1. Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) Instrument Preliminary Peer Review Thermal W. Tolson

2. Outline MIGHTI Overview Thermal Requirements Design Approach – Overall
Level 4 – Direct
Level 5 Derived
Temperature Limits
Design Approach – Overall
Thermal Design
Heat Pipe / Radiator Assembly
TEC to Heat Pipe Interface
Camera Housing
Optical Bench
Interferometer
Aft Optics
Baffle
Camera Electronics
Calibration Lamp
Mechanisms
Thermal Control Hardware
Thermal Model
Geometric Configuration
Giver-Receiver Information Exchange
Assumptions
Thermal Analysis
Results Summary
TEC Dissipation
Transient Results
Trade Studies
Testing
Plan Forward

3. MIGHTI Overview (1 of 3)
ICON
MIGHTI is a key instrument on the NASA Class C Ionospheric CONnection Explorer (ICON) Mission headed by the Space Sciences Laboratory (SSL) at UC Berkeley (Dr. Immel, PI)
MIGHTI is a limb imager with two orthogonal fields of view measuring velocity and direction of the thermospheric wind using the atomic Oxygen red and green lines (630.0 nm & nm) and the temperature using the molecular Oxygen atmospheric (A) band (762 nm).
ICON Spacecraft Bus Developed by Orbital
MIGHTI is based off the heritage designs of the SHIMMER instruments successfully flown on STS-112 (2002) And STPsat-1 (2007)
630.0nm
557.7nm
762.0nm
MIGHTI Behind (B)
MIGHTI Ahead (A)

4. MIGHTI Overview (2 of 3)
Camera Electronics box with an integral radiator
Calibration Lamp – Light source for calibration optics on both MIGHTIs
Two identical MIGHTI instruments, located at 90°±5°
575km Circular Low Earth Orbit
TBD Launch Vehicle – Pegasus Class (Mass Limitations)
Accelerated Schedule:
MIGHTI PDR = 4/22/14
MIGHTI CDR = 11/25/14 (Tentative)
MIGHTI PER = 7/9/15 (Tentative)
MIGHTI Instrument Delivery to U.C. Berkeley for Integration with Other Payloads = 11/23/15

5. MIGHTI Overview (3 of 3) – Instrument Layout
One Shot Door
Radiator
Baffle Assembly
Heat Pipe
Stepper Motor Control
Calibration Optics
Entrance Pupil &
Shutter Housing
Optical Bench
Transfer Optics
Enclosure
Optics Enclosure
Camera/Heat Pipe
Interface
Instrument Flexures
(2) near side (2) far side
Camera

6. Thermal Requirements: Level 4 – Direct (1 of 3)
Number
Requirement
M-4-1
The MIGHTI instrument shall be designed to operate on orbit for a minimum of 25 months.
M-4-2
The MIGHTI instrument shall not have any consumables other than component lifetime.
M-4-3
The MIGHTI instrument shall be designed for a near-circular orbit with a targeted altitude of 575 km at beginning of life (BOL).
M-4-4
The MIGHTI instrument shall be designed for an orbit with a targeted BOL inclination of 27 degrees.
M-4-5
The MIGHTI instrument shall be designed for an End of Life (EOL) orbit with a minimum altitude of 450 km.
M-4-6
The MIGHTI instrument shall be designed to accommodate orbit injection errors: +/ inclination error, +/-10 km insertion apse error, +/- 80 km non-insertion apse error (all errors are 3 sigma) without impact to top level requirements.
M-4-7
The MIGHTI post-launch checkout shall take less than 20 days, assuming a nominal ground contact schedule (5 passes/day).
M-4-28
The monochromatic interferogram fringe contrast, including the contrast reduction resulting from the detector sampling (pixel width) shall be greater than or equal to 76% % across the optical path difference interval, decreasing for increasing optical path.

7. Thermal Requirements: Level 4 – Direct (2 of 3)
Number
Requirement
M-4-131
The MIGHTI instrument shall be capable of meeting all operational requirements over > 90% of primary mission lifetime. This includes science measurements and calibration measurements.
M-4-132
The MIGHTI instrument shall withstand the Sun within the FOV not to exceed TBD minutes without serious degradation. (based on transit of the sun across the field of view at an angular rate determined by the orbital altitude)
M-4-133
The MIGHTI instrument shall be designed to maintain Allowable Flight Temperatures (AFTs) in survival mode for (TBD) minutes when the payload is pointed anywhere in the celestial sphere at any time during the mission.
M-4-134
The MIGHTI instrument shall have access to all radiators (hardware and FOV) required to keep instruments within their Allowable Flight Temperatures (AFTs). The MIGHTI instrument shall accommodate all radiators (hardware and FOV) required to keep the sensor portion of the instrument within its Allowable Flight Temperatures (AFTs).
M-4-135
The MIGHTI instrument shall accommodate survival heater and corresponding mechanical thermostats with power provided by the S/C (28 V +/-6 V) to maintain survival temperatures while the payload is off.

8. Thermal Requirements: Level 4 – Direct (3 of 3)
Number
Requirement
M-4-136
The MIGHTI instrument shall have heater(s), controlled by the ICP via a sensor feedback loop, to maintain the operational temperature range of the two interferometer enclosures to 25°C 0.1°C.
M-4-137
The MIGHTI instrument shall have heater(s), controlled by the ICP via a sensor feedback loop, and corresponding radiative surfaces to maintain the operational temperature range of the two optical benches to 20°C 2°C.
M-4-138
The MIGHTI instrument shall have thermo electric coolers, controlled by the ICP via a sensor feedback loop, and corresponding radiative surfaces to maintain the operational temperature of the two CCDs to -45°C [+0°C, -15°C].
M-4-139
The MIGHTI instrument shall accommodate four temperature sensors read by the S/C bus system. One on each CCD camera head and one on each optical bench. [TBD: sensors on cal lamps and camera electronics]

9. Thermal Requirements: Level 5 – Derived (1 of 2)
Number
Requirement
M-5-1
Thermal analysis shall include winter solstice , summer solstice , and equinox seasons.
M-5-2
Thermal control surface degradation is to take into account 25 months of orbital exposure
M-5-3
All components shall be kept within their operational limits when payload power is applied.
M-5-4
The MIGHTI Instrument shall preclude the use of liquid cryogens for cooling.
M-5-5
The MIGHTI Instrument shall preclude the use of expendable gases for cooling.
M-5-6
Thermal control during survival mode shall rely upon non-commandable means (Mechanical thermostats)
M-5-7
All components shall be kept within their survival temperature limits.
M-5-8
The interferometer housing shall be controlled to 25°C ± 0.1°C
M-5-9
The optical bench shall be controlled to 20°C ± 2°C
M-5-11
All components shall be kept within their survival temperature limits at all times.

10. Thermal Requirements: Level 5 – Derived (2 of 2)
Number
Requirement
M-5-12
MIGHTI shall add SC powered heaters during instrument I&T.
M-5-13
MIGHTI shall incorporate means of connecting SC powered heaters to harness during payload I&T.
M-5-14
SC powered heaters shall be sized to keep MIGHTI above survival temperature minimum limits.
M-5-15
Interferometer oven shall have sufficient temperature monitoring points to allow for precision control.
M-5-16
Control system shall have sufficient resolution, amplification, and noise filtering to allow for precision control.
M-5-17
Power Supply and Return lines for operating heaters shall be twisted pair.
M-5-18
Heaters shall be designed to minimize or negate the magnetic moments when power is supplied.

11. Thermal Requirements: Temperature Limits

12. Design Approach– Overall
Optical Bench Assembly
Thermally isolate from PIP & Baffle
Software (ICP) controlled active heater control to maintain temperature stability
Radiators sized to maintain active heater control margin (>30%) for all on orbit hot-cold operational conditions (MLI on non-radiating surfaces
Radiator, heater, and temperature sensor locations optimized to minimize spatial temperature gradients
NOTE: Design pending completion of ongoing analysis
Camera CCD
Thermally isolated TEC for CCD active thermal control; camera internal design by SDL
Fin radiator heat pipe assembly to transport and reject TEC dissipation and associated parasitic loads
Electronics
Passive radiator design; radiators sized to protect hot case limits (MLI on non-radiating surfaces)
Thermostat controlled operational heaters to protect cold limits as required
Thermostat controlled heaters to protect survival temperature limits
NOTE: survival / safe-mode analysis pending
Structure
MLI to damp orbital (day-night) temperature excursions

13. Thermal Design – Heat Pipe / Radiator Assembly
Fin Radiator
(2) 1/16” thick 6061 Al face-sheets
2.4 PCF Al core
A = 2 x 144 in2
Z93 white paint; both sides
Thermal isolation at supports (4 places)
Titanium flexure supports (2)
Heat Pipe
Dual bore 0.75” x 0.375” Al extrusion
Working fluid ammonia
he / hc = 1.5 / 2.5 W/in/oC
In plane
Exposed length MLI
Embedded in radiator core
Bonded to radiator face-sheets (2)
3/8” contact (2 sides) along radiator full length

14. Thermal Design – TEC to Heat Pipe Interface
Heat pipe clamp assembly
Thermally isolated from bench
Thermal design pending
TEC hot side interface
SDL design
need mCp = 119 J/oC
See power dissipation table in thermal model assumptions section
Heat pipe evaporator flange
Acontact = 1.75” x 2.75”
thermal gap filler h = 2.5 W/in2/oC
Heat pipe clamp / saddle
Mass to damp orbital transient temperature swings
Beryllium
m = kg (0.016 lb)
Material optimized to minimize absolute mass while maximizing thermal mass (mCp)

15. Thermal Design – Camera Housing
Thermally isolated from bench
<0.05 W/oC; verification/margin pending bench detailed analysis
560 mW internal electronics dissipation
Housing radiator area Z93 white paint or Ag Teflon tape
Partial radiator area on 2 sides shown
Required radiator area pending analysis
Non-radiator area and cabling MLI
MLI light seal at camera / bench interface
Thermostat controlled operational / survival heaters as required
Partial radiator area 2 sides
TEC hot side interface

16. Thermal Design – Optical Bench
Thermally isolated from PIP
Machined 6061 Aluminum
Internal dissipation negligible
Active heater control
Up to 3 operational circuits
Operational heaters software controlled
Operational heaters maintain 20oC +/- 2oC; transient & spatial
Heaters designed to maintain continuous active control (hot-cold environment range)
Design margin 30%
Survival heaters thermostat controlled
Heater size/location definitions pending ongoing analysis
Z93 white paint structure radiators
Radiator design & analysis ongoing
Non-radiating surfaces MLI
Interior high emissivity
Cover (not shown)
Passive
Diffuse high emissivity interior
MLI on outside surfaces
Interferometer Oven
Camera
Bench

17. Thermal Design – Interferometer
Thermally isolated from support structure
No internal dissipation
Cover
Thermally coupled to base plate
Active heater control; 3 temperature sensors
2 high resolution; 1 low resolution
1 heater circuit (multiple heaters)
Operational heaters maintain 25oC +/- 0.1oC; transient & spatial
Operational heaters designed to maintain continuous active control
Design margin 30%
Heater size/location definitions pending ongoing analysis
Outside surface MLI
Inside surface diffuse / high e
Base Plate
Thermally isolated from bench
Bottom side facing bench Al tape (low e)
Top side facing interferometer diffuse / high e
Cover
Top Plate
Fixed Top Interferometer Contacts
Interferometer
Base Plate
Spring Loaded Bottom Interferometer Contacts
Thermal Isolators

18. Thermal Design – Aft Optics
Aft Optics & Shutter Housing
Thermally coupled to bench
Thermally isolated from baffle
Internal dissipation negligible
Single temperature sensor
Active heater control
1 circuit (design pending analysis)
Operational heaters software controlled
Operational heaters maintain 20oC +/- 2oC; transient & spatial
Heaters designed to maintain continuous active control (hot-cold environment range)
Design margin 30%
Survival heaters thermostat controlled
Survival heater circuit combined with bench
Heater size/location definitions pending ongoing analysis
Z93 white paint structure radiators
Radiator design & analysis ongoing
Non-radiating surfaces MLI
Interior high emissivity
Entrance Pupil &
Shutter Housing
Stepper Motor
Aft Optics Enclosure

19. Thermal Design – Baffle
Baffle Structure
Thermally isolated from Aft Optics
Thermally isolated from supports
Passive thermal control
High emissivity interior
MLI on outside surfaces

20. Thermal Design – Camera Electronics
CEB radiator
12 W internal electronics dissipation
Assumed dissipation at radiator
Z93 white paint on front and fin back
CEB housing
Thermally isolated from PIP
Model assumes no conduction to PIP (conservative)
PIP temperature range -20oC to +40oC per SSL/Berkley
Interface conductance requirement TBD by SDL & SSL/Berkley
Housing and cabling MLI
Thermostat controlled survival heaters as required

21. Thermal Design – Calibration Lamp
Lamp Housing
8 W internal electronics dissipation
Assumed dissipation uniform over housing
Ag Teflon tape on housing
Thermally isolated from PIP
<0.05 W/oC
cabling MLI
Thermostat controlled survival heaters as required

22. Design Approach – Mechanisms
Aperture Door
Thermal design & analysis pending
Deployment heater as required
Stepper Motors
Thermal analysis pending
Aft optics motor MLI
Bench Motor radiates to OB cavity
Conduction at mounting interface
Low power duty cycle
Baffle Door
Baffle Door
Door Pin Puller
Optical Bench
Aft Optics
Stepper Motors

23. Thermal Control Hardware
Thermistors
Manufacturer: Measurement Specialties
Part # 311P18-06A101
5K Ohm 25oC
RTD’s
Manufacturer: Goodrich Corp.
Part # 0118MF-2000-A
2K Ohm resistance
Heaters
Manufacturer: Tayco
Type: TPC-6002 Flexible Kapton
Thermostats
Manufacturer: Honeywell
Type: 701 series bi-metallic/mechanical
MLI
1 outer Layer: mil Germanium Black Kapton (GBK)
13 middle layers: mil Aluminized Mylar (VDA2)
14 separators: B4A Dacron mesh
1 inner layer: 2 mil Kapton (VDA1)
Material Vendors: Sheldahl; Dunmore

24. Thermal Control Hardware
Temperature Sensor Specifications
Heater Specifications
Location
Type
Count
Monitored
Cal Lamp
THM 2
ICP
TEC cold side (A&B)
RTD
TEC hot side (A&B)
Optical Bench (A&B) 6
Interferometer (A&B)
(2 coarse,1 fine per IF)
Aperture motors (A&B)
(may not need) 4
Aft Optics (A&B)
(likely will need to add) SC
Camera Electronics 1
Door Actuator (A&B)
Camera Housing (A&B)
Circuit Zone
Bus
Control
Notes
Optical Bench (A&B) OP
ICP
1,5
Interferometer (A&B)
Aft Optics (A&B)
Camera Housing (A&B)
TSTAT
2,5
Camera Electronics
3,5
Calibration Lamp
SVL
4,6
Software controlled
Pending analysis
Current analysis indicates likely not needed
4 Pending survival / safe mode analysis
Operational bus 28-34V
Survival / Safe Mode bus 24-34V

25. Thermal Model: Geometric Configuration
Instrument Suite & Payload Interface Platform (PIP)
MIGHTI-B
Payload Interface Platform (PIP)
MIGHTI-A
Camera Electronics Box (CEB)
Calibration Lamp

26. Thermal Model: Geometric Configuration
MIGHTI Instrument Assembly
TEC Radiator
Baffle
Aft Optics
Radiator Supports (1 of 2)
Camera
Conductor-Heat Pipe to Radiator
Optical Bench
OB Cover

27. Thermal Model: Geometric Configuration
Camera Electronics Box (CEB) & Calibration Lamp
CEB Radiator
Calibration Lamp Housing
CEB Housing

28. Thermal Model: Giver-Receiver Information Exchange
Thermal Model Format
Autocad 2014; Thermal Desktop / SindaFluint -Version 5.6
ATK to SSL
Reduced MIGHTI instrument Assembly
MIGHTI-A; MIGHTI-B; Camera Electronics Box (CEB); Calibration Lamp
Include geometry; optical properties; thermal masses; conduction network; transient dissipations
SSL to ATK
Reduced PIP & Instrument Suite (geometry & optical properties only)
ATK to SDL
Preliminary CEB radiator size
CEB environmental and IR backload heat loads (transient)
SDL to ATK
CEB mechanical configuration & internal power dissipation
TEC hot side temperature vs. power profile

29. Thermal Model: Assumptions
Orbits
Beta = 50o
Beta = 0o
Beta = -50o
Altitude
Circular 576 km (nominal)
Evaluation of altitude range 450 km to 665 km pending
Vehicle Attitude
Operational: +Z Nadir / +X velocity vector
Beta angle versus Time of Year

30. Thermal Model: Assumptions
Optical Properties
Environments

31. Thermal Model: Assumptions
Component Power Dissipations
TEC Power Dissipation

32. Thermal Model: Assumptions
Component Masses (as modeled)
Cal Lamp – 1.5 kg
Baffle – 1.84 kg
Camera Electronics – 2.65 kg
TEC Hot Side – kg
Material Properties

33. Thermal Model: Assumptions
Mechanical
Multi-Layer Insulation (MLI) Effective Emittance
Larger blankets: e* = 0.01 to 0.03
Smaller blankets: e* = 0.03 to 0.10

34. Thermal Analysis: Results Summary
Operational Hot Case

35. Thermal Analysis: Results Summary
Operational Cold Case

36. Thermal Analysis: TEC Dissipation
TEC Hot Case Orbit Average Dissipation
TEC hot side parasitic heat load not included
Beta Angle
TEC A Orb Avg Dissipation (w)
TEC B Orb Avg Dissipation (w)
-50
3.42
6.46
2.09
2.25
+50
3.17
2.51

37. Thermal Model: Analysis Transient Results – TEC Hot Side
Hot – Beta -50° - MIGHTI A/B
Cold – Beta 0° - MIGHTI A Cold – Beta +50° - MIGHTI B

38. Thermal Model: Analysis Transient Results – Radiators
Hot – Beta -50° - MIGHTI-A Hot – Beta -50° - MIGHTI-B
Cold – Beta 0° - MIGHTI-A Cold – Beta +50° - MIGHTI-B

39. Thermal Model: Analysis Transient Results - Baffles
Hot – Beta +50° - MIGHTI-A Hot – Beta +50° - MIGHTI-B
Cold – Beta -50° - MIGHTI-A Cold – Beta -50° - MIGHTI-B

40. Thermal Model: Analysis Transient Results – Electronics
Hot – Beta -50° - Camera Electronics & Calibration Lamp
Cold – Beta +50° - Camera Electronics & Calibration Lamp

41. Trade Studies: Thermal Strap vs. Heat Pipe (1 of 2)
Advantages
Gravity independent testing
Reduced complexity and handling
No freeze protection necessary
Advantages
Light weight solution
Spreads heat along entire radiator length
Redundant heat pipes will slightly reduce operating temperatures during life
Flight heritage
Negligible end to end DT
Concerns
Mass (Only viable option is graphite)
# of Layers required for flexible strap portion likely not viable. K-Tech recommends max 10 layer strap. Our application requires a 1.75” x 2” solid >11 lb. to match pipe performance
Length increases as routing details are introduced
Significantly lower conduction through strap/bar thickness (relative to axial) introduces uncertainty in conductance to radiator
Flex Strap does not meet requirements for extreme beta angle seasonal conditions. Heavy solid bar would be required.
Concerns
Imposing system level test constraints to keep heat pipes in reflux orientation
Reflux test configuration will require starter heaters that may affect thermal balance
Operation in 0-g is not possible under acceleration

42. Trade Studies: Thermal Strap vs. Heat Pipe (2 of 2)
Summary of Results
Conclusion
Thermal strap not a viable option
3 lbm solid K-Core section does not meet requirements for high beta angle conditions
Likely mass required >6 lbm to meet requirements (11 lbm for heat pipe equivalent performance)
Heat pipes meet requirements for worst case on orbit conditions
2-3 lbm within practical application
Orbit average TEC dissipation reduced relative to strap
Heat pipe cost comparable to strap: ROM approximately $30-50K
Testing considerations/restrictions can be accommodated

43. Testing (1 of 2) Standards per GEVS GSFC-STD-7000A
Thermal vacuum qualification standards to ensure that the payload operates satisfactorily in a simulated space environment at more severe conditions than expected during the mission.
Component / Unit Level
Typically done by vendor
Applicable to components with power dissipation: camera, CEB, calibration lamp, motors, actuators
1 survival cycle
Minimum of 8 thermal vacuum operational temperature cycles
Minimum of 4 hours at each extreme of each temperature cycle
Subsystem / Instrument Level
Minimum of 4 operational thermal vacuum temperature cycles
Minimum of 12 hours at each extreme of each temperature cycle
Thermal balance: survival, hot operational, cold operational
Payload/Spacecraft Level
4 thermal vacuum operational temperature cycles (2 with project approval; dwell times doubled)
Minimum 24 hours at each extreme of each temperature cycle
Thermal balance as practical

44. Testing (2 of 2) Functional testing Test Margins
At each operational temperature plateau
Turn on test following recovery from survival plateau (usually combined with functional test)
Test Margins
See notes associated with temperature limits table
Considerations/limitations
Likely auxiliary GSE required for radiator temperature control; instrument & payload/SC level
GN2 / heater controlled panels
Heat pipes must be oriented to perform in “reflux” mode
Evaporator (TEC) must be lower than condenser (radiator) relative to gravity
No limitation for +Z axis vertical
For +Z axis horizontal vehicle must be clocked about Z axis to maintain reflux; approximately 90o rotation window

45. Plan Forward to PDR Optical Bench Assembly Heat Pipe Radiator Assembly
Includes bench, cover, aft optics, interferometer (no optical components except IF)
Complete high fidelity thermal models
Incorporate interface conductance effects per previous chart
Optimize radiator sizes, locations (NA for interferometer)
Define operational heater layout
Heat Pipe Radiator Assembly
Complete feasibility evaluation incorporating a short thermal strap at TEC/pipe interface
Effort to gain additional mechanical compliance to mitigate camera alignment/distortion issue
Camera
Complete housing radiator design
Determine if housing needs to be thermally coupled to optical bench
Camera Electronics
Good shape for PDR
Calibration Lamp
Refine housing radiator size/location
Other
Clarify all temperature limits
Survival / safe-mode analysis to determine heater requirements
Update PIP geometry to include star tracker radiator blockage effects (likely negligible)