The X-ray telescope consisted on a NaI (TI) crystal of effective area 97 cm3 and thickness 4 mm optically coupled to a 5 inches of diameter photomultiplier tube. The crystal was surrounded by both active and passíve collimators. The passive collimator was composed of a cylindrical graded shield of lead, tin and copper and the active collimator was a cylindrical plastic scintillator viewed by two 2 inches of diameter phototubes. A schematic diagram is shown at left. The pulses from the NaI crystal were sorted into fifteen continuous channels. All the information was recorded in a continuously moving photographíc film. An Am241 source came into the field of view of the telescope periodically and provided in-flight calibration of the detector at 16.5 and 59.4 keV during the entire period of the flight.
The axis of the telescope was kept inclined at a fixed zenith angle and the telescope was mounted on an oriented platform. The orientator was programmed to look at different azimuthal directions. The aspect of the telescope was monitored by a pair of flux gate magnetometers which provided the aspect information continuously in analog form as well as in digitized form once in several seconds.
The entire instrument including the orienting system was enclosed in a pressurised gondola with a thinned top.
Balloon launched on: 3/8/1973 at 19:37 utc
Launch site: TIFR National Balloon Facility, Hyderabad, India
Balloon launched by: National Balloon Facility, Tata Institute of Fundamental Research
Balloon manufacturer/size/composition: Zero Pressure Balloon Winzen Strato Film (tow+main) 118.200 m3
Flight identification number: 262
End of flight (L for landing time, W for last contact, otherwise termination time): 3/9/1973
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): 7 h
Payload weight: 270 kgs
Overall weight: 597 kgs
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