Visible afterglow counterparts have now been detected for two GRBs (970228 and 970508) but are absent, with Lopt/Lγ ratios at least two orders of magnitude lower, for other GRBs, e.g., 970828. The causes of this variation are unknown. Any correspondence which could be discovered between the γ-ray properties of a GRB and its Lopt/Lγ would be useful, both in determining the GRB mechanisms, and in...

A novel design for a compact gamma-ray spectrometer is presented. The proposed system allows for spectroscopy of high-flux multi-MeV gamma-ray beams with MeV energy resolution in a compact design. In its basic configuration, the spectrometer exploits conversion of gamma-rays into electrons via Compton scattering in a low-Z material. The scattered electron population is then spectrally resolved ...

he X-Ray/Gamma-Ray Spectrometer on the Near Earth Asteroid Rendezvous (NEAR) spacecraft will remotely sense X-ray and gamma-ray emissions from the surface of near-Earth asteroid 433 Eros and look for characteristic “signatures” in those emissions to determine its elemental composition. During the planned 10 months of orbits about Eros beginning in early 1999, data returned from the instrument w...

We present the design and analysis of a new gamma ray spectrometer for planetary science that uses an array of CdZnTe detectors to achieve the detection efficiency needed for orbital measurements. The use of CdZnTe will provide significantly improved pulse height resolution relative to scintillation-based detectors, with commensurate improvement in the accuracy of elemental abundances determine...

To illustrate the spatial resolution of measurements of Mercury’s surface elemental composition by the Gamma-Ray Spectrometer on the MESSENGER spacecraft after one year of orbital observations, we have simulated a global coverage map of the 846-keV iron gamma-ray count rate. The simulated map suggests that distinct geologic units larger than 800 km in horizontal dimension will be discernable wh...

The modeled performance of the Alpha Magnetic Spectrometer (AMS) as a high-energy (0.3 to 100 GeV) gamma-ray detector is described, and its gamma-ray astrophysics objectives are discussed.

The modeled performance of the Alpha Magnetic Spectrometer (AMS) as a high-energy (0.3 to 100 GeV) gamma-ray detector is described, and its gamma-ray astrophysics objectives are discussed.