Purpose of the flight and payload description
The payload was composed by an stack of plastics, emulsions, and iron absorbers. The figure at left show the composition of the stack. The upper portion of it contained a motor-driven, shiftable layer of G-2 emulsion + Lexan polycarbonate + Daicell cellulose nitrate so that events occurring at ceiling altitude could be singled out. The iron slab was inserted to bring the total thickness to 1 g/cm2 so that tracks of nuclei with velocity much less than that for the geomagnetic cutoff on which the balloon flew, could be easily recognized and discarded.
The upper and lower emulsion layers were of type G-2 and were used mainly for following tracks through the stack. The most sensitive plastic, Daicell, recorded relativistic nuclei with Z>30, but because of its non-uniform composition and response, it was only used for location of tracks of heavy nuclei in the stack. In the other hand, the Eastman cellulose triacetate without plasticizer (CTA) was quite uniform in composition and reliable in response, so it was used to identify nuclei with Z>40.
Details of the balloon flight
Balloon launched on: 9/26/1968 at 19:33 cdt
Launch site: Columbia Scientific Balloon Facility, Palestine, Texas, US
Balloon launched by: National Center for Atmospheric Research (NCAR)
Balloon manufacturer/size/composition: Zero Pressure Balloon Winzen 10.600.000 cuft (0.7 mil. Stratofilm)
Balloon serial number: SF 305.86-070-NSC-09 Serial Nº 276
Flight identification number: 434P
End of flight (L for landing time, W for last contact, otherwise termination time): 9/28/1968
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): 42 h
Landing site: In Big Springs, Texas, US
Payload weight: 1486 lbs.
The balloon was launched on 26 September 1968 using a 10.6 million cubic feet balloon. It floated at an altitude of approximately 126,500 feet for a period of 42 hours and 6 minutes. This flight established a new duration record for a NCAR balloon mission.
- Balloon liftoff Roundup Vol. 7 Nº 26, October 11 1968 pag. 1
- NCAR Scientific Balloon Facility Annual Report, 1968 p. A-35 National Center for Atmospheric Research, January 1969
- Observation of Cosmic-Ray Particles with Z > 35 Physical Review D, vol. 8, Issue 6, pp. 1707
- Study of the Charge Spectrum of Extremely Heavy Cosmic Rays Using Combined Plastic Detectors and Nuclear Emulsions Physical Review D, vol. 3, Issue 4, pp. 815
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