In order to measure the charged massive particles encountered by satellites in space, the Paul Scherrer Institute has developed in collaboration with the Swiss Compagnie Industrielle Radioelectrique, CIR under ESA contract No. 11108/94/N1/JG(SC) the Radiation Environment Monitor.
The REM instrument provides local particle fluxes with some discrimination in both, particle species and energy.

In the period from 1994 to 1998 two REM instruments were operational in space and delivered a wealth of data.