Fears grow over fate of Mars Polar Lander

Robert Owen (rowen@technologist.com)
Sat, 04 Dec 1999 22:50:35 -0500

Fears grow over fate of Mars Polar Lander mission By Michael Miller

PASADENA, Calif., Dec 4 (Reuters) - Fears that America may have lost its second space mission to Mars in three months grew on Saturday after repeated attempts through the night to contact two microprobes sent to the surface by the Mars Polar Lander failed.

The Mars Climate Orbiter, a satellite and the lander's sister ship which was to have helped its exploration of the red planet by acting as a relay station from the Martian surface to Earth, was lost in September through human error when scientists mixed up English and metric measurements.

A spokeswoman at NASA's Jet Propulsion Laboratory in Pasadena said engineers working through Saturday night tried three times to get in touch with the grapefruit-sized microprobes, sending signals from the Mars Globe Surveyor satellite orbiting the planet 250 miles (400 km) above its surface, but each attempt had been met with silence.

``We just don't know (what happened),'' said project manager Richard Cook.

Cook was pinning his hopes on Saturday on a theory that the lander had fallen asleep, or gone into a ``safe mode'' about 20 minutes after a safe landing.

He said the craft's onboard computer was programmed to go into a safe mode if one of the lander's many instruments had failed or was playing up.

``If it was asleep, which in essence is what happens in a safe mode, then the
lander would not be able to hear us when we sent instructions,'' he said. It is programmed to stay in a safe mode for 18 hours and would not wake up until Sunday evening.

Cook also theorised that the lander's gyro compass may have been damaged in the landing and that it was lost, not knowing its geographical position on Mars and therefore unable to find Earth with its antenna.

But he also offered the disheartening scenario that the cruise stage which carried the lander and the two probes from Earth might have failed to separate from the lander, sending the joined craft plummeting to the surface.

``We don't know that it separated successfully. We were not receiving
telemetry (signals) at that point,'' Cook said.

The NASA team made three frustrating attempts on Friday to contact the lander, and by Saturday morning Surveyor had tried unsuccessfully to contact the probes from 90 percent of all possible angles available to it.

Copyright 1999 Reuters Limited. All rights reserved.

Robert M. Owen
The Orion Institute
57 W. Morgan Street
Brevard, NC 28712-3659 USA