Athena Review: Space Exporation and Remote Sensing: Mars Polar Lander

Athena Review: Remote Sensing and Space Exploration

The Mars Polar Lander

In December, 1999, after days of attempts by NASA engineers to establish contact with the Mars Polar lander had yielded nothing, the spacecraft was considered lost during landing. While NASA's programs of Mars explorations have had many successes, it appeared the craft burned up in entry through the Mars atmosphere.

NASA’s Mars Polar Lander was intented as the second installment in NASA's long-term program of robotic exploration of Mars managed by the Jet Propulsion Laboratory (JPL), a division of the California Institute of Technology, for NASA's Office of Space Science in Washington, D.C. JPL's industrial partner is Lockheed Martin Astronautics in Denver. These explorations began with the 1996 launches of the currently orbiting Mars Global Surveyor and the Mars Pathfinder lander and rover, and also included the recently lost Mars Climate Orbiter.

[Fig.1: The Mars Polar Lander, with instruments labelled (NASA/JPL/Caltech).]

Like the successful Mars Pathfinder spacecraft in 1997, the Polar Lander was designed to travel straight into the Martian atmosphere, using an aeroshell and parachute to slow its initial descent. Once the heat shield was jettisoned, a camera was set to record the landing site as the spacecraft descends. These images would be transmitted to Earth after landing. The Polar Lander did not use airbags as did the larger Pathfinder lander, but employed onboard guidance and retro-rockets to make a soft landing. About 10 minutes before touchdown, the spacecraft was designed to release the two small basketball-sized microprobes called Deep Space, meant to crash and penetrate into the Martian surface, then to communicate with the orbiting Global Surveyor. These two microprobes were also, unfortunately, lost during descent, with no data transmitted.

The spacecraft was intended to land on layered terrain near the edge of Mars' south polar cap, during relatively mild weather conditions a few weeks after the seasonal carbon dioxide frosts have disappeared. Instruments on the lander were to record and analyze data on surface materials, frost, weather patterns and atmosphere. The lander's primary goal was to investigate Mars' current water resources by digging into the layered terrain at the poles, using a 2-meter-long robotic arm whose camera would show the surface material and reveal fine- scale layering. The robotic arm could also place soil samples in a thermal and evolved gas analyzer (TEGA), which would heat the samples to detect water and carbon dioxide. An onboard weather station, meanwhile, would take daily readings of wind temperature and pressure, and seek traces of water vapor. The Martian surface surrounding the spacecraft was to have been recorded by a stereo imager. Also onboard the lander is a light detection and ranging (LIDAR) experiment provided by Russia's Space Research Institute. The instrument detects and determines the altitude of atmospheric dust hazes and ice clouds above the lander. Inside the instrument is a small microphone designed to record the sounds of wind gusts, blowing dust, and the mechanical operations onboard the spacecraft itself.

The carefully thought out experiments of the lander weredesigned to begin shortly after the expected landing on December 3, 1999, and to operate on the surface of the red planet for 60 to 90 Martian days (24 hours, 37 minutes each) through the planet's southern summer, or into February or March, 2000. Its mission would end when the spacecraft can no longer withstand the cold and dark of lengthening nights, and the return of the Martian seasonal polar frosts.

Unfortunately, though the experiments were designed so well, the mechanics of the landing, with all its complex telemetry and time delay problems, were unsuccessfully executed by what NASA had hailed as a "low budget" Polar Lander team.

[For more information on NASA and JPL/Caltech, see http://www.jpl.nasa.gov

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