RADIATION-DOSIMETRY MEASUREMENTS DURING US SPACE-SHUTTLE MISSIONS WITH THE RME-III

Time-resolved radiation dosimetry measurements inside the crew compart ment have been made during recent Shuttle missions with the U.S. Air F orce Radiation Monitoring Equipment-III (RME-III), a portable battery- powered four-channel tissue equivalent proportional counter. Results f rom the first six missions are presented and discussed. Half of the mi ssions had orbital inclinations of 28.5 degrees with the remainder at inclinations of 57 degrees or greater; altitudes ranged from 300 to 60 0 km. The determined dose equivalent rates ranged from 70 to 5300 mu S nu/day. The RME-III measurements are in good agreement with other dos imetry measurements made aboard the vehicles. Measurements indicate th at medium- and high-LET particles contribute less than 2% of the parti cle fluence for all missions, but up to 50% of the dose equivalent, de pending on the spacecraft's altitude and orbital inclination. Isoconto urs of fluence, dose and dose equivalent rate have been developed from measurements made during the STS-28 mission. The drift rate of the So uth Atlantic Anomaly is estimated to be 0.49 degrees W/yr and 0.12 deg rees N/yr. The calculated trapped proton and GCR dose for the STS-28 m ission was significantly lower than the measured values.