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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
System
August 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
System
August 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
System
August 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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Detector Spacecraft
Solar Array
(7 m^2, projected area)
ORBIT CONFIGURATION
Optic Spacecraft
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OPTIC SPACECRAFT (DIFFERENT VIEWS)
Different views
of the Optic spacecraft
Spacecraft
Subsystem
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This view: spacecraft subsystems removed
MAXIM Pathfinder Thermal
System
August 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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Payload
DETECTOR SPACECRAFT
Fixed
Solar Array
(6m^2 shown)
Stowed
Orbit
Spacecraft
Spacecraft Subsystems are mounted in
this volume
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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
System
August 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)
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