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Electro emissive (Esther) devices are thin sheets, whose infrared emissivity can be varied reversibly by electrical charging. Bonded to external surfaces of spacecraft radiators, they allow active control of the heat radiated to space while consuming negligible electrical energy. Due to the very low mass and power consumption of that novel component for space craft thermal control, considerable cost savings in development and operation can be achieved. In the current phase of the development the performance of the Esther devices, achieved in the laboratory, is optimised (where necessary) and consolidated. The applied processes of the thin film technology and the internal structure and materials of the different layers have been optimised w.r.t. reproducibility and stable performance. The manufacturing and the functional test of the Esther devices has been standardised and a number of prototypes were produced (about 200).

Electro emissive devices, called ESTHER, are thin sheets - similar to solar cells - whose infrared emissivity can be varied reversibely by electrical charging. Bonded to external surfaces of spacecraft radiators, they allow active control of the heat radiated to space while consuming negligible electrical energy. Applying this novel component for spacecraft thermal control, considerable cost savings in spacecraft development and operation can be achieved. Progress in the design and manufacturing process has been made since the first puplication in July '92 /1/ revealing an increased variability of emissivity and an increased duty cycle stability. The material selection process was facilitated by the exposure of material samples to the space environment during two spaceflight missions and the subsequent material analyses.