NASA has slowed the process of bringing the Mars Odyssey into a tighter orbit around Mars, delaying the unmanned probe's first snapshots of the Red Planet.
Odyssey had been expected to take its first image of Mars on Sunday but that was pushed back to Tuesday because the initial atmosphere-skimming maneuver was being extended.
``We're just being conservative,'' said mission manager David Spencer at the National Aeronautics and Space Administration's Jet Propulsion Laboratory. ``We've added a couple steps ... and are going at it more slowly.''
Despite the delay, the $297 million mission ``couldn't be going better,'' Spencer said.
Odyssey, on a mission to study the mineral makeup of Mars' surface and look for deposits of frozen water, reached the planet on Tuesday.
The probe began a process called aerobraking on Friday, using friction with the Martian atmosphere to slow down and drop lower. It passed within 98 miles of the surface for about seven minutes. The process was repeated at lower altitudes Saturday and Sunday.
When completed in January, the aerobraking will reduce Odyssey's egg-shaped, 181/2-hour orbit and make it more circular. The spacecraft then will fire small thrusters to achieve a 21/2-hour, 250-mile-high mapping orbit.
The limiting factor on how aggressively aerobraking can be conducted is heating of Odyssey's winglike solar array due to friction. Damage from too much heat could reduce its ability to provide power.
``The density (of atmosphere) that was experienced was very consistent with our predictions,'' Spencer said. ``We are very pleased. We are right on schedule.''
The spacecraft is to begin photographing the planet from a site over the south pole.
The Odyssey mission is intended to map the distribution of minerals and chemicals across the surface of Mars and provide daily weather reports. It also will seek out signs of frozen water deposits 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.