Energetic neutral atom imaging by the Astrid microsatellite

The microsatellite Astrid carried the first instrument (PIPPI, Prelude in Planetary Particle Imaging) specifically designed to perform energetic neutral atom (ENA) imaging. It made measurements from a low altitude (1000 km) polar orbit in the energy range similar to 13-140 keV. The ENA images, obtained from near-pole vantage points, adequately reflect general morphological features of the ring current such as a global dawn-dusk asymmetry. The detected ENA peak fluxes (500-2000 cm(-2)s(-1)sr(-1)keV(-1) for 26-37 keV) and structure of the ENA images correlate well with magnetospheric activity throughout the entire data set. The Astrid results demonstrate a considerable potential for ENA imaging from low altitude polar orbits. High ENA fluxes, large angular size of the generation region and simultaneous sampling over all local times are major advantages of such imaging. (C) 1997 COSPAR. Published by Elsevier Science Ltd.