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Phase Change Material for Temperature Control of Imager or Sounder on GOES Type Satellites in GEO
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External Online Source: http://www.techbriefs.com/component/content/article/16595
Author and Affiliation:
Choi, Michael(NASA Goddard Space Flight Center, Greenbelt, MD, United States)
Abstract: An imager or sounder on satellites, such as the Geostationary Operational Environmental Satellite (GOES), in geostationary orbit (GEO) has a scan mirror and motor in the scan cavity. The GEO orbit is 24 hours long. During part of the orbit, direct sunlight enters the scan aperture and adds heat to components in the scan cavity. Solar heating also increases the scan motor temperature. Overheating of the scan motor could reduce its reliability. For GOES-N to P, a radiator with a thermal louver rejects the solar heat absorbed to keep the scan cavity cool. A sunshield shields the radiator/louver from the Sun. This innovation uses phase change material (PCM) in the scan cavity to maintain the temperature stability of the scan mirror and motor. When sunlight enters the scan aperture, solar heating causes the PCM to melt. When sunlight stops entering the scan aperture, the PCM releases the thermal energy stored to keep the components in the scan cavity warm. It reduces the heater power required to make up the heat lost by radiation to space through the aperture. This is a major advantage when compared to a radiator/ louver. PCM is compact because it has a high solid-to-liquid enthalpy. Also, it could be spread out in the scan cavity. This is another advantage. Paraffin wax is a good PCM candidate, with high solid-to-liquid enthalpy, which is about 225 kJ/kg. For GOES-N to P, a radiator with a louver rejects the solar heat that enters the aperture to keep the scan cavity cool. For the remainder of the orbit, sunlight does not enter the scan aperture. However, the radiator/louver continues radiating heat to space because the louver effective emittance is about 0.12, even if the louver is fully closed. This requires makeup heater power to maintain the temperature within the stability range.
Publication Date: Jun 01, 2013
Document ID:
20130013816
(Acquired Jul 09, 2013)
Subject Category: MAN/SYSTEM TECHNOLOGY AND LIFE SUPPORT
Report/Patent Number: GSC-16546-1
Document Type: NASA Tech Brief
Publication Information: NASA Tech Briefs, June 2013; 14; (SEE 20130013804)
Financial Sponsor: NASA Goddard Space Flight Center; Greenbelt, MD, United States
Organization Source: NASA Goddard Space Flight Center; Greenbelt, MD, United States
Description: 1p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright; Distribution as joint owner in the copyright
NASA Terms: GEOSYNCHRONOUS ORBITS; GOES SATELLITES; PHASE CONTROL; RELIABILITY; SATELLITE ORBITS; SOLAR HEATING; TEMPERATURE CONTROL; THERMAL ENERGY; THERMAL STABILITY
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