TES maps and measures the geology and atmosphere of Mars.
TES integrates three instruments — a Michelson Fourier transform spectrometer, a solar-albedo bolometer, and a thermal-emission bolometer — within a single sensor assembly. The primary TES mission is to study the geology of Mars: the composition of surface rocks and ices. It also studies the composition, particle size, and temporal distribution of atmospheric dust; and locates carbon dioxide condensate clouds so that their temperature, height, and distribution can be determined. To achieve this, the spectrometer measures electromagnetic flux in the 200 to 1600 cm-1 (6.25 to 50 µm) spectral range with 5 cm-1 resolution. TES also measures broadband solar reflectance and thermal emittance in the 0.3 - 2.7 µm and 4.5 - 100 µm bands to reveal the energy balance in the polar regions and to map the thermophysical properties of the Martian surface.
TES scans the Martian surface with three coregistered 2 x 3 detector arrays, two of which are broadband thermal arrays, while the third is located in the image plane of a Michelson interferometer. Onboard processing of the array data performs offset, gain correction, and Fourier inversion of the interferogram to generate a 150 or 300 "color" spectrum. This powerful onboard signal-processing capability provides an effective 40:1 data compression ratio with respect to the bandwidth that would be required to transmit the unprocessed interferogram data. As a result, TES makes very efficient use of the low-power, low-data-rate communication links that typify interplanetary spacecraft.
The first TES was launched aboard the Mars Observer in September 1993, and in-transit operation showed the instrument to be working well. After contact was lost with that spacecraft, NASA contracted with Arizona State University and Raytheon for a second TES for launch aboard the Mars Global Surveyor (MGS). The new instrument was launched aboard the MGS spacecraft on November 7, 1996, and completed the mapping phase of the mission January 31, 2001. The MGS instruments continued to perform until mission controllers lost contact on November 2, 2006. To date, TES has collected over 40 million spectra of the Martian surface.