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Mars mapping postponed.

A damaged solar panel will delay until March 1999 a mission to map the surface composition and atmosphere of Mars. The 1-year delay might also shorten the study, initially planned to last 2 years.

Mars Global Surveyor arrived at the Red Planet in September and was scheduled to settle into its final orbit in January 1998. According to that plan, mapping would have begun in March of that year.

Trouble arose in early October, a few weeks after the start of aerobraking, the fuel-saving technique that Surveyor relies on to reshape its orbit. In the aerobraking maneuver, the craft dips down into Mars' denser upper atmosphere to trim its elliptical orbit into the circular path designed for mapping (SN: 10/18/97, p. 246).

Aerobraking had been going according to plan until part of the upper atmosphere unexpectedly grew thicker. The extra pressure exerted on the craft during its maneuvers caused the panel to flap back and forth. Flight controllers feared it would snap off or suffer irrevocable damage, so they suspended aerobraking for 3 weeks.

Studies revealed that the solar panel could continue to function if aerobraking were slower. With this strategy, which NASA adopted on Nov. 7, the craft does not dip as deeply into the upper atmosphere and so is exposed to lower pressures.

The duration of these maneuvers, as well as a 6-month hiatus in the spring of 1988 while Mars moves into an optimal alignment with the sun, adds a calendar year--half a Mars year--to the time required for Surveyor to attain its mapping orbit, says mission manager Glenn E. Cunningham of NASA's Jet Propulsion Laboratory in Pasadena, Calif.

From the point of view of Surveyor, the orbital modifications will mean that the side of Mars that would have been dark will be sunlit and vice versa. That will make no difference in data gathering if Surveyor orbits the Red Planet for an entire Martian year, as planned. However, the mission may be shortened to ensure adequate funding for the next craft, the Mars '98 orbiter, scheduled to arrive in September 1999.
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Title Annotation:the Mars Global Surveyor will not begin mapping the planet until Mar 1999, the delay is due to a damaged solar panel
Author:Cowen, Ron
Publication:Science News
Article Type:Brief Article
Date:Dec 6, 1997
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