Planning for Post MSL Mars Begins

This week, NASA’s scientific advisory group on future exploration of Mars, MEPAG, will meet and begin planning a new roadmap for exploring Mars. The previous roadmap had tentative plans for a sophisticated solar powered rover in 2016 followed – with the order to be decided – by a Mars Science Orbiter (MSO), a network mission, and a Mars sample return mission. The cost overruns on the 2011 Mars Science Laboratory require a new roadmap. The funds will not be there to carryout the previous roadmap.

The timing for a new roadmap fits will with the schedule for the planetary Decadal Survey in progress that will lay out the priorities for mission for the next decade. MEPAG’s roadmap will serve as its input to the Decadal process and will have to compete with other good roadmaps from other disciplines. If my back of the envelope analysis of the budget options for the next decade were correct, there is not likely to be funds for as ambitious a campaign of missions as there has been for the last decade and a half. It could be that the Mars community may get just one moderate sized ($600M – 1B) and one small ($400 – 500M) mission. Contrast that with the Mars Global Surveyor orbiter (1997), Pathfinder (1997), Mars Odyssey (2001), Spirit and Opportunity (2004), the Mars Reconnaissance Orbiter (2006), Phoenix (2008), and the planned Mars Science Laboratory (2011). (There were also two missions launched and lost in 1998. Europe also is exploring Mars with its Mars Express, but that is funded by a different space agency.) However, if Mars receives less in the next decade, it will be so that other destinations such as Jupiter and Europa can be reached.

Traditionally, presentations from the MEPAG meetings are posted to the web a few days after the meeting. This time, one presentation has been posted ahead of the meeting on options for a Mars Science Orbiter in a post MSL overrun world. (Since this presentation is pre-meeting, it may change between the time of this blog and the meeting.) This presentation gives an idea of the types of belt tightening that the Mars community may look at across the roadmap. (See here for the most recent description of the previous MSO plan.) MSO has a high scientific priority since it would follow up on the discovery of short-lived methane in the Martian atmosphere, which could be the result of either on-going geologic activity or life.

NASA has planned a major science orbiter, MSO, for sometime in the mid-2010s for some time. The mission has had three goals, listed below in priority order. (Unless otherwise noted, quotes are from the presentation.) I also list the instrument(s) foreseen for each goal with cost estimates from a previous 2007 MSO report ( Report from the 2013 Mars Science Orbiter (MSO) Second Science Analysis Group.) The instrument costs and weights were estimates that may have changed by now.

1a. “Measure concentrations of a suite of trace gases of photochemical and radiative importance, including methane and potential molecular species related to characterizing its origins and loss (life cycle process); emphasis is on detection (bright source, limb path, spectral survey) and low-spatial resolution mapping.” This priority follows up on the detection of short-lived methane gas in the Martian atmosphere. Key goals are to nail down the amount of methane and other short-lived gases and their sources. Instrument: Solar occultation FTIR spectrometer (42 kg, $35M)

1b. “Measure those aspects of atmospheric state needed to constrain photochemical and dynamical (transport) models (T, dust) and to provide context for trace gas detections (dust, H₂O); emphasis is on extending climate record used to validate climate simulations.” This goal both places the detection of trace gases in context and extends our knowledge of the Martian atmosphere. Instruments: Wide-angle camera (MARCI-like) (1 kg, $1M); Thermal-IR spectrometer (TES-like) (10 kg, $12M).

2. “The second priority is to improve temperature and water vapor measurement accuracy in the presence of dust and to better characterize atmospheric transport by making wind measurements and mapping temporal variations of key transported species (e.g., CO) and methane with good spatial resolution.” Instrument: Sub-millimeter spectrometer (35 kg, $35M)

3. “Investigate surface changes as recorded in surface properties and morphologies due to seasonal cycling, aeolian movement, mass wasting, small impact craters, action of present water.” This goal would be met through imaging of the Martian surface at 1 m or better resolution. Key imaging targets would be the polar layered terrain; aeolian features, gullies, avalanches, and dune movement; and formation of small impact craters over time. Instrument: 1 m camera (20 kg, $25M)

4. “HiRISE-class imaging (~30 cm resolution) for certification of future landing sites.” This would involve re-flying a camera with similar capabilities as the HiRISE instrument on the Mars Reconnaissance Orbiter. Instrument: (65 kg, $45M)

An additional goal, to carry a telecommunications package to communicate with future landers also was assumed. Also, only one high resolution camera would be flown. If budgets allowed, the HiRISE-class camera would replace the 1 m resolution-class camera.

The full up MSO mission was at one time estimated at over $1B in real year (i.e., inflation adjusted) dollars. Its cost in today’s dollars would probably be $800 – 900M if I’m doing my back of the envelope math right. A mission with those costs may no longer be affordable. The presentation offers two alternative missions.

MSO-min[imum] would fulfill only the 1a and 1b priorities (plus fly the telecommunications package.) MSO-lite would add priority 2. With either of these proposals, this becomes a strictly atmospheric (plus communications relay) mission. In this case, the orbit would be a high-inclination orbit (~74 degrees) optimized for repeated solar occultations of the atmosphere above all locations of the Martian surface (except the polar regions). The solar occultation FTIR spectrometer uses the bright light of the sun to detect trace gases in the atmosphere.

Both of these missions would forgo the high resolution camera (and the near polar orbit that would optimize global surface imaging at the expense of an optimized distribution of solar occulations). The issue for carrying a high resolution camera is not just the cost of the camera. The camera requires an ultra-stable platform (no jittering of the camera allowed!), precise pointing capabilities, significant data storage, and a hefty communications system to send the data back to Earth. The 2007 reported noted, “Unfortunately, achieving spatial resolution of 5-10 cm, under current state of the art, increases both mass and cost significantly, and largely becomes the only scientific goal for MSO. Also, spacecraft stability could become the limiting factor in resolution rather than the telescope.” Lower resolutions (even 1 M) bring similar problems.

The MEPAG presentation doesn’t list costs for MSO-min or MSO-lite. The MAVEN orbiter that will study the upper atmosphere of Mars, however, will cost $480M. It seems reasonable to assume that this represents a base cost estimate for an MSO mission with each additional goal met perhaps driving the cost incrementally higher.

With the discovery of methane in the Martian atmosphere, MSO is likely to be a high priority. MEPAG may have a difficult time deciding when to recommend its flight. NASA has said that it would like to contribute up to $400M to ESA’s 2016 ExoMars rover. If it does, it seems unlikely that it will have funds to fly MSO in the same launch opportunity. In that case, it may be 2018 or 2020 before MSO launches.