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A computer based data acquisition and power control system has been designed and installed for conducting thermal test at 4M thermal vacuum chamber of ISRO Satellite Centre(ISAC), Bangalore, INDIA. The system consists of four main units viz. Temperature Signal Processing Unit(TSPU), Power and Control Unit(PACU), Spacecraft telemetry and thermal vacuum chamber facility data interface unit and Data Processing Unit(DPU). The system has capability of monitoring 512 thermocouple channels, 700 spacecraft telemetry thermal related parameters, facility parameters including chamber Vacuum level, chamber contamination level using Quartz Crystal Monitor data and 128 numbers of heat-flux/temperature control channels. TSPU and PACU are VME based system. DPU is based on Pentium processor with hot redundancy using Redundant Array Of Inexpensive Disks(RAID) to takeover in case of failure of a server. All the subsystem and their peripherals are networked using TCP/IP on Ethernet.

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%.

“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.

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.

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.