Web Extra     October 24, 2001

Odyssey orbits Mars

On Tuesday night, NASA fired away into a new phase of martian exploration. After a 200-day journey, the Odyssey spacecraft fired its main engine for the first and only time — sending itself into orbit around the Red Planet. Launched on April 7, Odyssey has logged more than 285 million miles to reach Mars. Aboard the spacecraft are several scientific instruments to map the mineral and chemical make-up of the martian surface. “There’s quite a bit of anticipation and excitement as Odyssey will provide yet another database to add to our archive to better understand Mars,” says James Dohm, a hydrologist at the University of Arizona who studies Mars.

At 10:26 p.m. Eastern time last night, Odyssey’s main engine burned more than 579 pounds of propellant for 19.7 minutes. And at 10:55 p.m., flight controllers at Deep Space Network stations picked up the first radio signal from the spacecraft as it emerged from behind Mars. "How sweet it is! Putting the Odyssey spacecraft into orbit is an achievement that each and every American should take pride in," said NASA Administrator Dan Goldin at a news conference following Odyssey's successful orbit burn.

The fire of the main engine will brake Odyssey’s speed and slow its trajectory into an egg-shaped elliptical orbit around Mars. As the spacecraft orbits, it will repeatedly brush against the top of the atmosphere, so-called aerobraking, to reduce the long, 19-hour elliptical orbit into a shorter, 2-hour circular orbit. Odyssey will orbit 400 kilometers above Mars, an ideal altitude for the mission’s science data collection.

A neutron spectrometer, designed at Los Alamos National Laboratory, will map the presence of water in the upper meter of Mars’ soil, allowing scientists to better understand the planet’s climate history and hydrology. The neutron spectrometer will also measure fast neutrons, indicative of iron, to map Mars’ basaltic lava, as well as measure the seasonal variation of dry ice snowfall at the poles and help to convert gamma ray data from a gamma-ray spectrometer to determine the elemental composition of  the planet.

NASA’s 1,600-pound spacecraft also hosts a thermal-emission imaging system, a high-energy neutron detector and a radiation monitor. By late January or early February, all instruments aboard Odyssey will begin sending data about Mars back to Earth for a planned 917 days.

NASA has continuing coverage of the 2001 Mars Odyssey mission.

Lisa M. Pinsker

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