MAVEN Mission

Science@NASA has a nice article on the motivation behind the 2013 MAVEN mission to study Mars' atmosphere.  To whet your appetite, here are a couple of quotes:

"Nov. 6, 2009: Once upon a time — roughly four billion years ago — Mars was warm and wet, much like Earth. Liquid water flowed on the Martian surface in long rivers that emptied into shallow seas. A thick atmosphere blanketed the planet and kept it warm. Living microbes might have even arisen, some scientists believe, starting Mars down the path toward becoming a second life-filled planet next door to our own.
But that's not how things turned out."

"One way or another, scientists believe, Mars must have lost its most precious asset: its thick atmosphere of carbon dioxide. CO₂ in Mars's atmosphere is a greenhouse gas, just as it is in our own atmosphere. A thick blanket of CO₂ and other greenhouse gases would have provided the warmer temperatures and greater atmospheric pressure required to keep liquid water from freezing solid or boiling away."

"MAVEN will be the first mission to Mars specifically designed to help scientists understand the ongoing escape of CO₂ and other gases into space. The probe will orbit Mars for at least one Earth-year. At the elliptical orbit's low point, MAVEN will be 125 km above the surface; its high point will take it more than 6000 km out into space. This wide range of altitudes will enable MAVEN to sample Mars's atmosphere more thoroughly than ever before."

Editorial Thoughts:  A lot of science doesn't involve flashy exploration or engaging images.  MAVEN and the Lunar GRAIL missions are solid examples of the planetary missions that collect data that tell important stories only after careful analysis.  As the easy missions to many destinations are completed, these are the yeomen missions that will fill in important gaps in our understanding of processes.  [Note: A previous version of this entry mentioned a lunar GRACE mission when I meant to say GRAIL mission.  They are similar missions, but the former studies the gravity field of the Earth and the latter will do the same for the moon.]


Resources:

Science@NASA article:  http://science.nasa.gov/headlines/y2009/06nov_maven.htm

MAVEN website: http://lasp.colorado.edu/maven/

 

Proposed Discovery Venus Radar Mission

A few posts ago (http://futureplanets.blogspot.com/2009/10/venus-new-frontiers-radar-mapping.html), I wrote about proposed radar missions to remap Venus at higher resolution.  At that time, the idea of doing this within a New Frontiers budget (~$650M) was an eye opener for me.  I listened into part of the most recent VEXAG meeting, and learned of a Discovery mission (~$425M) that could remap Venus. 

The principle investigator, Dr. Sharpton, sent me the following synopsis of the mission: "RAVEN, utilizes the latest in the RADARSAT lineage, extending back to 1996 (RADARSAT 1 launched in Nov. '95).  We can accomplish reconnaissance level mapping of Venus at 30-m/px and map about 25% of Venus each cycle (a venusian day).  Alternatively, we could map about 3% of the planet at 3-m resolution each cycle.  Obviously, we would want to have a combination of resolution modes and have overlap so that we can extract topography.  Topographic resolutions would be on the order of 20m vertical resolution and either 300-m postings (if using 30-m images) or 30-m postings (with 3-m images).  If InSAR turns out to be feasible (we believe it will), the vertical resolutions would drop to a meter or less."

Dr. Sharpton pointed me to an AGU abstract about the mission.  Since there is no easy way to link to AGU abstracts, I'm posting parts of it below.  You can search for it and other planetary abstracts athttp://agu-fm09.abstractcentral.com/planner

RAVEN – High-resolution Mapping of Venus within a Discovery Mission Budget
V. L. Sharpton1; R. R. Herrick1; F. Rogers2; S. Waterman3
1. University of Alaska Fairbanks, Fairbanks, AK, USA.
2. The Boeing Company, Huntington Beach, CA, USA.
3. Alliance Spacesystems, Boulder, CO, USA.

It has been more than 15 years since the Magellan mission mapped Venus with S-band synthetic aperture radar (SAR) images at ~100-m resolution. Advances in radar technology are such that current Earth-orbiting SAR instruments are capable of providing images at meter-scale resolution. RAVEN (RAdar at VENus) is a mission concept that utilizes the instrument developed for the RADARSAT Constellation Mission (RCM) to map Venus in an economical, highly capable, and reliable way. RCM relies on a C-band SAR that can be tuned to generate images at a wide variety of resolutions and swath widths, ranging from ScanSAR mode (broad swaths at 30-m resolution) to strip-map mode (resolutions as fine as 3 m), as well as a spotlight mode that can image patches at 1-m resolution. In particular, the high-resolution modes allow the landing sites of previous missions to be pinpointed and characterized... Our current estimates indicate that within an imaging cycle of one Venus day we can image 20-30 percent of the planet at 20–30-m resolution and several percent at 3-5 m resolution. These figures compare favorably to the coverage provided by recent imaging systems orbiting Mars. Our strategy calls for the first cycle of coverage to be devoted to imaging large geographic areas (e.g., Thetis Regio) at 20–30-m resolution with interleaved observation of pre-selected targets at high resolution. The second cycle will include additional imaging, but the focus will be repeat-pass coverage to obtain topography for a significant fraction of the first-cycle targets... All components of the spacecraft are expected to remain operational well beyond the nominal mission time, so global mapping at 10 m or better resolution during an extended mission is conceivable."

First Decadal Mission Assessments

A major criticism of both the last astronomy and the last planetary Decadal Surveys was that they prioritized ill-defined mission concepts whose true cost was severely under estimated.  As a result, both fields have had embarrassingly large cost overruns on key projects -- the James Webb Space Telescope and the Mars Science Laboratory -- that prevented other high priority missions from being started such as an Europa orbiter.

This time, the planetary Decadal Survey has a major focus on defining and costing missions.  The approach is to do "Rapid Mission Architecture" studies on a large number of missions to get an idea of the engineering requirements and technical readiness.  Then a smaller set of missions judged to be high priority will get full mission studies that are intended to flesh out the details of implementation.  Then a small number of missions will receive detailed cost estimates.  As I understand the process, to be proposed as a priority mission, a mission has to make it through all three stages, and not all missions that get through the costing stage will make the shorter list of recommended missions.  Only a minority of proposed missions will make the cut at each level of assessment and progress to the next stage.

Three organizations -- NASA Goddard, John Hopkin's APL, and NASA's JPL -- will perform the rapid architectures and full mission studies.  Then an outside firm will prepare the cost estimates.

The majority of missions that will enter the process will be proposed by the community itself through the hundreds of White Papers and many panel meetings.  To kick start the process, however, the panels and steering committee selected several missions prior to the delivery of the White Papers.  Early assessment doesn't mean anything in terms of priority.  The goal was to even out the work flow for the organizations involved by getting a head start.

Steve Squyres, chair of the process, listed the first wave of missions in a letter to the community.  You can read the full letter at http://www.lpi.usra.edu/decadal/vexag/newsletters/100309.pdf.  The rest of this blog entry quotes the sections that list the first wave of missions to assessed. As an editorial note, I'll point out how wide ranging the types of missions are.  A wide net appears to be being cast to find the intersection of the best science return and the best mission readiness and cost effectiveness.

"Prior to receiving the white papers, each panel met to identify a first set of candidate missions for study. Mission candidate studies were then reviewed and approved by the steering group, and an organization (APL, Goddard, or JPL) was chosen to conduct each study. These studies are just getting underway. IT IS IMPORTANT TO NOTE THAT THESE ARE JUST THE FIRST SET OF MISSION CANDIDATE STUDIES, selected before the white papers were received. There will be many more that have been motivated by the white papers once the white papers have been assessed.

"Six of the studies are of the type known as “Rapid Mission Architecture” studies. These are high-level studies of overall mission architecture that we expect to take a few weeks. The purpose of these studies is to explore the trade space for a mission candidate, and identify a “point design” for possible subsequent study in much greater depth.

"The six Rapid Mission Architecture studies are:

• Mercury lander mission (APL)
• Venus near-surface mobile explorer mission (Goddard)
• Mars 2018 skycrane capabilities study (JPL)
• Uranus system mission (APL)
• Neptune/Triton mission (JPL)
• Enceladus flyby/sample return mission (JPL)

"There are also two full mission studies. These will be more time-consuming and labor-intensive, and are intended to take these mission concepts to the point where they are ready for a full independent cost estimate. The two full mission studies are:

• Mars trace gas orbiter mission (Goddard)
• Titan lake mission (JPL)

"There is also one small study to be conducted by JPL that doesn't fit any of the above categories; this study will identify possible targets for Near Earth Object missions.

"In addition to the eight studies listed above, two mission concept studies have been identified that have already been done to a level of maturity such that an independent cost estimate should be possible. Independent cost estimates for each of those will be performed as soon as the company performing the cost estimates is under contract. Those two mission concepts are:

• Mars trace gas orbiter mission studied to date by JPL
• Comet surface sample return mission studied to date by APL.

"Note that undergoing an independent cost estimate is a necessary but not sufficient condition for a mission candidate to be included in the final SolarSystem2012 plan. Again, I stress that most of the studies will be commissioned once the white papers have been assessed! "

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