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Description of design principles of thermocontrol system for small subsatellites Magion- 4, 5 and thermal behavior during two years of flight exploitation are presented. Passive type of thermocontrol system is intended to support the temperature level (-10…50) °C in inner volume of equipment compartment at solar subsatellite orientation and in temporary Earth shadow. Heat energy balance of the object at required temperature range is provided by utilization of radiating surfaces with defined areas, by thermal coupling of hot and cold subsatellite parts and by adaptation of constructive subsatellite elements to solve thermal tasks. Survey of telemetric date concerns temperature state of the main major parts of satellite are under consideration as well.

An approach to the creation of passive radiative cooling system ensuring temperature levels less than 220K for the optical sensor of scientific space equipment elements is considered. The system is intended for the arbitrary orientation-in-space function under solar radiation. Theoretical analysis of the application field of this system, using heat pipes with constant and variable thermal resistance in a range of solar constant variation (500…2700)W/m2 is given. Experimental results on system models, in which two engaged in parallel thermodiodes with freon-22 and ammonium were used, showed the possibility to attain device temperature levels less than 220 K at the solar constant magnitude 1400 W/m2 and device heat release under (1…2) W.

Heat pipes efficiency for space thermal engineering is widely recognized and illustrated. Among majority of heat transfer tasks the heat pipe employment for high precision optical devices' thermal control is interesting and challenging. The main heat pipe functions are associated with a) heat removal tasks in the wide temperature range (90 ÷ 300 K), b) heat transfer and redistribution inside/outside of system, c) providing of isothermality of mounting plate (seats) of devices; d) regulating of temperature in selected device or group of devices. The brief description of technical realization example of heat pipe application in peculiarities of small satellite design is subject of this report.