Remote planetary geochemical exploration with the NEAR X-ray/gamma-ray spectrometer

The X-ray/gamma-ray spectrometer (XGRS) instrument onboard the Near Earth A steroid Rendezvous (NEAR) spacecraft will map asteroid 433 Eros in the 0.2 keV to 10 MeV energy region. Measurements of the discrete line X-ray and ga mma-ray emissions in this energy domain can be used to obtain both qualitat ive and quantitative elemental composition maps of the asteroid surface. Th e NEAR X-ray/gamma-ray spectrometer (XGRS) was turned on for the first time during the week of 7 April 1996. Rendezvous with Eros 433 is expected duri ng December 1998. Observations of solar X-ray spectra during both quiescent and active periods have been made. A gamma-ray transient detection system has been implemented and about three gamma-ray transient events a week have been observed which are associated with either gamma-ray bursts or solar f lares. (C) 1999 Elsevier Science B.V. All rights reserved.