Description of the payload

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 and scientific outcome

Launch site: Scientific Flight Balloon Facility, Fort Sumner, (NM), US  
Balloon launched by: National Scientific Balloon Facility (NSBF)
Balloon manufacturer/size/composition: Zero Pressure Balloon SF3-459.37-080-NSXCHR-ST
Balloon serial number: W39.57-3-03
Flight identification number: 370N

Observations of Cyg X-1, NGC 4151 and the Crab Nebula.

External references and bibliographical sources

Images of the mission

Rollout from the hangar of the GRIS pauload