Solar Maximum Mission (SMM)
HXRBSThe primary objective of HXRBS was to study hard X-ray spectra of solar flares on time scales as short as 10 ms. The Principal Investigator was K. Frost. The HXRBS instrument could also be used for observing the hard X-ray spectra of gamma-ray bursts which fell within the field of view of the detector. The HXRBS detector consisted of a CsI (Na) scintillator with a radius of 4.67 cm and thickness of 0.64 cm. The crystal was surrounded on all sides (except for the solar direction) by a CsI (Na) shield of thickness 3.2 cm. Events were pulse height analyzed in 15 channel energy spectra from 30-500 keV. The time resolution was 128 ms. However, the total count rate over the same energy ranges was recorded every 10 ms. The HXRBS threshold for detecting a gamma-ray burst was 1e-7 ergs/sq-cm (E > 30 keV). Since the SMM views the Earth during the nighttime portion of each orbit, only about 1 event on 40 is detected with a pi/6 sr field of view for which the spectra are not badly contaminated by the shield-processed contributions. Between launch and mid-1985, more than 15 gamma-ray bursts were seen by the HXRBS.
GRSThe GRS was designed for investigation of the gamma-ray spectrum of solar flares. The Principal Investigator was E. Chupp. The main detector was an array of 7 gain-controlled 7.6 cm diameter x 7.6 cm thick NaI(Tl) detectors. A complete spectrum was obtained every 16.38 s in the energy range 0.3 - 9.0 MeV. The number of counts in the 4.2-6.4 MeV range was read out every 2.048 s. The number of counts in a 50 keV wide window around 300 keV was read out every 64 ms. The spectrometer was shielded by a 2.5 cm thick annulus of CsI(Na) and a 25 cm diameter x 7.6 cm thick back detector. The shield elements defined a field of view of 135 degrees (FWHM) in the solar direction. The CsI back detector and the 7 NaI detectors together provided an effective area of ~ 100 sq-cm and 4 energy channels from 10-100 MeV. The number of counts in these energy channels was read out every 2.048 s. The experiment was complimented by a pair of 8 sq-cm x 0.6 cm thick NaI(Tl) detectors which measured the X-ray portion of the spectrum every 1.024 s in the energy range 13-182 keV. The GRS detection threshold for gamma-ray bursts in the field of view was ~ 5e-6 ergs/sq-cm (E > 300 keV). Between launch and mid-1985, GRS detected at least 75 bursts.
[NSSDC SMM Archive] [HEASARC SMM Catalog] [NASCOM SMM Catalog]
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