X-ray imagers can provide large-scale maps of bremsstrahlung x rays produced by electron precipitation into the atmosphere. Complete day and night coverage is obtained and the electron energy spectra at each position in space can be derived from the measured x-ray energy spectra. Early x-ray imagers were limited in field of view and to one map for each pass over the emitting regions. The Magnetospheric Atmospheric X-ray Imaging Experiment, launched on a TIROS satellite,
makes time-space mappings by scanning a 16-pixel pinhole camera. The data distinguish intensity variations of a fixed auroral feature from motion of a steadily radiating feature. However, the spatial deconvolution is complex and features stay in the field of view for only ~10 mm. These problems will be resolved by a high-altitude (~9 Re) imaging spectrometer PIXIE on the ISTP/GGS Polar Satellite to be launched in 1994. PIXIE's position-sensitive proportional counter will continuously image the entire auroral zone for periods of hours.