THE MARS GLOBAL SURVEYOR MISSION

The Mars Global Surveyor (MGS) spacecraft was launched in November 1996 and was inserted into Mars orbit in September 1997. NASA’s Jet Propulsion Laboratory managed the MGS spacecraft development and manages the mission operations. Lockheed Martin Astronautics, Denver, Colorado, designed and built the MGS spacecraft and provides mission operations support. Aerobraking reduced the orbit period to 2 hours by early February 1999. After more than 900 orbits of aerobraking, two propulsive maneuvers raised the spacecraft out of the atmosphere and established the mapping orbit. Mapping operations commenced on March 9, 1999. During mapping the spacecraft operates in a low-altitude, near-circular, near-polar, 2 p.m./ 2 a.m. Sun-synchronous orbit with a short repeat cycle. The science objectives of the MGS Mission were to be accomplished over the course of a full Mars year (687 days) of mapping ending on February 1, 2001. Most of these objectives, those that do not depend upon mapping over the full Mars year, have been substantially met. About 100 scientific papers have been published or accepted in referred journals, including five "cover" papers in Science and Nature. Significant achievements of MGS at Mars during the first mapping year include: (i) the discovery of a significant remnant magnetization of the Martian crust, (ii) the ellipsoidal shape of Mars is flattened by ~20km and the center of figure is offset by nearly 3km, (iii) the best topograhic model for any planet, (iv) thick layered sequences of strata, (v) the wide occurrence of basaltic rocks in the south and andesitic rocks in the north, (vi) the absence of pervasive weathering based on thermal emission spectra, (vii) detection of coarse-grained hematite deposits, (viii) observations of current aeolian processes, (ix) a reliable estimate of the volume of the polar caps, (x) clear evidence of a sapping origin of many channels and (xi) significantly improved understanding of atmospheric dynamics from continuous observations.