Gamma-ray burst observations from the UCB/LASL experiment of ISEE-3

The University of California at Berkeley (UCB)/Los Alamos Scientific Laboratory (LASL) gamma-ray burst experiment on board ISEE-3 is described and initial results of the experiment are presented. The instrument consists of an X-ray spectrometer originally designed to monitor solar emission continuously over the energy range 4.8-1264 keV with additional electronics to record data from the intense, short-lived gamma ray bursts at a very high rate and with good timing accuracy. Since the launch of ISEE-3 into a heliocentric orbit at the inner Lagrangian point in August, 1978, the UCB/LASL experiment has detected and recorded 12 gamma-ray bursts, including the unusually intense burst of November 4, 1978, which exhibited most of the classical gamma-ray burst characteristics, the intense burst of November 19, 1978, with an atypical time history and an unusually hard spectrum, and the extended burst of March 7, 1979. The spectral and temporal data demonstrate the diverse nature of the gamma-ray burst phenomenon, and are currently being combined with those of the Pioneer Venus Orbiter and Venera 11 and 12 to obtain accurate burst locations.