Energy Range
53–88 keV; 69–1150 keV
The gamma-ray monitor instrument consisted of a 2.25 inch diameter x 1.5 inch thick CsI(Tl) crystal surrounded by a plastic scintillator. The plastic served as a particle rejector. The crystal was viewed by a single photomultiplier. The monitor was on continuously except for the passage through the magnetotail, which occurred every 4.14 days. In addition to monitoring the rates of total intensity, particle intensity, and gamma-ray intensity, energy spectra of the incident gamma-rays were measured in 14 channels. The gain of the system was cycled through 4 positions, with changes being made roughly every week for purposes of in-flight calibration. Thus, some data were taken with a 69–1150 keV energy range, while other data were taken with a 53–88 keV range.
The IMP 7 gamma-ray data were collected in 2 modes: a continuous accumulation of data for 40.9 s into 14 energy channels and a 40.9 s collection mode during which data are collected only when the satellite rotation caused it to face the Sun.
