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

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

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

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

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

MAXIM OPTIC SPACECRAFT (DIFFERENT VIEWS) Different views of the Optic space- craft Spacecraft Subsystem 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

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

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

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)