GRAPWG - Gamma Ray Astronomy Program Working Group. NASA committee.

GRIS - Gamma-Ray Imaging Spectrometer. A high-energy Ge spectroscopy experiment. Flown on 9 balloon flights since 1988.

HEGRA - High Energy Gamma Ray Astronomy. A collaboration of mainly German institutions, operating an eventual array of 5 individual telescopes with two currently in place.

HETE - High-Energy Transient Experiment. NASA small mission designed for multiwavelength studies of gamma-ray bursts. Initial launch failed December 1996, possible reflight in 1999.

HEXTE - High-Energy X-ray Timing Experiment. The high energy 15-250 keV instrument onboard RXTE.

HTXS - High Throughput X-ray Spectroscopy. Mission concept for high-resolution X-ray spectroscopy and hard X-ray (5 - 50 keV) imaging. Incorporates the NGXO, LAXSM, and HXT concepts. Intermediate Class.

INTEGRAL - International Gamma Ray Astrophysics Laboratory. ESA observatory designed for fine spectroscopy (E/IE = 500) and accurate imaging (~10 arcmin) in the 15 keV to 10 MeV range. Two main instruments onboard: spectrometer which employs high-spectral-resolution Ge detectors and imager which employs high-spatial-resolution CdTe and CsI detector. Launch scheduled for 2001.

MIDEX - Medium Explorer. NASA program for $70M missions (not including launch). Weight limit is ~1300 kg.

MO&DA - Mission Operations and Data Analysis. NASA program for funding operations and data analysis for flight missions.

OSSE - Oriented Scintillation Spectroscopy Experiment on CGRO. Spectrometer with 4 x 11 deg. field-of-view. Energy range is 0.05-10 MeV.

RXTE - Rossi X-ray Timing Explorer. NASA explorer mission for X-ray timing. Two instruments cover 2-200 keV with narrow (~1 ) fields-of-view. One instrument is an all-sky monitor in 2-10 keV band. Launched in 1995.

SMEX - Small Explorer. NASA program for $35M missions (not including launcher). Weight limit is ~500 kg.

SMM - Solar Maximum Mission. Launched in February 1980 and operating till 1989, SMM made hard X-ray and gamma-ray observations of the Sun and other astrophysical sources.

SR&T - Science Research and Technology. The NASA program which handles proposals for technology development.

TGRS - Transient Gamma-Ray Spectrometer. A sensitive Ge spectrometer launched in 1994 aboard the WIND spacecraft.

VERITAS - Very Energetic Radiation Imaging Telescope Array System. A proposed array of 10m optical reflections as a next-generation Air Cerenkov telescope.