GRIS (Gamma-Ray Imaging Spectrometer) + PORTIA

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.

Balloon launched on: 10/25/1995 at 21:43 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 SF3-459.37-080-NSXCHR-ST
Balloon serial number: W39.57-2-15
Flight identification number: 409N
End of flight (L for landing time, W for last contact, otherwise termination time): 10/26/1995 at 8:15 utc
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): 35 h
Landing site: 30 miles E of Alice Springs, Australia
Payload weight: 5932 lbs

Observations of the galactic center, galactic plane and galactic pole.

• GRIS web site at Goddard Space Flight Center archive
• Great Moments in GRIStory at NASA's Goddard Space Flight Center website
• NASA Balloon Flights (1989-1998) in NASA Historical Data Book, Vol. VII: NASA Launch Systems, Space Transportation, Human Spaceflight, and Space Science, 1989-1998