The Mars Global Surveyor mission was a robotic space probe launched by NASA on November 7, 1996 to map the Martian surface and study its climate and geology. The Surveyor operated for nearly 10 years, making it one of the longest-lived spacecraft at Mars. It completed its primary mission in early 2001 and continued performing science until contact was lost on November 2, 2006.
The Mars Global Surveyor was one of the most successful missions ever flown to Mars. All of its major objectives were accomplished, including mapping 98% of the Martian surface with an accuracy of better than 90 m (300 ft). In addition, the spacecraft made important discoveries about Mars’ atmosphere and interior. Perhaps most importantly, it helped lay the groundwork for future missions to Mars by providing critical data about landing sites and potential resources.
The mission began with a launch aboard a Delta II rocket from Cape Canaveral Air Force Station in Florida on November 7, 1996. After a journey of almost 10 months, the spacecraft arrived at Mars on September 11, 1997 and entered orbit around the planet. Over the next year-and-a-half, the Surveyor slowly lowered itself into an elliptical polar orbit using aerobraking maneuvers. This final orbit had a period of just under two hours and an altitude that ranged from 250 km (160 mi) at periapsis to 8700 km (5400 mi) at apoapsis. From this vantage point, the spacecraft could image almost the entire Martian surface with resolutions as high as 5 m (16 ft).
The primary science instruments aboard the Surveyor were a camera system known asMars Orbiter Camera (MOC), a thermal emission spectrometer calledThermal Emission Spectrometer (TES), used to measure infrared emissions from Martian rocks and soils in order to determine their compositions; magnetometers; radar equipment; and an ultraviolet spectrometer called Ultraviolet/Visible Imaging Spectrometer(UVIS). These instruments allowed scientists to study Mars in unprecedented detail from orbit.
In addition to these imaging and remote sensing instruments,the Surveyor also carried two experiment packages designedto study Mars’ gravity field: The Laser Retroreflectorsfor Lunar Observations(LRLO)and The Doppler Tracking System(DTS). LRLO consistedof four corner cube reflectors that could be usedby lasers fired from Earthto make very precise measurementsof distance between Earthand Mars—and hence determinethe value of G—Newton’sgravitational constant—withunprecedented accuracy. DTSmade use of Doppler shiftsto measure tiny fluctuationsin velocity caused bychanges in Newton’sgravitational constantover time or space scales much too smallto be detected directlyby other means.”