The Gamma-Ray Spectrometer (GRS) was one of two instruments on the Solar Maximum Mission (SMM) which independently monitored cosmic gamma-ray bursts from SMM's launch in February 1980 until the end of the mission in 1989. The GRS was designed for investigation of the gamma-ray spectrum of solar flares (Forrest, D.J. et al. 1980, Sol. Phys., 65, 15). The main detector was an array of seven gain-controlled 7.6 cm diameter X 7.6 cm thick NaI(Tl) detectors. A complete spectrum was obtained every 16.38 seconds in the energy range 0.3-9 MeV. The number of counts in three energy windows covering the 4.2-6.4 MeV range was read out every 2.048 seconds. In addition, the number of counts in an approximately 50 keV wide window near 300 keV was read out every 64 milliseconds. The spectrometer was shielded by a 2.5 cm thick CsI(Na) annulus and a 25 cm diameter X 7.6 cm thick CsI(Na) back detector. The shield elements defined a field of view of approximately 135 degrees (FWHM) in the solar direction. The CsI back detector and the seven NaI detectors together provided a high-energy spectrometer with approximately 100 cm<sup>2</sup> effective area and four energy channels from 10 to 100 MeV. The number of counts in those high-energy channels was read out every 2.048 seconds. The experiment was complemented by two 8 cm<sup>2</sup> X 0.6 cm thick NaI(Tl) detectors which measured the X-ray portion of the spectrum every 1.024 seconds in the range from 13 keV to 182 keV. This database table was created by the HEASARC in the early 1990s based on tables supplied by the SMM Project and was subsequently revised in February 2002. This is a service provided by NASA HEASARC .
