The Mars Global Surveyor mission: description, status, and significant result

The Mars Global Surveyor (MGS) spacecraft entered an elliptical orbit at Mars on September 11, 1997. Until March 1999 it acquired scientific data from decreasing-sized orbits as it alternated between aero-braking and nadir-pointing modes. This time period provided tremendous advances in our knowledge of the shape and topography, the gravity field, the magnetic field, and the atmospheric structure and dynamics of Mars. In April 1999 MGS entered its planned two years in the mapping mode. In this mode the high-gain antenna tracks Earth so that the instruments can take data continuously and so that the camera system can return high-resolution data in real-time. IR spectral and temperature data, as well as high-resolution images are providing new insight into the geologic evolution of Mars. All data is being archived at about six month centers so that it is available in electronic format to the international community.