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There is strong evidence that water-ice is relatively abundant within permanently shadowed lunar surface materials, particularly at the poles. Evidence for water-ice has been observed within the impact plume of the LCROSS mission and is supported by data gathered from the Lunar Exploration Neutron Detector (LEND) and the Lunar Prospector Neutron Spectrometer (LPNS). Albedo neutrons from the Moon are used for detection of hydrogen, where the epi-thermal neutron flux decreases as hydrogen content increases. The origin on the concentration of water within permanently shadowed regions is not completely understood, and the Lunar Polar Hydrogen Mapper (LunaH-Map) mission is designed to provide a high-resolution spatial distribution of the hydrogen content over the southern pole using a highly elliptical, low perilune orbit. The LunaH-Map spacecraft is a 6U cubesat consisting of the Miniature Neutron Spectrometer (Mini-NS). Mini-NS is not collimated, requiring a low altitude to achieve a higher spatial resolution compared to previous missions. To develop a compact neutron detector for epi-thermal neutrons, the Mini-NS comprises of 2-cm thick slabs of CLYC (Cs 2 LiYCl 6 ), which provide a sensitivity similar to a 10-atm, 5.7-cm diameter He-3 tubes, as used in LPNS. The Mini-NS digital processing electronics can discriminate by shape and height to determine signal (albedo neutrons) from background (cosmic rays). The Mini-NS achieves a total active sensing area of 200 cm 2 and is covered with a cadmium sheet to shield against thermal neutrons. The research and development on the detector modules show a robust design ready for space flight.

The Mars Odyssey spacecraft was launched on 7 April 2001 and went into orbit around Mars on 24 October 2001. One of the primary scientific instruments carried on the spacecraft is a germanium gamma-ray spectrometer that will measure the elemental composition of Mars. Cruise measurements taken during July and August 2001 are used to characterize the energy resolution of the detector and to measure and identify the background gamma rays. These gamma rays originate in the detector, in material surrounding the detector, and from the spacecraft. More than 110 gamma rays were observed in the background spectrum. The sources of most of these gamma rays were tentatively identified. Understanding the sources of the background gamma rays is important for the future when using the orbital data to determine the composition of Mars.

An X-ray and Gamma-ray spectrometer (XGRS) is onboard the Near Earth Asteroid Rendezvous (NEAR) spacecraft to determine the elemental composition of the surface of the asteroid 433Eros. The Eros asteroid is highly non-spherical in physical shape and the development of data management and analysis methodologies are in several areas a divergence from traditional remotely sensed geographical information systems techniques. Field of view and asteroid surface geometry must be derived virtually and then combined with real measurements of solar, spectral and instrument calibration information to derive meaningful scientific results. Spatial resolution of planned geochemical maps will be improved from the initial conditions of low statistical significance per integration by repeated surface flyovers and regional spectral accumulation. This paper describes the results of a collaborative effort of design and development of the NEAR XGRS instrument ground system undertaken by participants at the Goddard Space Flight Center, University of Arizona, Cornell University, Applied Physics Laboratory, and Max Plank institute.

Two new small satellites will be launched in late 1996, each carrying x-ray and gamma-ray detectors capable of high spectral resolution while operating at or near room temperature. The Argentinean Satellite de Aplicaciones Cientificas B (SAC-B) and the Small Spacecraft Technology Institute Clark mission will each carry several arrays of x- ray detectors primarily to study solar flares and gamma ray bursts. Arrays of small (8 mm X 8 mm X 2 mm thick) cadmium zinc telluride detectors will provide x-ray measurements in the 5 - 60 keV range with an energy resolution of 2 - 4 keV. Arrays of both silicon avalanche photodiodes (APDs) and P-intrinsic-N photodiodes will provide energy coverage from 2 to 20 keV with approximately 1 keV resolution. High energy data from 30 to 300 keV will be obtained on SAC-B using CsI(TI) scintillators coupled to silicon APDs, resulting in significant savings in weight, power, and volume relative to conventional CsI- photomultiplier systems.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.