PASADENA, Calif. -- NASA's Mars Odyssey spacecraft has delayed its first photo shoot of the Red Planet until at least Tuesday after scientists decided to slow the spacecraft's entry into the atmosphere, a mission official said Sunday.
The slowing is not the result of any problems with the unmanned probe that reached Mars and entered orbit last Tuesday, said mission manager David Spencer of NASA's Jet Propulsion Laboratory.
"We're just being conservative," he said. "We've added a couple steps to the walk-in phase and are going at it more slowly."
Scientists are trying to avoid any problems caused by friction from Odyssey's descent into the atmosphere. Too much friction could hurt the winglike 75-square-foot solar array that powers Odyssey, although a catastrophic failure is unlikely, Spencer said.
The slowing means the spacecraft will take longer to tighten its orbit of Mars and reach an optimum altitude for the photos, which had been expected Sunday.
Despite the delay, the $297 million mission "couldn't be going better," Spencer said.
The probe began the process called aerobraking on Friday to tighten its orbit. It passed within 98 miles of the surface of Mars while entering the atmosphere for about seven minutes.
Odyssey took its second dip into the atmosphere on Saturday, coming within about 84 miles. Its third maneuver was scheduled for Sunday morning but results were not expected to be known until later in the day. The "drag passes," which ultimately will bring Odyssey within about 60 miles of Mars, use atmospheric friction to shave time off the egg-shaped 18 1/2-hour orbit the probe entered after it reached the planet. Odyssey is expected to have a 2 1/2-hour circular orbit 250 miles above the planet when the aerobraking is complete in January.
Using aerobraking instead heavy loads of propellant allowed the probe to be cheaper and smaller.
The spacecraft is to begin photographing the planet from a site over its south pole Tuesday. Scientists hope the images will reveal information about the atmosphere and help determine whether they can measure its temperature and whether dust storms exist.
The Odyssey mission is intended to map the distribution of minerals and chemicals across the surface of Mars and provide daily Martian weather reports. It also will seek out frozen deposits of water that might help determine whether life ever existed on the Red Planet.
Two 1999 missions with similar studies failed: The Climate Orbiter flew too close to the planet because of a mix-up between English and metric units, and the Polar Lander likely plunged to the surface because of a software error.
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