Performance Characteristics of the ASTER Cryocooler in Orbit

Abstract

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) was developed by the Japanese Ministry of Economy, Trade and Industry (METI) for installation in the NASA EOS Terra spacecraft. The ASTER instrument consists of a visible and near-infrared radiometer (VNIR), a short-wave infrared radiometer (SWIR) and a thermal infrared radiometer (TIR). Two cryocoolers are required to cool the infrared detectors for the SWIR and the TIR subsystems.

In the first functional checkout of the two subsystems in orbit, the SWIR cryocooler cooled the PtSi detector to an operating temperature of 77 K in a cooldown time of 22 minutes, and the TIR cryocooler cooled the MCT detector to an operating temperature of 80 K in a cooldown time of 23 minutes.

The two cryocoolers have been smoothly working in orbit for over 2 years. The temperature of each detector has stabilized in the allowable temperature range. Long-term data have been acquired on the cooling performance and power consumption (or motor current) under normal operating conditions for each cryocooler, and they have also been evaluated based on the detector temperature and temperature stability in this phase.

With the recognition that the coolers completed fabrication and qualification testing about four years before launch, and now have acquired over two years operation in orbit, it is clear that the performance requirements for the ASTER cryocoolers have been met. This paper summarizes both the ground test results prior to launch as well as the on-orbit performance characteristics of the ASTER cryocoolers.