# Presentation: 274547

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

**Dan Nguyen**
**May 13-17, 2002**

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

**Thermal**

## 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

## 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

## Optics Spacecraft

- MLI on other
- exposed sides

- Sun

- Radiator
- with
- Louver

- Hub radiator
- used when
- separated

- Heat pipe coupler
- used when together

## Detector Craft

- Spacecraft
-   radiators

- MLI blankets

- Sunshield

## 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

## Backup Slides

## 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

## Mission Sequence

- Launch

- Transfer Stage

## Component LayoutHub 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)

## Component LayoutDetector

- 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