In-flight radiation measurements on STS-60

Area of Science:

• Space Science and Radiation Dosimetry
• International Collaboration in Space Research

Background:

• The Shuttle-Mir Science Program (Phase 1) facilitated joint investigations between the US and Russia.
• Understanding the space radiation environment is critical for astronaut safety and mission planning.

Purpose of the Study:

• To conduct the first direct comparison of various dosimetric measurement techniques between the US and Russia.
• To characterize the radiation environment aboard Space Shuttle flight STS-60.

Main Methods:

• Utilized a variety of instruments to measure crew radiation exposure, absorbed doses, neutron fluence, dose equivalent, linear energy transfer (LET) spectra, and proton energy spectra.
• Employed tissue equivalent proportional counters (TEPCs) and thermoluminescent detectors (TLDs) for radiation measurements.
• Analyzed trapped and galactic cosmic radiation, including the effects of spacecraft attitude on dose rates.

Main Results:

• Demonstrated good general agreement between US and Russian dosimetric measurements.
• Observed that the AP8 Min trapped proton model overestimates absorbed dose by approximately 1.8 times.
• Measured absorbed dose rates of ~298.5 microGy/day, with significant variations (up to a factor of 2) due to spacecraft attitude changes.

Conclusions:

• The study validated the effectiveness of multiple dosimetric techniques through international collaboration.
• Spacecraft attitude is a significant factor influencing radiation dose rates in low-Earth orbit.
• The westward drift of the South Atlantic Anomaly (SAA) was estimated at 0.22 degrees/year.