1. SuperNova / Acceleration Probe Thermal System Wes Ousley November 16, 2001

2. SNAP Thermal P2 Wes Ousley 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

3. November 16, 2001 SNAP Thermal P3 Wes Ousley Overall View Spacecraft bus Detector radiator Solar array (alternating cells and OSR’s)

4. November 16, 2001 SNAP Thermal P4 Wes Ousley OTA Thermal Concept 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

5. November 16, 2001 SNAP Thermal P5 Wes Ousley Instrument Diagram

6. November 16, 2001 SNAP Thermal P6 Wes Ousley Detectors Mounted to molybdenum plate  High-conductivity, low CTE Aluminum foil S-links couple plate to radiator (2m 2 ) 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)

7. November 16, 2001 SNAP Thermal P7 Wes Ousley Detector layout Moly plate

8. November 16, 2001 SNAP Thermal P8 Wes Ousley Conclusions Telescope thermal requirements met with 100W heater budget Detector temperatures at required level  Detector thermal gradients can be reduced by added mass or cost