Wednesday, December 22, 2010

Compelling Planetary Science Missions: Mars Geophysical Network and Mars Polar Climate Missions

This continues a series of posts inspired by a similar set of posts at Future Planetary Exploration blog selecting the 5 most compelling missions from the Planetary Science Decadal Survey list.  This follows 3 reviews of potential Mars missions.  Here I make my personal selection from that list.

After some consideration, I decided not to include the MAX-C rover in my list of most compelling Planetary Science missions from the Decadal Survey list.  The mission science is compelling, the raw idea of a rover exploring and selecting Martian samples for return to the Earth is right, the mission is in a reasonably advanced state of development, and it has international cooperation and multi-mission implications.  Thus, it is not to be set aside lightly, and as you'll eventually see I'm not setting it aside lightly.  However, the estimated mission cost is just too much for me, and I'm worried about the new rover delivery mechanism.  Demonstration of the Sky Crane at Mars, combined with validation that a Network Pathfinder could be added to the mission with minimal risk and cost, might be enough to squeeze MAX-C into my top 5 most compelling missions, but those things haven't happened yet.

It's all about opportunity cost and risk.

This is easy for me to do because I haven't been waiting for those Mars samples for half a career.  I suspect that if I had been, I'd have made a different choice.

Having dealt with MAX-C, the question now becomes which Mars mission will I choose for my "most compelling" list - Mars Geophysical Network or Mars Polar Climate Mission?

The answer: All 3 of them.  Or all 4 of them.

I think I'd better explain.

In the last couple posts, I described a number of potential Mars Polar Climate and Mars Geophysical Network mission options.  Some key options include:

2 Mars Geophysical Network powered landers - $1,015M (New Frontiers)
1 Mars Geophysical Network powered lander - $720M (Discovery)
Mars Polar Climate Orbiter - Climate and Weather - $613M (Discovery)
Mars Polar Climate Orbiter - Energy Balance and Composition - $629M (Discovery)
Mars Polar Climate Orbiter - Polar Science - $866M (New Frontiers)
Mars Phoenix Class Lander - Sightseer - $751M (Discovery)
Mars Phoenix Class Lander - Subsurface Sampler - $860M (New Frontiers)
MER Class Rover - $1,049 (New Frontiers)

My selection for the 3rd most compelling mission from the Decadal Survey list is a combined Mars Polar Climate mission consisting of an orbiter and a lander.  Thus 2 of the Mars Polar Climate options above would be selected.  These should be mutually supportive with remote sensing and ground truth in-situ observations of the same physical entities.  The orbiter can also help the lander through its telecommunications capability (which would be supplied by NASA to the mission as standard procedure for Mars orbiters).

I selected the Mars Polar Climate mission for a variety of reasons.  It addresses science questions about climate that are relevant to our situation on Earth.  Mars offers another extreme environment and history to compare to Earth, just as Venus does as explained in the Future Planetary Exploration blog's choice of a Venus Climate mission as the second compelling mission.  In addition, the mission has potential as an astronaut scout sort of operation (i.e. a science substitute for a robotic precursor mission).  The missions could be a good fit for collaboration with any funding that may appear in NASA's Exploration Technology Demonstration or Robotic Precursor efforts.  With additional mass budgets, they offer plenty of opportunity for super-charging with instruments from non-NASA space agencies, too.  Of course the missions go after big Planetary Science questions about Mars, too.  The missions follow up on technology and science demonstrated and advanced in earlier Mars missions, so the risk of cost overruns, mission failure, or unimportant science is lower than it otherwise might be.  Also, assuming no cost overruns, the missions are affordable.  For example, if we select the "Climate and Weather" orbiter as a revival of the "Mars Scout" line, and also select the subsurface sampler as our New Frontiers mission (since these Decadal Survey selections are supposed to be for New Frontiers and Flagship missions), we are only (if I may use that word when talking about huge amounts) at $613M + $860M = $1,473M.

My selection for the 4th most compelling mission is the Mars Geophysical Network Mission.  Since the science value of this mission goes up considerably with 2 landers rather than 1 lander (as, for example, the seismometers will return much more valuable data with simultaneous, time-synchronized data collections at different locations than the mere location of 2 landers at 2 distinct geographical locations would suggest), I'll select the $1,015M New Frontiers powered landing option with 2 landers.  Still the 3 missions combined are $2,488M, which isn't much more than the estimated MAX-C cost.  Had I selected the single Geophysical Network lander delivered on a Falcon 9 rocket (i.e. the Discovery class version), the 3 missions would cost less than MAX-C.  Like the Mars Polar Climate missions, the Mars Geophysical Network Mission addresses fundamental Mars science, gives lots of opportunities for international collaboration and thus more capable missions, and presents interesting possibilities for collaboration with potential NASA Exploration Technology Demonstration and Robotic Precursor efforts.

I've picked particular variants from the selections above, but I think the basic idea would work with other choices.  For example, we could switch the polar deposit Subsurface Sampler to the Mars Polar Climate rover (exchanging instrument mass for mobility).  This might be justified on grounds of mission science return or keeping our ability to develop Mars rover missions.  We could switch back and forth between Discovery and New Frontiers levels as funding allows and external participation (or lack thereof) encourages.  Call it the Flexible Path at Mars.

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