JPL: Mars Polar Lander Update

Brian D Williams (
Tue, 9 Nov 1999 10:38:54 -0800 (PST)


               Mars Polar Lander Mission Status
                      November 8, 1999

     Engineers say they are close to resolving a potential 
problem on NASA's Mars Polar Lander uncovered by the NASA panel appointed to investigate the recent loss of the Mars Climate Orbiter.

The NASA investigation board, chaired by Art Stephenson, director of NASA's Marshall Space Flight Center, Huntsville, Ala., found that cold temperatures could affect the performance Mars Polar Lander's descent engine, which begins firing at about 2 kilometers (about 1 = miles) altitude during the descent to Mars surface. As a result of the finding, a team of engineers at NASA's Jet Propulsion Laboratory, Pasadena, Calif., has developed procedures to warm up the engine system prior to firing. In addition, the team has analyzed descent engine performance at a range of temperatures to assess its predicted performance upon arrival.

Updated operations plans call for turning on propellant system heaters several hours prior to the spacecraft's entry into Mars' atmosphere. This strategy will increase the expected temperature of the descent engines to 8 degrees Celsius (46.4 degrees Fahrenheit). Analysis indicates that at this temperature, the engines will perform as designed.

Ground-based testing of an actual descent engine was conducted last week at the descent engine manufacturer's test facility. The initial test results suggest acceptable engine start-up performance is achieved when the catalyst bed, where engine firing initiates, is at temperatures as low as -20 degrees Celsius (-4 degrees Fahrenheit). More ground-based test firings are scheduled to better characterize engine performance at various temperatures.

On Wed., Nov. 10, NASA will release the investigation board findings on the loss of Mars Climate Orbiter and recommendations for the Mars Polar Lander mission, which lands on Mars Dec. 3.

Mars Polar Lander successfully performed its third course correction on Oct. 30, and another maneuver to fine-tune the flight path is scheduled for Nov. 30. The spacecraft remains in good health.

On Nov. 1, the spacecraft's landing radar system was turned on for the first time since launch and successfully performed its internal self-test. Test results show the unit's integrity is sound, and all electrical functional test results were within the expected range. The landing radar will not be turned on again until landing day. The radar system is activated just after separation of the lander's heat shield, following parachute deployment, and begins searching for the surface. Once the system recognizes the Martian surface, it must generate data for approximately 60 seconds, providing altitude and velocity measurements to the spacecraft's onboard guidance system for powered descent.

Mars Climate Orbiter was lost as it was entering orbit around Mars on Sept. 23. The orbiter and lander are part of a series of missions in a long-term program of Mars exploration managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, Washington, D.C. JPL's industrial partner is Lockheed Martin Astronautics, Denver, Colo. JPL is a division of the California Institute of Technology, Pasadena, Calif.