COUNTER TELESCOPE + X-RAY COUNTER + ION CHAMBER + EMULSIONS

This flight was part of a balloon expedition to study cosmic rays in the vicinity of the equator during the International Quiet Sun Year (IQSY) organized and managed by the National Center for Atmospheric Research as a joint United States - India activity. The program was conducted in Hyderabad, India during the late winter and early spring of 1965.

The main instrument on this flight was an experiment provided by the AFCRL designed to measure the charge spectrum and the time variation of the heavy primary cosmic rays. The experiment consisted of a three-detector (one Cerenkov, two scintillators) telescope, linear amplifiers, logic circuitry, 300-channel pulse height analyzer, and onboard recording. The package turned itself on and off automatically at 75,000 ft and could be launched 'unattended.' The flights performed during the IQSY-EQEX experiment were the first of a series of such measurements to be made through a sunspot cycle.

Adittional payloads onboard were:

A self-recording ion chamber to obtain equator values for total ionization as part of complete latitude curve during period of minimum solar activity. The instrument was provided by the University of Minnesota group led by John R. Winckler;

A X-RAY Counter developed by the University of California aimed to measure atmospheric gamma ray as a continuation of an already performed measurement campaign carried out in Minneapolis and in New Mexico, thus completing a three-point latitude survey. Also using the low gamma ray background near the equator the scientists examined the quiet sun for X-ray emission in the 10 to 100 kev region.

Finally an Emulsion plastic particle detector provided by Tata Institute of Fundamental Research was also onboard to try to detect in the plates traces of heavy primary cosmic rays.

Balloon launched on: 3/12/1965
Launch site: Osmania University Campus, Hyderabad, India  
Balloon launched by: Raven Industries Inc.
Balloon manufacturer/size/composition: Zero Pressure Balloon Winzen 2.940.000 cuft (0.7 Mil. Stratofilm)
End of flight (L for landing time, W for last contact, otherwise termination time): 3/12/1965
Landing site: Aborted flight due to balloon failure.
Campaign: No Data IQSY-EQEX
Payload weight: 550 lbs

Since the AFCRL counter telescope was the primary experiment, the flight train was developed around it. A key frame platform similar to the previous flights was constructed to fit the base of the AFCRL instrument container. The balloon control instrumentation and Dr. Anderson's X-ray counter were placed on either side of the main experiment. Suspended below the main package on a 35-ft nylon line was the Winckler ion chamber. In similar fashion, the Bristol beacon was suspended 3 ft below the key frame platform. The TIFR flip emulsion stack was positioned on a bamboo framework approximately 4 ft from the center line of the configuration. Ballast was contained in two equally spaced hoppers to preclude any change in balance as ballast was expended.

Because of the numerous instruments on this flight, the complete system was assembled and weighed as a unit. The assembly was quite bulky and difficult to handle. The overhead door clearance was limited; therefore, the instrument load was rolled outside, then loaded on the truck for delivery to the launch field. The balloon was laid out and the inflation started while it was dark. Inflation required approximately 1 hr and was completed 45 min before scheduled launch at 0600. The surface wind was calm to 3 mph and was in line with the balloon layout. The balloon was released; however, it was unable to lift more than 2/3 of the balloon off the ground. The package was immediately cut free to prevent any damage. The balloon was pulled down and several holes were located in the top section about 10 to 15 ft from the top end fitting. Apparently, the balloon had been leaking during inflation and continued till launch, a period of about 1.5 hr. The loss of lift was estimated at 500 to 550 lb. The flight was delayed till the next day since it was necessary to reload the helium and the crane was not immediately available.

• Ballooning Support for Cosmic-Ray Experiments NCAR Technical Note NCAR/TN-20, September 1966