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Thermal Design Parameters

High Earth Orbit, 3Re to 25Re, 3 day period Primary mirror diameter 2m Hubble is 2.3m diameter OTA very sensitive to temperature changes 2 micron vertical shift would defocus image Detectors at 140K, area 0.3m 2 , passively cooled. Thermal Design Parameters. Overall View. Solar array

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Thermal Design Parameters

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  1. High Earth Orbit, 3Re to 25Re, 3 day period Primary mirror diameter 2m Hubble is 2.3m diameter OTA very sensitive to temperature changes 2 micron vertical shift would defocus image Detectors at 140K, area 0.3m2, passively cooled Thermal Design Parameters

  2. Overall View Solar array (alternating cells and OSR’s) Detector radiator Spacecraft bus

  3. Hubble-type OTA thermal design Thermal control required for primary mirror, secondary mirror, and aft optics No heaters baselined for secondary truss structure – must be very low CTE Secondary mirror adjustments for significant changes in secondary structure temps Heater power estimate 100W Scaled-down Hubble test result: 85W for primary and secondary mirrors TCS Conduction loss thru primary structure significant Power to heat aft optics: 15W OTA Thermal Concept

  4. Instrument Diagram

  5. Mounted to molybdenum plate High-conductivity, low CTE Aluminum foil S-links couple plate to radiator (2m2) Estimated 32W cooling required (D. Pankow) Heat pipes recommended to raise efficiency of radiator Plate of 3mm thickness yields about 1.2C gradient among detectors Finer control can be achieved by: Thicker plate (higher mass) Heat pipes mounted to plate (low mass, cost of ~200K) More thermal control zones (higher cost) Detectors

  6. Detector layout Moly plate

  7. Telescope thermal requirements met with 100W heater budget Detector temperatures at required level Detector thermal gradients can be reduced by added mass or cost Conclusions

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