HIGH T-C LEADS FOR REMOTE-SENSING APPLICATIONS

Several NASA programmes designed to monitor the earth's atmosphere fro m space utilize infrared detectors which operate at or below 4.2 K for optimum performance. At present, the detectors are maintained at cryo genic temperatures by a stored volume of liquid helium. These detector s must be electrically linked to amplification electronics and data st orage instruments maintained at 80 K. The electrical connections over the temperature gradient account for approximate to 20% of the total h eat load on the Dewar for some systems, accelerating the boil-off of l iquid helium cryogen and reducing the operational lifetime of the spac e-borne instruments. The recent discovery of high temperature supercon ductors has provided an opportunity to develop electrically conductive , thermally insulating links to bridge this thermal gradient. This pap er describes the modelling of the thermal transport properties of thic k film, high T-c electrical bridges across a 4.2-80 K temperature grad ient and the impact of such devices on a spaceborne remote sensing sys tem.