Plutonium Balance

The coming crunch in plutonium-238 supplies to power planetary missions to destinations with limited or no solar power options has been discussed several times in this blog (see Resources, below). The plan had been to deal with this problem in two ways. First, NASA would switch from using the MMRTG power systems to ASRG power systems, reducing demand for plutonium by about a factor six. Second, the United States would fund the creation of new facilities to produce new supplies of plutonium.

The first part of the plan is moving forward, and NASA has announced that an ASRG power supply will be available for the next Discovery mission. (Proposers do not have to use the ASRG, but since NASA wants a flight test of this technology, proposers who do propose it would seem to have an advantage.) Unfortunately, SpaceNews reports that Congress has decided not to fund the start up of the new facilities planning in the FY10 budget.

At first glance, Congress' stance seems uninformed. However, careful reading of a National Academy of Sciences report on the topic shows the issue to be more nuanced. Someplace between half and two-thirds of the projected use of plutonium-238 were projected to support manned exploration of the moon in the 2020s. That exploration is now seriously in doubt as the United States rethinks is manned exploration plans.

In addition, almost half of the planetary exploration use of plutonium-238 is dedicated to the Jupiter Europa Orbiter (JEO). That mission is currently expected to use MMRTG technology. If it does, the plutonium-238 supply would be exhausted by that mission. If JEO were to switch to ASRG technology, NASA would have sufficient plutonium-238 to last into the mid-2020s. It would not run out of plutonium 238 until it tried to build a second outer planets flagship mission. In the meantime, the existing plutonium-238 supply would support a number of missions.

I put together the following table using figures from the National Academy report. Red figures show a deficit supply. The two columns of plutonium-238 requirements vary only in the amount of plutonium used by JEO.

In a time of record budget deficits and uncertainty about whether there is an immediate plutonium-238 supply problem, Congress decided to not fund the start up of a new supply until requirements become clear with the announcement of a new manned exploration program by President Obama. Unfortunately, the delay likely will put NASA in a bind for JEO planning. The agency doesn't want to commit a $3B mission to an unproven technology. My guess is that NASA might now decide to delay JEO to around a 2020 launch to give ASRG technology more time to mature. (I suspect that other budget concerns would delay the launch to that time frame, anyway.)

Resources:

SpaceNews article: http://www.spacenews.com/policy/pu-238-restart-denied-with-final-passage-energy-bill.html

National Academy of Science report: http://www.nap.edu/catalog.php?record_id=12653

Previous blog entries on the plutonium supply problem and ASRGs
http://futureplanets.blogspot.com/2008/12/plutonium-supply.html
http://futureplanets.blogspot.com/2009/01/solution-to-plutonium-problem.html

Also, if you do a search for ASRG on this blog (see search window in upper left top banner), you can find summaries of several potential Discovery missions that would use this power supply.

Two Strategies for Mars Rover Instruments

ESA and NASA are both planning small Flagship ($1-2B each) rover missions to explore Mars in 2018. The agencies have recently decided to merge their efforts to pool costs. As plans stand now, NASA will provide the launch vehicle and a skycrane entry-descent-and landing system. Each agency will provide its own rover, which will be simultaneously delivered to the same location by the skycrane system.

They idea of sending two rovers to the same location has caused a lot of raised eyebrows (to put it mildly) at Unmanned Spaceflight. In this blog entry, I want to explain why this isn't necessarily as stupid as it sounds and to discuss what I think may eventually happen.

In any mission, there's are fundamental tradeoffs that drive the mission design made to keep costs reasonable. For ExoMars, that key tradeoff was to acquire samples using a deep drill (up to 2 m) that would get beneath the level of organic sample degregation. Samples would then be processed by a very sophisticated set of instruments housed inside the rover. A fundamental tradeoff to this approach is that ExoMars will not have a robotic arm to acquire samples or place instruments in contact with rocks or soil. (The Mars Science Laboratory Curiosity will use a sample arm with a drill to deliver samples to its own internal suite of instruments as well as place instruments in contact with the surface.)
NASA's 2018 MAX-C rover has a primary task of selecting, acquiring, and caching samples for a potential future Mars sample return mission. The system to acquire, handle, and store the samples is quite complex and heavy (tens of kilograms). As a result, there is insufficient mass and space for a suite of internal instruments. Instead, the mission proposes to have a set of highly advanced contact instruments on a robotic arm. Unlike MER and MSL, these instruments will be able to study micro-variations in composition across the contact point much as might be done in a terrestrial laboratory with a sample. The instruments can examine the contact area in multiple spectra, measure elemental and minerological composition, and measure organics (if present). The instruments are potentially light, perhaps 15 kg (probably not including the robotic arm, although the presentations are not clear on that point). Currently, many of these contact instruments are in a low state of technology readiness, but with nine years to flight, there's time to address that issue.
ExoMars also will carry a ground penetrating radar and a power wide- and narrow-angle camera system. MAX-C presumably would also carry a capable imaging system and tentative plans have it carrying a spectrometer on the mast for remote identification of surface composition.

No single rover can do it all. If you want to sample deep beneath the surface, have a sophisticated laboratory of instruments inside the rover, have sophisticated contact instruments, and acquire and cache samples, you need multiple rovers. Flying ExoMars and MAX-C to the same location would provide complimentary, not redundant, measurements.

Editorial Thoughts: In a world with unlimited budgets, flying two rovers to the same location would be wonderful. In a world of constrained budgets, it seems unlikely to me to happen (but please, ESA and NASA, prove me wrong). So, if we are reduced to one rover, what should it look like? That depends on priorities, and your's, mine, and the scientific community's may be quite different. But here are mine. I think the idea of a deep drill with an internal laboratory is compelling, but the number of samples is likely to be limited either by drill life or the number of experiment chambers. (An ExoMars presentation states that there would be six sample acquisitions.) I also think that the idea of an infinitely reusable suite of contact instruments on an arm is powerful. (An arm also allows measuring locations on the sides of rocks, hillslopes, and rock/soil faces that would be challenging or impossible for a deep drill.)

Caching samples is less compelling to me. Before the flight of ExoMars, we won't know, for example, how important it is to acquire samples from deep beneath the surface. What happens if the site you dedicated a rover to sample turns out not to be the one you want to return samples from? And will Europe and the U.S. actually fund a $5-6B return mission? For me, the more compelling sequence of missions is to study several locations with science oriented rovers such as ExoMars and MSL. Then, if funding for a sample return comes through, fly a rover dedicated to acquiring samples followed by the return vehicle. (Note: The Mars scientific community would disagree with this and is willing to forgo a much more sophisticated suite of instruments on MAX-C to kick start the move towards a sample return.)

If budgets or landed weight limits restrict the 2018 to a single rover, what I think would be compelling would be to add an arm with micro-scale contact instruments to an ExoMars rover. The arm and its instruments would be relatively light (20 - 25 kg?) become a complete subsystem that can be developed and supplied by NASA, simplifying the development interfaces.

In the best of all worlds, I would advocate enhancing ExoMars with the MAX-C arm and instruments for 2018. Then I'd fly MAX-C in 2020 with its arm and instruments and caching to either the same site (if ExoMars finds compelling reasons to make it the site for a sample return) or to a new site (or possibly the Mars Science Laboratory site if it is the compelling site). All it takes is money.

As the following two slides highlight, the question of how to merge the two missions is one the two space agencies are wrestling with.

Resources:

All images and slides are from the following presentations:

ExoMars: ESA’s Mission to Search for Signs of Life

Proposed 2018 Mars Astrobiology Explorer-Cacher (MAX-C) Mission

LADEE

NASA has written an article on the 2012 Lunar Atmosphere and Dust Environment Explorer (LADEE). This mission will characterize the lunar atmosphere before human exploration "pollutes" it. The article is a nicely written summary of the mission's science.

Resources:

Article http://science.nasa.gov/headlines/y2009/23oct_ladee.htm

LADEE website http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=LADEE

Decadal Survey Democracy in Action

The Decadal Survey in progress is going to great lengths to ensure that the entire planetary science is included in setting priorities for the next decade. It has set up a number of panels to work out priorities for different subsets of targets. The Small Bodies panel has set up a web page where community members can vote on priorities.

The poll begins by asking members to rank possible scientific priorities such as, "Relating the history and processes of our solar system with other solar systems," and "Determining early conditions in the solar system (e.g., compositional gradient, early formation history)."

Two options are presented for a Flagship mission, "Cryogenic Comet Nucleus Sample Return," and other (with a place to specify one's alternative).

Ten options are presented for a New Frontier's mission: "Sample return from a volatile-rich NEO [Near Earth Object] not represented in our meteorite collection, Multiple main belt asteroid rendezvous, Phobos/Deimos sample return, Flyby of unexplored ice dwarf [in the Kuiper belt beyond Neptune] (e.g., Haumea), Comet surface sample return, Mega-multiple flybys of main belt asteroids, Multiple target flyby of satellite (e.g., Triton) and small TNO [Trans-Neptune Object], Main-belt asteroid sample return, Jupiter Trojan rendezvous, and other."

The survey has space to answer the question, "What are the most important science goals that can be addressed by Discovery-class missions?" The survey goes on to ask about priorities for research facilities and technology development."

The survey closes by asking what seems to me to be the key question of the survey, "Balancing priorities - In the event of negative budget pressure on the planetary budget, what is the priority for preserving program funding?" Options are "Technology development programs, Discovery class missions, Flagship class missions, Research and Data Analysis programs, New Frontier class missions, and Other."

Results will be made public in a future Small Bodies panel meeting.

Japan's Planet-C/Akatsuki

Japan has just announced a name for its forthcoming 2010 Venus orbiter. The spacecraft will be called "Akatsuki," meaning Dawn.

This is a clever mission that will focus on the super rotation of Venus' atmosphere. While the solid body of Venus rotates very slowly (243 Earth days), the atmosphere itself rotates very quickly and circumnavigates the globe in 4 to 5 days. This mismatch has lots of scientific implications, which are nicely summarized on the science background tab of JAXA's Akatsuki web page (http://www.stp.isas.jaxa.jp/venus/E_sci.html).

Resources:

Mission webpage: http://www.stp.isas.jaxa.jp/venus/top_english.html

An earliers summary on this blog: http://futureplanets.blogspot.com/2009/03/vexag-part-2-japanese-venus-climate.html

New MSL Problems

Spaceflight Now has a long article on new problems for the Mars Science Laboratory (MSL, now named Curiosity). Reportedly, the company supplying the titanium, which is used throughout the rover, produced one or more batches of the metal that did not meet spec. The MSL project will have to go through each part of the rover to determine whether good titanium was used and if not, whether it matters.

While this is bad news for the rover, the metal apparently was also used in several Air Force aircraft, which may put people's lives at risk.

The titanium problem may force a mission delay beyond 2011 (next launch opportunity would be 2013): "Engineers may not finish testing on MSL's titanium until the the middle of next year, leaving little time to replace the metal if it does not meet specifications."

In more bad news, even without this problem, the mission's costs are increasing again and possibly up to another $115M above the previously allocated $400M to cover new problems. The article discusses that somewhere between the currently supplied $32M in additional funding and $115M, NASA may have to delay or cancel another mission to raise the funds. A delay of the launch until 2013 would presumably require even more funds.

Resources: Spaceflight Now article http://spaceflightnow.com/news/n0910/20titanium/index.html

Venus New Frontiers Radar Mapping Mission

A number of previous blogs have looked at possible NASA missions to explore Venus in the coming decade. (See this blog entry for links to the full set.) As discussed in those blogs, exploration of our sister world is hampered by the lack of funds for a Flagship (>$1B) mission given likely commitments of Flagship class missions to Mars and Jupiter-Europa. A number of missions ideas to study the planet from within the atmosphere or on the surface have been proposed. More recently, a proposal for a New Frontiers (~$650M) mission to continue the radar mapping of Venus has been published in a Decadal Survey White Paper.

Until this paper, I had been under the assumption that radar mapping missions that would meaningfully exceed the Magellan resolution (more on that below) would require a Flagship class mission. In fact, an orbiter estimated at over a $1B to do this has been proposed as part of a Flagship mission for the 2020s. This White Paper and an abstract for the upcoming Fall American Geophysical Union (AGU) meeting makes the case that a capable mission could be done in the New Frontiers program. (It's not clear whether the AGU abstract is discussing a Flagship or New Frontiers class mission, but the science rational remains the same either way. There doesn't appear to be any overlap in the authors of the White Paper and the AGU abstract, so different classes of missions may be being proposed.)

Venus has previously been mapped by NASA's Magellan spacecraft in the early 1990s. The resolutions were crude: 100 - 150 meters horizontal resolution in the mapping mode and 80 meter vertical topography measured every 8 - 10 km. Imaging radar mapped the terrain at 100 - 150 m. As the AGU abstract states, "Our state of knowledge about Venus is currently analogous to our knowledge of Mars in the post-Viking era, and a high-resolution imaging radar mission to Venus could revolutionize our understanding of Venus in the way that the Mars Global Surveyor mission did for Mars."

From http://www.lpi.usra.edu/decadal/vexag/venusGeoFinal.pdf

The crux of the proposed New Frontiers mission is to improve topographic resolution dramatically. Several schemes are discussed that would return different resolutions, presumably at different mission costs. One to two meter vertical resolution at 1 km spacings is given as an example of a reasonable implementation. A synthetic aperture radar (SAR) could also image selected targets at ~10 m for a few percent of the planet. (This is much the same strategy that the very high resolution cameras on Mars orbiters have employed to revolutionize our understanding of that world.) The paper also briefly discusses how the Venus Express instruments have mapped albedo differences in the surface of Venus in the near IR band, with the suggestion that enhanced mapping using this approach might be an additional study for this orbiter.

The White Paper gives a number of examples of how the enhanced radar mapping would advanced our understanding of Venus. I'll give a summary of one example here. Roughly 20% of Venus is covered by highland "continents" which are crossed by linear features known as tesseras. Currently, there are two theories about the origin of the highlands: They represent ancient crustal units, or they have been gradually built up over the history of Venus. The proposed mission would be able to determine if the surrounding plains intersect the tesseras at a sharp angle (indicating ancient origin for the tessaras) or a gradual angle (indicating gradual formation).

The AGU abstract gives a long summary of what might be learned. (I normally don't like to quote this much material from other websites, but the AGU abstracts can't be linked with simple URLs.) The abstract states, "Such a mission would substantially further our understanding of Venus by means of: (1) assessing the fundamental framework of the planet's geologic history (e.g., catastrophic change, slow evolution, uniformitarian) by imaging key stratigraphic contacts; (2) expanding the global framework of geomorphic unit types and relative stratigraphy with reconnaissance surveys of large geographic provinces; (3) directly detecting volcanic and tectonic activity through imaging of flows and fault-related activities (e.g., landslides) that occur between imaging passes; (4) monitoring present-day volcanic and tectonic activity with repeat-pass InSAR deformation studies; (5) constraining the nature of Venusian geologic volcanic and tectonic processes, and their relationship to mantle convective processes; (6) understanding the role of eolian processes in modifying the surface and the use of eolian features as stratigraphic markers (e.g., parabolic features) through detailed examination; (7) constraining Venusian impact processes, particularly the role of the atmosphere in the ejecta emplacement process; (8) constraining the processes responsible for the abrupt decrease in emissivity at high altitudes; (9) selecting landing sites for future missions; and (10) identifying past landers/probes to place them in geologic context."

Resources:

Past blog entries on Venus mission concepts

White Paper http://www.lpi.usra.edu/decadal/vexag/venusGeoFinal.pdf

AGU website http://agu-fm09.abstractcentral.com/login Search for abstract, P33A-1281, "The Rationale for a New High-resolution Imaging Radar Mission to Venus."

Article on new ExoMars plan

Aviation Week and Space Technology has posted a short article on the new (and now approved pending financial scrutiny) ExoMars plan. As previously discussed in this blog, the mission breaks into these pieces:

2016

ESA orbiter for telecommunications and trace gas measurements
ESA entry, descent, and landing demonstration with a large battery supporting an instrument package
NASA supplied launch

2018

ExoMars rover with drill (no arm as on the MER and MSL rovers)
NASA supplied skycrane landing system for precision landing
NASA supplied launch

Editorial Thoughts: There's a hot debate at Unmanned Spaceflight on why anyone would send scientific instruments to Mars and not at least bolt on some solar panels for long lived experiments. (Look towards the end of this thread.) Previous articles have suggested that the instrument package might be engineering instruments only, in which case long life would be redundant. If there would be true scientific instruments, they might be ones (e.g., radar sounding of the subsurface, or a surface image pan) that would have less return from repeated measurements. My guess is that sticking to batteries is ESA's way of preventing feature creep -- add just a solar array and these few instruments -- that end up driving mission requirements and costs skyward.

The AWST article also mentions that NASA may provide a rover to accompany the ExoMars rover. (Based on Decadal Survey meetings, both rovers might be landed by the same skycrane descent system.) It would not surprise me if NASA's proposed 2018 rover slips to 2020 to smooth out funding issues and allow development of the Jupiter Europa orbiter. However, I want to emphasize that this is purely my speculation.

Please vote

Vote on the website on whether you prefer full blog entries or only the first few lines posted to news readers. (Realized that this was buried too far down in previous blog entry for people scanning in news readers to see.)

An Anniversary and a Question

I began this blog a year ago. At the time, I expected to post perhaps every couple of weeks as news on future planetary exploration became available. Two-hundred forty-eight entries later, it appears that that estimate was bit low. Of course, I hadn't counted on the Mars Science Laboratory slip, nor the wealth of information made public for the selection of the outer planets Flagship mission, nor the Decadal Survey in progress.

I have followed the twists and turns of planning for future planetary missions now for almost thirty years. Before the advent of the web, it was a painful process of reading Aviation Week and Space Technology every week, going through NASA technical reports, and looking through conference papers. Today, there is such a flood of information on the web that I'm not sure that it's any easier to keep up.

For many years, I assumed that I was the only person interested in following the development of exploration roadmaps and the politics behind them. (Probably not coincidentally, my first career was a planner and then manager of products and product roadmaps for a large high tech company. If you want to talk about twists and turns and politics...) Now I know that I'm not the only person interested in this topic. Currently, the site is visited by 1,200 - 1,300 unique visitors a month.

I do have a question for you. Many of you probably follow this blog through a news reader. I have the option to either post the entire blog to readers or only the first few lines (the current setting). I've set up a new poll on the site to ask which you prefer.

So, thank you for your interest and comments. Suggestions for improvement to the web are always welcome (vkane56[at]hotmail.com). The next couple of years should be fun as the Decadal Survey process continues and as a number of in-flight missions reach their targets.

- Van

China's Moon Plans

Aviation Week has an online article discussing the Chinese space agency's plans for manned and unmanned lunar exploration. The manned plans do not yet have government approval. The approval status of the unmanned missions is not mentioned.

The next step in Chinese lunar exploration will be the Chang'e 2 orbiter a year from now that will image the moon at 10 m resolution. Chang'e 3 will land a rover (no date given), while a mission late in this coming decade will return a lunar sample.

Options for Venus in the Coming Decade

In a previous blog entry, I discussed the quandaries that scientists focusing on the inner planets (ex Mars) face. That seems especially true for Venus science. First, Venus is just plain hard to study: the atmosphere is opaque except for a few narrow spectral bands and the surface is literally hell that requires advanced engineering to even reach, much less to operate on for several hours. In addition, many of the easy missions have been done. The basic radar mapping was completed in the 1990s. ESA's Venus Express and Japan's upcoming orbiter address the obvious atmospheric questions. The next steps in Venus exploration will require highly capable orbiters with advanced radars or difficult to design and test landers. The only easy missions left that I'm aware of are balloons to float in the upper atmosphere for long term chemical and dynamics studies. (In this, Venus is one of the easier planets to study since its dense atmosphere makes balloons extra buoyant, although there are the problems of designing the deployment system and surviving air laced with sulfuric acid.)

Despite these challenges, Venus is a world ripe for study because it is the only other large terrestrial planet in the solar system (Mars and Mercury being substantially smaller). Understanding why Venus ended up so different from Earth is likely to tell us a lot about how terrestrial worlds operate.

From http://www.spacepolicyonline.com/pages/images/stories/PSDS_IP1_Smrekar_VEXAG.pdf

The U.S. Venus science community is advocating a $3+B flagship mission for the 2020s that would involve a sophisticated orbiter, two landers that could survive for a day to make in-depth analysis of surface samples, and two balloons. The technology for this mission is not yet ready, and NASA is already committed to two to three flagship class missions for the coming decade between Mars and Jupiter-Europa. So for this decade, the request is for the technology development that would enable this mission to be ready for selection a decade hence.

In the meantime, the Venus science community would like to see one or more Discovery (~$450M) and New Frontiers (~$650M) missions sent to the evening star. In the former category, the community lists several concepts. (As an editorial aside, I'll note that a number of Venus Discovery missions have been proposed, but none selected. It's not clear what is necessary to break this track record.) In a previous blog entry, I discussed a number of New Frontiers mission concepts. One of those has been described in more detail in a White Paper, and I'll describe it in more detail in the next blog entry.

From http://www.spacepolicyonline.com/pages/images/stories/PSDS_IP1_Smrekar_VEXAG.pdf

Editorial Thoughts: For this blog entry, I'll close with a couple of observations. It appears that the VEXAG (an advisory group of Venus scientists) would prioritize a Venus atmospheric probe/lander as its highest New Frontiers priority, a balloon mission as its second highest priority, and a radar mapper as its third priority. All of these capabilities are included within the concept of Russia's Venera D mission for mid to late this decade. From what I can tell, Venera D is in the early planning stages and the Russian's are seeking international participation. One approach to NASA participation would be to provide one or more of the elements within these three concepts. I expect that Russia would prioritize a lander that builds on its history of Venus landers as something it will do in house. The French, with their expertise in balloons and experience with the Vega balloons, might contribute the balloon portion. NASA could contribute the orbiter. All partners could contribute instruments to each platform.

Should this kind of cooperation not be possible, then if NASA and Russia both build one or more landers, then Venus is a big and varied place. Eventually, we'll need a number of landers to understand its story.

Resources:

Venus VEXAG justification for exploring Venus and mission priorities (from a Decadal Survey meeting)

Venus Flagship mission concept (from a Decade Survey meeting)

Summary of New Frontiers mission concepts (from this blog)

Venus New Frontiers lander concept (from this blog)

Venus balloon concept and a Discovery mission concept (from this blog)

Titan Mare Probe

Space.com has an article on the proposed Titan Mare Explorer that would float a probe on one of that moon's seas. I believe that all the material in the article has been presented in this blog, but it makes a nice read. http://www.space.com/businesstechnology/091014-titan-boat-mission.html

Next Steps for Mercury Exploration

In the first of a series of missions that will look at possible priorities for inner planetary missions, this post will look at future goals for Mercury exploration.

In the Decadal Survey Inner Planets panel meeting, a single presentation looked at Mercury goals. Missions in progress (NASA's Messenger which will enter orbit in 2011) and ESA/JAXA's BepiColombo orbiters (to enter orbit 2020) will provide a detailed examination of Mercury's surface, interior (through gravity mapping), and magnetosphere. The next logical step would be Mercurian landers or a sample return, but those are challenging goals (more on that in a bit).

The reasons for exploring Mercury. From http://www.spacepolicyonline.com/pages/images/stories/PSDS_IP1_Solomon_MESSENGER.pdf

From 2011 through 2012 and possibly into 2013 with an extended mission, MESSENGER will provide the first detailed global examination of Mercury. This mission, though, is a Discovery mission (~$450M), although it manages to cram eight instruments weighing 50 kg within that budget.

BepiColombo, by contrast, will have two orbiters, one optimized to study the surface and the other to study the magnetosphere. The two craft will carry 16 instruments instruments between them. The mission's ESA budget at ~770 euros (not including instruments) is equivalent to a small to medium flagship mission flown in NASA's budgeting.

From http://www.spacepolicyonline.com/pages/images/stories/PSDS_IP1_Solomon_MESSENGER.pdf

The combination of the two missions is equivalent to flying the Galileo mission to Jupiter with the Jupiter-Europa flagship mission scheduled to follow it eight years later (instead of 25 years later as will happen -- keep your fingers crossed -- for Jupiter).

The presentation to the Inner Planets panel listed two possible goals for follow on missions to Mercury. The first would be a lander or a sample return to provide in situ measurements of the surface composition. The other would be a lander to explore the polar regions of Mercury and their ice fields.

Editorial Thoughts: Post BepiColombo exploration of Mercury clearly is beyond the scope of the current Decadal Survey. Both the Messenger and the BepiColombo missions will revolutionize our understanding of this world. Planning for lander and sample return missions should await their results. Whenever these missions are planned for, landers for Mercury will be difficult. It is a hard world to reach because of its location deep within the gravity well of the sun. (MESSENGER requires multiple planetary gravity assists while BepiColombo will use an ion propulsion stage plus five gravity assists.) Once the lander arrives, it will have to deal with three month nights, long durations out of sight with Earth, and surface temperatures that can reach 600 degrees C at the equator. This seems like a full Flagship scale mission.

To me, the key measure of Mercury's importance to the planetary community will be whether the Decadal Survey recommends allocating resources to developing technologies to enable missions in the 2020s.

BepiColombo also illustrates the challenges of flying highly capable missions within cost constrained budgets. Originally budgeted at 650M euros, the mission exceeded that cap by 120M euros, and narrowly avoided cancellation. (Note: ESA budgets, unlike NASA budgets, do not include the cost of the missions instruments, so the true cost of the mission is higher than these figures.)
Resources:

Decadal Survey presentation: Mercury After MESSENGER

MESSENGER mission website

BepiColombo mission website

SpaceNews article: BepiColombo Narrowly Avoids Cancellation

Inner Planets Missions

The next series of posts will look at potential missions to some of the orphans in NASA's planetary exploration program: The inner planets ex Mars but including the moon.

NASA's last mission to Venus was the Magellan radar mapping mission that mapped that world from 1990 to 1994. The last science mission to the moon was in the Apollo missions. (The currently orbiting Lunar Reconnaissance Orbiter was funded as a pathfinder to future manned missions and not as a science mission, even though some scientific questions will be addressed.)

The exception to the orphan status is Mercury, which is the target of the MESSENGER mission, which has accomplished three highly productive flybys and will enter orbit in about 18 months.

Other space agencies have recent, current or planned missions for these worlds. Russia will send its Venera-D mission to orbit, balloon, and land at that world mid decade. ESA and JAXA have a combined mission with two orbiters planned for Mercury. ESA has an active orbiter at Venus, and JAXA has a Venus orbiter planned to study its atmosphere for the early part of the coming decade. And a slew of science oriented lunar orbiters have just completed their missions.

All of this activity puts U.S. scientists in something of a bind. To build upon recent and planned missions by other nations, they must propose sophisticated new missions. Sophisticated tends to equal expensive, and NASA's planetary budget is likely to be largely devoted to Mars and Jupiter-Europa for the coming decade.

The next few posts will look at proposed strategies and missions to advance exploration of the inner planets in light of these constraints.

A Parting Look at Primitive Body Sample Return

A number of the last posts have looked at mission priorities for primitive bodies being formulated for the U.S. Decadal Survey. This post will close out that series by looking at a series of presentations from last May at an ESA sponsored meeting.

Sample returns from comets and asteroids rank high in priorities for missions to primitive bodies in the priorities being set by the scientific community. ESA and Japan (JAXA) are both considering missions to return samples from a near Earth asteroid. For ESA, this mission is a candidate for selection as the next medium class science mission, but the proposed Marco Polo mission doesn't fit within the ESA budget. For JAXA, this would be a follow on mission to the troubled HAYABUSA mission. The two agencies are investigating options for combining these missions.

ESA held a conference last May on near Earth asteroid sample return. Quite a large number of presentations are posted on the meeting website (http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=43784). I won't try to summarize all the presentations, but will instead provide highlights.

The ESA defined mission appears to still be in definition, with a several spacecraft configurations under consideration from true landers to touch-and-go sampling.

Samples would be returned to Earth in the mid-2020s after a year and a half remotely studying the asteroid and collecting samples.
Less information is available on the website for the JAXA mission. In fact, the overview presentations for both the ESA and JAXA missions were not posted. However, some ideas for the potential science compliment of a JAXA mission can be found at http://sci.esa.int/science-e/www/object/doc.cfm?fobjectid=45164.

Two presentations were made for possible NASA New Frontiers near Earth sample return missions. Neither gave out many details on the missions -- this is a competitive field. However, the OSIRIS-REx presentation shows the dedication needed to win selection. The team prepared proposals for three sequential Discovery (~$450M) mission competitions. In the last competition, the team was a semifinalist, but wasn't selected because the review board felt that the mission was too risky for the mission budget. The team planned to submit a New Frontiers (~$650M) mission proposal for the competition in progress.

A summary presentation laid out the key technical risk and political challenges facing the Marco Polo mission. Based on what I've read, the technical problem highlighted applies to sample return from any asteroid or comet -- we know too little about the surface properties to be sure what technique(s) might work. (But this issue is being worked on; see Small Body Sampling Techniques being Developed at JHU/APL.)

ESA-NASA Mars Cooperation Tentatively Approved

Space News reports that ESA's governing body has given tentative approval to the joint NASA-ESA Mars program. Full approval awaits costing out the joint program to ensure that it fits within funds available.

Under the plan, ESA and NASA will cooperate on a 2016 trace gas orbiter and relay orbiter. ESA will also demonstrate a Mars entry and landing system. [This system is likely to be too small for future rovers, but may be the right size to land possible 2020 Mars network science stations.]

In 2018, ESA and NASA will both launch rovers to Mars. Per a recent tidbit from the Decadal Survey meetings, both landers may be delivered by the same sky crane landing vehicle. In this case, the ESA rover will sample the subsurface and the NASA lander will sample the surface and cache sample for a potential Mars sample return mission.

Venera -D Plans

The BBC has a long article on plans for Russia's Venera-D lander. The mission would include an orbiter, a lander that would survive on the surface for a day, multiple balloons, and perhaps even a free flying kite. Details on the mission apparently haven't been worked out. Russia recently hosted a conference inviting international participation in the mission. The current launch target is for 2016, but the French space agency CNES has said a delay until 2018 would be needed for it to participate. The article points out that the recent delay of the Phobos-Grunt mission could have a ripple effect, pushing Venera-D to 2018.

Editorial Thoughts: It's good to see Russia building on its Venus mission experience with a return to this planet. This is an ambitious plan. It's equivalent to at least a small flagship mission (~$1.2B) in NASA's planning.

The solar system is a large place. The bulk of NASA's planetary spending for the next decade is likely to go to Mars and Jupiter-Europa. ESA's planetary budget will largely go to its Mercury mission and (if approved) a Jupiter-Ganymede mission and possibly a series of joint Mars missions with NASA. Venus has been an ignored step child for too long. Venus Express broke a long drought in missions, and it will soon be joined by a Japanese orbiter. It's been 26 years since a probe (the Soviet Union's Venera 16) entered the atmosphere, though, to conduct in situ measurements.

I hope that Venera-D will be just the first of a series of Russian missions that will involve the world-wide Venus science community.

Resources

BBC article

Venera-D webpage

Enceladus Mission Concept Tidbits

Minutes of the Decadal Survey panel meetings continue to be posted. See the previous post for a long summary of the first set of meetings.

In the last couple of days, two more minutes were posted. The outer planet Satellites Panel held a second meeting to consider missions to examine in more detail. The minutes include a couple of interesting tidbits on possible Enceladus missions. "New astrodynamics techniques open up new possibilities for multiple Enceladus flybys at high inclination, with additional flybys of other Saturnian satellites. It is also possible with current trajectory techniques to orbit two or more moons in one mission, for example Titan and Enceladus." Other astrodynamics studies may enable a StarDust like sample return from Enceladus: Low cost flyby sample return mission for Enceladus follows Stardust model, with modifications made for capture of volatiles. These mission concepts, collectively called LIFE, must address the following challenges: 1) sample capture velocity of 15-20 km/s, which presents problems for sample integrity; 2) long mission durations (~15 yr); 3) high cost. Some potential resolutions were discussed, including: 1) a new trajectory was found by JPL group, which gives ~3 km/s sampling speed; 2) mission duration can be reduced to 13.5 years, with multiple sampling flybys." Source: Satellites Panel Meeting 2

In addition, the Primitive Bodies Panel minutes provides good summaries of the white papers submitted to that panel. Most of that information has been summarized in a series of blog entries over the last two weeks. The writer of the minutes did not include notes on the discussions, so I did not spot any new information. However, this is a good summary if you are interested.

All of the notes of the panel meetings can be found at the Decadal Survey website. There are not unique URLs for the notes, but you can find them by scrolling down the page to 'Past Meetings.' The Decadal Survey website is: http://sites.nationalacademies.org/SSB/CurrentProjects/ssb_052412

Lots of Tidbits

This blog entry will be different than most with lots of tidbits covering a wide array of topics, primarily from recent meetings for the Decadal Survey in progress.

The first tidbits come from a SpaceNews article on the joint ESA-NASA exploration program that would the two agencies programs. On Oct. 7 and 8, ESA's ruling council will receive a formal recommendation from ESA's Director-General to merge the two programs. Approval of the joint program apparently is not assured because of objections to redefining ESA's ExoMars mission. However, if the merged program is not approved, it is not clear that ExoMars can fit within the budget the member states are willing to fund. If the joint program is not approved, then NASA will try to do the Trace Gas Orbiter (which will track down amounts and sources of ephemeral gases such as methane) within a ~$450M budget (which would make it Scout/Discovery mission class). Also see tidbits below for more on the ExoMars rover and the Trace Gas Orbiter. Source: U.S., Europe Making Progress on Joint Mars Exploration Plan

The rest of the tidbits come from the Decadal Survey in progress. Five panels have been formed that will set priorities for missions within their respective areas of outer planet Satellites, Giant Planets, Inner Planets (including Earth's moon but excluding Mars), Primitive Bodies (comets, asteroids, trans-Neptunian objects, etc.), and Mars. These panels met separately over the course of August and early September. All have posted extensive notes from the meetings (but no presentations) except the Primitive Bodies panel. The focus of the notes varies from minimal coverage of the presentations and extensive coverage of the discussions to the reverse. Often, the most interesting tidbits come from the discussions. The notes usually don't make it clear whether the discussion points represented the views of one person, the consensus of the room, or something in between. So take that into account in reading these tidbits. Also, the notes from the four meetings run to dozens of pages; I'm only pulling out highlights here.

All of the notes can be found at the Decadal Survey website. There are not unique URLs for the notes, but you can find them by scrolling down the page to 'Past Meetings.' The Decadal Survey website is: http://sites.nationalacademies.org/SSB/CurrentProjects/ssb_052412

Juicy Tidbit: "The [ExoMars] mission team is quite interested in using the MSL Sky Crane system, due to its small landing error ellipse (15km ellipse vs. 75km with older system) and ability to land a large payload. However, the current plan is to fit two rovers on a pallet (MAX-C [a NASA rover] type + ExoMars), and this has not been studied. Additionally, if two rovers are going to be delivered to the same place, then we need to make sure that (1) We have compelling reasons (can do rover-to-rover imaging, MAX-C can cache subsurface samples collected by ExoMars), (2) These rovers have complementary and not overlapping capabilities, (3) We do not compromise the science objectives of either rover." However, "We also need to consider what happens if only one rover can be landed in 2018. ESA interest is very strongly committed to Exo-Mars and collaboration with NASA on TGM is tied to assistance with Exo-Mars. Currently, we cannot accommodate two rovers in MSL-type heatshield envelope." Source: Mars Panel notes

Decadal Survey Process

This Decadal Survey will place a heavy emphasis on doing high quality cost assessments of 10-15 missions that address the highest priority science goals. Substantial money has been set aside (~$1.5M per panel to be divided between the highest priority concepts selected by each panel). A substantial portion of each meeting was devoted to presentations by JPL, John Hopkin's Advanced Physics Lab (APL, which has developed several successful planetary missions), and NASA's Goddard Spaceflight Center on the capabilities of those institutions to carry out the definition of the mission concepts. The formal cost assessments will come from an independent company.

The total budget for planetary missions in the coming decade will be ~$12B. However, the budget the Decadal Survey can prioritize will be less because already approved missions for the next decade are untouchable. The latter group would include the already approved Juno, Mars MAVEN, Lunar GRACE, and Mars Science Laboratory (Curiosity). By the time the process completes in a couple of years, the Mars Trace Gas Orbiter, the Jupiter Europa Orbiter, a new Discovery mission, and a new New Frontiers mission may also be on the already approved list. The Survey can, however, have influence into the following decade by prioritizing technology development for missions in the following decade. (Missions with ready to use technology have a much better chance of approval than missions that require substantial technology development as was witnessed in selection of Jupiter-Europa as the destination of the next outer planets mission over Saturn-Titan-Enceladus.) Source: Inner Planets panel.

Results of the Previous Decadal Survey

The previous Decadal Survey had identified a list of unprioritized candidate New Frontiers missions, and the list was expanded in a mid-decade review. "An overview of the New Frontiers mission selection process was provided, and it was noted that five more missions had been added to the New Frontiers list of possible missions, but that they were not prioritized. It was noted that the primary decision mechanism had become cost and Technical Readiness Level (TRL), rather than the underlying science goals." Source: Inner Planets panel. [I would not be surprised if the same held true for Discovery mission selection, also.]

The Juno Jupiter orbiter was specified in the previous Decadal Survey as an orbiter and an atmospheric probe. The reason for the dropping of the probe illustrates the importance of technology development: "- The “P” in JPOP (the concept mission that is planned to fly as Juno) is for probe; probe is not in the technology list because the technology to make the proposed probes was assumed to be available. In reality the technology was “lost” when the heat shield company that made the Galileo probe heat shield closed. Had probe technology been explicitly prioritized, perhaps Juno would still have probes. The lesson is: for every mission proposed, the technology should be known or in the prioritized list of new technology. Otherwise the technology may not be developed and the mission will not fly. Considerations should also be made for technologies necessary for future missions, even if they are further in the future than the next 10 years." Source: Giant Planets Panel

Mars Panel

The specificity of the proposed Mars program after MSL (2011) and MAVEN (2013) is much more mature than for the other panels. The proposed missions and costs quoted in the notes are:
2016: Trace Gas Orbiter (TGO) with costs ranging from ~$450M (per the SpaceNews article) to $750M with an instrument suite consisting of a "solar occultation spectrometer, sub-millimeter spectrometer, WA camera, thermal-IR spectrometer, and high-res camera." Adding data relay capabilities to TGO to support rovers takes the mission out of the New Frontiers class (~$650M). [It's not clear from the notes whether the $750M includes relay capabilities (my understanding from past presentations) or if relay capabilities pushes costs further toward $1B.]
2018: ESA Exo-Mars
2018: NASA Mars Astrobiology Explorer-Cacher ($1.5 - 2.0B) that would both carry out scientific studies of surface material and collect and store samples for possible return to Earth by a future sample return mission.
2020: A network of geophysical landers with prices for a single station in the $450M range, three stations in the $650M range, and four is "substantially harder" [I've seen $1-1.2B in previous presentations for a four lander mission]. A single mission can prove the technology and set bounds on Mars' seismology, but at least 2 and really 3 are needed to determine the source location and four stations (three on one side of the planet and the fourth on the opposite side) to really explore the internals of the planet.
2020's: Sample return (assuming substantial investments in technology development in the 2010s).

Put together, the 2010's Mars program, excluding MSL and MAVEN is in the range of $3.5 - $4B.


Giant Planets Panel

Except for the Jupiter-Europa orbiter (for which the study of Jupiter itself will not be a priority for instrument selection), the priorities for this panel are still to be set. Concepts for a Neptune flyby (the Argo mission, which would also fly by a number of other worlds), a Uranus orbiter, and atmospheric probes of the outer planets were presented. The order of priority for atmospheric probe targets is Saturn, Neptune, Jupiter, and finally Uranus. Existing heat shield materials for Mars and Saturn are too weak to be used for entry into a giant planet's atmosphere. [The notes did not address the question of whether the shield material used for the StarDust Earth re-entry would work for some of the gas giants.] Their remains sufficient material from the Galileo mission for two Galileo class probes, but the facilities to test heat shields has been disassembled.


Satellites Panel

"There was consensus to give more attention to flyby missions gathering valuable science while also fitting within a New Frontiers (NF) cost cap. The 2003 Survey gave little attention to flybys due to the impression that the “era of flybys” was over. MESSENGER has shown that new technology makes flybys effective at gathering large amounts of high-quality data." [The notes don't say whether these would be flybys from a flyby craft a la New Horizons and Argo or flybys of moons by an craft in orbit around a gas giant.]

"In their deliberations, OPAG has found that limiting mission classes to Discovery, NF and Flagship handicaps outer solar system exploration. Opportunities to advance science on a NF budget are limited in the outer solar system and Flagship missions are rare. They encouraged NASA to develop a “small Flagship” or enhanced NF class of mission that would fly more frequently than current Flagship missions. An approximate budget of $1.2B per mission would be expected."

"Several questions probed the possibility of breaking up a Flagship mission of three components into a mix of NF missions or a NF mission and a Flagship mission. This would reduce and amortize the cost over time and simplify the mission. The lake lander and orbiter could both fly independently, but the balloon needs the orbiter for data relay. The imager and radar subsurface profiler have such high data rates that direct-to-Earth communications are unrealistic. It would be desirable for the orbiter and lander to work in concert to provide critical context, but is not necessary, particularly for seasonally unchanging areas."

"During the nominal mission, TiME (a probe that would float on a Titan sea) should drift close enough to shore to be able to image the surrounding land. Cassini radar imagery indicates very low wave activity, but prevailing winds should push the spacecraft a long distance."

In addition to the missions mentioned above, there were presentations on the Jupiter Europa Orbiter, the Io Volcanic Observer Mission, a Uranus orbiter, and the Argo Triton flyby.


Inner Planets Panel

"The International Lunar Network (ILN) is an initiative by nine space agencies to achieve network science at the Moon. NASA involvement in lunar network science has been remanded to the decadal survey for prioritization. Passive and active geophysical experiments from 2 or 4 landers (to act as “anchor nodes” for the ILN) are proposed to determine the interior structure and composition of the Moon. Current plans are for a 2018 launch and 6 years of continuous operation. The spacecraft architecture concept is mature, and the same design could be morphed into another mission. The current design falls in to the New Frontiers cost bracket."

"The three most important Venus missions in order of priority are: Venus In-Situ Explorer [an atmospheric probe and lander], Venus Atmospheric Explorer [a balloon] and Venus Geophysical Satellite [that would enhance mapping of the surface from orbit]"
There were also presentations on a 2020s Venus flagship mission (technology development is needed in the 2010s to meet this launch date) and on Mercury exploration beyond MESSENGER where an extended MESSENGER mission will be asked for and ESA will launch a sophisticated orbiter to arrive late in the decade.