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Prior to successful launch of IRS-1A, two different thermal balance tests were carried out, one on the Structure Thermal Model using heater pad technique and second on Engineering Model, using solar simulation technique. The temperature match was found to be better for extreme cold case in STM test and for EOL case in solar simulation test and not so good for other cases. An attempt was made to find out the reasons for this mismatch, but the exact reason could not be ascertained. The flight temperatures were predicted, based on solar simulation test data, which matches well with on orbit data.

The first Indian Remote Sensing Satellite, IRS-1A, has a mono-propellant Reaction Control System(RCS) for orbit and attitude correction. In early phase of spacecraft life some anomaly in fuel mass calculations was observed and one group of tanks were emptied much earlier than expected. This paper explains how heating/cooling rates of propellant tanks and comparison with theoretically calculated temperature response were used for sorting out the anomaly.

The total hemispherical emittance of different Thermal Control Coatings viz. Chemglaze Black Paint Z-306, 3M Black Paint, ECP-2200, Whittakar White Paint APA-247 4 and Astral Aluminium Paint PSG-173 being used in different spacecrafts for thermal control purpose were measured in the temperature range 115K-375K using steady state calorimetrie method. Measurements were done on a disc shaped sample with built in heater and an evacuated low temperature radiation receiver is used for the test environment. Experimental results and error estimation are presented here. The results indicate that the emittance increases with increase of temperature for all the coatings. Along with the experimental results, temperature dependence of the emittance relation for each of these coatings is also presented. Facilities and measurement technique used here are capable of providing the results better than ±3.0 % at the lowest temperature of the measured temperature range.

The measurement of coefficient of thermal expansion of CFRP strut which is planned to be used in Indian Remote Sensing Spacecraft (IRS-1C) has been measured from -10°C to +50°C using an electronic digital indicator. A suitable test rig was designed and fabricated to carry out this measurement in the required temperature range. The coefficient of the thermal expansion results obtained with this testing and technique are accurate to ± 13.4% and the repeatability of this measurement is better than ± 1.3%.