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Thermal control materials of different types are being used on the spacecraft for temperature control viz. Thermal control tapes, Thermal control paints, Anodised surfaces and Optical solar reflectors. This paper covers the measurement of emittance at different temperatures on various Optical Solar Reflectors ( OSR ) both rigid and flexible types. The rigid OSRs evaluated are OCLI - USA, PPE - UK and ISRO - INDIA. The flexible OSR is from SHELDAHL - USA. The emittance of the OSRs were measured in the temperature range 223K - 373K using steady state calorimetric method. Measurements were done on a square sample with OSRs affixed on each face. The sample has a built in heater and an evacuated low temperature radiation receiver is used for the test environment. Experimental results, temperature dependence of the total hemispherical emittance relation for each of these OSRs and error estimation are presented in this paper.

“Tinned Copper Braid” is planned to be used in IRS-1C spacecraft for the thermal control of the detector of the “Middle Infra Red” (MIR) band of LISS III Camera. The thermal conductance of the braid was evaluated experimentally in the temperature range of -65°C to +35°C by employing the calorimetric technique. The measured thermal conductance of the 215mm long copper braid varies from 0.051 to 0.056 W/°C at different temperatures in the specified range. An error estimation has been performed which shows a maximum uncertainty of better than ± 5% on the conductance value measured.

Integral black anodizing and gold plating on Mg-Li alloys were developed for spacecraft thermal control applications. The influence of various process conditions have been investigated to optimise the process. The deposits were characterized by morphological studies, adhesion test, thickness measurement, microhardness evaluation and porosity inspection. The space worthiness of the coatings has been evaluated by humidity, thermal cycling, and thermovacuum tests and measurement of optical properties. The high solar absorptance and infrared emittance (αs = 0.95, εIR = 0.93) value of black anodic film showed that these can be effectively utilized to improve heat radiation characteristics. The gold coating on the other hand provides the infrared emittance as low as 0.03, is extremely suitable in minimising the radiative coupling with other components within the spacecraft.