'Follow the water' emerged as the mantra for NASA's Mars programme in the late 1990s. The intent of the Mars Exploration Rover (MER) missions was essentially to act as robotic field geologists, to map the rocks and soils around their landing sites with specific attention to minerals and formations that might indicate the presence or history of liquid water. These rovers were considerably larger than Sojourner. Although loss of solar power due to dust deposition on the arrays was expected to limit their lifetime to a few tens of days, both rovers are still operating at the time of writing, over 1.5 Martian years since their arrival, and have traversed a combined total of over 16.2km. Of particular note are the number and quality of images returned (Figure 17.9). For more details, see the case study, Chapter 27.
Prime contractor Launch site, vehicle
Launch date Arrival date Landing site co-ordinates End(s) of mission(s) Mass(es)
Search for and characterize a variety of rocks and soils that hold clues to past water activity Determine the distribution and composition of minerals, rocks and soils surrounding the landing sites Determine what geologic processes have shaped the local terrain and influenced the chemistry Perform 'ground truth' of surface observations made by Mars orbiter instruments Search for iron-bearing minerals, identify and quantify relative amounts of specific mineral types that contain water or were formed in water Characterize the mineralogy and textures of rocks and soils and determine the processes that created them Search for geological clues to the environmental conditions that existed when liquid water was present and assess whether those environments were conducive to life
JPL/Cornell ETR, Delta 2 (7925) Spirit (MER-A) 10/06/2003 04/01/2004 14.57° S, 175.47° E (Gusev crater)
Opportunity (MER-B) 07/07/2003 25/01/2004 1.95° S, 354.47° E (Meridiani Planitia)
Primary mission 90 days; still operating into 2007 Entry mass MER-A 827 kg, MER-B 832 kg. Backshell & parachute 209 kg, heat shield 78 kg. Landed mass 540 kg incl. lander platform 348 kg and 185 kg rover.
Mars Exploration Rovers
Delivery architecture Thermal aspects
Landing speed(s) Active operations
(deployments, etc.) Key references
• Pancam panoramic camera (Bell)
• APXS alpha-particle-X-ray spectrometer (Rieder)
• Mossbauer spectrometer (Klingelhofer)
• Microscopic imager (Herkenhoff)
• RAT rock abrasion tool (Gorevan)
• Descent camera
• Navigation camera
• Two hazard cameras
The Project Scientist is Steven Squyres
Separation from cruise stage on approach
Warm electronics box; thermal control via gold paint, aerogel insulation, heaters, thermostats and radiators
Solar cells (gallium indium phosphide/gallium arsenide/ germanium) and batteries; peak is 100 W near local noon early in mission. Power varies with time of day, season and rover tilt; dust accumulation periodically cleared by wind gusts
Two-way DTE with high or low-gain antennas or by UHF relay (128 kbits s— via Mars Global Surveyor, Mars Odyssey or Mars Express orbiters
Incorporates IMUs in rover and backshell. Entry at 5.55 km s— 1 (relative) or 5.65(A), 5.72(B) km s— 1 (inertial), flight path angle —11° . 2.65 m diameter, 70° blunt half-cone, ablative SLA-561 aeroshell. Spin-stabilised. Max deceleration 6.3 g. Parachute deployment at 8.6 km altitude, 131 m s— 1 Heatshield separation 20 s later. Lander lowered from backshell on bridle 10 s later. Radar altimeter acquires ground at 2.4 km altitude. Descent images acquired for DIMES (descent image motion estimation system). Airbags (Pathfinder configuration but strengthened) inflated 8 s before landing, 284 m altitude. Retro-rockets and TIRS (transverse impulse rocket system) fired 6 s before landing, 134 m altitude. Bridle cut 3 s before landing, 10 m altitude. Initial landing 354 s after entry. Bounces and rolls up to 1 km.
Rover 'stand-up', solar array and HGA deployment, rover operations (av. speed 1 cm s— \ max 5 cms— Robotic arm
J. Geophys. Res. 108(E12), 2003; Science 305(5685), 2004 and 306(5702), 2004; Squyres, 2005; http://mars.jpl.nasa.gov/; http://athena.cornell.edu/. See also Mars Exploration Rover Landings Press Kit, NASA, 2004
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