Preliminary assessment of Termoskan observations of Mars

In February and March, 1989, the Termoskan instrument onboard the Phobos '88 spacecraft acquired a limited set of very high resolution observations of the 8–12 μm thermal emission from Mars' equatorial regions. Simultaneous and coincident observations were acquired in the 0.5 to 1.0 μm region also. We have evaluated quantitatively about 25% of those data and find close agreement with the lower-resolution Viking Orbiter Infrared Thermal Mapper (IRTM) observations, demonstrating the accuracy of the Termoskan system. Termoskan's thermal emission panoramas display limb brightening at the morning limb, which we interpret as arising from the presence of a diurnal ice crystal haze there. Detached hazes at high altitude also are evident in the visible panorama of the evening limb. The Phobos '88 orbit enabled Termoskan to record the visible shadow from the Martian moonlet Phobos and to measure the surface thermal response to that shadow's passage. Analysis of one such data set shows that the uppermost fraction of a millimeter is two to four times more insulating than the uppermost centimeters sensed by the IRTM experiment. The Termoskan data are of direct importance to the planning and execution of the PMIRR and TES experiments of the U.S. Mars Observer mission to be launched in 1992. An improved version of Termoskan is planned for the Mars '94 mission of the U.S.S.R. Those data will be of still higher surface resolution and, thus, complement well the expected PMIRR and TES global data sets.