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 1.5 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.