Purpose of the flight and payload description

In this flight were transported two instruments: a large area phoswich array provided by the Imperial College Group and a large area proportional counter developed by the University of Tasmania. The goal of the flight was to investigate hard cosmic X-ray sources from the southern hemisphere.

The large area phoswich array consisted of 12 identical modules totalling 1600 cm2. Each module had a primary 2 mm thick NaI crystal backed by a 14 mm thick CsI crystal, and a 2° FWHM field of view produced by a tantalum honeycomb collimator; passive shielding was used to block background radiation through the sides. Photons were detected in 31 energy channels over the range 16-200 keV.

The other instrument was a multilayer, multianode proportional counter with an area of 5200 cm2 and 21 cm active depth, filled with Xenon at 1 atmosphere. Its 10-100 keV range was spanned by 20 energy channels. A thin alloy honeycomb collimator defined the 2° FWHM field of view, while the rear and sides were screened by a graded shield. Background due to charged particles was also removed by active screening.

Details of the balloon flight

Balloon launched on: 12/1/1981 at 21:03 local
Launch site: Australian Balloon Launching Station, Alice Springs, Australia  
Balloon launched by: National Scientific Balloon Facility (NSBF)
Balloon manufacturer/size/composition: Zero Pressure Balloon Winzen 433.248 m3 (12.70 Microns Stratofilm)
Balloon serial number: W15.3-2-05
Flight identification number: 184N
End of flight (L for landing time, W for last contact, otherwise termination time): 12/2/1981 at 14:34 local
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): F 10 h 10 m
Payload weight: 1116 kgs

During the flight were observed these sources: GXI+4, GX5-1, Nova Oph. 1977, IC 4329A but with relatively short exposures times due to a pointing malfunction.

External references

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