Abstract : A survey was made to determine the state of the art of various methods of cooling to cryogenic temperatures for potential adaptation to spaceborne systems. The study included evaluation of mechanical closed-cycle refrigerators, open-cycle expendable systems, passive radiation concepts which utilize the low temperature of the deep space environment, and thermoelectric devices. The following mechanical refrigeration cycles were evaluated: Vuilleumier, Stirling, Gifford-McMahon/Solvay, Brayton and Claude. Open-cycle expendable systems evaluated were high-pressure gas coupled with Joule-Thomson expansion, cryogenic liquids in both the subcritical and supercritical state, solidified cryogens, and liquids storable at room temperature.