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Solution for Direct Solar Impingement Problem on Landsat-7 ETM+ Cooler Door During Cooler Outgas in Flight
Technical Paper
1999-01-2677
ISSN: 0148-7191, e-ISSN: 2688-3627
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English
Abstract
There was a thermal anomaly of the landsat-7 Enhanced Thematic Mapper Plus (ETM+) radiative cooler cold stage during the cooler outgas phase in flight. With the cooler door in the outgas position and the outgas heaters enabled, the cold stage temperature increased to a maximum of 323 K when the spacecraft was in the sunlight, which was warmer than the 316.3 K upper set point of the outgas heater controller on the cold stage. Also, the outgas heater cycled off when the cold stage was warming up to 323 K. A corrective action was taken before the attitude of the spacecraft was changed during the first week in flight. One orbit before the attitude was changed, the outgas heaters were disabled to cool off the cold stage. The cold stage temperature increase was strongly dependent on the spacecraft roll and yaw. It provided evidence that direct solar radiation entered the gap between the cooler door and cooler shroud. There was a concern that the direct solar radiation could cause polymerization of hydrocarbons, which could contaminate the cooler and lead to a thermal short. After outgas with the cooler door in the outgas position for seven days, the cooler door was changed to the fully open position. With the cooler door fully open, the maximum cold stage temperature was 316.3 K when the spacecraft was in the sunlight, and the duty cycle of the outgas heater in the eclipse was the same as that in the sunlight. It provided more evidence that direct solar radiation had entered the gap between the cooler door and cooler shroud. Cooler outgas continued for seven more days, with the cooler door fully open. The corrective actions had prevented overheating of the cold stage and cold focal plane array (CFPA), which could damage these two components. They also minimized the risk of contamination on the cold stage, which could lead to a thermal short.
Citation
Choi, M., "Solution for Direct Solar Impingement Problem on Landsat-7 ETM+ Cooler Door During Cooler Outgas in Flight," SAE Technical Paper 1999-01-2677, 1999, https://doi.org/10.4271/1999-01-2677.Also In
References
- Landsat-7 Mission Operations Center Temperature Data of ETM+ April 15 May 31 1999 Gooddard Space Flight Center Greenbelt, MD
- Landsat-7 ETM+ ICD 1995 Goddard Space Flight Center Greenbelt, MD 1995
- Landsat-7 ETM+ ICD 1997 Goddard Space Flight Center Greenbelt, MD 1997
- Choi, M. K. “Thermal Assessment of Landsat-7 ETM+ Radiative Cooler in Thermal Vacuum Tests and in Flight,” 34th IECEC Aug. 1-5 Vancouver, B. C., Canada Paper No. 1999-01-2628
- Choi, M. K. “Significance of Landsat-7 Spacecraft Level Thermal Balance and Thermal Vacuum Test for ETM+ Instrument,” 34th IECEC Jul. Aug. 1-5 Vancouver, B. C., Canada Paper No. 1999-01-2676