A Weather Satellite for Mars

The first interplanetary weather satellite will reach Mars in the wee hours on Thursday. But don't expect daily weather reports anytime soon. NASA's Mars Climate Orbiter (MCO) will start monitoring the planet's atmosphere no earlier than March 2000.

At 4:50 a.m. EDT tomorrow morning, the spacecraft will fire its engines for 16 minutes, thereby easing into a highly elliptical orbit. Using friction from the tenuous upper layers of the atmosphere in a technique known as aerobraking, MCO will round out its orbit gradually over the next few months before settling in at an altitude of 421 kilometers.

MCO's first mission will be to serve as a radio relay station for its sister craft, Mars Polar Lander, which is the second part of NASA's $330 million Mars '98 Project. The lander is due to touch down about 800 kilometers from the frigid south pole on 3 December, after which it will analyze soil samples.

Starting in March, MCO will scan the planet's atmosphere for 23 months, until January 2002--a full martian year. An infrared radiometer will send back data on temperature and water vapor content, while a camera will capture cloud patterns, storm activity, and dust distribution. "Mars Climate Orbiter will do what weather satellites [in Earth orbit] do," says project scientist Richard Zurek of NASA's Jet Propulsion Laboratory in Pasadena, California. Knowing the climate of other planets may give scientists a better idea of what might happen to Earth's.

After 2002, the weather satellite might turn into a telecom satellite once again, serving as a communications relay for future Mars landers. Besides NASA, the European Space Agency, the French agency CNES, and the Japanese agency NASDA have plans for future visits to Mars.

--GOVERT SCHILLING

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