The Mars Global Surveyor (MGS) mission is the first successful orbiter mission to Mars since the Viking program in 1976. MGS was launched in 1996 and arrived at Mars on November of 1997, a few months after Mars Pathfinder. Its mission is to comprehensively map the entire Martian surface. It also carries a laser altimeter which can measure the topography of Mars.
The Mars Global Surveyor mission was designed to use the technique of “aerobraking” for the first time as a mission-critical step. Aerobraking had been successfully demonstrated in the final days of the 1988 Magellan mission to Venus. MGS began in a highly-elliptical orbit and used its solar panels to resist the Martian atmosphere as it dipped down during the low point of its orbit. Panels at the ends of the solar panels were designed to increase drag on the spacecraft during aerobraking.
However, a problem arose when the latch on one of the solar panels appeared to crack, and the panel hinged itself past its designed position. Mission operatiors had to design an aerobraking procedure that was less stressful on the cracked solar panel. As a result, aerobraking took much longer than anticipated. Originally, the mapping phase was to begin in the spring of 1998, but because of the delay did not begin until over a year later on April 4th, 1999. Overwise, the mission has been very successful, and no other problems have been encountered to date.
Because of the longer aerobraking phase, the mission was able to return some science results and images of Mars during a few brief hiatuses from aerobraking. The probe has already made discoveries about volcanism on Mars, and has taken the best pictures yet of Martian features like Olympus Mons and Valles Marineris.
Mapping of the Martian surface took one Martian year, or 687 days. Once completed, scientists and mission planners had for the first time a first-class resource — a complete high-resolution surface map of Mars with topographical details — for scientific exploration and future missions. In addition, MGS has successfully served as a data relay satellite for surface missions, such as the Mars Exploration Rovers.