Mars Lander Engine Likely Cut Off Early

March 28, 2001 -- Inadequate software probably led to the descent engines of the Mars Polar Lander shutting off early, sending the ill-fated NASA spacecraft smashing into the planet’s surface last December, two review boards reported today.

But the underlying problem, the panels said, was trying to do too much with too little, resulting in missions that had little chance of success.

NASA today also canceled its next Mars lander, which had been scheduled for launch next year. That spacecraft shared a design very similar to the Mars Polar Lander’s. A companion orbiting spacecraft will be launched as planned.

Landing at 130 Feet UpThe Mars Program Independent Assessment Team, headed by Tom Young, a retired Lockheed Martin executive vice president and former director of NASA’s Goddard Space Flight Center, found that the process of unfolding the landing legs during descent could have inadvertently triggered sensors telling the onboard computer it was already on the ground.

“This resulted in a premature shutdown of the engines,” Young said at a news conference at NASA’s Washington, D.C. headquarters this afternoon. Shutting down the engines would have sent the lander into a free fall for the final 130 feet, accelerating it to 50 mph. The computer could have easily been programmed to ignore the spurious signals, he said.

A review board at NASA’s Jet Propulsion Laboratory, whose report was also released today, came to the same conclusions.

Four full-scale tests of the landing sequence after the mishap by Lockheed Martin, the builder of the spacecraft, all resulted in early engine cutoffs. “In all four, the lander would have failed,” Young said. “So I think it almost certain if the lander got to this particular part of the mission, this is the cause of the lander failure.”

Before launch, engineers performed the same test with the Mars Polar Lander, but a wiring mistake cut off all signals from the sensors, and the test was never repeated.

‘Most Probable’

Other causes for the failure were possible, the report said, butthe engine shutdown was the most likely.

More fundamentally, the report says the Mars Surveyor ’98 program, consisting of Climate Orbiter and Polar Lander, was underfunded by at least 30 percent and understaffed, and that the staff that was assigned was inadequately trained. Those conditions led to “unacceptably high risk,” Young said.

Richard Cook, the spacecraft’s project manager, said about the report: “It seems on balance pretty fair.”

In retrospect, many of the problems pointed out have become more obvious. “At the time, we were very much advocates of making it happen,” Cook said. “We’re used to having work very hard. It’s hard sometimes to say, is this normal working hard or beyond what’s reasonable? We have high expectations we can do the impossible or pretty close. In this case, maybe we were doing something that was impossible.”

Two probes that were to land independently after being carriedto Mars by the mother ship also failed. The report sharply criticizes almost all parts of that project, from management to testing to risk assessment, and concludes “the microprobes were not ready for launch.”

The omission of any radio communication between the lander and Earth during landing was a “major mistake,” Young said. “As a result, we have no information from the lander itself to us what went wrong.”

When last heard from last Dec. 3, Mars PolarLander was healthy and on target, just 12minutes shy of its scheduled touchdown onMars. Neither the $165 million lander nor the microprobes were ever heard from again.

That disappearance followed the embarrassing destruction of the Mars Polar Lander’s companion spacecraft, Mars Climate Orbiter, two months earlier. The cause of that mishap was quickly pinpointed: a failure to convert navigation data from English units to metric. That pushed the Climate Orbiter off course, too far down into the Martian atmosphere.

Management Didn’t Manage

Young’s panel was also highly critical of themanagement and organization system at the Jet PropulsionLaboratory, the California center in charge of NASA’s Mars program.

“The current organization at JPL is not appropriate tosuccessfully manage the Mars program,” said the report of the MarsProgram Independent Assessment Team.

The report said NASA, JPL and the nation’s aerospace industryhave the capability to mount a Mars exploration effort, but thereare “significant flaws” in the way the program is now managed.

Ed Weiler, the space agency’s associate administrator for space science, announced a series of changes to the Mars program, including the appointment of a person to oversee the entire program. NASA headquarters will also set up a reserve fund that projects can tap into if necessary.

“In hindsight, we have asked them to do the impossible,” Weiler said.

Weiler announced that the lander half of the Mars Surveyor 2001 program has been canceled, although the scientific instruments planned for the mission will be completed. The instruments might be flown with later landers, he said.

John Pike, a space analyst at the Federation of American Scientists, who has criticized NASA for not recognizing that its “faster, cheaper, better” had become “too fast and too cheap” found the latest reports to be “candid and thorough.”

“They were very clear the last round of missions was underfunded,” Pike said. “They restructured the next round to reduce budget pressures. I think in terms of a clear candid diagnosis of the problem and a good set of solutions to the problem, it’s all extremely encouraging.”

The Associated Press contributed to this report.