Spaceborne autoranging infrared viewing system for thermal mapping of fluids in a microgravity condition

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The European Space Research and Technology Centre (ESTEC) has developed a small, space qualified and TV compatible IR viewing system able to visualize thermal flows in fluids in microgravity. This instrument is a part of the diagnostics of a Spacelab facility, namely the Autonomous Fluid Physics Module (AFPM) flown on the last Spacelab D2 mission (April to May 1993). One of the main objectives of the research is to enable monitoring changes in the surface temperature of a fluid following the application of different stimuli. The only way to achieve this without disturbing the fluid under test is to use nonintrusive infrared measurement techniques. Starting from a basic commercial item, the Agema 870 scanner, ESTEC designed and built a thermal mapping diagnostic system provided with an autoranging capability that allows real-time temperature measurement in the range from 0 to 80°C and with a frame rate of 6 images/s. The geometrical resolution is 70 x 70 pixels in a field of view of 130 x 1 30 mm, which maps out the full temperature distribution of a typical fluid column experiment. An automatic compensation of the background noise at room temperature keeps the minimum resolvable temperature difference (MRTD) figure below 0.2°C. Therefore, the overall accuracy of the system allows one to follow the evolution of the complex phenomena related to the heat convection and mass transport effects at the surface of fluids in a weightlessness environment. The general design of the thermal mapping diagnostic (TMD) system is described and the technical solutions adopted to achieve the scientific goals of the investigation carried out with the AFPM are presented.