Purpose of the flight and payload description

The X-ray detector system consisted of 3" NaI(Tl) crystal scintillator whith a thickness of 3 mm, a same area's plastic scintillator with a thickness of 30 mm and a cellular collimator with 4º x 20º FWHM field of view. The whole detector assembly was surrounded by a guarded shield of lead and tin, and a magnetic shield except in the window of the detector. Anti-coincidence shielding against background charged particles was provided by a scintillator's signal with the method of pulse rise-time discrimination. Two detector sets were mounted with each axis inclined at 4º from the zenith. The detector's axis were controlled from the ground by telecommand to orientate them alternately to north (OFF-mode) and south (ON-mode). At the time of ON-mode, Cyg X-1 was in the detctor's field of view while at OFF-mode, the source can't be observed. Inflight calibration was performed by telecommand using an onboard source of AM124 radio isotope each time the mode was changed.

Details of the balloon flight

Balloon launched on: 10/7/1972 at 5:25 utc
Launch site: Sanriku Balloon Center, Iwate, Japan  
Balloon launched by: Institute of Space and Astronautical Science (ISAS)
Balloon manufacturer/size/composition: Zero Pressure Balloon model B15 15.000 m3
Flight identification number: B15-21
End of flight (L for landing time, W for last contact, otherwise termination time): 10/7/1972 at 11:31 utc
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): 6 h 6 m

The instrument was launched on October 7, 1972, at 5:25 UTC from the Sanriku Balloon Center, in Iwate prefecture. The balloon reached the ceilling altitude at 7:50 UTC and then floated at an altitude between 34.88 km and 35.38 km. The payload was separated from the balloon at 11:31 utc

External references

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