UNIRAD is a software package developed by BIRA/IASB
for ESA to evaluate radiation-belt and solar particle event fluences
and doses expected in a spacecraft from a definition of the mission
characteristics. The UNIRAD suite of programs provides information
about the radiation environment in an arbitrary Earth orbit, predicting
satellite exposures to particle fluxes, the resulting radiation
dose, and the resulting damage-equivalent fluences for solar cell
degradation calculations. Recently, UNIRAD
has been extended with two new programs that model the anisotropy
of trapped particle flux distributions at low altitudes.
Various problems have been identified in the existing "NASA"
radiation belt models AE-8 and AP-8. New models developed in
the ESTEC/TEC-EES-sponsored TREND study (Trapped Radiation ENvironment Development) are being
added to UNIRAD. These models include:
- new trapped proton flux maps based on data from
- AZUR (proton telescopes),
- SAMPEX (PET) and
- UARS (PEM) data,
- and trapped electron models developed with data from
- CRRES (MEA) and
WWW-based access to UNIRAD
is also being developed as part of the Space
Environment Information System (SPENVIS).