A spacecraft's transition from interplanetary cruising to arrival has proved to be one of the most challenging phases in the exploration of Mars.
In 1993, contact with NASA's Mars Observer was lost as the satellite neared Mars, probably after a fuel-system explosion. Six years later, a mix-up between imperial and metric units in calculating trajectory put the Climate Orbiter too close to Mars, causing it to burn up in the atmosphere. The Polar Lander vanished three months later, probably because a software error caused it to plunge to the surface.
The back-to-back losses in 1999 underscored the difficulty of getting to Mars: Fewer than one-third of the 30 missions launched to the planet by the United States and other countries since 1960 have succeeded.
The two botched missions also forced the space agency to scale back what had been an ambitious program to explore the planet.
Originally, Odyssey was supposed to be joined by a spacecraft that would put a rover on the surface of Mars. But the lander was scrapped, leaving Odyssey to wend its way alone to Mars after its launch last April.
To avoid another fiasco, NASA added staff, did extra checks on software and took precautions to prevent a repeat of the imperial-metric mix-up.
Despite the recent failures, NASA has continued to explore Mars from orbit via the Global Surveyor, which arrived in 1997 and has transmitted thousands of highly detailed images of the Martian surface and dust storms in its atmosphere.
Odyssey was equipped with two instruments to map the distribution of minerals and search for water across the dusty surface of Mars. Liquid water is considered a necessary element for life; finding reservoirs could help determine whether life ever existed on the Red Planet.
A third instrument was designed to measure radiation on Mars and how that might endanger humans if they are ever sent to explore the planet.
Odysseya box seven feet (2.1-metres) long, five feet (1.6 metres) tall and eight feet (2.5 metres) wide, with an 18-foot (5.6-metre) solar panel and antennaswas also designed to help pick landing sites for future missions, including twin rovers NASA intends to launch in 2003.
Copyright 2001 The Canadian Press
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