During the two part Aerobraking phase, the MGS spacecraft skimmed through the Martian atmosphere and used the drag force on the extended solar panels to slowly reduce the eliptical orbit from 44 hours down to 16 hours. The second part eventually converted the long, eliptical orbit into a 2 hour circular, polar orbit for Mapping operations. TES regularly collected data throughout the MGS aerobraking event to assist the earthbound spacecraft engineers as they guided MGS through this dangerous dance. The TES dataset proved to be so valuable that it was collected for every Mars mission that launched during the TES lifetime: the Mars 2001 Odyssey, the 2003 Mars Rovers, and the 2005 Mars Reconnisance Orbiter.

Orbit 5

SEP 19, 1997

These images represent the Martian surface temperature as measured by the TES. The purple areas are the coldest, about -200°F (140K), while the red areas are the warmest at about 30°F (270K). Click on the image for a larger version.

The two image panels shown above represent two points along each MGS Aerobraking orbit (see figure).

• The left panel is approximately centered on the south pole and was obtained when TES was approaching the farthest point away from Mars in the orbit. The warm, sunlit day side is to the right of the pole, and the cool, night side is to the left of the pole. The shape of image results from observing the full disk of Mars.
• The right panel was obtained when TES was approaching the closest point to Mars in the orbit. The equator is centered horizonally in this view, and the north and south polar regions are off the image at the top and bottom respectively. Unlike the left panel, the image shape results from the circular shape of the TES field of view (like a telescope); the right image only shows a partial view of the full disk of Mars.

The progression of Mars seasons through time are dramatically displayed by observing the changes in the left panels from the earliest to the latest orbits. When MGS first arrived at Mars (Sept 1997, Orbit 5), the season was northern hemisphere fall/southern hemisphere spring. Stepping forward through the images shows the temperatures dropping in the north, and simultaneously rising in the south. The carbon dioxide ice cap that developed during the previous winter, slowly sublimates and shrinks as we complete this phase of aerobraking (Feb 1998, Orbit 127).