A built-in test circuit determines the dead time, a measure of how many events have been missed due to the response time of the detector electronics and an important parameter for subsequent data processing on ground. Data processing Raw data are disseminated by using a modem to download data from a personal computer at the control centre. Spacecraft and experiment housekeeping data are also routinely accessible. Data then undergo quick-look processing to ensure that the instrument is operating correctly and that housekeeping is within limits, and to check for anomalous environment events such as particle events. PSI are responsible for further detailed data evaluation to build a radiation environment data base and to provide inputs for updating the environment models.
Several corrections have to be applied to the data during detailed evaluation.
The type and thickness of the dome material and the setting of pulse height thresholds in the REM processing electronics allow one detector to be optimised for electrons and the other for protons. But this does not fully prevent a few protons from being counted by the electron detector, and to a lesser extent, a few electrons counted by the proton detector, errors which fortunately can be measured and a corrected. Calibration Prior to launch, the REM was extensively calibrated at PSI using high energy protons and electrons, and the angular dependence was measured as part of this calibration. Using the calibration data, in orbit data and modelling, it is possible to derive detector response functions which should allow the extraction of data on particle type, energy and flux. At the time of writing the REM has been in operation for 38 full orbits and the data already show that the STRV REM will be able to provide very high quality environment data with a great amount of detail.