IN-FLIGHT RADIATION MEASUREMENTS ON STS-60

A joint investigation between the United States and Russia to study th e radiation environment inside the Space Shuttle flight STS-60 was car ried out as part of the Shuttle-Mir Science Program (Phase 1). This is the first direct comparison of a number of different dosimetric measu rement techniques between the two countries. STS-60 was launched on 3 February 1994 in a nearly circular 57 degrees x 353 km orbit with five U.S. astronauts and one Russian cosmonaut for 8.3 days. A variety of instruments provided crew radiation exposure, absorbed doses at fixed locations, neutron fluence and dose equivalent, linear energy transfer (LET) spectra of trapped and galactic cosmic radiation, and energy sp ectra and angular distribution of trapped protons. In general, there i s good agreement between the U.S. and Russian measurements. The AP8 Mi n trapped proton model predicts an average of 1.8 times the measured a bsorbed dose. The average quality factor determined from measured line al energy, gamma, spectra using a tissue equivalent proportional count er (TEPC), is in good agreement with that derived from the high temper ature peak in the (LiF)-Li-6 thermoluminescent detectors (TLDs). The r adiation exposure in the mid-deck locker from neutrons below 1 MeV was 2.53 +/- 1.33 mu Sv/day. The absorbed dose rates measured using a tis sue equivalent proportional counter, were 171.1 +/- 0.4 and 127.4 +/- 0.4 mu Gy/day for trapped particles and galactic cosmic rays, respecti vely. The combined dose rate of 298.5 +/- 0.82 mu Gy/day is about a fa ctor of 1.4 higher than that measured using TLDs. The westward longitu de drift of the South Atlantic Anomaly (SAA) is estimated to be 0.22 /- 0.02 degrees/y. We evaluated the effects of spacecraft attitudes on TEPC dose rates due to the highly anisotropic low-earth orbit proton environment. Changes in spacecraft attitude resulted in dose-rate vari ations by factors of up to 2 at the location of the TEPC.