SPACE.com -- Panel Uncovers Potentially Fatal Problem on Polar Lander


	Panel Uncovers Potentially Fatal Problem on Polar Lander By Andrew Bridges Chief Pasadena Correspondent posted: 08:27 pm ET 08 November 1999

Panel Uncovers Potentially Fatal Problem on Polar Lander

PASADENA -- A NASA board appointed to investigate the loss of the Mars Climate Orbiter has uncovered a problem that if left uncorrected could doom its sister mission, the Polar Lander, as it makes its powered descent to the martian south pole on Dec. 3.

The investigative board, led by NASA Marshall Space Flight Center Director Art Stephenson, found that cold temperatures could cause the Landers descent engine, which will begin firing when the spacecraft is just 1.5 miles (2 kilometers) above the Martian surface, to malfunction.

The engines are designed to fire for about 40 seconds, slowing the Lander to a velocity of about 5.4 mph (8.6 kph) for its three-legged touch-down.

Were the engines to misfire, or not fire at all, the Lander - slowed only by its parachute - could hit the surface at 180 mph (288 kph), destroying it.

To avoid such a scenario, engineers at NASAs Jet Propulsion Laboratory have developed a plan to use propellant system heaters to warm the engine several hours before the spacecraft enters Mars atmosphere. The plan will increase the temperature of the descent engines to 46 degrees Fahrenheit (8 Celsius).

Analyses performed at JPL in Pasadena, Calif., Indicate the engines will perform as designed at that temperature.

To be certain, the so-called "tiger" team of engineers assigned to study the problem analyzed descent engine performance at a range of temperatures to assess its predicted performance.

Since the Mars Climate Orbiter was lost Sept. 23, NASA has focused its attention on the Polar Lander, checking and rechecking all aspects of the mission as it approaches its Dec. 3 rendezvous with Mars.

On Wednesday, the investigative board will present its findings on the loss of the Climate Orbiter, as well as its recommendations for Polar Lander.

The Polar Lander remains in good health. On Nov. 1, the spacecrafts landing radar system was turned on and tested for the first time since launch. The system is crucial since it must generate the altitude and velocity data necessary to ensure the spacecraft correctly executes its powered descent to the surface.