NaI active anticoincidence shielding for rejection of background events. The instrument had a three-sigma narrow line sensitivity of 1.7 x 10−4 picohenries per square centimeter per second at 500 keV over 12 hours, and a field of view (FWHM) of 17 degrees at 500 keV. The experimental payload had a weight of , and used 350 Watts of power. It relied on a momentum wheel for azimuth control, and a magnetic pointing reference, with a star tracker and sun sensor for verification. The instrument delivered telemetry at a rate of 55.2 kbps. Team The principal investigator of the GRIS project was Jack Tueller, with co-investigators Scott Barthelmy, Lyle Bartlett, Neil Gehrels, Marvin Leventhal, Juan Naya, Ann Parsons, and Bonnard Teegarden. References External links GRIS scientific results Summary of GRIS flights from 1988 to 1995 Description of the GRIS mission by co-investigator Neil Gehrels Gamma-ray telescopes Spectrometers Balloon-borne telescopes Goddard Space Flight Center