Thermal design of Landsat-7 ETM+ Earth/space background simulators

In the Landsat-7 observatory thermal balance/thermal vacuum (TB/TV) test, deployments of the radiative cooler door and full aperture calibrator (FAC) of the Enhanced Thematic Mapper Plus (ETM+) scanner will be tested. A space background simulator (SBS) to simulate the space radiative heat sink for the cooler aperture and the interior of the cooler door has been designed, built and tested in a vacuum chamber. The SBS is an open loop cryogenics system using a liquid helium dewar. Results of the SBS thermal vacuum test showed that it satisfactorily operated and simulated the space radiative heat sink. An Earth background simulator (EBS) to simulate the equivalent heat sink temperature for the mapper aperture of the scanner has also been designed and built. It also protects the FAC and FAC actuator from being exposed to the liquid nitrogen cooled chamber walls. This paper presents the thermal design of the SBS and EBS, and the SBS thermal vacuum test and its results.