Workshop on Mars 2001 2549.pdf

MARS SURVEYOR PROGRAM 2001 MISSION OVERVIEW. R. Stephen Saunders, Jet Propulsion Lab, MS 180- 701, 4800 Oak Grove Dr., Pasadena, CA 91109 Ronald.S.Saunders@jpl.nasa.gov.

The Mars Surveyor Program 2001 mission to Mars was struments including a robotic arm with camera. The arm initially a key element in the Mars sample return sequence will deploy a Moessbauer spectrometer to determine the of missions. A capable rover, carrying the Cornell Athena oxidation state of iron in the soil or rocks. The arm will be instruments, would be placed on Mars to roam over several used to deploy the rover and dig to a depth of up to 0.5 m to kilometers, select samples, and place them in a cache for deliver soil to the Mars Environmental Compatibility As- return by a subsequent mission. Inevitably, budget con- sessment Experiment (MECA), the soil and dust characteri- straints forced descopes. At one critical point, the landed zation experiments. The Mars In Situ Propellant Precursor payload consisted only of the HEDS (Human Exploration Experiment (MIP) will perform experiments to assess tech- and Development of Space) payloads selected for testing nology needs for in situ propellant production and produce environmental properties of the surface for future human oxygen from the Martian atmosphere. The lander counter- exploration. Then Congress intervened and put back some part to the orbital radiation experiment will allow assess- of the funding that had been deleted. NASA Headquarters ment of how the radiation hazards on the surface might be next redefined the payload to include as many of the Athena mitigated by the atmosphere or other factors. The lander instruments as possible, to be distributed between the will carry a panoramic camera bore-sighted with a thermal lander deck and a Sojourner class rover. This payload would emission spectrometer (PanCam/MiniTES). This combina- then be placed on a modified version of the Mars Polar tion will provide guidance to the rover and allow compari- Lander (MSP’98) rather than on the much larger, and more son between the mineralogical data from MiniTES and the expensive, lander that had been originally designed for the elemental data from the APXS. The lander will carry a de- mission. With this functionality restored the ’01 mission scent imaging system (MARDI) to provide nested images remains an important and pivotal element of the Mars Sur- from parachute deployment down to the surface. The basic veyor Program. It completes the Mars Observer objectives flight systems for the orbiter and lander use MSP’98 heri- with the gamma ray spectrometer mapping. This mission tage. There will be extensive outreach activities using the will largely complete the global characterization phase of rover and the robotic arm. Students all over the world will Mars exploration and mark the beginning of focused surface participate in Red Rover Goes to Mars, a program that will exploration leading to return of the first samples and the be carried out by the Planetary Society. search for evidence of past martian life. MSP’01 also is the first mission in the combined Mars exploration strategy of With safety as the first consideration, the process of site the HEDS and Space Science Enterprises of NASA. This selection for the Mars 2001 lander is driven by science and mission, and those to follow, will demonstrate technologies heavily constrained by the Mars environment. NASA has and collect environmental data that will provide the basis established a long-range strategic framework for Mars ex- for a decision to send humans to Mars. The NASA explora- ploration. The Mars Surveyor Program will explore Mars tion strategy for Mars includes orbiters, landers and rovers along three thematic lines: (1)search for life, (2) understand launched in 2001 and 2003 and a sample return mission to climate history, and (3) map resources including geology be launched in 2005, returning a sample by 2008. The pur- and geophysics. pose of the rovers is to explore and characterize sites on Mars. The 2003 and 2005 missions will select rocks, soil The selection of a landing site will be constrained by cost and atmosphere for return to Earth. driven requirements placed on spacecraft design by the Martian environment. The basic requirements on the land- Potential landing sites for 2001 include ancient highlands ing site for the Mars Surveyor 2001 mission are as follows: where there might have been subsurface hydrothermal envi- ronments that have been excavated by recent impacts, and (1) The landing site latitude shall be within the latitude ancient channels and lakes. In addition to the GRS, the 2001 region from 12°S to 3°N. orbiter carries a thermal emission imaging system (2) The maximum elevation of the landing site with re- (THEMIS), consisting of a spectrometer and imager that spect to the Mars reference ellipsoid shall be less than will map the mineral abundance at selected sites, and a or equal to 2.5 km. 99% of terrain within the predicted radiation experiment, MARIE, to assess radiation hazards to 3-sigma landing footprint ellipse must meet this re- humans. The rover is similar to the 1997 Pathfinder So- quirement. journer rover, with an upgraded Alpha Proton X-ray Spec- (3) The surface pressure at the landing site must be less trometer (APXS) experiment that will be carefully cali- than 10.66 mbar (and winds below 20 m/s ) to open brated under Martian conditions on Earth, and again on solar panels, This surface pressure exists at an eleva- Mars shortly after landing. The APXS will perform ele- tion of roughly -3 km . mental analysis on rock and soil samples for all elements except H and He. The rover cameras will also be calibrated. The following is a summary of the top level considerations The lander carries a suite of Space Science and HEDS in- for landing site location. Workshop on Mars 2001 2549.pdf

MSP’01 MISSION OVERVIEW: R. S. Saunders

cumulation. Assuming this rate of degradation without Lander lifetime as a function of landing site latitude other compensation, the Rover would ‘die’ after 5 months at and lander tilt: any latitude. A more detailed assessment of dust accumula- tion effects is currently underway. Latitude 0° Tilt 16° Tilt 12°S 92 days 84 days In summary, safety considerations will be the primary factor 3°N 111 days 107 days in site selection. The collective wisdom of the NASA sci- ence community will be tapped to make the right decision. Note: The Mission Requirement for Lander lifetime is 21 All of this will be constrained by the realities of the Mars days with a planned mission of at least 90 days. environment. For more detailed and complete description of the constraints, see Golombek (this conference). Landing Accuracy: 3°N Landing footprint 26 km end-to-end,10 km cross- The Mars '01 lander payload is an excellent one for studying track (99-centile). soils. Soils can be found virtually anywhere on Mars, so the 12°S Landing footprint 20 km end-to-end, 12 km mission will do substantial new science in the event of any cross-track (99-centile). safe landing. Safety is therefore of the utmost importance.

Consider the capabilities of the vehicle and the payload Landing Risk: (particularly limits on landing accuracy and limited mobil- ity). Given the instrument capabilities and those physical The project requires that the maximum fractional area of the limits, the best new science is likely to come from landing landing site covered by rocks shall be no greater than 0.12, somewhere within ancient highland crustal materials. including uncertainties. Areas with excessive dust are to be avoided. The minimum acceptable rock abundance is 0.05. Within the above engineering and scientific constraints, the The maximum landing site surface slope the lander can final site should be chosen so as to: tolerate is 10°. The project requires that the selected land- - maximize total mission duration ing site shall provide a 0.95 probability that the terrain - maximize rock abundance slope upon landing does not exceed 10°. - maximize large-scale topography in the visible distance, particularly if Power considerations could be an important factor in site it exposes stratigraphy selection for the rover. During the Mars Pathfinder mission, - maximize the chances of finding aqueous minerals dust accumulation was observed on both the rover and lander solar panels. Solar panel energy production degraded by a factor of 0.2% per sol, apparently due to such dust ac-