Purpose of the flight and payload description
The GRIS instrument consists of an array of seven coaxial n-Type germanium detectors surrounded by a thick active NaI shield/collimator. Located above this assembly is an active NaI coded-aperture mask for imaging and precise source location. The seven germanium detectors are each enclosed in individual cryostats. This design (rather than a single large multi-detector cryostat) was chosen for two principal reasons: to minimize the internally produced background and for easier replacement of individual detectors, as well as upgrades and modifications.
The instrument is mounted in a gondola offering a conventional azimuth-over-elevation pointing system with a momentum wheel for azimuth control. Coarse pointing control used the earth's magnetic field as a reference. A CID camera was used to image star fields and the sun to obtain an independent and more accurate measure of the absolute pointing direction.
Details of the balloon flight
Balloon launched on: 4/30/1988 at 19:59 utc
Launch site: Australian Balloon Launching Station, Alice Springs, Australia
Balloon launched by: National Scientific Balloon Facility (NSBF)
Balloon manufacturer/size/composition: Zero Pressure Balloon N29I-8/8/8/8T-28.40
Balloon serial number: R 28.40-3-107
Flight identification number: 249N
End of flight (L for landing time, W for last contact, otherwise termination time): 5/1/1988 at 23:44 utc
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): 24 h
Landing site: 174 miles NW of Longbeach, New South Wales, Australia
Observations of the supernova SN1987A, the Galactic center and the Crab Nebula.