Sunday, January 25, 2009

Needed: New Mars Exploration Plan

NASA appears to be on track to minimize the impact of the Mars Science Laboratory (MSL) delay and cost overrun to the Mars program. The impact on the Mars program past MSL, however, is potentially large. Key technology development such as precision landing and technologies for Mars sample return apparently will cease for the next two years. NASA’s thoughts on doing a Mars rover on its own in 2016 are gone. With that mission gone, NASA will face the problem of how to keep its teams with rover expertise together. NASA also faces the problem of ensuring that an orbiter is available to act as a telecommunications relay for future landed missions.

The cumulative impacts of these challenges are well understood in the planetary science community. The Planetary Science Subcommittee (PSS), which is a group of scientists that advises NASA on its planetary program, has called on NASA to formulate a new Mars exploration roadmap.

NASA’s Mars program had been focused on a Mars sample return (MSR) mission in the early to mid-2020s. Given the suspension of the development of key technologies, that date appears to be problematic. The estimated $3-5B price tag (to be split among several space agencies) is also problematic. (Editorial comment: MSR has been studied for the last 20 years at least. The technology challenges are significant. I suspect that costs at or greater than $5B are probably most realistic, but have no inside knowledge.)

It will take time for a new Mars program to gel. In the meantime, based on past exercises in developing Mars roadmaps, we can expect that the roadmap issues to revolve around several opportunities, challenges, and philosophical viewpoints.

Opportunities

What scientists would like to do at Mars after MSL and the MAVEN (upper atmosphere-oriented orbiter to launch in 2013) has been established in a number of planning exercises (read the results of the most recent here and here). The following paragraphs summarize the key opportunities that have been identified.

Mars has shown itself to have around a dozen distinct terrain types that show evidence of past water. It would be desirable to explore several of them with rovers. (Opportunity is exploring one type (with a limited instrument suite); MSL will explore another; ESA’s ExoMars (2016) will presumably explore another.) NASA and other space agencies could fruitfully spend a decade or more sending rovers to interesting spots on Mars. The rovers also could collect and cache samples for a future MSR.

For as long as MSR missions have been studied, a parallel goal has been to place a network of stations around the Martian surface. Continuous measurements of seismic activity, meteorology, and heat flow from multiple stations would address key questions about the interior and atmosphere of Mars.

Rovers and network stations require an orbiter to act as a telecommunications relay if significant amounts of data are to be returned. The Mars Odyssey and Mars Reconnaissance Orbiter (MRO) serve that role now. Mars Express and MAVEN can also acts as relays, but they have highly elliptical orbits that reduce their effectiveness for this role. NASA seems to believe that it needs to put a new, highly capable orbiter in place every 8-10 years to ensure a high probability of an operating orbiter being in place.

Once an orbiter is added to the roadmap, the question becomes which science instruments to also add. NASA has decided to focus the next large orbiter on climatology and atmospheric chemistry. Follow on orbiters could study the surface with a variety of instruments.

The ultimate goal of Mars missions for almost two decades, though, has been to return carefully selected samples from the Martian surface. That would allow the incredibly sensitive instruments in Earth laboratories (that couldn’t be replicated as spacecraft instruments) to be brought to bear in the studies of Mars. We have samples of Mars delivered as meteorites, but we don’t know where they came from and they don’t represent the high priority sites scientists want to sample.

Challenges

Money is the obvious challenge. A mid-sized rover (larger than MER, smaller than MSL) could cost $1.6B, a network mission $1.2B, a Mars orbiter $1.1B, and the MSR mission $3.5B (although I’ve read estimates in articles that go up to $5B). (Cost estimates from this document and are real year, i.e., inflated dollars from this document.) All this adds up to $3.9B without MSR and $8.4-10.4B with MSR. The team that most recently examined options for NASA’s Mars roadmap assumed annual budgets in the $450-550M (current year dollars) range. (It appears that the budget was assumed to inflate by 3% a year.) Even with inflating budgets (and NASA’s budget in recent years has semi-regularly been frozen at previous year’s levels) this roadmap is a 15-20 year plan, or 8-10 Congresses, 4-5 Presidential elections, and probably an economic cycle or two.

NASA needs to keep its Mars entry, landing, and descent and rover technology teams together. That is tough to do without a major active program. To deal with this problem, the plan (it appears to have been a working plan rather than a formally approved plan) before the MSL slip was to launch a rover mission in 2016 and an orbiter in 2018. Post MSL slip, NASA cannot afford its own rover in 2016 and will do a joint rover mission with ESA. (NASA will be the junior partner, so I don’t know if this mission would serve to keep key technology teams together.) Doing a rover mission in 2018 may keep the technology teams together, but pushes the replacement for what will then be very old orbiters to 2020.

NASA’s previous roadmap had the goal of doing the MSR mission as soon as possible. That mission, though, requires new technologies be developed. That new technology development will be suspended to pay for the MSL cost overruns. That means that NASA will have to restart those efforts in 2-3 years and then allow the new technologies to reach maturity before it can fly MSR.

Philosophy

Every mission roadmap has certain assumptions built into it that I refer to here as a philosophy. One such assumption is that Mars will retain the high priority (and high proportion of NASA’s planetary budget) that it has now.

Another key assumption is that progress in understanding Mars is best served by flying MSR at the earliest opportunity. Another approach would be to wait an additional 5-10 years. In that time period, fly multiple rovers that increase our knowledge of the surface and ready-to-return caches of samples. That way, proponents of this view hold, we have a better chance of returning the most important sample. The technology for MSR could continue to mature in parallel. Those favoring MSR at the earliest date prevailed in the previous roadmap discussions.

Another key assumption is the level of international cooperation. ESA, JAXA, and Russia, for example, can clearly mount sophisticated missions to Mars. Other nations can or will be able to soon send missions to Mars. ESA and NASA are planning to cooperate on a 2016 rover mission. Discussions are underway to make MSR a multi-agency effort. International efforts, though, are complicated and can tangle up missions in the domestic politics and budgets of each partner. Cooperation will be done, but how much does a space agency want to make its Mars roadmap dependent on partners?


It’s clear that the teams developing NASA Mars roadmap and partner teams at other agencies will have a lot to ponder to try to put the puzzle pieces together into a coherent, feasible, and saleable roadmap.

5 comments:

  1. Wouldn´t it be an option to refly the MER mission? It should be cheaper to rebuild a flight proven vehicle than constructing a completely new one from scratch. So by sending MER-identical rovers, maybe with a slightly different instrument suite, to several high priority landing sites would make sense to me. They could scout the area and if they make a significant discovery a bigger rover with a more powerful set of instruments could follow.

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  2. What you suggest is a viable strategy.

    I'll explain the thinking as I understand it that has led to a plan for a mid-sized rover.

    The MER rovers have limited scientific capability designed to identify materials that have been modified by water ("follow the water"). The MERs have achieved that and the Mars Express and Mars Reconnaissance Orbiter have identified many locations with water modified materials. The new goal is to search for organics, which require new instruments and hence more capable rovers.

    In addition, the MER's descent and landing system limited the range of landing sites. As I recall, it was hard to find two good sites. A future rover needs advanced entry and landing systems to expand the range of landing sites.

    Once these two issues are addressed, a larger and more capable rover (and entry and descent system) is needed.

    On the other hand, I know some geologists who focus on Mars who would be happy to have MER rovers put down in interesting geological locations, even if we aren't looking for organics.

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  3. Ok, i understand the thinking. Thanks for your answer.
    By the way great blog! I think I´ll stick around here for a while if you don´t mind :)

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