Sunday, December 16, 2012

LIFE: Sample Return for Enceladus

Geysers of Enceladus photographed by the Cassini spacecraft.  Credit: NASA

Last week, a proposal for a sample return from Enceladus described at the American Geophysical Union conference received fairly wide-spread coverage in the space-related press.  The descriptions generally were fairly short, however.  Here, I’ll provide additional details from a paper describing the mission that was published this past summer.

The mission, called Live Investigation for Enceladus (LIFE), would be a descendent of the Discovery Stardust mission that captured dust grains from comet Wild-2 during a flyby.  The Stardust spacecraft captured the grains in a disk of aerogel, which has exceptionally low density for a solid.  That low density preserved most of the material of the grains despite the 6.1 kilometer per second flyby.  Several key members of the Stardust team are principles in the LIFE proposal.

LIFE would replicate that method and add a second capture method to return samples from the geysers of Enceladus, Saturns E ring (believed to be formed from the material in the geysers), and the upper reaches of Titan’s atmosphere. 

The appeal of the mission is that it could return samples from a potentially life-bearing subterranean ocean at Enceladus.  Like Europa’s ocean, Enceladus’ ocean appears to possess all the ingredients necessary for life: water, energy (the tidal forces that are heating the icy crust for form the ocean), and contact with rocky material that provides the elements needed for complex organic molecules.  (There are alternative explanations for the geysers that don’t require an ocean, but the evidence increasingly points to an ocean being the most likely source.)

While Europa’s ocean is sealed by kilometers of ice, Enceladus conveniently spews an estimated 150-300 kilograms of water into space every second.  The grains, though, are tiny and dispersed: Think of a particle of cigarette smoke every square meter by the time the geyser’s plume are 80 kilometers above the surface.  The small amount of material that could be analyzed by a spacecraft flying through the plume would make chemical analysis difficult for an instrument that must function within the mass, volume, and power constraints of a spacecraft.  Instruments in Earth laboratories, however, would be able to make those measurements.  The goal of LIFE is to get the ice grains to the laboratories.

Since the spacecraft would fly close to Titan and through the E ring on its way to and from Enceladus encounters, it would collect samples from those sources, too.

Capture of samples during flybys was considered by the Decadal Survey but the technical issues were considered daunting.  

LIFE depends on several key elements to keep the total mission flight time to less than 14 years (compared to previous estimates of 26 years) and the costs within the Discovery budget (~$500M):
  • The mission would make use of one of the last available gravity assists from Jupiter for a Saturn-bound mission by launching by 2019 (the next time the planets are aligned correctly comes in 2058).
  • The spacecraft would enter Saturn orbit and use an unspecified number of Titan flybys to enable flybys of Enceladus at between 2 and 3 kilometers per second (compared to previous estimates of ~7 km/second)
  • A new form of aerogel, one-fifth the density of the aerogel carried by Stardust, would be used.  Between the low encounter speed and the lower density aerogel, particles would experience a factor of five lower effective entry impacts than the particles encountered by Stardust.  A rotating cover with a slit on top of the aerogel disk would expose only a portion of the surface for each flyby, allowing the source of each particle to be known.
  • A deposition system would provide a second sampling system that would encase whole grains atop a film to better preserve complex and volatile compounds.   This system was originally planned for the Stardust mission but dropped to reduce costs.
  • The sample would be kept at below freezing temperatures to preserve the icy materials and any organic compounds

The spacecraft would also carry three instruments to conduct measurements while in the Saturn system.  A much more capable mass spectrometer than that carried by Cassini would make direct chemical measurements of the geysers, the E ring, and Titan’s upper atmosphere.  An infrared spectrometer derived from the Rosetta VIRTIS instrument would both image Titan’s surface and study the composition of its atmosphere and Encledus’ geysers.  A camera, carried primarily for optical navigation, would also image the dynamics of the geysers.   Both spectrometers would be derived from instruments developed in Europe; presumably the LIFE versions of these instruments would be paid for by their sponsoring European nations, helping to keep the mission’s costs within the Discovery budget.

Conceptual design for the LIFE spacecraft

Editorial Thoughts: This is a sweet concept being proposed by a team that has shown that it can a deliver successful mission within the Discovery budget.

 The opportunity to sample an icy moon’s ocean is unique to Enceladus and would come decades before any mission that would reach pockets of Europa’s oceans.  The instrument suite would replicate that proposed for the Journey toEnceladus and Titan (JET) mission that had the goals of imaging Titan’s surface and improving on Cassini’s measurements of the composition of Titan’s atmosphere and the geysers.  (The imaging spectrometer would make use of spectral windows in Titan’s atmosphere to improve on the coarse images possible with Cassini’s spectrometer.  However, it’s not clear whether the instrument proposed would match the resolution proposed for JET, and it’s not clear how many encounters with Titan would be done.)

The basic techniques planned for LIFE could also be used for a poor man’s comet sampling where a spacecraft would rendezvous with a comet and then repeatedly fly through its jets to collect ice and dust particles at very low velocities. 

LIFE, however, faces several challenges in going from a concept to an approved mission.  First, to keep flight times short, it may have to be selected in the next Discovery competition.  Current and potential future budget cuts may delay that competition until the mission could not be built in time to launch in 2019.  (The article does not discuss fall back trajectories for reach Saturn.  They exist, but would take longer.  Each additional year of flight likely would cost another $7-10M per year in operating costs.)

Another challenge is that the mission would take close to fourteen years to return its paydust.  (Sorry, pun intended.)  Other proposed missions would return science much more quickly.  The instruments on board would provide data while the spacecraft orbits Saturn, but the article doesn’t discuss how extensive the science campaign would be.  If it were as extensive as that planned for the JET mission, then that might make up for the long flight period.

The biggest challenge facing the mission appears to be one that the paper highlights: the facilities that would house and handle the samples returned.  Because life may exist within Enceladus’ ocean, the highest level of quarantine for the samples once they reached Earth would be required.  The paper’s authors write, “the cost for planetary protection alone could exceed the cost estimate for the proposed LIFE mission.  Consequently, the impact of planetary protection costs would have a potential extinguishing effect on LIFE and other sample return missions.”

LIFE is a clever concept; I hope the authors find a way to resolve the planetary protection issue.  This concept is easily in my top two Discovery missions that I'd like to see fly.

I previously wrote about the LIFE proposal here.  You can read the paper's abstract here.

Saturday, December 8, 2012

Thoughts on the Selection of MSL-2020

Much has been written about the announcement that NASA will launch a second Mars Science Laboratory to Mars in 2020.  Reactions have ranged from ecstatic to dumb founded depending on where another Mars rover mission fits in each poster's priorities.

One criticism of the decision has been that NASA has made it clear that caching samples for eventual return to Earth is a possibility, but one that will compete with other scientific opportunities.  There will be only so many dollars and so much mass and volume available for the science payload.  The Decadal Survey report, however, made it clear that another Mars rover was a priority only if that rover the caching element of a series of missions to return samples.

However, it appears that the President's Office of Management and Budget (OMB) also has made it clear that they will not support sample return with its $6-8B price tag.  As one report put it, the James Webb Telescope's cost overruns have soured OMB on multi-billion dollars space ventures.  In other words, the Decadal Survey's number one priority didn't get the sale.  OMB appears to be okay with Mars missions in general, so long as they are no more than modestly expensive.  In fact, Mars offers advantages as a destination -- short flight times, lots of developed technology, good science, proven public appeal.  (My prediction: sample return will occur only if a rover finds organic pay dirt that strongly hints at life, present or past.)

Why didn't NASA turn to the second ranked priority, a Europa mission?  We don't know, but I'll speculate.  The latest, many flyby version of the mission has been costed to approximately $2B, approximately half the cost estimate of an orbiter mission from a few years ago.  I believe that that cost doesn't include the launch, which would add another 10% or more, taking the total cost to more than $700M greater than the cost of MSL-2020 with launch.  NASA's planetary program simply doesn't have the funding for the current version of the Europa mission (or the third priority, a Uranus orbiter).  (When asked when a Europa mission will fly, the head of NASA's science program said that the cost would have to come down to the range of MSL-2020 (presumably including the launch)).

Another option would have been to use the money for MSL-2020 for a New Frontiers mission and a Discovery mission, which would cost approximately the same amount (some additional funding probably would be needed for the launches).  Here, I believe that NASA faced a strategic management decision.  JPL is a unique asset for planetary exploration.  It needs a large mission to keep its skills current and its workforce engaged.  (If you're good enough to work at JPL, lots of businesses would like your resume.)  JPL might or might not win the competitions for the New Frontiers and Discovery mission and the winning missions might not technically challenge JPL.

So, MSL-2020 fits the budget envelope, gives JPL a major project, and will do good science (if not necessarily the top ranked science from the Decadal Survey).  In my former career as a strategic planner for a large high tech company, I think I would have advocated for the same decision in an era of declining budgets.  As a private citizen, I would have preferred to see the Europa mission fly, but MSL-2020 is a good consolation prize.

The announcement left some key questions open.  First, what is the budget for developing the payload for MSL-2020?  Technology advances since Curiosity's instrument selection means that some awesome options are in development.  Taking them to flight readiness, though, may require a substantial budget.  Working in a lab as a breadboard is one thing.  Guaranteed reliability on the surface of Mars within a tight mass and volume constraint is another.

The answer to that first question will help the mission's science definition team tackle the second question: What are the scientific priorities for the mission?  Take proven instruments to a new location?  Deliver next generation instruments?  Cache samples?  I suspect that it may be a combination of the three.  One possibility might be to refly some of the ExoMars instruments (which have the added benefit that they are not paid for by NASA).  I'd personally like to see the ExoMars deep drill flown to get samples from well below the surface at a second site to a sophisticated instrument suite.

Then there is the question of what follows MSL-2020?  This new rover fits within the budget cap only because JPL has a substantial supply of flight ready spares.  Those won't be available for a third MSL.  Does NASA fly additional missions to Mars in the 2020's or turn its attention elsewhere?  Those decisions will need to be made well before the next Decadal Survey is due around 2022.

And finally, what about the rest of the solar system?  By my reading of NASA's projected planetary budgets, MSL-2020 consumes most of the budget once the Mars MAVEN orbiter and InSight landers and the OSIRIS-REx asteroid sample return missions launch.  Without a budget increase, follow on New Frontiers and Discovery missions to other targets may be few and far between.  I hope that Congress' proposals to increase the planetary budget by $100-150M over OMB's last budget proposal to Congress occur.  That small amount per year could breathe new life into these smaller mission programs.

 I have found other good commentary (not all of which I agree with, but it's well reasoned and written) on NASA's decision at the following blogs: Vintage Space,

NASA’s Plan for Mars Makes the Old New Again; Planetary Society,


Thursday, December 6, 2012

Mars Science Laboratory 2

The first week of December every year, I need to decide between attending two conferences, a forest ecology conference and the American Geophysical Union (AGU) conference.  This year, I chose the latter, which was right for my current professional work, but wrong for my advocation, future planetary exploration planning.  At AGU this year, NASA announced that it will fly a second Mars Science Laboratory (Curiosity) rover to Mars.

My conference and a deadline for getting a draft of manuscript for a paper to co-authors has left me with little time this week.  Phil Horzempa has stepped in with his account NASA's announcement. 


 On December 4, 2012, NASA announced that they would launch an MSL-class rover to Mars in 2020.  This decision helps to put some clarity in NASA's Mars Exploration Program after years of uncertainty.  Van has covered some of that turmoil in earlier posts.   

Now that the dust has settled, we can look forward to two new exciting Mars rover missions in the coming decade: ESA's ExoMars 2018 rover and NASA's MSL-2.  Perhaps the split was unavoidable.  To constrain costs, ESA and NASA tried several options to conduct a joint rover mission.  One mission plan was to deliver two rovers (one from each agency) to the same landing site using a modified MSL-1 Skycrane.  The latest incarnation called for one, joint-effort, rover to be delivered to the surface of Mars via the Skycrane.  It seems, however, that the rover may have been more of a European creation since ESA's ExoMars rover was so far along in its development cycle.  This would have meant that JPL's rover team would have little to do for the foreseeable future.  Its expertise has been honed over a decade of Mars missions.   One can conjecture as to why NASA withdrew from cooperation with ESA for the ExoMars rover.  One possibility is that, in return for a large investment of funds, NASA was not going to be able to maintain the team of artisans at JPL who designed and built MSL-1.  They are a national asset.  So, in the end, perhaps the Mars community is better off with this split.  Instead of two rovers, or only one rover, at one site, there will now be two capable rovers exploring two separate sites on Mars. 

A recurrent plea in the planetary community has been for the re-use of common spacecraft, i.e., don't keep re-inventing the wheel.  It is heartening to see that NASA seems to have accepted this idea, at least for now.  Earlier this year, NASA chose the InSight Mars geophysics mission that will re-use the Phoenix lander design.  A lot of effort went into transforming the Mars 2001 Lander into a robust, well-tested soft lander.  That system is now ready to host Discovery-class payloads.  Several ideas were presented at the Mars Concepts Workshop in June.   The Phoenix spacecraft bus is a low-cost means of getting to Mars' surface and we may see it used several times in the coming decades.

MSL-2 not only will benefit from existing designs and testing but also from a supply of flight ready spares built for MSL-1, Curiosity.

This week, NASA chose to fly what is essentially MSL-2.  NASA's chief of the unmanned Science
Directorate, John Grunsfeld, spoke about the decision at this week's AGU meeting.  Apparently, this step has been cleared by the President’s Office of Management and Budget, which approves NASA’s budget proposals

This mission will re-use the aspects of MSL-1 that took much effort to design, develop and test.  These include the large heat shield, the large parachute, the guided entry system, the Skycrane, the MMRTG, and the actuators that caused so much consternation.  Instead of being abandoned, these technologies will be used again.  Therein lies much of the logic behind the reduced cost of MSL-2.  In addition, the JPL team will get to apply lessons-learned from their effort to build MSL-1. 

There has been talk of a solar option for MSL-2.  However, part of the cost savings for MSL-2 means taking advantage of the engineering that has already been done for MSL-1, including the use of an MMRTG.  If a solar option were pursued, then a lot of systems engineering would need to be re-done.  For instance, MSL-1 utilizes the heat from its RTG to warm its electronics during the bitter cold of Martian nights.   For the lowest cost and highest performance, the MMRTG is the best option. 

In fact, there appear to be a number of flight-qualified spares from MSL-1, including an MMRTG, which could be used in MSL-2.  The backup MMRTG seems to have been Pu-238 fueled already.  If true, then that would provide some answer as to the availability of Pu-238 for this mission.  How that fuel would be utilized is still to be determined since there will be a good amount of radioactive decay over the next 8 years before launch.  It may need to be “mixed” with fresh Pu-238. 

The subject of parts obsolescence will be addressed early on.  There are probably parts vendors that either have gone out of business, or who no longer manufacture a given part. 

As to whether this mission could be moved up to 2018 with enough funding, there are other  considerations.  Mainly, 2018 is not that far away and it would be a tight squeeze trying to get the instruments built and tested by then.  A launch in 2020 actually allows a greater variety of instruments to be considered for MSL-2's payload. 

The launch window in 2020 is more favorable than the 2011 window used by MSL-1.  This opens up more of the Martian surface to landing site possibilities.  

A Science Definition Team will be assigned soon to define goals for the mission.  In addition, an Announcement of Opportunity for the instruments should be released this coming summer.  Caching samples for Mars Sample Return is open for debate.  Scientists could decide that resources on MSL-2 would be better utilized for in-situ studies. 

Associate Administrator Grunsfeld pointed out that Mars exploration presents an opportunity for synergy between NASA's manned and unmanned flight programs.  He pointed out President Obama's challenge to fly a manned orbital mission to Mars in the 2030s.   What this means for the MSL-2 mission is anybody's guess since he did not go into detail.  However, the involvement of the agency's manned flight effort could provide some funding support.  It could also mean that some of the payload would be aimed at providing data for future manned missions to the Red Planet.  We already see this with the RAD instrument on board MSL-1. 

Dr. Grunsfled mentioned that they could have flown a 2018 mission instead of the 2020 MSL-2, but, because of the budget, it would have been a down-scaled orbiter.  They decided to wait 2 years to get a surface mission.   The estimated cost of $1.5 Billion for MSL-2 includes a launch vehicle.

With reference to other aspects of NASA's unmanned Science program, he indicated that NASA will continue to try to do a Europa mission.  Costs are getting almost low enough for a new start, but they are not quite there yet.  Van has written several posts reviewing the efforts to design lower-cost Europa missions. 

So, we now know the plan for NASA's Mars exploration over the coming decade.  One of the remaining questions concerns the landing site for MSL-2.  My vote is for a landing in, or near, Mariner Valley.  It would allow for spectacular views and science.  

Sunday, December 2, 2012

ESA Extends Its Mars Planning, But…

Buried among the major announcements from the recently concluded ministerial meeting were other decisions that may impact planetary exploration in the coming decade.  I discussed the two most prominent of these decisions relevant to planetary exploration in my last post; ESA approved the ExoMars joint implementation agreement with Russia, and decided not to proceed with a German-backed lunar lander.

Buried in the news were two other items, one positive for planetary exploration the other not.

I’ll start with the positive news.  ESA has viewed the ExoMars orbiter and rover missions as the first two missions in what would be a continuing set of missions to explore Mars.  The space agency has investigated a number of possible missions for the first half of the 2020’s.  Two missions could have been ESA’s contribution to a joint Mars sample return mission with NASA: a precision lander with a rover to fetch cached samples and/or an orbiter to collect the samples delivered to Martian orbit and bring them back to Earth.    With the delay (potentially indefinite) of NASA’s contributions to a sample return, ESA has shelved these two concepts.

Two other concepts were approved for continued study by ESA for potential launch in 2022 and/or 2024.  The Inspire geophysical network mission would deliver 3 landers to Mars with a seismometer, a weather station, heat flow probe, and possibly other instruments.  (Details have not been released, likely because the concepts appear to be in the earliest planning stages.)  This network of stations would build on the single station geophysical NASA InSight mission (2016) and the Russian geophysical station planned to accompany the ExoMars rover (2018).  If either of these stations still operates if and when the Inspire stations arrive, they would add additional nodes to the network.
Inspire mission concept.  Click on image for a larger version.

The second mission concept would be for a Phobos sample return mission called Phootprint.  Returning a sample of Phobos, which may be accumulated rubble left from the formation of Mars or rubble blasted off the planet by asteroid strikes, is a worthy scientific goal in its own right.  Russia attempted a similar mission, and American scientists have proposed their own equivalent missions several times for the Discovery program.  In addition to the scientific goals, the mission would also develop much of the hardware needed for the eventual Mars sample return orbiter.

Phootprint mission concept.  Click on image for a larger version. 
The decision at the Ministerial mission was to proceed with mission studies to better define the concepts and prepare them to enter development.  At the next Ministerial meeting planned for 2015, ESA’s managers plan to seek approval to begin development on one or both of the missions.

The less positive news for ESA’s science program was that the ministers decided to freeze its budget for the next several years (after a small bump from the contributions of two new ESA members).  Inflation will rob the science program of its purchasing power each year at a projected rate of 2-3% per year.  One news article quoted and ESA science manager as saying that among the options may be to delay to cancel a mission.  Typically, agencies push budget cuts onto the missions least far along in selection or development.  If ESA does this, then either its next medium mission selection may be delayed or the JUICE Jupiter-Ganymede mission may be pushed out.

The ExoMars mission may also impact the science budget.  ESA has only one mandatory program, the science program.  Other programs, such as the one that funds ExoMars and possibly Inspire and Phootprint, are optional programs.  To date, not enough funds have been committed to implement the ExoMars missions.  As a result, ESA management is looking at possible contributions the science program could make.  One idea is to have Russia supply the JUICE launcher.  That would save the science program money late in this decade, but the ExoMars program needs funding mid-decade.  Another idea is for the science program to directly fund a portion of the ExoMars missions, which would conduct excellent science.  With that flat budget, though, the potential for ripple effects to other science missions such as JUICE seem possible.

You can download the presentation where I found the slides above from here.