Microsatellite BIRD (Bispectral InfraRed Detection), mass 92 kg, sizes 550×610×620 mm was put on October 22, 2001 in a sun-synchronous orbit. The passive thermal control system (TCS) provided a temperature range of −10…+30 °C for a payload. It is assembled from precision optical instruments and housekeeping equipment with average power about 35 W. In the observation mode a power consumption peak of 200 W is occurred during 10-20 min.
The TCS ensured a thermal stable design of the payload structure and is realised by heat transfer elements (conductors and grooved heat pipes), which thermally connected the satellite segments, two radiators, multilayer insulation and low-conductive stand-offs.
Three years in space have brought an enormous volume of telemetric data about thermal performance of the TCS, based on information from temperature sensors, power consumption, attitude relative to Sun and Earth. The TCS successfully supported the required temperature level of satellite components during the whole period of exploitation. Nevertheless, the authors aimed at analysing the temperature history during these years for the main units of housekeeping equipment such as radiator, payload platform, power supply subsystem, board computer, power supply system, communication and draw conclusions on possible changes in performance. A survey is conducted for the following time scales: payload operation time (10-30 min), one orbit (96 min), shortly after launch and current time.