Search Results

INSAT-2A spacecraft carries on-board a Very High Resolution Radiometer (VHRR) as one of the major payloads for the purpose of meteorological observations. The thermal infrared (IR) detector of the Radiometer requires cooling to cryogenic temperature for its operation at any of the set points in the range of 105 K to 115 K for optimum performance. A passive radiant cooler has been designed and realised indigenously to meet this requirement. A computer oriented mathematical model has been developed which simulates the on-orbit thermal environment and predicts the performance of the cooler for various sun illumination conditions. INSAT-2A spacecraft has completed more than one year of its successful operation on-orbit now. It has been observed that a minimum patch control power margin of 4.7 mW exists for beginning of life (BOL) condition i.e. 5th August, 1992.

A super insulated (multi layer insulation) heat shield has been designed and implemented for the 440 N Liquid Apogee Motor (LAM) of INSAT-2A and INSAT-2B satellites. The design had been arrived at its final configuration after a series of test and detailed analysis of the test data. An effective conductivity and emissivity for the shield insulation assembly was estimated and used for predicting the flight performance.

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.