Sep 21, 1999

Weather Satellite Nears Mars

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Mars Climate Orbiter is set to go into orbit around the Red Planet.




September 21, 1999: Mars Climate Orbiter, the first of two NASA spacecraft to reach Mars this year, is set to go into orbit around the red planet to become the first interplanetary weather satellite and a communications relay for the next lander mission to explore Mars.


The orbiter will fire its main engine at 1:50 a.m. Pacific Daylight Time on Thursday, September 23, 1999, to slow itself down so that it can be captured in orbit around the planet. Signals confirming the event will be received on Earth about 11 minutes later at 2:01 a.m.

"The curtain goes up on this year's Mars missions with the orbit insertion of Mars Climate Orbiter," said Dr. Sam Thurman, flight operations manager for the orbiter at NASA's Jet Propulsion Laboratory, Pasadena, CA. "If all goes well, the happily-ever-after part of the play will be the successful mission of the Mars Polar Lander that begins in December followed by the mapping mission of the orbiter that is set to begin next March."


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Once captured in orbit around Mars, the orbiter will begin a period of aerobraking. During each of its long, elliptical loops around Mars, the orbiter will pass through the upper layers of the atmosphere each time it makes its closest approach to the planet. Friction from the atmosphere on the spacecraft and its wing-like solar array will cause the spacecraft to lose some of its momentum during each close approach. As the spacecraft slows with each pass, the maximum altitude of the orbit will decrease and the orbit will become more circular.

Mars Climate Orbiter's first assignment after it completes aerobraking will be to serve as the communications relay for its sibling spacecraft, Mars Polar Lander, set to land near the south pole on December 3. After the Lander's surface mission ends in February 2000, the orbiter's science mission begins with routine monitoring of the atmosphere, surface and polar caps for a complete Martian year (687 Earth days), the equivalent of almost two Earth years.


Left: This image is the first view of Mars taken by the Mars Climate Orbiter (MCO) Mars Color Imager (MARCI). It was acquired on 7 September 1999 at about 16:30 UTC (9:30 AM PDT), when the spacecraft was approximately 4.5 million kilometers (2.8 million miles) from the planet. [more info]


"We're interested in what happens during all the seasons of a Mars year. Weather is what happens from day-to-day and the long term effect of all of that is climate," said Dr. Richard Zurek, project scientist for the orbiter at JPL. "Mars Climate Orbiter will do what weather satellites do - it will take pictures of clouds, it will look for storms and it will try to understand the atmospheric winds by measuring temperature and pressure and by watching how the atmospheric distributions of dust and water vapor change with time."

Today the Martian atmosphere is so thin and cold that it does not rain; liquid water placed on the surface would quickly freeze into ice or evaporate into the atmosphere. The temporary polar frosts which advance and retreat with the seasons are made mostly of condensed carbon dioxide, the major constituent of the Martian atmosphere. But the planet also hosts both water-ice clouds and dust storms, the latter ranging in scale from local to global. If typical amounts of atmospheric dust and water were concentrated today in the polar regions, they might deposit a fine layer on the ground year after year. Consequently, the top meter (or yard) of the polar layered terrains could be a well-preserved tree-ring-like record showing tens of thousands of years of Martian geology and climatology.


Right: A simulated view of Mars as seen from Mars Climate Orbiter on September 23, 1999 when the spacecraft is scheduled to fire its main engine.


The orbiter carries two science instruments: the Pressure Modulator Infrared Radiometer, a copy of the atmospheric sounder on the Mars Observer spacecraft lost in 1993; and the Mars Color Imager, a new, light-weight imager combining wide- and medium-angle cameras. The radiometer will measure temperatures, dust, water vapor and clouds by using a mirror to scan the atmosphere from the Martian surface up to 80 kilometers (50 miles) above the planet's limb. The radiometer was provided by JPL, supported by Oxford University and Russia's Space Research Institute; its principal investigator is Dr. Daniel McCleese of JPL.


Recent Headlines
December 3: Mars Polar Lander nears touchdown

December 2: What next, Leonids?

November 30: Polar Lander Mission Overview

November 30: Learning how to make a clean sweep in space
Meanwhile, the imager will gather horizon-to-horizon images at up to kilometer-scale (half-mile) resolutions, which will then be combined to produce daily global weather images. The camera will also image surface features and produce a map showing objects the size of a football field with 40-meter (130-foot) resolution in several colors, providing global views that will help create a season-to-season portrait of the planet. The camera was provided by Malin Space Science Systems, San Diego; CA; its principal investigator is Dr. Michael Malin, who also provided the camera for the currently orbiting Mars Global Surveyor.


Mars Climate Orbiter is managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, Washington, DC. Lockheed Martin Astronautics, Denver, CO, is the agency's industrial partner for development and operation of the Orbiter. JPL is a division of the California Institute of Technology.



Related Stories:

NASA Announces Mars Landing Site -- Mars Polar Lander to arrive on smooth, layered terrain. August 25, 1999 NASA NASA Science News

Unearthing Clues to Martian Fossils -- The hunt for ancient life on Mars is leading scientists to an otherworldly place on Earth called Mono Lake. June 11, 1999 NASA NASA Science News

The Red Planet in 3D -- New data from Mars Global Surveyor reveal the topography of Mars better than many continental regions on Earth. May 27, 1999 NASA NASA Science News

Search for life on Mars will start in Siberia -- Russian and NASA scientists will look for life forms in the inhospitable realm of Siberian permafrost. May 27, 1999 NASA NASA Science News

Stormy weather on Mars -- During the recent close approach of Mars to Earth, NASA's Hubble Space Telescope spotted a gigantic storm swirling near the Red Planet's north pole. May 19, 1999 NASA NASA Science News

Mars unveils a magnetic personality -- Plate tectonics on the Red Planet might have important consequences for ancient Martian life. Apr 30, 1999 NASA NASA Science News

Plate tectonics on Mars? -- Magnetic stripes on the surface of Mars are similar to fields in the sea floors of Earth. Apr 29, 1999 NASA NASA Science News

A close encounter with the Red Planet -- Mars makes its closest approach to Earth in 1999. Apr 23, 1999 NASA NASA Science News

A new face on Mars has scientists smiling -- MGS beams back pictures of the "Happy Face Crater". Mar. 12, 1999 NASA NASA Science News

Related Sites:

Mars Climate Orbiter - official web site at NASA/JPL

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NASA's Office of Space Science press releases and other news related to NASA and astrophysics


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