ36 suggests it is most similar to the CM1 chondrites.

"We are interested in the interaction of the organic material with solar radiation. Organic does not always mean volatile and it is likely that even a heavily space weathered surface would have interesting organic chemistry. One of our objectives is to understand the effect of this 'space weathering' on carbonaceous material. However, we have evidence that the surfaces of near-Earth objects may be refreshed during exceptionally close planetary encounters. Tidal forces are strong enough to turn small bodies inside out, especially if they are rubble piles. This is good news for us since 1999 RQ36 is likely to have had multiple close encounters with the Earth in its recent history. If these theories are correct, NEOs with Earth close approaches may be ideal material to sample relatively fresh, low-space-weathering material right on the surface. These are some of the hypotheses that our mission will be testing."

The following press release from NASA's Goddard Space Flight Center gives more background on the Tagish Lake meteorite has reveal and possibly previews the kinds of discoveries to be enabled by the OSIRIS-REx samples.

Asteroid Served Up "Custom Orders" of Life's Ingredients

06.09.11

Some asteroids may have been like "molecular factories" cranking out life's ingredients and shipping them to Earth via meteorite impacts, according to scientists who've made discoveries of molecules essential for life in material from certain kinds of asteroids and comets. Now it appears that at least one may have been less like a rigid assembly line and more like a flexible diner that doesn't mind making changes to the menu.

In January, 2000, a large meteoroid exploded in the atmosphere over northern British Columbia, Canada, and rained fragments across the frozen surface of Tagish Lake. Because many people witnessed the fireball, pieces were collected within days and kept preserved in their frozen state. This ensured that there was very little contamination from terrestrial life.

This is one of the Tagish Lake meteorite fragments. Credit: Michael Holly, Creative Services, University of Alberta.
Full-resolution copy "The Tagish Lake meteorite fell on a frozen lake in the middle of winter and was collected in a way to make it the best preserved meteorite in the world," said Dr. Christopher Herd of the University of Alberta, Edmonton, Canada, lead author of a paper about the analysis of the meteorite fragments published June 10 in the journal Science.

"The first Tagish Lake samples -- the ones we used in our study that were collected within days of the fall -- are the closest we have to an asteroid sample return mission in terms of cleanliness," adds Dr. Michael Callahan of NASA's Goddard Space Flight Center in Greenbelt, Md., a co-author on the paper.

The Tagish Lake meteorites are rich in carbon and, like other meteorites of this type, the team discovered the fragments contained an assortment of organic matter including amino acids, which are the building blocks of proteins. Proteins are used by life to build structures like hair and nails, and to speed up or regulate chemical reactions. What's new is that the team found different pieces had greatly differing amounts of amino acids.

"We see that some pieces have 10 to 100 times the amount of specific amino acids than other pieces," said Dr. Daniel Glavin of NASA Goddard, also a co-author on the Science paper. "We've never seen this kind of variability from a single parent asteroid before. Only one other meteorite fall, called Almahata Sitta, matches Tagish Lake in terms of diversity, but it came from an asteroid that appears to be a mash-up of many different asteroids."

By identifying the different minerals present in each fragment, the team was able to see how much each had been altered by water. They found that various fragments had been exposed to different amounts of water, and suggest that water alteration may account for the diversity in amino acid production.

"Our research provides new insights into the role that water plays in the modification of pre-biotic molecules on asteroids," said Herd. "Our results provide perhaps the first clear evidence that water percolating through the asteroid parent body caused some molecules to be formed and others destroyed. The Tagish Lake meteorite provides a unique window into what was happening to organic molecules on asteroids four-and-a-half billion years ago, and the pre-biotic chemistry involved."

If the variability in Tagish Lake turns out to be common, it shows researchers have to be careful in deciding whether meteorites delivered enough bio-molecules to help jump-start life, according to the team.

"Biochemical reactions are concentration dependent," says Callahan. "If you're below the limit, you're toast, but if you're above it, you're OK. One meteorite might have levels below the limit, but the diversity in Tagish Lake shows that collecting just one fragment might not be enough to get the whole story."

Although the meteorites were the most pristine ever recovered, there is still some chance of contamination though contact with the air and surface. However, in one fragment, the amino acid abundances were high enough to show they were made in space by analyzing their isotopes.

Isotopes are versions of an element with different masses; for example, carbon 13 is a heavier, and less common, variety of carbon. Since the chemistry of life prefers lighter isotopes, amino acids enriched in the heavier carbon 13 were likely created in space.

"We found that the amino acids in a fragment of Tagish Lake were enriched in carbon 13, indicating they were probably created by non-biological processes in the parent asteroid," said Dr. Jamie Elsila of NASA Goddard, a co-author on the paper who performed the isotopic analysis.

The team consulted researchers at the Goddard Astrobiology Analytical Lab for their expertise with the difficult analysis. "We specialize in extraterrestrial amino acid and organic matter analysis," said Dr. Jason Dworkin, a co-author on the paper who leads the Goddard laboratory. "We have top-flight, extremely sensitive equipment and the meticulous techniques necessary to make such precise measurements. We plan to refine our techniques with additional challenging assignments so we can apply them to the OSIRIS-REx asteroid sample return mission."

OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security -- Regolith Explorer) is a Goddard-managed mission, led by the University of Arizona, that will be launched toward asteroid "1999 RQ36" in 2016 and return a sample to Earth in 2023. The OSIRIS-REx team is led by Dr. Michael Drake, Director of the University of Arizona's Lunar and Planetary Laboratory.

The Tagish Lake research was funded by the Natural Sciences and Engineering Research Council of Canada, the Alberta Ingenuity Fund, and NASA.

Goals of ESA's Mars Demonstration Lander

2011-06-14T19:22:00.000-07:00

In the previous post, I reported on the instruments planned for ESA's 2016 demonstration Mars lander. Questions have been asked as to why this lander will be purely battery powered with a life on the surface of a day or two. I wrote to Giacinto Gianfiglio, ExoMars System Engineering Manager, and asked him why solar panels allowing longer life had not been included. He replied,

"In a larger Lander configuration indeed there were deployable solar array panels foreseen, but this solution would have implied:

- soft landing with air bags (that we have now discarded for volume-mass-cost reasons)
- deployable panels of the landed structures (that we have now discarded for volume-mass-cost reasons)

We have also changed the mission objectives from a relatively long life lander (one to two months) to a "demo" lander of only about two days of surface life time ... this enables to survive with just batteries .... and gain all this is to save volume-mass-cost."

This lander is part of a larger effort by ESA to develop technologies to explore Mars that also includes development of the capabilities needed to design and operate a rover on Mars. ESA's website states:

"The task of MREP [Mars Robotic Exploration Preparation Programme] is to define and prepare for the next steps that Europe will take after these [the 2016 mission]... ESA has a distinguished history of space science missions, but the demands of Mars Sample Return (MSR) mission mean moving the Agency far out of its technological comfort zone. ESA does not currently have expertise in precision soft-landing probes and operating them on planetary surfaces, identifying and retrieving samples and then – as is a requirement for MSR – having them take off again to dock remotely in Mars orbit. Then there is the difficulty of preserving the samples in pristine condition and getting them safely through re-entry back to the surface of the Earth... MREP sets up a framework for more systematic and structured international cooperation with the United States and other exploration partners in the decades to come, enabling an increased number of missions than either partner could achieve alone. The target is to have Europe present on each mission slot to Mars - which is every two years - as mission leader or important contributor."

Editorial Thoughts: Why create program focused technology development? The U.S. Decadal Survey report had this to say about the importance of technology development in enabling planetary missions: "Continued success of the NASA planetary exploration program depends upon two major elements. It is axiomatic that the sequence of flight projects must be carefully selected so that the highest priority questions in solar system science are addressed. But it is equally important that there be an ongoing, robust, stable technology development program that is aimed at the missions of the future, especially those missions that have great potential for discovery and are not within existing technology capabilities. Early investment in key technologies reduces the cost risk of complex projects, allowing them to be initiated with reduced uncertainty regarding their eventual total costs."

The Decadal Survey report included two examples of how focused technology development programs enabled subsequent planetary missions. The Solar electric propulsion (SEP) had been proposed for many solar system exploration missions, but none of those proposals had been implemented. In 1998, NASA launched the Deep Space One mission to demonstrate the use of SEP and a number of other technologies. While the spacecraft carried out limited science goals during encounters with the asteroid Braille and the comet comet Borrelly, the focus was on technology development and gaining experience operating a SEP spacecraft. The demonstration of this technology led to NASA accepting the use of SEP in the Discovery Dawn mission to the large asteroids Vesta and Ceres. (And allowing us to enjoy the in depth mission updates of JPL's Marc Rayman, who has participated in both missions.) The second example was the development and operation (on Earth) of a series of rovers and the Mars Pathfinder landing system that enabled the Mars Spirit and Opportunity missions at Mars.

Today's ExoMars program is part of a joint ESA-NASA Mars exploration program that allows the two agencies to share costs. As a result, the ExoMars program has had to be significantly modified and delayed to match NASA's technical and budget requirements. Through the replans, ESA has continued its focus of using the ExoMars program to develop its technical capabilities so that it can be an equal player in the joint Mars program with NASA. The decision to fly a demonstration lander with a focus on technology development with minimum science goals appears to come from that continued focus.

There has been a lively debate at the Unmanned Spaceflight forum as to whether this demonstration lander is a good investment for ESA. I generally don't care to comment on political issues (and where to allocate investments is a political decision; my opinion is no more valid than those of my readers). I will point out that right now the future of landed missions on Mars is subject to the whims of the U.S. political system as only NASA possesses developed Mars entry and landing technology. Having a second space agency invest in these capabilities does not seem unreasonable. What kinds of missions might make use of this technology? If the joint NASA-ESA sample return program doesn't move forward (and likely won't past 2018 without a higher projected planetary budget for NASA), ESA could use this technology for post 2018 rovers, polar landers, or geophysical stations. Once the technology is developed, it will be much easier to approve missions that use it, just as it was to approve the Dawn and Mars Exploration Rover missions once their underlying technologies were proven entities.

Instruments for ESA's Mars Landing Demonstrator

2011-06-11T00:08:00.000-07:00

The European Space Agency posted the press release below on its website. The science goals are quite limited -- this is a technical demonstration project and the lander will function for just two to four days on the surface. The landing site is Meridiani Planum, for which we already have many images from the Opportunity Mars rover. You can read about the goals and technology of the demonstrator at http://exploration.esa.int/science-e/www/object/index.cfm?fobjectid=47852

Entry, descent and surface science for 2016 Mars mission

10 June 2011
ESA and NASA have announced the scientific investigations selected for their 2016 ExoMars lander demonstrator. They will probe the atmosphere during the descent, and return the first ever data on electrical fields at the surface of Mars.

The demonstration lander on the surface. Click on image to see full illustration of the landing process. Credit: ESA

The EDM Entry, descent, and landing Demonstrator Module is part of the joint ESA/NASA ExoMars Trace Gas Orbiter mission to be launched in 2016 for arrival at Mars nine months later.
Although its main goal is to demonstrate European entry, descent and landing technologies for future visits to Mars, it will also offer some limited, but useful, scientific opportunities.
“The EDM will be landing during the dust storm season,” says Jorge Vago, ExoMars Project Scientist. “This will provide a unique chance to characterise a dust-loaded atmosphere during entry and descent, and to conduct interesting surface measurements associated with a dust-rich environment.”

“Although its main goal is to demonstrate European entry, descent and landing technologies for future visits to Mars, it will also offer some limited, but useful, scientific opportunities.”

For the descent phase, two proposed investigations called Entry, Descent and Landing (EDL) Science and IDEAS (Investigations During Entry and Atmospheric Science) were selected and combined into one Entry and Descent Science programme.
The joint team will use the module’s entry, descent and landing engineering data to reconstruct its trajectory and determine the atmospheric conditions.
Once on the surface, the DREAMS (Dust characterisation, Risk assessment, and Environment Analyser on the Martian Surface) scientific payload will function as an environmental station for the two to four days of the surface mission.


The ExoMars Trace Gas Orbiter

To achieve this, teams of scientists and engineers from nine countries around the world will develop a dedicated suite of sensors to measure the wind speed and direction (MetWind), humidity (MetHumi), pressure (MetBaro) and surface temperature (MarsTem), and to determine the transparency of the atmosphere (ODS).
DREAMS will also make the first measurements of electrical fields at the planet’s surface with its MicroARES detector. Electrical fields are likely to be generated when grains rub against each other in the dust-rich atmosphere, so landing during the dust storm season increases the chance of being able to study this charging and its consequences.
In addition to the surface payload, a colour camera system on the EDM will deliver valuable additional scientific data, as well as spectacular images. No design has yet been chosen for the camera, but a decision is expected before the end of this year.
“The selection of these science investigations complements the technological goals of the EDM,” says Dr Vago. “This has been an important step that will allow our team to move on to the development of this important mission element.”
http://exploration.esa.int/science-e-media/img/e7/EDM_Landing_p3.jpg

This is rocket science

2011-06-08T18:06:00.000-07:00

Because NASA's planetary missions on the whole have been so incredibly successful, many of us outside the process can forget how incredibly complicated it can be. A just released audit (see post on the journal Nature's blog, Space News, and Space Ref) gives examples of the issues still to be addressed on the Mars Science Laboratory as it prepares to launch. From what I've read, this seems normal at this stage (read Steven Squyres' book on the Mars Exploration Rovers for more examples of pre-launch issues).

I once had lunch with a planetary scientist who began his career in the 1950s. He told me that in the late 1950s, he came to believe we would never send probes to other planets because statisticians had shown that you could never achieve the reliability necessary for the missions to succeed. Of course, the various space agencies proved him wrong (often with dramatic failures that served as learning opportunities). When I think of the great advances brought by the space age, I am less impressed by the technical wonders and more impressed by the management systems that can deal with these levels of complexity, especially for missions such as MSL that expand the technical capabilities on so many fronts. This audit is part of the management system, in this case providing an outside review of issues.

Enabling the 2018 ESA-NASA Mars Rover

2011-06-07T21:24:00.000-07:00

Aviation Week and Space Technology has an article on the on-going challenges of combining the ESA and NASA rovers into a single rover for the 2018 mission. It doesn't sound as if there are fundamental problems, but rather the proverbial problem of trying to fit a lot of capability into a fixed (and smaller budget).

We may get more detail at the international Mars Exploration Analysis Group (MEPAG) meeting next week.

OSIRIS-REx: More than a Sample Return Mission

2011-06-06T02:18:00.000-07:00

The Martian moon Phobos, which may be a captured asteroid. This image shows the complexity of the surfaces of small, primitive bodies. Phobos, with a mean diameter of 11.1 km is many times larger than the OSIRIS-REx target, asteroid 1999 RQ36. Credit: HiRISE, MRO, LPL (U. Arizona), NASA

"The Near-Earth Asteroid Rendevous (NEAR) mission to 433 Eros demonstrated that even small asteroids are covered with complex and substantial regoliths, which are heterogeneous in texture and detailed in composition. To understand the geologic evolution of asteroids, regoliths must be studied in detail, and their variability must be characterized both vertically and horizontally... To maximize the science return from such a mission, it is essential to select the most interesting locales on the asteroid, a goal that implies a global reconnaissance of the target body."

-- New Frontiers in the Solar System An Integrated Exploration Strategy [2003 Planetary Decadal Survey]

[An asteroid sample return mission] "should have the following science objectives...":

"Map the surface texture, spectral properties (e.g., color, albedo), and geochemistry of the surface of an asteroid at sufficient spatial resolution to resolve geologic features (e.g., craters, fractures, lithologic units) necessary to decipher the geologic history of the asteroid and provide context for returned samples.
"Document the regolith at the sampling site in situ with emphasis on, e.g., lateral and vertical textural, mineralogical, and geochemical heterogeneity at scales down to the submillimeter.
"Return a sample to Earth in an amount sufficient for molecular (or organic) and mineralogical analyses, including documentation of possible sources of contamination throughout the collection, return, and curation phases of the mission."

-- Opening New Frontiers in Space: Choices for the Next New Frontiers Announcement of Opportunity [2008]

The selection of the OSIRIS-REx New Frontiers mission to return a sample from a near-Earth asteroid has been widely reported. As the quotes that open this post state, simply returning a sample of an asteroid is only part of a robust sample return mission. It is also important to try to understand the history of the asteroid. While OSIRIS-REx's target asteroid, 1999 RQ36, is believed to represent a primitive composition that will likely tell us much about conditions in the early, pre-planet solar system, the body has experienced over four billions years' worth of events. This tiny body, 575 m in diameter, is likely a fragment of a larger asteroid. Since its separation from its original parent body, this asteroid will have been pounded by numerous collisions and may well be a pile of rubble with materials from various depths of its parent body jumbled together and exposed on the surface. That material on the surface from which the sample will be taken has been exposed for an unknown period of time to the baking and irradiation of the sun, which may have modified its composition.

All of these factors require that a robust sample return mission also be able to fully characterize the surface and interior of its target asteroid. Earlier versions of this mission, then called only OSIRIS, focused only on the sample return. The recently approved version of the mission includes a suite of instruments to remotely study this body:

Camera Suite (OCAMS) Provides long-range acquisition of 1999 RQ36, along with global mapping, sample-site characterization, sample acquisition documentation, and sub-mm imaging
Visible and IR Spectrometer (OVIRS) Provides mineral and organic spectral maps and local spectral information of candidate sample sites from 0.4 - 4.3 μm•
Thermal Emission Spectrometer (OTES) Provides mineral and thermal emission spectral maps and local spectral information of candidate sample sites from 4 - 50 μm
X-ray Imaging Spectrometer (REXIS) instrument as a student collaboration experiment. This instrument will be built by MIT and Harvard students and is designed to map the abundances of major elements on the surface of the asteroid
Laser Altimeter (OLA) Provides ranging data; global topographic mapping; and local topographic maps of candidate sample sites
Spacecraft Telecom Radio science provides RQ36 mass and gravity field maps

OSIRIS-REx Spacecraft and Instruments

The suite of instruments are synergistic. The cameras, for example, will document the physical structure of the surface, providing clues to past events. The OVIRS and OTES instruments will measure different portions of the visible and infrared spectra to understand the composition of the surface minerals. The REXIS instrument, by contrast, will look at the elemental composition of the surface. (A simple analogy of the difference between elemental and mineralogical composition: Bread and cake have similar 'elemental' compositions based on flour, water, and sugar, but the combination of those elements result in distinct 'mineralogies'.) The laser altimeter and radio science together will map the shape of the surface and distribution of mass inside RQ36, which together will provide clues to the interior structure.

The instruments on OSIRIS-REx will have dual purposes. While they will help us understand the composition and history of this body, they will also help mission planners to plan the sample acquisition. The cameras and laser altimeter will reveal the physical geography of potential sample sites, while the spectrometers will reveal the composition. (My guess: Mission controllers will select a site that has the best mixture of materials on the surface to sample the greatest heterogeneity.)

The OSIRIS-REx spacecraft will spend more than a year studying 1999 RQ36. By the end of this period, it will probably be, square-meter-for-square-meter, the most intensively studied body in the solar system.

OSIRIS-REx is not the only mission that aims to return a sample of a likely primitive small body. Russia's Phobos-Grunt mission will leave this year on a round trip to the Martian moon Phobos, which may be a captured asteroid. (RQ36 is a B-type asteroid, while Phobos is a likely C-type body, which are both believed to represent relatively unaltered samples of the non-volatile early solar system.) Russia's mission will carry a number instruments to characterize its target moon. In fact, it's instrument suite is more wide ranging than OSIRIS-REx's, with both remote sensing and surface instruments.

OSIRIS-REx and Phobos-Grunt will be joined this decade by the Hayabusa 2 mission, which will also sample a primitive, C-type asteroid. It appears that Hayabusa 2 will, like Hayabusa 1, carry a number of remote sensing instruments to characterize its target and plan for the sample acquisition. The European Space Agency is also considering a primitive asteroid sample return mission, Marco Polo-R, for the 2020s that will likely carry several remote sensing instruments.

The OSIRIS-REx mission will also carry a sampling mechanism.

Background:

The OSIRIS-REx team has posted a fact sheet on the mission: http://uanews.org/files/osiris-rex/OSIRIS-REx_Factsheet.pdf All images in this post, except the image of Phobos, are from the fact sheet and are reused with permission.

RQ36 background: http://en.wikipedia.org/wiki/(101955)_1999_RQ36

Several articles in Wikipedia provide background on the types of asteroids:

Overview: http://en.wikipedia.org/wiki/Asteroid_spectral_types

C-type asteroids: http://en.wikipedia.org/wiki/C-type_asteroid

B-type asteroids (which are considered a sub-type of C-type asteroids): http://en.wikipedia.org/wiki/B-type_asteroid

A New Frontiers Icy-ocean Moon Mission?

2011-06-02T21:34:00.000-07:00

In a previous career, I managed strategic planning teams in a large high tech firm. In the larger planning exercises, it wasn't unusual for events to change the playing field enough that by the time we completed our analyses, some of the key underlying assumptions had changed.

With that background, I watched the Decadal Survey process as both an interested citizen and as a former practicioner of strategic planning. I came away impressed with both the process and the results. A measure of the thoroughness of the process is we have a plan that holds up well despite a large cut in projected funding that occured during the process.

Still, the process did have some underlying assumptions that changed with projected funding cuts. One assumption was that a scaled back Europa orbiter mission (JEO) teamed with ESA's proposed Jupiter Ganymede Orbiter (JGO) might be funded in the next decade. The former now looks unlikely and the latter is in competition against two other good proposed missions. Because of those assumptions, the survey assumed that the planetary community's highest priority icy-ocean moon mission might fly. As a result, the Survey members did not pursue studies of a minimum cost Europa missions or of low cost Titan multi-flyby or orbiter. The Survey included a study for a Ganymede orbiter and concluded that, "the key required Ganymede flight system elements are being developed and demonstrated for Jupiter applications on the Juno mission," and "a Ganymede orbiter mission appears to be technically feasible with no required technology development," but, "the mission was not given further consideration because of the likelihood that the ESA Jupiter Ganymede Orbiter would achieve most of the same science goals." (All quotes in the post are from the Survey report.)

The committee did forsee that JEO and JGO might not fly in the coming decade, and recommended a Flagship-class Uranus orbiter and Enceladus orbiter missions as backups to provide compelling new science on icy moons (although the Uranus orbiter's study of the moons might have been limited). The report noted that, "In particular, because of the broad similarity of its science goals to those of JEO, NASA should consider flying the Enceladus Orbiter in the decade 2013-2022 only if JEO is not carried out in that decade." In the current budget situation, it seems likely that neither of these missions as proposed are likely to be funded, either.

So, at the moment, the study of icy-ocean moons depends on JGO winning its selection competition and/or the Discovery Titan Mare Explorer (TiME) winning its selection competition. That raises the question of whether NASA should at some point reconsider New Frontiers class missions to the icy moons of Jupiter and Saturn.

NASA may have a partial answer, but not be able to share it with the public. At least two multi-flyby outer planet moon missions were proposed for the current Discovery selection: the Journey to Enceladus and Titan (JET) and an Io mission. Part of the review process would have been a technical and fiscal feasibility assessment. If these missions were judged feasible, then the Discovery program would be one mechanism to continue the exploration of the outer moons. (NASA, quite correctly, keeps the reviews confidential and shares them only with the proposers.) The fact that neither of these missions made it to the final candidate list should not a priori lead to the conclusion that they were weak proposals. TiME is an strong proposal that, as I understand it, must be selected in this competition to launch by mid decade to reach the northern lakes of Titan before the changing seasons hide them from direct communication with Earth.

NASA and its planetary science community may conclude that a New Frontiers class mission may still be desired, either because Discovery mission are not feasible to continue the exploration of the outer planet moons or to enable more complex missions. Among the missions that might be considered could be:

A Ganymede orbiter with multiple flybys of Callisto and perhaps Europa if ESA does not select JGO
A very scaled back Europa orbiter (although these feels like a stretch to me within a New Frontiers budget)
An Enceladus and Titan multiflyby mission. (Several versions of this type of mission were considered by the Survey, and one had possible costs that were not too far outside the budget for future New Frontiers missions.)

As a former practitioner of strategic planning, I am not one to call for changes to a just published plan -- that defeats the entire purpose of a rigorous process. Can there be a middle ground that doesn't immediately reopen the recommendations of the Decadal Survey yet can allow flexibility?

Following the previous Survey, an interim committee met several years later and recommended adding to the list of proposed missions to be considered for New Frontiers mission. A similar process in the middle of this decade has been speculated about in some of the meetings I've listened to.

So what might the criteria be for considering adding a Jupiter or Saturn icy moon mission to the list? Perhaps the process might be something like this. First, wait and see how the JGO and TiME missions fare, how icy-moon missions fare in future Discovery mission selections, and how budgets actually develop. Then, if a New Frontiers mission to these moons still is compelling, commission studies to develop the concepts and confirm their costs using the same rigorous process followed for the Decadal Survey. If the missions appear technically and fiscally feasible, then use a panel of senior scientists to revisit the list of New Frontier candidates for the second selection near the end of this decade. (The current competition with OSIRIS-REx as the selected mission, was NF 3; NF 4 would be selected mid-decade followed by NF 5 late this decade or early in the next.) If an outer planets mission were to be added, then either the Io multiflyby or Saturn probe mission might be dropped to keep the candidate list balanced among the types of solar system missions. (In this spirit, the near Earth asteroid sample return mission was to be dropped for the NF 4 and NF5 competitions regardless of the NF 3 selection because the Trojan asteroid tour and rendezvous mission was added to the list to reflect the priorities in the primitive bodies community.)

In a nutshell, allow events to play out and if a revisit of the list of candidate missions appears appropriate, follow a rigorous process that the entire community would see as fair and considered.

ESA Approves Funds for Joint Mars Missions with NASA

2011-05-28T03:59:00.000-07:00

2016 Trace Gas Orbiter releasing the demonstration lander

Space New reports that ESA has cleared funding to continue work on the 2016 joint Mars mission with NASA. In that mission, ESA will provide the orbiter and a demonstration lander, while NASA will provide the launch and fund the instruments. ESA's budgetary rules had required it to issue a stop work order and seek approval for a new program following changes in NASA's ability to fund the joint 2016 and 2018 missions, which were a single program within ESA.

It appears that this approval also covers the joint 2018 rover mission, although the article is not totally clear on that point. The rover mission is still in the early re-definition phase following the Decadal Survey recommendation that NASA's contribution to the mission be capped. That meant that the previous plan where each agency would supply its own orbiter was no longer feasible.

See this post for a description of the Trace Gas Orbiter instruments.

Mars Science Laboratory Apparently OK

2011-05-27T07:33:00.000-07:00

In a follow up to a report that the backshell for the Mars Science Laboratory may have been damaged, Aviation Week and Space Technology reports that apparently there is no damage and provides more detail on the mishap.

Asteroid Sample Return Mission Selected

2011-05-25T23:14:00.000-07:00

NASA announced the selection of the OSIRIS-REx near-Earth asteroid sample return for the next New Frontiers mission, beating out a Venus lander and a lunar sample return mission. Bruce Moomaw wrote about the OSIRIS-REx mission for this blog, and his description can be found here. There are also articles at Space News and at the Planetary Society's blog site. NASA press release site also includes a video (which I can't watch with my current slow internet while I'm traveling): http://www.nasa.gov/topics/solarsystem/features/osiris-rex.html

With the two Japanese Hayabusa sample return missions (one completed and another in development), this means we'll have samples from three near-Earth asteroids. ESA is also considering its own near-Earth asteroid sample return, Marco Polo.

The press release itself is copied below. And congratulations to the winning team which submitted versions of this mission at least twice and I think perhaps three times.

May 25, 2011

Dwayne C. Brown
Headquarters, Washington
202-358-1726
dwayne.c.brown@nasa.gov

RELEASE: 11-163

NASA TO LAUNCH NEW SCIENCE MISSION TO ASTEROID IN 2016

WASHINGTON -- NASA will launch a spacecraft to an asteroid in 2016 and
use a robotic arm to pluck samples that could better explain our
solar system's formation and how life began. The mission, called
Origins-Spectral Interpretation-Resource
Identification-Security-Regolith Explorer, or OSIRIS-REx, will be the
first U.S. mission to carry samples from an asteroid back to Earth.

"This is a critical step in meeting the objectives outlined by
President Obama to extend our reach beyond low-Earth orbit and
explore into deep space," said NASA Administrator Charlie Bolden.
"It's robotic missions like these that will pave the way for future
human space missions to an asteroid and other deep space
destinations."

NASA selected OSIRIS-REx after reviewing three concept study reports
for new scientific missions, which also included a sample return
mission from the far side of the moon and a mission to the surface of
Venus.

Asteroids are leftovers formed from the cloud of gas and dust -- the
solar nebula -- that collapsed to form our sun and the planets about
4.5 billion years ago. As such, they contain the original material
from the solar nebula, which can tell us about the conditions of our
solar system's birth.

After traveling four years, OSIRIS-REx will approach the primitive,
near Earth asteroid designated 1999 RQ36 in 2020. Once within three
miles of the asteroid, the spacecraft will begin six months of
comprehensive surface mapping. The science team then will pick a
location from where the spacecraft's arm will take a sample. The
spacecraft gradually will move closer to the site, and the arm will
extend to collect more than two ounces of material for return to
Earth in 2023. The mission, excluding the launch vehicle, is expected
to cost approximately $800 million.

The sample will be stored in a capsule that will land at Utah's Test
and Training Range in 2023. The capsule's design will be similar to
that used by NASA's Stardust spacecraft, which returned the world's
first comet particles from comet Wild 2 in 2006. The OSIRIS-REx
sample capsule will be taken to NASA's Johnson Space Center in
Houston. The material will be removed and delivered to a dedicated
research facility following stringent planetary protection protocol.
Precise analysis will be performed that cannot be duplicated by
spacecraft-based instruments.

RQ36 is approximately 1,900 feet in diameter or roughly the size of
five football fields. The asteroid, little altered over time, is
likely to represent a snapshot of our solar system's infancy. The
asteroid also is likely rich in carbon, a key element in the organic
molecules necessary for life. Organic molecules have been found in
meteorite and comet samples, indicating some of life's ingredients
can be created in space. Scientists want to see if they also are
present on RQ36.

"This asteroid is a time capsule from the birth of our solar system
and ushers in a new era of planetary exploration," said Jim Green,
director, NASA's Planetary Science Division in Washington. "The
knowledge from the mission also will help us to develop methods to
better track the orbits of asteroids."

The mission will accurately measure the "Yarkovsky effect" for the
first time. The effect is a small push caused by the sun on an
asteroid, as it absorbs sunlight and re-emits that energy as heat.
The small push adds up over time, but it is uneven due to an
asteroid's shape, wobble, surface composition and rotation. For
scientists to predict an Earth-approaching asteroid's path, they must
understand how the effect will change its orbit. OSIRIS-REx will help
refine RQ36's orbit to ascertain its trajectory and devise future
strategies to mitigate possible Earth impacts from celestial objects.

Michael Drake of the University of Arizona in Tucson is the mission's
principal investigator. NASA's Goddard Space Flight Center in
Greenbelt, Md., will provide overall mission management, systems
engineering, and safety and mission assurance. Lockheed Martin Space
Systems in Denver will build the spacecraft. The OSIRIS-REx payload
includes instruments from the University of Arizona, Goddard, Arizona
State University in Tempe and the Canadian Space Agency. NASA's Ames
Research Center at Moffett Field, Calif., the Langley Research Center
in Hampton Va., and the Jet Propulsion Laboratory in Pasadena,
Calif., also are involved. The science team is composed of numerous
researchers from universities, private and government agencies.

This is the third mission in NASA's New Frontiers Program. The first,
New Horizons, was launched in 2006. It will fly by the Pluto-Charon
system in July 2015, then target another Kuiper Belt object for
study. The second mission, Juno, will launch in August to become the
first spacecraft to orbit Jupiter from pole to pole and study the
giant planet's atmosphere and interior. NASA's Marshall Space Flight
Center in Huntsville, Ala., manages New Frontiers for the agency's
Science Mission Directorate in Washington.

Where Should MSL Land?

2011-05-24T21:14:00.000-07:00

Ryan Anderson has a nice summary of the current views on the four candidate Mars Science Laboratory landing sites at his blog. Science has nice images of the landing sites. We should find out early this summer which site NASA will select.

Editorial Thoughts: What a great set of choices! If I were really pressed, I would probably go with Mawrth because it likely has the oldest materials available for study. However, any of these sites would be great to explore.

Mars Science Laboratory May Have Been Damaged

2011-05-24T21:00:00.001-07:00

Aviation Week and Space Technology reports that the backshell for the Mars Science Laboratory may have been damaged. If it was, this may put the launch this year at risk.

Reducing Costs of an Europa Orbiter

2011-05-22T01:13:00.000-07:00

Prior to the announcement of the Discovery candidate missions, I had been exploring options to explore th outer planets within the new fiscally constrained environment. Previous posts had looked at options for Discovery missions. The inclusion of the Titan TiME lake probe makes it more likely that at least some Discovery outer planet missions may be possible and scientifically competitive.

Today, I want to consider options for a much reduced cost Europa orbiter. I'll start by stating that I don't know how much costs can be reduced. ESA's proposed Jupiter Ganymede Orbiter would approximately fit within the new proposed New Frontiers budgets planned for the next competition. (Direct cost comparisons using public information are difficult between ESA and NASA missions, because they use different accounting rules and the exchange rates may not reflect actual purchasing power.) JGO, however, doesn't face the extreme radiation that an equivalent Europa mission would face. The costs of radiation hardened electronics and additional shielding certainly would add substantial costs if the same mission were flown to Europa. NASA's Jupiter Europa Orbiter study group estimated that the cost of a minimal mission would be approximately FY07 $2.1B (although the report didn't specify the exact set of options behind that estimate). However, the same group also estimated that the cost of the full JEO mission would be FY07 $2.7B or $3.8B in real year costs. The Decadal Survey estimated the real year JEO costs would be $4.7B, putting the FY07 $2.1B minimum cost estimate in doubt.

This post, therefore, may be an exercise if futility -- there may be no way to orbit Europa for less than a major Flagship cost in an era where Flagship missions don't appear affordable. From the meetings I've listened to, however, the Europa science community would like to see how low the cost of the minimally justifiable mission could be driven. I'll explore two related areas where costs might be reduced: limiting the science goals and shortening the time in Europa orbit.

The JEO study team carefully laid out priorities for studying Europa and for the instruments supporting each study. The phasing of the mission timeline also corresponded to those priorities. One approach to defining a minimally acceptable mission would be to pare back the priorities to a minimum core, which also reduces instruments and potentially time needed in orbit. Because the radiation damage is cumulative over time, the shorter the orbital mission, the lower the cost to design a radiation hardened spacecraft and instruments.

The JEO study team identified four overall goals (for simplicity, I won't reproduce the list of sub goals) and core supporting instruments in priority order:

"Ocean -- Characterize the extent of the ocean and its relation to the deeper interior" -- Laser altimeter and radio science for gravity measurements
"Ice -- Characterize the ice shell and any subsurface water, including their heterogeneity, and the nature of surface-ice-ocean exchange" -- Ice penetrating radar
"Chemistry -- Determine global surface compositions and chemistry, especially as related to habitability" -- Visible-IR Imaging Spectrometer, UV Spectrometer, Ion and Neutral Mass Spectrometer
"Geology -- Understand the formation of surface features, including sites of recent or current activity, and identify and characterize candidate sites for future in situ exploration" -- Thermal Instrument, Narrow Angle Camera, Wide Angle Camera and Medium Angle Camera"

In addition to these instruments were a magnetometer and a plasma instrument to characterize the induced Europan magnetosphere as a method to explore the ocean and the coupling of the surface with Jupiter's magnetosphere.

The relationship between instruments and goals is more complicated than that I presented here (which comes from the summary charts in the front of the report). The exhaustive detail charts in the body of the report shows that several instruments could contribute multiple goals. The wide-angle camera, for example, would contribute to the ice, chemistry, and geology studies. The JEO report authors concluded that the minimum instrument set should be:

Radio Science
Laser Altimeter
Near-IR spectrometer (less capable than the Visible-IR Imaging Spectrometer planned for JEO)
Ice penetrating radar
Wide and medium cameras
Magnetometers
Plasma instrument

A new proposal for a pared down mission might further reduce this list and probably would recommend less complex instruments than envisioned for JEO. If the new proposal were to address just the ocean and ice goals, the cameras and spectrometer might be dropped. Those instruments also require the high data rates, and dropping them would reduce power and communications requirements.

The second place to look for mission savings would be in the length of time spent in orbit around Europa. The JEO study members identified several distinct mission campaigns, with earlier campaigns addressing higher priority goals:

Europa Campaign 1, Global Framework (200 km orbit, ~28 days): First order characterization of the ocean and ice shell through studies of tidal deformation (laser instrument), gravity (radio science), and magnetic field (magnetometers and plasma instrument). Global stereo and color maps (wide angle camera). Identification of shallow water and deep ocean search (ice penetrating radar). Measurements of surface composition (Visible-IR Imaging Spectrometer operating in a profiling mode where the 1-D location directly beneath the spacecraft would be measured in contrast to the mapping mode where 2-D images are produced)

Europa Campaign 2, Regional Processes (100 km orbit, ~43 days): The studies from campaign 1 continue, and higher resolution studies at regional scales are added.

During these first two campaigns some targeted studies using the full instrument suite were planned. Two campaigns, however, were planned for higher resolution studies, Europa Campaign 3: Targeted Processes (1-2 months), and Campaign 4: Focused Studies (~5 months). These additional campaigns would also provide time for more orbits that would narrow the spacing between ground tracks for the laser altimeter and ice penetrating radar.

The JEO authors listed 3.5 months as the minimally acceptable mission, but perhaps in the new budget realities just the 28 days of Campaign 1 or an additional month or two for Campaign 2 would constitute the minimum mission.

You can download the JEO report at http://opfm.jpl.nasa.gov/library/

Editorial Thoughts: Defining a new lower cost Europa mission will be a multifaceted approach where every possible cut in goals may reduce costs in multiple areas. (For simplicity, and because I'm not a spacecraft engineer, I didn't discuss the power or data requirements that would also be intertwined with all these elements.) The final proposal has to do more than meet a budget figure, however, it must also provide compelling science equal to that which other missions for the same budget might provide. If a mission were defined that could fit within the New Frontiers budget but carried only a laser altimeter and radio science, would this be a compelling use of >$1B of NASA's budget when the same amount might return a sample from a comet or put a lander on Venus? I don't know the answer, but I expect that this question will be in the minds of the team that relooks at an Europa orbiter.

One Decadal Survey White Paper (A budget phasing approach to Europa Jupiter System Mission Science) by David E. Smith of the Goddard Spaceflight Center recommended splitting the JEO goals across three smaller missions. The total cost for implementing the JEO science was expected to be about the same as for JEO, but the costs could be spread over a number of missions. My impression is that the goal of the paper was to point out that there were alternative approaches to exploring Europa rather than to present a rigorous analysis of particular mission concepts that would provide solid feasibility and cost estimates that would form the basis for a mission proposal. Rather the paper pointed to the direction of reducing mission goals as the way to reduce costs for individual mission. In the current budget constrained environment, my feeling is that the Europa community will get at most one scaled back mission, and not a series.

My sense in having read many reports (but having no expertise, so take this with a large grain of salt) is that the minimum mission that would be scientifically compelling for the cost could focus on only the ocean and ice priorities but with some attention to the chemistry and geology goals. I speculate that a minimum mission might consist of:

2 months in orbit, 200 km
Ice penetrating radar
Wide-angle color camera
Profiling near IR Spectrometer
Magnetometer
Laser altimeter
Radio science

Even within this limited mission scope, there is considerable room for examining options. An European mission study (IAC-04-Q.2.a.02 SYSTEM CONCEPTS AND ENABLING TECHNOLOGIES FOR AN ESA LOW-COST MISSION TO JUPITER/EUROPA) estimated the mass of this instrument set at 18 kg while the equivalent JEO instruments would have been 75 kg. Eighteen kilograms seems like it might be on the low side, but there may well be room to reduce costs by lowering instrument capabilities.

The European study also showed that there may be many ways to skin the Europa orbiter cat. It recommended a truly minimalistic solar powered Europa orbiter that used a second relay craft in orbit around Jupiter to send the data back to Earth. I expect that we'll see some creativity as the science community tries to find a way to enable an Europa orbiter.

Junocam

2011-05-16T20:19:00.000-07:00

The upcoming Juno Jupiter orbiter will include a camera that was originally intended for use as a public outreach tool. The engineers at Malin Space Science Systems, which designed the Junocam camera, have enhanced it to include some scientific capabilities, including a near-IR band to map methane abundance. You can read their press release at http://www.msss.com/news/index.php?id=24.

Juno will also carry an infrared imager provided by the Italian Space Agency: (http://juno.wisc.edu/spacecraft_instruments_JIRAM.html) and an ultraviolet imaging spectrometer.

Editorial Thoughts: Juno is an excellent mission on all accounts and will greatly deepen our understanding of Jupiter's origins, structure, atmosphere, and magnetosphere. It should also, thanks to Junocam, provide stunning images of Jupiter's cloud decks as the spacecraft passes close to the planet. The armchair explorer in me is hoping for a close up of the Great Red Spot.

Current Summaries of Discovery Candidate Missions

2011-05-13T10:36:00.000-07:00

Jim Adams, Deputy Director for NASA's Planetary Science Division made a presentation on May 10 with summaries of the three recently selected Discovery mission candidates. Unlike much of the information available on these proposals which is often two or more years old, these summaries should reflect the current state of the proposals.

You can read the entire presentation at http://solarsystem.nasa.gov/docs/Adams%20PPS%2005102011.pdf. The one slide summaries of the missions begin on slide 12. Double click on the images to read the full slides.