MAXIM Pathfinder THERMAL CONTROL SYSTEM PRESENTATION August 19, 1999 Wes Ousley NASA/GSFC Code 545

1. MAXIM Pathfinder THERMAL CONTROL SYSTEM PRESENTATION August 19, 1999 Wes Ousley NASA/GSFC Code 545 301-286-2213 (IMDC)

2. MAXIM PathfinderThermal SystemAugust 5, 1999 MAXIM mission thermal requirements can be accommodated with passive thermal control systems (blankets, heaters, heat pipes, thermo-electric coolers) • Optics module requires gradients to be minimized • Composite structure (near-zero CTE), sun side insulated • Radiators on anti-sun side control component temperatures • Detectors require fine temperature control near 170K • Thermo-electric coolers and heat pipes • Both modules require aperture sunshades to meet thermal requirements

3. MAXIM PathfinderThermal SystemAugust 5, 1999 Mission Requirements • Optics spacecraft: • Required pointing stability is 300 marcsec • Payload power dissipation is 259 Watts • Detector spacecraft: • Detectors require 170K temperature • Payload power dissipation is 313 Watts • Flyaway orbit eliminates earth effects • Both spacecraft point one side to the sun, +/- 5O • Allowable thermal deflection from off-pointing is severely limited

4. MAXIM PathfinderThermal SystemAugust 5, 1999 Thermal Design Features Optical satellite • Pointing requirements dictate: • Mirror structure and spacecraft components must be thermally isolated • Mirror structure must be low-CTE composite to minimize deflections • Use of current flight spacecraft composite materials produces significant deflections • Thermal baffles required on front end (like AXAF) and back end (like C-X) • Heat pipes are required for spacecraft component temperature control • Radiators on anti-sun side easily accommodate power requirements • Radiators could be sized to reduce 30W prop heater power needs • Body-mounted solar array max temp would be about 100OC if fully populated

5. MAXIM ORBIT CONFIGURATION Detector Spacecraft Solar Array (7 m^2, projected area) Optic Spacecraft

6. MAXIM OPTIC SPACECRAFT (DIFFERENT VIEWS) Different views of the Optic space- craft Spacecraft Subsystem This view: spacecraft subsystems removed

7. MAXIM PathfinderThermal SystemAugust 5, 1999 Thermal Design Features Detector satellite • Detector requires a thermo-electric cooler to achieve 170K • Heat pipes transport TEC power and electronics dissipation to radiators • Radiator margins over 100% for spacecraft components and payload package • Hydrazine propulsion system heaters total 30 W (lines, tanks, valves, etc.) • Cold gas system would need no significant heater power

8. MAXIM DETECTOR SPACECRAFT Payload Fixed Solar Array (6m^2 shown) Stowed Orbit Spacecraft Spacecraft Subsystems are mounted in this volume

9. MAXIM Detector Baffle Range Sensors Baffle Detector / CCD/ QC Cryogenics Payload Volume Range Sensors Enlarged View of Baffle DETECTOR SPACECRAFT

10. MAXIM PathfinderThermal SystemAugust 5, 1999 Conclusion • Passive thermal control can accommodate instrument and spacecraft requirements. • Advanced composite structure required to meet pointing spec • Telescope and detector baffle systems will be challenging • Each spacecraft operational heater power totaled 30 watts (for hydrazine prop systems)