Infared Spectrometer
Spectral measurements of the thermal (IR) emission by the Martian surface and atmosphere were obtained to determine (1) the atmospheric composition, including polyatomic life-related molecules, (2) the surface temperature along the track of view, (3) the surface composition, (4) the surface topography, (5) the composition of the polar cap, and (6) the bright limb IR emission characteristics. The experiment, mounted on the bottom of the octagonal scan platform of the spacecraft, used an IR spectrometer that consisted of a telescope, optical focusing lenses and mirrors, a variable-wedge interference filter that selected the wavelengths reaching the detectors, and cooled IR detectors. The spectra observed covered the wavelength region of 1.9 to 14.3 micrometers and were provided by channel 1 (4.0 to 14.3 micrometers), which operated on emitted light from the planet and continued to obtain measurements on the dark side of the planet, and channel 2 (1.9 to 6.0 micrometers), which operated on reflected solar radiation. The instrument telescope had a field of view of 2 deg and, thus, at closest approach (about 3,100 km) the geographical resolution was about 120 km by 3 km and, during a single scan, about 120 km by 120 km. The spectral resoltion obtained was 0.5 to 1 %. About 29 min of data were obtained during the Mariner 6 near-encounter equatorial scan on July 31, 1969. However, due to the failure of the channel 1 cryostat, only channel 2 measurements were obtained. The quality of the data is excellent.