Atmospheric Results from the MGS Horizon Science Experiment

The Horizon Science Experiment (HORSE) utilizes the Mars Horizon Sensor Assembly (MHSA) on the Mars Global Surveyor (MGS) orbiter to measure 15-micron band thermal emission from the Martian atmosphere. During the first two phases of aerobraking, from September 1997 to May 1998, and from September 1998 to March 1999, one of the four MGS quadrants was pointed well onto the planet consistently during the near-periapsis aerobraking passes, allowing the device to obtain data on the latitudinal variation of middle atmospheric temperature (0.2 - 2.0 mbar). Of particular interest during the first phase (L(sub s) = 182 - 300 deg) were the effects of a prominent dust storm at L(sub s) =224 deg, and wavelike behavior in the strong temperature gradient near the north polar cap. Additional information is contained in the original extended abstract.