A long-duration balloon payload for hard X-ray and gamma-ray observations of the sun

A balloon payload designed to study the processes of energy release, particle acceleration, and heating of the active corona in hard X-ray microflares and normal flares is described. An array of liquid nitrogen-cooled germanium detectors together with large area phoswich scintillation detectors provide the highest sensitivity (about 500 sq cm) and energy resolution (not greater than 0.7 keV) ever achieved for solar hard X-ray (about 15-600 keV) measurements. These detectors were flown in February 1987 from Australia on a long duration radiation controlled balloon flight (LDBF) which provided 12 days of observations before cutdown in Brazil. The payload includes solar cells for power, pointing, and navigation sensors, a microprocessor controlled data system with VCR tape storage, and transmitters for GOES and ARGOS spacecraft. This successful flight illustrates the potential of LDBFs for solar flare studies.