ELECTRON DETECTOR

This flight was part of a program developed at the Department of Physics, Imperial College of Science and Technology in London, with support from the Cosmic Rays and Space Physics Group to measure low-energy primary cosmic ray electrons. The scientific objectives focused on investigating the intensity and time variation of primary cosmic ray electrons, studying potential solar modulation effects, and examining any diurnal variations in the electron flux. The researchers aimed to better understand cosmic ray sources, their propagation through interstellar space, and solar influences on cosmic radiation.

In the scheme at left we can see the electron detector. The scientific instrument consisted of a cosmic ray detector designed to measure primary cosmic ray electrons in the energy range of 30 MeV to 1500 MeV. The detector utilized a three-element coincidence telescope system with a plastic scintillator, an inclined Perspex element, and a liquid Cerenkov detector using FC75 as the radiating medium. The Cerenkov detector set a lower velocity threshold corresponding to β = 0.78. For electron identification and energy measurement, the instrument employed a lead-scintillator sandwich detector comprising three lead blocks of 2, 3, and 6 radiation lengths, each followed by plastic scintillator detectors made of NE102A. The geometric factor of the telescope was 9.8 ± 0.5 cm sr.

Balloon launched on: 8/5/1967 at 21:38 utc
Launch site: Kiruna Geophysical Observatory, Sweden  
Balloon manufacturer/size/composition: Zero Pressure Balloon  
End of flight (L for landing time, W for last contact, otherwise termination time): 8/6/1967 at 14:00 utc
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): ~ 17 h

The flight was conducted from Kiruna, Sweden on August 5th, 1967. The balloon launch occurred at 21:38 UTC, reaching a floating altitude of 3.7 g/cm of residual atmosphere by 23:45 UTC. During its ascent, the balloon drifted approximately 60 miles north. Data transmission was achieved through a 0.1 W FM transmitter operating at 137 MHz, with reception at both Kiruna and Andennes, Norway. The flight continued until 14:00 UTV on August 6th, 1967, when the balloon had descended to 4.5 g/cm of residual atmosphere. Throughout the flight, the balloon continued to drift northward, starting at 65.3°N and reaching 68.2°N by the end of the observation period.

• The intensity and time variation of primary cosmic ray electrons NASA technical report, Mar 01, 1968