HALE

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• HALE
• THERMAL CONTROL SYSTEM
• PRESENTATION
• July 9, 1998
• Ted Michalek
• NASA/GSFC 545
• 301-286-1956 (office)
• 302-286-2213 (IMDC)
• ted.michalek_at_gsfc.nasa.gov

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HALE Thermal SystemJuly 9, 1998

• Agenda
• Mission level requirements/assumptions
• MDI requirements and accommodation
• TRACE requirements and accommodation
• Spacecraft requirements and accommodation
• Conclusions

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HALE Thermal SystemJuly 9, 1998

• Mission-Level Requirements, Assumptions,
  Constraints
• Orbit
• Baseline Geosynchronous orbit circular, i28,
  24 hour period
• Note results unaffected if geosync orbit is
  slightly elliptical
• Two shadow seasons per year, centered about
  winter/summer solstice
• Max shadow 70 minutes
• Attitude
• 3-axis stable, inertially pointed. (Axis Z
  Sun, X/Y Solar Arrays)
• Telescopes sun-center pointed within TBD arc-sec,
  results in essentially no solar flux on side
  viewing radiators (edge-to-sun)
• Instrument
• Spacecraft to Payload Interface baseline has
  payloads thermally isolated
• Coatings
• External thermal control coatings must be
  electrically conductive for electro-static
  discharge (ESD) control

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HALE MDI Thermal System Requirements and
Accommodation July 9, 1998

• Design Accommodation
• Instrument thermally isolated from mounting
  structure
• Dedicated optics package radiator, edge-to-sun
• Oven with proportionally controlled heater for
  optics package temperature stability
• Dedicated CCD radiator, edge-to-sun, with CCD
  isolated from warm optics
• Proportionally controlled heater to control
  temperature drift
• Choice of coatings properties to control front
  window temperature eclipse response must be
  assessed
• Dedicated remote electronics radiator,
  edge-to-sun

• Requirements/Assumptions
• Average optical package operating temperature
  10C to 30C
• Maintain optical package stability lt0.1C/hr
  (stable environment)
• Lowest possible CCD temperature, less than -80C
  during normal operation
• Nominal front window temperature 20C
• Remote electronics package, with 18 watts
  nominal dissipation, operating temperature -10C
  to 40C

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HALE MDI Thermal System Additional Comments
July 9, 1998

• Basic SOHO thermal design should fit HALE
  mission
• HALE environmental sinks are more variable than
  SOHO
• Periodic views of earth (IR and albedo) will
  affect cold CCD radiator by as much as 10C
  effect has been analyzed by MDI thermal engineer
  and the results appear acceptable
• Eclipse operation
• Optics oven powered during eclipse to enable
  immediate operation after eclipse
• Temperature response of front window and effect
  on thermal/optical stability of the optics vs.
  immediate return to operations needs to be
  assessed
• Remote electronics cooldown during longest
  eclipse appears acceptable, shown powered during
  eclipse in Power System loads summary for
  control, to maintain power/temperature stability
  within telescope
• Paint identified, white S13GLO, is not
  considered electrically conductive other options
  exist, are being investigated for use on SXI
• Conductive OSRs (quartz tiles)
• Electrically conductive silicate paints
• Conductive composite
• Standard multilayer insulation (MLI) covers all
  but radiator and optics

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HALE TRACE Thermal System Requirements and
Accommodation July 9, 1998

• Design Accommodation
• Instrument thermally isolated from
  spacecraft/mounting structure
• Ring radiator on circumference of the telescope
  tube near front
• Dedicated anti-sun CCD radiator, with CCD
  isolated from warm optics
• Proportionally controlled heater to control
  temperature drift
• Dedicated anti-sun camera electronics radiator,
  isolated from CCD
• Decontamination heaters
• Dedicated remote electronics radiator

• Requirements/Assumptions
• Telescope operating temperature 0C to 40C
• CCD less than -60C during normal operation
• Remote electronics package, with 25 watts
  nominal dissipation, operating temperature 0C to
  40C (?)

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HALE TRACE Thermal System Additional Comments
July 9, 1998

• Basic TRACE/SMEX thermal design should fit HALE
  mission
• Telescope is powered during eclipse to enable
  immediate operation after eclipse
• Temperature response of front window and effect
  on thermal/optical stability of the optics vs.
  immediate return to operations needs to be
  assessed
• TRACE/HALE remote electronics radiator sizing
  estimates indicate radiator will cover entire
  top and portions of side, depending on view of
  warm solar array
• TRACE/SMEX remote electronics originally designed
  to use its base as a heat sink (removal)
  surface HALE configuration will utilize a top
  radiator may require repackaging unless original
  design supports HALE configuration
• Remote electronics cooldown during longest
  eclipse appears acceptable, however, it is shown
  powered during eclipse in Power System loads
  summary for control, to maintain
  power/temperature stability within telescope
• Paint used on TRACE/SMEX, white S13GLO, is not
  considered electrically conductive other options
  exist, are being investigated for use on SXI
• Conductive OSRs (quartz tiles)
• Electrically conductive silicate paints
• Conductive composite
• Standard MLI covers all but radiator and optics

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HALE Spacecraft Thermal System Requirements and
Accommodation July 9, 1998

• Design Accommodation
• Dedicated battery radiator, edge-to-sun, one side
  facet of SMEX Lite bus, with battery isolated
  from spacecraft
• Battery heater will provide control
• Other equipment utilizes 7 available side facets
  of SMEX Lite bus, plus portions of anti-sun
  surfaces
• Battery will heat during eclipse within
  acceptable limits
• Spacecraft will cool during eclipse within
  acceptable limits
• Hydrazine system will require MLI and controlled
  heaters, TBD watts (expected in the 10s range)

• Requirements/Assumptions
• Battery operating temperature 0C to 20C
• All other equipment 0C to 40C
• Dissipation constant during sunlit portions of
  mission, with continuous transmitter operation
• Reduced power during eclipse
• Propulsion system requirements are TBD
  (hydrazine system will require 10C to 50C)

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HALE Spacecraft Thermal System Additional
Comments July 9, 1998

• Battery radiator estimated at 50 of the
  available side facet area.
• Other spacecraft equipment requires 1 m2, with
  lt0.8 m2 available on 7 remaining side facets,
  requires portion of anti-sun surfaces
• SMEX Lite Communication Hub radiator requirement
  exceeds radiator area available locally, within
  its bay -- must transfer portion of this heat to
  an adjacent bay may require doubler, heat
  straps, or heat pipes
• Battery will heat during eclipse because it will
  be discharging, expected to heat within
  acceptable operating range
• Cooldown of other spacecraft equipment during
  longest eclipse appears acceptable survival
  heaters will be enabled but should not come on
• MLI will cover all but radiators
• Hydrazine system will require MLI, and tank,
  line and valve heaters for thermal control
• Gimbal mechanism for high-gain antenna will
  require heater, coatings, MLI

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HALE Thermal SystemSpacecraft
ConfigurationJuly 9, 1998
TRACE ring radiator
MDI CCD radiator
Propulsion tank
Gimbal mechanism
Instrument remote electronics radiator
Battery radiator
Spacecraft side radiators
TRACE CCD and Camera radiators
Spacecraft anti-sun radiators
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HALE Thermal SystemJuly 9, 1998

• Conclusions
• HALE Thermal System primarily passive, with
  operational heaters for control of Instrument
  optics and CCDs, battery, gimbal mechanism and
  propulsion (hydrazine)
• Heaters for instruments assumed included with
  instrument power budgets provided
• Propulsion system heaters not specifically sized,
  not included in Thermal entry of Power Loads
  Summary
• Existing MDI and TRACE Thermal Designs should be
  applicable to HALE mission with minor
  modifications

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