UV ionospheric remote sensing with the polar BEAR satellite

Some recent work interpreting and analyzing data obtained by the AIRS sensor on the Polar BEAR satellite is briefly described. The Polar BEAR satellite was launched in November 1986 into a nearly circular 1000 km orbit with an orbital inclination of 89.5 degrees and a nodal regression of 0.05 degrees per day. In the course of a year the satellite experiences all local times twice a year. One of the instruments on Polar BEAR is the Auroral Ionospheric Remote Sensor (AIRS). AIRS was described previously and some of the early data from that instrument also was presented. Briefly, in its primary operating mode AIRS was designed to return four simultaneous images of the atmospheric radiation at Northern latitudes, in the far and near ultraviolet (UV) and the visible at 6300 A. Two of the data streams originate from photomultipliers at the exit plane of a one eighth meter far UV spectrometer. The other two data streams originate at photomultipliers behind narrow band UV and visible filters. A single telescope illuminates both the spectrometer entrance slit and the filtered detectors. In the normal imaging mode of operation, on a three second cycle the line of sight of all four channels is deflected from horizon to horizon perpendicular to the orbital path by a plane mirror at the entrance to the telescope.