Validation of Landsat-7 ETM+ MEM thermal improvement in thermal vacuum tests and in flight due to lower louver set points

摘要

The Enhanced Thematic Mapper Plus (ETM+) Main Electronics Module (MEM) power supply heat sink temperature is critical to the Landsat-7 mission. It is strongly dependent on the thermal louver design. A lower power supply heat sink temperature increases the reliability of the MEM, and reduces the risk of over heating and thermal shutdown. After the power supply failures in ETM+ instrument thermal vacuum tests no.1 and no.2, the author performed detailed thermal analyses of the MEM, and proposed to reduce the louver set points by 7°C. At the 1998 Intersociety Energy Conversion Engineering Conference (IECEC), the author presented a paper that included results of thermal analysis of the MEM. It showed that a 7°C reduction of the louver set points could reduce the maximum power supply heat sink temperature in thermal vacuum test and in flight to below 20°C in the cooler outgas mode and in the nominal imaging mode, and has no significant impact on the standby heater duty cycle. It also showed that the effect of Earth infrared and albedo on the power supply heat sink temperature is small. The louver set point reduction was implemented in June 1998, just prior to ETM+ thermal vacuum test no.3. Results of the thermal vacuum tests, and temperature data in flight validate the MEM thermal performance improvement due to the 7°C reduction of the louver set points.