 Edward E. Fenimore of the Los Alamos National Laboratory was PI for this experiment.GRAD was another technology demonstration program to test the suitability of bismuth germanate in gamma-ray detectors, the suitability of n-type, high-purity germanium gamma-ray detectors for space, the performance of an advanced gamma-ray spectrometer and to study the gamma ray background around the shuttle, as well as the gamma-ray spectrum of the sun and the Galactic Center.The instrument is non-steerable and is pointed by moving the Shuttle.