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Passive dosimetry aboard the Mir Orbital Station: external measurements
E R Benton1, E V Benton, A L Frank
1Eril Research, Inc., San Rafael, CA 94915-0788, USA. eric@erilresearch.com
Radiation Measurements
|November 21, 2002
Summary
Spacecraft radiation exposure was measured outside the Mir Orbital Station. Results show significant dose reduction with shielding, with higher levels near solar maximum.
Area of Science:
- Space science
- Radiation physics
- Astrophysics
Background:
- Spacecraft in Low Earth Orbit (LEO) are exposed to significant radiation.
- Understanding radiation shielding is critical for astronaut safety and mission success.
- Previous measurements lacked detailed data for low shielding depths (<1 g/cm² Al equivalent).
Purpose of the Study:
- To conduct the first measurements of mean dose equivalent rate and average quality factor on the exterior of a LEO spacecraft.
- To assess the effectiveness of low-level shielding (<1 g/cm² Al equivalent) against space radiation.
- To compare radiation levels during solar maximum and solar minimum.
Main Methods:
- Utilized stacks of Thermoluminescent Dosimeters (TLDs) to measure absorbed dose.
- Employed CR-39 Plastic Nuclear Track Detectors (PNTDs) to measure Linear Energy Transfer (LET) spectrum.
- Combined TLD and PNTD data to determine mean total dose rate, mean dose equivalent rate, and average quality factor.
- Employed Atomic Force Microscopy (AFM) for LET spectrum analysis in the least shielded layer to prevent detector saturation.
Main Results:
- Mean dose equivalent rate and average quality factor were measured as functions of shielding depth.
- Radiation levels near solar maximum (June 1991) were higher than those near solar minimum (1997).
- Both mean dose rate and mean dose equivalent rate decreased by nearly four orders of magnitude within the first g/cm² of shielding.
- Observed significant attenuation of trapped electrons and low-energy trapped protons by shielding.
Conclusions:
- Low-level shielding (<1 g/cm² Al equivalent) is highly effective in reducing spacecraft radiation exposure.
- Space radiation environment varies significantly with the solar cycle.
- The methodology provides crucial data for improving radiation protection strategies in LEO missions.
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