FIGURE 3.1 The radiation environments of the International Space Station: the three regions of space around Earth where penetrating radiation occurs. SOURCE: NRC, 2000, Figure 1.1, p. 8.

Crew Exposure Modeling Capability

SRAG’s modeling tools include radiation transport codes and computer-aided-design-based geometry evaluation tools. These tools are used as part of an information feedback loop, and real measurements are used to refine the process continuously. This allows SRAG to react to changes in the on-orbit environment and to anticipate and plan for periods of potentially hazardous exposure.

Radiation Monitoring Instruments and Dosimeters

The present suite of detectors used to monitor the radiation environment during manned missions includes passive dosimeters (crew passive dosimeter [CPD] and radiation area monitor [RAM])1 and active


A CPD is a small set of thermoluminescent detectors (TLDs) encased in a Lexan holder. The material responds to radiation via electronic excitation states in the various TLD materials. After exposure, the amount of absorbed energy (dose) is determined by applying heat and measuring the amount of visible light released as these excited states are returned to equilibrium. A CPD is carried by each member of the crew during the entire mission and analyzed upon return to Earth. Identical to the CPD, RAMs are placed throughout the volumes of both the ISS and the space shuttle; the ISS RAMs are swapped out during the periodic shuttle servicing and supply missions.

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