OSSE Preprint No. 6 The Oriented Scintillation Spectrometer Experiment Instrument Description

The Oriented Scintillation Spectrometer Experiment (OSSE) on the Arthur Holly Compton Gamma Ray Observatory satellite uses four actively shielded NaI(Tl)-CsI(Na) phoswich detectors to provide gamma-ray line and continuum detection capability. in the 0.05-10 MeV energy range. The instrument includes secondary capabilities for gamma-ray and neutron detection between 10 and 250 MeV. The detectors have 3.8-degrees x 11.4-degrees (FWHM) fields of view defined by tungsten collimators. Each detector has an independent, single-axis orientation system which permits offset pointing from the spacecraft Z-axis for background measurements and multitarget observations. The instrument, and its calibration and performance, are described.