MAXIM Pathfinder

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

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MAXIM Pathfinder Thermal 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

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MAXIM Pathfinder Thermal 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

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MAXIM Pathfinder Thermal 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

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MAXIM
ORBIT CONFIGURATION
Detector Spacecraft
Optic Spacecraft
Solar Array (7 m2, projected area)
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MAXIM
OPTIC SPACECRAFT (DIFFERENT VIEWS)
Different views of the Optic space- craft
Spacecraft Subsystem
This view spacecraft subsystems removed
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MAXIM Pathfinder Thermal 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

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MAXIM
DETECTOR SPACECRAFT
Payload
Fixed Solar Array (6m2 shown)
Stowed
Orbit
Spacecraft
Spacecraft Subsystems are mounted in this volume
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MAXIM
Detector Baffle
Range Sensors Baffle
Detector / CCD/ QC Cryogenics
Payload Volume
Range Sensors
Enlarged View of Baffle
DETECTOR SPACECRAFT
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MAXIM Pathfinder Thermal 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)