1. Final Version Wes Ousley Dan Nguyen May 13-17, 2002 Micro-Arcsecond Imaging Mission, Pathfinder (MAXIM-PF) Thermal

2. Final Version MAXIM-PF, May 13-17, 2002 Goddard Space Flight Center Thermal Page 2 Summary  Concept meets scientific instrument requirements  Maintain mirror modules at 20+/- 0.1 o C, mirror structures at 20+/- 1 o C  Accommodate detector CCDs at –100 o C  Accommodate cryo-coolers to cool “Super Star Tracker” to 7 o K  Maintain other instrument support equipments between –10 o C and 40 o C  Spacecraft Bus requirements met  Maintain Optic Hub, Free-Flyer and Detector spacecraft within operational temperatures over Phase 1 and Phase 2 observations  Thermal system resource requirements  TCS mass is about 50% MLI blankets and 40% heat pipe systems  Hub: 15kg, 80W heaters (Phase 1 total), $650K hardware, $1M manpower  Detector craft: 27kg, 10W, $1.1M hardware, $2.5M manpower  Average FF: 13kg, 10W, $500K hardware, $400K manpower

3. Final Version MAXIM-PF, May 13-17, 2002 Goddard Space Flight Center Thermal Page 3 Design Features  Optics Spacecraft  Maintain mirror module temperatures with MLI and heaters  Mini sun shield for each mirror module minimizes impact of sun angle  Radiator on a no-sun side of each spacecraft  Phase 1 Optics Hub  All FF radiators blocked, except the one directly anti-sun  Louver on the exposed radiator minimizes heater power  Bottom-facing radiator not sufficient to keep Hub spacecraft cool  Heat pipe coupling transports some heat from Hub to exposed radiator via releasable junction  Detector Spacecraft  Sunshield required to keep instruments cool  Extreme thermal isolation required for SST and CCD detector system  CCD temperature controlled with radiator and heaters  Cryocooler radiator on spacecraft  Locate all radiators on the anti-sun sides  Heat pipes transport heat from spacecraft components to radiator

4. Final Version MAXIM-PF, May 13-17, 2002 Goddard Space Flight Center Thermal Page 4 Optics Spacecraft MLI on other exposed sides Sun Radiator with Louver Hub radiator used when separated Heat pipe coupler used when together

5. Final Version MAXIM-PF, May 13-17, 2002 Goddard Space Flight Center Thermal Page 5 Detector Craft Spacecraft radiators MLI blankets Sunshield

6. Final Version MAXIM-PF, May 13-17, 2002 Goddard Space Flight Center Thermal Page 6 Trades and Studies  Thermally couple hub and free flyers in Phase 1  Reduces heater power (now 80W)  Mass and hardware costs would increase; very difficult to test  Distribute radiators on free flyer sides, so heat pipes not needed  Reduces system mass and cost by about 18kg, $1M  Phase 1 heater power increases by over 300W  Large sunshield for each free flyer and hub  Slightly increases thermal stability  Increases mass and complexity  Distribute radiators on detector craft, so fewer heat pipes needed  Reduces system mass and cost by about 12kg, $500K  Component location becomes critical, and heater power increases  Critical thermal system parameters  Thermal isolation of mirrors, SST/cryocooler system, cold CCD and radiator  Heat pipe systems design and testability

7. Final Version MAXIM-PF, May 13-17, 2002 Goddard Space Flight Center Thermal Page 7 Backup Slides

8. Final Version MAXIM-PF, May 13-17, 2002 Goddard Space Flight Center Thermal Page 8 Instrument Accommodations  Mirror Modules  Radiate heat to space passively through MLI.  Require 1.5W of heater power to maintain each module at 20 o +/-0.1C  Utilize sunshields to minimize temperature fluctuations  Thermally isolate mirror modules from spacecraft deck  CCD Camera  Cool detectors to –100 o C using dedicated radiator on the anti-sun side  Detector electronic heat dissipation combine with spacecraft dissipation  Super Star Tracker  Utilize ACTDP cryo-cooler to maintain tracker at 7 o K  Radiate cryo-cooler rejected heat at the spacecraft radiator sized to maintain at 10 o C

9. Final Version MAXIM-PF, May 13-17, 2002 Goddard Space Flight Center Thermal Page 9 Mission Sequence Launch Transfer Stage Science Phase #1 Low Resolution 200 km Science Phase #2 High Resolution 1 km 20,000 km

10. Final Version MAXIM-PF, May 13-17, 2002 Goddard Space Flight Center Thermal Page 10 Component Layout Hub Core & Petal Hub Core Hub Petal (6) LOS Laser Detector S/C Payload Adapter Fitting Optical Module (9) Optical Module (11) Comm Antenna (S/C to S/C 0.3 m)

11. Final Version MAXIM-PF, May 13-17, 2002 Goddard Space Flight Center Thermal Page 11 Component Layout Detector Solar Array (4.5 m 2 ) Comm Antenna (Ground/SpaceCraft 0.5 m) Comm Antenna (S/C to S/C 0.3 m) Comm Antenna (Ground/SpaceCraft 0.5 m) LOS laser receiver CCD Camera CCD Electronics