Wes Ousley

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

• Concept meets scientific instrument requirements
• Maintain mirror modules at 20/- 0.1oC, mirror
  structures at 20/- 1oC
• Accommodate detector CCDs at 100oC
• Accommodate cryo-coolers to cool Super Star
  Tracker to 7oK
• Maintain other instrument support equipments
  between 10oC and 40oC
• 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

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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

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Optics Spacecraft
Sun
Hub radiator used when separated
Radiator with Louver
MLI on other exposed sides
Heat pipe coupler used when together
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Detector Craft
Sunshield
MLI blankets
Spacecraft radiators
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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

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Backup Slides
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Instrument Accommodations

• Mirror Modules
• Radiate heat to space passively through MLI.
• Require 1.5W of heater power to maintain each
  module at 20o/-0.1C
• Utilize sunshields to minimize temperature
  fluctuations
• Thermally isolate mirror modules from spacecraft
  deck
• CCD Camera
• Cool detectors to 100oC 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
  7oK
• Radiate cryo-cooler rejected heat at the
  spacecraft radiator sized to maintain at 10oC

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Mission Sequence
Launch
Transfer Stage
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Component LayoutHub Core Petal
Hub Core
Hub Petal (6)
Detector S/C Payload Adapter Fitting
Optical Module (9)
Optical Module (11)
Comm Antenna (S/C to S/C 0.3 m)
LOS Laser
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Component LayoutDetector
Solar Array (4.5 m2)
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 Electronics
CCD Camera