Final Version

Wes OusleyDan Nguyen

May 13-17, 2002

Micro-Arcsecond Imaging Mission, Pathfinder (MAXIM-PF)

Thermal

MAXIM-PF, May 13-17, 2002Goddard Space Flight Center

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Final Version

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

MAXIM-PF, May 13-17, 2002Goddard Space Flight Center

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Final Version

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

MAXIM-PF, May 13-17, 2002Goddard Space Flight Center

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Final Version

Optics Spacecraft

MLI on other exposed sides

Sun

Radiatorwith

Louver

Hub radiatorused whenseparated

Heat pipe couplerused when together

MAXIM-PF, May 13-17, 2002Goddard Space Flight Center

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Final Version

Detector Craft

Spacecraft radiators

MLI blankets

Sunshield

MAXIM-PF, May 13-17, 2002Goddard Space Flight Center

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Final Version

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

MAXIM-PF, May 13-17, 2002Goddard Space Flight Center

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Final Version

Backup Slides

MAXIM-PF, May 13-17, 2002Goddard Space Flight Center

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Final Version

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

MAXIM-PF, May 13-17, 2002Goddard Space Flight Center

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Final Version

Mission Sequence

Launch

Transfer Stage

Science Phase #1

Low Resolution

200 km

Science Phase #2

High Resolution

1 km

20,000 km

MAXIM-PF, May 13-17, 2002Goddard Space Flight Center

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Final Version

Component LayoutHub 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)

MAXIM-PF, May 13-17, 2002Goddard Space Flight Center

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Final Version

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 Camera

CCD Electronics