LEGRI Instrument Health

LEGRI has been operating successfully on MINISAT-01 since its switch-on the 22nd of May 1997. HouseKeeping (HK) data have been continuously received for nearly two years by LEGRI SOC in Valencia, and subsequently checked on a daily basis and then stored for long term monitoring analysis. LEGRI HouseKeeping data include three critical operating parameters: temperature, power and polarisation voltages. Six temperature sensors are spread over the different LEGRI units: Detector Unit, Data Processing Unit, High Voltage Unit and Star Sensor. Voltages are measured at eight different points. Detector Unit temperature and polarisation voltage are the critical parameters for LEGRI operation. Solid state detectors are sensitive to changes not only in polarisation but also in temperature. Around one and a half million of measurements for each of the HK fourteen parameters have been recorded and analysed. The data show a very remarkable stability, within the expected margins, and the averages are very close to the optimal design values. Special attention has been paid to the detector polarisation voltages analysis with a mean value of 286 +/- 2 V when the detectors are operating. Thermal control over all the LEGRI units shows a remarkable stability in their temperatures.On the detector plane a mean value of T-det = 13 +/- 2 degreesC has been found. We can therefore conclude that LEGRI as a system has been operating within its optimal design conditions. We also want to point out the excellent performance of the MINISAT-01 thermal control system.