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A System Failure at Mars
10 November 1999 7:00 pm
WASHINGTON, D.C.--The loss of the Mars Climate Orbiter (MCO) spacecraft in September, when the unwitting use of English units during mission navigation sent the craft plummeting into the martian atmosphere, reflects the failure of mission team members to fully follow existing checks and balances, investigators told a press conference here today. Why they neglected to do so remains unclear, but NASA's new "faster, better, cheaper" approach to planetary missions is taking some of the blame.
"The navigation team realized as the spacecraft approached Mars that it was coming in lower than intended," says head of the investigation board Arthur Stephenson, director of NASA's Marshall Space Flight Center in Huntsville, Alabama. "They never saw that the spacecraft was in jeopardy. They were more worried about tuning the orbit than a catastrophic loss. They asked for a trajectory correction maneuver; this was denied for good reason--the team was not ready to perform it. There was not time."
Failing to ensure that a last-minute trajectory correction could actually be performed was just one of eight contributing factors that turned an oversight--calculating force during navigation in pound-seconds rather than the specified newton-seconds--into a catastrophe. Other problems included the navigators' unfamiliarity with the peculiarities of this spacecraft's behavior, poor communication between different spacecraft teams, and navigation team understaffing. With these failures in mind, the board has recommended changes in the operation of the Mars Polar Lander due to arrive at Mars on 3 December. They include beefing up staffing of the navigation team and using a second, independent means of determining the spacecraft's trajectory.
In recent years, NASA has overhauled its system for sending spacecraft to the planets so that more, smaller missions could fly at lower overall cost. But NASA officials denied that their scrimping affected MCO. "We have to remember faster, better, cheaper includes following the rules," says NASA associate administrator for space science Edward Weiler, adding, "They weren't followed this time." Noel Hinners, vice president for flight systems at Lockheed Martin Astronautics in Denver, which built and operated MCO, begs to differ. "There is a faster, better, cheaper effect here," he says. It's a matter of sufficient staffing--perhaps 10% more--to make sure the checks and balances work. "It's nothing big, but it takes time and money."