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Trapped Radiation ENvironment model Development

Time Dependent Radiation-Belt Space Weather Modelling

Salammbô simulation The space environment constitutes a severe and multifaceted hazard to manned and unmanned spacecraft. Energetic particles geomagnetically trapped in the Van Allen radiation belts are an important part of this hazardous environment. These particles induce latch-ups or single event upsets in electronics, ionising and non-ionising dose, and degradation of solar panels. With the increasing demand for low-cost missions and for ever more sensitive electronics, engineering tools to model both the radiation environment and its effects on the spacecraft elements and crew have to be more and more accurate. Therefore, a series of studies (Trapped Radiation ENvironment model Development, TREND) have been funded by the ESA Technology Research Programme to improve existing radiation environment models and the software tools used to predict the radiation experienced by spacecrafts.

Strv-1b/REM Ap15 dependent model The TREND-4 study addresses two specific aspects:

  • the storm-time behaviour of trapped electrons in the outer part of the radiation belts;
  • the anisotropy and variability on different time scales of the trapped protons at the inner edge of the radiation belts.
These two populations have in common that they are both driven by space weather conditions. The outer-belt electron population is affected by magnetic storms or sub-storms while the inner-edge proton population is affected by the seasonal and solar-cycle variation of the Earth's atmosphere.

East-West proton anisotropy

Data from Meteosat-3/SEM-2, CRRES/MEA and Strv-1b/REM have been combined with Salammbô simulations to study the electron population during eight substorms. The confrontation of the resulting Salammbô maps with the data has allowed an evaluation and improvements of the Salammbô code. The Strv-1b/REM electron data have been correlated with magnetospheric driving parameters. The CRRES/MEA and Strv-1b/REM data have also been mapped into Ap15 dependent models of the outer electron belt.

SAMPEX/PET Proton flux

Data from MIR/REM have been analysed to extract the proton flux anisotropy in the altitude range of the MIR and ISS stations. The physical processes driving the proton fluxes at low altitudes have been reviewed. Alternative coordinates to order proton flux measurements at low altitudes have been investigate. Data from SAMPEX/PET have been used to build a model map of the L < 2 proton flux and to analyse secular, solar-cycle and seasonal variations of the proton population over a period of five years.

The UNIRAD programme suite has been extended to include products of the TREND-4 study. These products will be available in the SPENVIS system. Results have been presented at international meetings and publications.

Project made under ESTEC Contract No. 11711/95/NL/JG - CCN No. 1 to WO No. 3