Lander's software suspected Michael Cabbage Sentinel Space Editor

Published in The Orlando Sentinel on March 23, 2000

CAPE CANAVERAL -- NASA investigators have concluded the loss of the $165 million Mars Polar Lander in December was likely caused by the accidental shutdown of the spacecraft's engines as it descended toward the planet's surface.

NASA sources familiar with the investigation told The Orlando Sentinel on Wednesday that a failure report scheduled to be released next week lists a software error as the prime suspect. The potentially fatal flaw was discovered weeks after the botched Dec. 3 landing by engineers testing a similar system planned for use on a 2001 Mars mission.

The ill-fated Polar Lander was equipped with 12 thrusters designed to lower it gently to a site near the Martian South Pole. Sensors installed on the spacecraft were to shut down the thrusters when the lander made contact with the ground.

Investigators theorize that because of the flawed software, the sensors may have mistaken a jolt caused by extension of the landing legs for the actual touchdown. In that case, the thrusters would have stopped firing several hundred feet above the surface, sending the spacecraft crashing down to certain destruction.

Mission scientists will never be sure exactly what happened because no data were sent back during the Polar Lander's descent. But engineers acknowledged last month the software glitch was one of many problems being looked at. After additional study, a NASA source familiar with the probe says the defect now is considered the closest thing to "a smoking gun."

"There were a number of possibilities that could have caused the failure," said the source, who spoke on the condition of anonymity. "But if everything else had gone perfectly up until then, that would have been a show-stopper."

An investigation team headed by Tom Young, a former manager with spacecraft manufacturer Lockheed Martin, delivered the results of its two-month investigation to NASA on March 15. Agency officials have been in the process of reviewing the report and planning their response. Public release is tentatively scheduled for Tuesday.

The report is expected to detail widespread problems in the Mars program at NASA's Jet Propulsion Laboratory -- the agency's lead center for interplanetary exploration -- and at contractor Lockheed Martin. Sweeping changes are expected, including a management overhaul and radical rethinking of future Mars exploration plans.

"It's sobering reading," said Don Savage, a spokesman at NASA headquarters in Washington who would not discuss specifics of the report. "I think it's going to be a good thing for NASA in the long term and a real wake-up call. There's a fairly comprehensive list of what needs to be done."

The Young investigation follows two other reports released March 13 detailing problems in the Mars Climate Orbiter program and casting doubt on NASA's "faster, better, cheaper" approach of developing and launching inexpensive space probes. The $125 million Climate Orbiter, a companion craft to the Polar Lander, is believed to have crashed or burned up in the Martian atmosphere on Sept. 23 because of flawed navigation software.

Speculation about the Young investigation's findings has been rampant in recent weeks.

NASA took the unusual step Wednesday of issuing a news release to debunk a United Press International story alleging the Polar Lander may have been doomed by a temperature problem with its braking thrusters.

According to UPI, the thrusters failed to work properly during low-temperature preflight testing designed to simulate the super-cold conditions of space. The story said "an unnamed space official" altered the test conditions until the thrusters passed.

The report also claimed NASA discovered the flaw shortly before the lander's disappearance and withheld the information.

"That is categorically false," Savage said. "This was not something that came up two or three days before landing and was hidden."

Nevertheless, the story spread like wildfire over the Internet and broadcast outlets. NASA administrator Dan Goldin was grilled on the subject during a Capitol Hill hearing Wednesday.

NASA officials point out that a Nov. 10 report on the Climate Orbiter's failure publicly detailed recommendations for dealing with the Polar Lander thruster issue -- including earlier activation of heaters on the spacecraft's fuel lines -- well before landing. Mission managers tested the fix before landing and were satisfied the procedure would work.

NASA sources also flatly denied the thrusters ever failed acceptance testing, but acknowledged the tests may have been conducted at temperatures higher than they should have been.

http://orlandosentinel.com/automagic/news/2000-03-23/NWSMARS23032300.html

-- Martin Thompson (mthom1927@aol.com), March 23, 2000