Purpose of the flight and payload description

The X ray detector, provided by the University of Maryland, consisted of an uncollimated NaI(Tl) scintillation crystal 12.7 cm in diameter by 1.27 cm thick with a 0.381 mm thick aluminum front window. The field of view of this detector was a cone of about 45º half angle about the zenith. The omnidirectional geometric factor over the upper hemisphere was 476 cm2. The instrument measured x-rays in two integral energy channels (>25 and >500 kev) and seven differential energy channels (25-45, 45-65, 65-95, 95-125, 125-175, 175-250, and 250-500 kev) .

In this flight was also carried onboard a Very Low Frequency (VLF) receiver (0-5 kHz) provided by the Norwegian Institute of Cosmic Physics (NICP). The basic telemetry used was a PCM-FM-FM based system with the digital x-ray data impressed on a 93 kHz VCO while the analog data from the VLF receiver was impressed on a 165 kHz VCO.

This balloon mission formed part of a special Siple-Roberval campaign which included VLF direction-finding measurements in the Roberval area by groups from Stanford University, the University of Southampton, and the University of Tokyo. The scientific objectives of the balloon flights were to investigate ionospheric effects, in particular precipitation phenomena, induced by natural VLF signals and by signals from the Siple transmitter, to perform direction-finding measurements on the magnetospheric signals from the Siple transmitter in order to evaluate results from various types of direction-finding systems and to study the positions, movements, relation to the plasmapause, etc., of transmitter signal paths.

Details of the balloon flight

Balloon launched on: 7/4/1975 at 5:01 utc
Launch site: Roberval, Quebec, Canada  
Balloon manufacturer/size/composition: Zero Pressure Balloon  
End of flight (L for landing time, W for last contact, otherwise termination time): 7/4/1975 at 6:30 utc

External references

  • Balloon Program Trip report of the University of Maryland to Roverbal, Quebec, July 1975

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