The High Resolution Gamma-Ray and Hard X-Ray Spectrometer (HIREGS) program was conducted at UCSD in collaboration with the Space Science Laboratory at UC Berkeley under the direction of Professor Robert Lin. The prime objective of the HIREGS program was to study energetic processes in the solar atmosphere via high-resolution spectroscopic observations of X-Ray and Gamma-Ray emissions generated during solar flares. The HIREGS instrument and flight system, in conjunction with the observing capabilities available using Long Duration Balloons in Antarctica offered a qualitatively new window on flare particle acceleration processes since most of the features of the hard x-ray continuum produced by the energetic elections were previously unresolved by the scintillator detectors used in space missions. Additional objectives were pursued in the latter HIREGS flights to study galactic cosmic gamma-ray line emissions from sources such as positron annihilation and the decay of 26Al.
At the heart of the HIREGS flight system was an array of 12 segmented intrinsic Germanium detectors enclosed in a Bismuth Germanate shield. A number of novel subsystems were developed to support the HIREGS program. These included solar power arrays and controllers, on-board data logging, and an autonomous control system for operation of HIREGS in a long duration environment wherein ground contact was not possible for most of the float duration.
Four flights of the HIREGS system were conducted over a six year period, accumulating over 50 days of observations while circumnavigating the Antarctic continent. Unfortunately, due to lack of solar activity during the flights, no large flares were observed. Detector systems developed for HIREGS, as noted above, did serve as the basis for the SMM mission several years later. Long Duration Ballooning technology, developed for HIREGS advanced the state-of-the-art for ballooning in general, and served as the basis for many successful subsequent flights in Antarctica.