Re-Analysis of Data on the Space Radiation Environment above South-East Asia

Abstract : A new analysis has been performed on the HRM-III gamma ray detector data collected from Shuttle missions STS-41B, 41C, 41D, 41G and 51A. The new analysis shows no evidence for the existence of enhanced levels of radiation in low-Earth orbit over South-East Asia (ie in the area bounded by longitudes 100 E to 190 E and latitudes 10 S to 15 N) as previously suggested. Variations in the detector count rates with geophysical location are shown to be consistent with the variation of the cosmic ray flux with geomagnetic latitude, and also show expected increases due to the South Atlantic Anomaly (SAA) and outer belt electrons. However, at times poor quantitative agreement is found between the expected positions of the SAS or outer electron belt, and the Shuttle's geophysical location on the occasions when high count rates were observed. It is believed that this lack of correlation is a result of the sensitivity of the trapped particle environment to geophysical position and magnetospheric activity. Keywords: Great Britain, Radiation belts, Space shuttle, Cosmic rays, Radiation monitoring, Trapped radiation.