MARS ODYSSEY
Roughly 800 things could keep the Mars Odyssey from reaching a suitable orbit around the Red Planet in October, and Roger Gibbs has investigated every one of them.
Prior to launching the $165 million spacecraft in April, the flight systems manager and his team at NASA's Jet Propulsion Laboratory in Pasadena, California, spent $11 million and the equivalent of 50 years' time identifying and trying to eliminate every possible snafu - any one of which could end the $300 million mission.
As the Odyssey gets closer to its destination, Gibbs continues troubleshooting. His team relies on a methodical engineering technique called fault-tree analysis, first applied to the Minuteman ballistic missile by Boeing in the early '60s. The Odyssey team began by listing all of the mishaps that could occur during each phase of the mission. It then identified the causes that might lead to those errors, graphically representing each as a branch. NASA's resulting tree is four levels deep and consumes 60 spreadsheets.
The analysis has been used to piece together the failures of the Challenger space shuttle, the Climate Orbiter, and the Polar Lander. Gibbs' work marks the first time it's been applied so extensively before disaster strikes. Even so, the cards are stacked against the Odyssey. Of the 30 Mars missions attempted by the US, Russia, and Japan, fewer than a third have been successful. Yet Gibbs is convinced that he and his cohorts have exorcised any remaining ghosts from the machine.
Not surprisingly, the NASA team pays particular attention to problems that plagued earlier Mars missions, most notably the confusing of US measurements and metric units, which resulted in the premature demise of the Climate Orbiter. The Odyssey is 100 percent metric, and its onboard computer checks each of the 200,000-plus parameters generated during the mission for numerical errors before propagating them through the system. "We have wrung out the design as much as humanly possible," explains Gibbs. "And we expect it to work very well."
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