INSTRUMENT OVERVIEW
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    The Gamma Ray Burst Detector (OGBD) experiment was an omnidirectional gamma-ray detector employing two Phoswich scintillation 
    spectrometers sensitive to photons from 0.1 to 2.0 MeV, used with logic circuitry to detect the beginning of a gamma event and 
    to initiate a period of rapid data collection. Data were stored in a memory unit for subsequent transmission to Earth. 
    Confirmation that a true gamma event had occurred was obtained by comparison with results from other experiments in Earth satellites. 
    This experiment provided long-baseline time correlations necessary for calculating accurate source locations.
 
    The purpose fo the OGBD was to observe intense, short duration emissions of high energy photons, known as gamma-ray bursts, from 
    astronomical sources. With the long baseline from Earth to Venus, correlations with near-Earth observations can provide directional 
    information with a higher precision than is available from Earth alone. Determinations with accuracies of under one arc minute are 
    possible.
 
    The experiment comprised two CsI photomultiplier detector units, mounted on opposite sides of the periphery of the instrument platform, 
    giving a full-sky 4 pi steradian field of view. Each contained a scintillation crystal, 3.8 cm in diameter and 3.2 cm long, phoswiched 
    within and optically bonded to a 0.5 cm thick shell of Pilot B plastic scintillator used for charged particle suppression. Each was 
    optically coupled to a photomultiplier tube. They were passively shielded from low energy radiation by a jacket of 0.25 mm lead foil 
    and the sensor housing. The instrument had a mass of 2.8 kg and used 1.3 W power.
 
    The OGBD could detect photons from 0.1 to 2.0 MeV energy, and obtain coarse spectral information using pulse height analysis. It had five 
    channels, a full 0.1 to 2.0 MeV channel, and four channels covering 0.1-0.2 MeV, 0.2-0.5 MeV, 0.5-1.0 MeV, and 1.0-2.0 MeV. The normal 
    accumulation time for the channels was 11.7 ms, a time-to-spill algorithm recorded the total intensity in time bins of 11.7 ms to 0.25 ms, 
    depending on the count rate.
 
    A temporary pretrigger memory would continuously store 3 seconds of data, if a rapid increase in count rate triggered the internal logic 
    to begin recording, the 3 seconds of data would be automatically added to the 20 kb buffer. The buffer would continue to record for up to 
    28 seconds of event data. The detector went into operation on 21 May 1978, one day after launch. It operated continuously until the end of 
    the PVO mission in October 1992.