Mars Global Surveyor (MGS) was designed to recover the mission objectives of Mars Observer, which was lost in 1993. MGS launched November 7, 1996 and was successfully put into orbit around Mars on September 11, 1997. Over the course of a full Martian year, MGS will study Mars' surface features, atmosphere, and magnetic properties.
The Thermal Emission Spectrometer (TES) is a Michelson interferometer that measures the thermal infrared energy emitted by Mars. This information will be used to study the composition of the rock, soil, ice, atmospheric dust, and clouds.