Huston, Stuart L. | Search NASA

NASA NTRS2002

Natural and Induced Environment in Low Earth Orbit

The long-term exposure of astronauts on the developing International Space Station (ISS) requires an accurate knowledge of the internal exposure environment for human risk assessment and other onboard processes. The natural environment is moderated by the solar wind which varies over the solar cycle. The neutron environment within the Shuttle in low Earth orbit has two sources. A time dependent model for the ambient environment is used to evaluate the natural and induced environment. The induced neutron environment is evaluated using measurements on STS-31 and STS-36 near the 1990 solar maximum.

Wilson, John W.↗

NASA NTRS1999

New Trapped Proton Model

The space radiation environment is of crucial importance to all manned and unmanned space activities. As spacecraft and their systems and instruments have become more sophisticated, they have also become more susceptible to the space radiation environment. New requirements for the radiation models have made it evident that the existing models are now inadequate. NASA, ESA, and other agencies are consequently working to develop new models. In particular, under NASA's Space Environments and Effects (SEE) program, a new model has been developed which correctly models the solar cycle variations in the trapped proton flux at low altitudes. This model is now being merged with the U.S. Air Force model based on data from the CRRES satellite; the resulting model will be a replacement for the current models. In this paper we discuss the models currently available and their drawbacks. We also discuss the development of the new model and present some preliminary results.

Huston, Stuart L.↗