3 MIGHTI Overview (1 of 3)ICONMIGHTI 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 OrbitalMIGHTI is based off the heritage designs of the SHIMMER instruments successfully flown on STS-112 (2002) And STPsat-1 (2007)630.0nm557.7nm762.0nmMIGHTI Behind (B)MIGHTI Ahead (A)
4 MIGHTI Overview (2 of 3)Camera Electronics box with an integral radiatorCalibration Lamp – Light source for calibration optics on both MIGHTIsTwo identical MIGHTI instruments, located at 90°±5°575km Circular Low Earth OrbitTBD Launch Vehicle – Pegasus Class (Mass Limitations)Accelerated Schedule:MIGHTI PDR = 4/22/14MIGHTI 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 DoorRadiatorBaffle AssemblyHeat PipeStepper Motor ControlCalibration OpticsEntrance Pupil &Shutter HousingOptical BenchTransfer OpticsEnclosureOptics EnclosureCamera/Heat PipeInterfaceInstrument Flexures(2) near side (2) far sideCamera
6 Thermal Requirements: Level 4 – Direct (1 of 3) NumberRequirementM-4-1The MIGHTI instrument shall be designed to operate on orbit for a minimum of 25 months.M-4-2The MIGHTI instrument shall not have any consumables other than component lifetime.M-4-3The MIGHTI instrument shall be designed for a near-circular orbit with a targeted altitude of 575 km at beginning of life (BOL).M-4-4The MIGHTI instrument shall be designed for an orbit with a targeted BOL inclination of 27 degrees.M-4-5The MIGHTI instrument shall be designed for an End of Life (EOL) orbit with a minimum altitude of 450 km.M-4-6The 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-4-7The MIGHTI post-launch checkout shall take less than 20 days, assuming a nominal ground contact schedule (5 passes/day).M-4-28The 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) NumberRequirementM-4-131The MIGHTI instrument shall be capable of meeting all operational requirements over > 90% of primary mission lifetime. This includes science measurements and calibration measurements.M-4-132The 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-4-133The 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-4-134The 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-4-135The 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) NumberRequirementM-4-136The 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-4-137The 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-4-138The 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-4-139The 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) NumberRequirementM-5-1Thermal analysis shall include winter solstice , summer solstice , and equinox seasons.M-5-2Thermal control surface degradation is to take into account 25 months of orbital exposureM-5-3All components shall be kept within their operational limits when payload power is applied.M-5-4The MIGHTI Instrument shall preclude the use of liquid cryogens for cooling.M-5-5The MIGHTI Instrument shall preclude the use of expendable gases for cooling.M-5-6Thermal control during survival mode shall rely upon non-commandable means (Mechanical thermostats)M-5-7All components shall be kept within their survival temperature limits.M-5-8The interferometer housing shall be controlled to 25°C ± 0.1°CM-5-9The optical bench shall be controlled to 20°C ± 2°CM-5-11All components shall be kept within their survival temperature limits at all times.
10 Thermal Requirements: Level 5 – Derived (2 of 2) NumberRequirementM-5-12MIGHTI shall add SC powered heaters during instrument I&T.M-5-13MIGHTI shall incorporate means of connecting SC powered heaters to harness during payload I&T.M-5-14SC powered heaters shall be sized to keep MIGHTI above survival temperature minimum limits.M-5-15Interferometer oven shall have sufficient temperature monitoring points to allow for precision control.M-5-16Control system shall have sufficient resolution, amplification, and noise filtering to allow for precision control.M-5-17Power Supply and Return lines for operating heaters shall be twisted pair.M-5-18Heaters shall be designed to minimize or negate the magnetic moments when power is supplied.
12 Design Approach– Overall Optical Bench AssemblyThermally isolate from PIP & BaffleSoftware (ICP) controlled active heater control to maintain temperature stabilityRadiators sized to maintain active heater control margin (>30%) for all on orbit hot-cold operational conditions (MLI on non-radiating surfacesRadiator, heater, and temperature sensor locations optimized to minimize spatial temperature gradientsNOTE: Design pending completion of ongoing analysisCamera CCDThermally isolated TEC for CCD active thermal control; camera internal design by SDLFin radiator heat pipe assembly to transport and reject TEC dissipation and associated parasitic loadsElectronicsPassive radiator design; radiators sized to protect hot case limits (MLI on non-radiating surfaces)Thermostat controlled operational heaters to protect cold limits as requiredThermostat controlled heaters to protect survival temperature limitsNOTE: survival / safe-mode analysis pendingStructureMLI to damp orbital (day-night) temperature excursions
13 Thermal Design – Heat Pipe / Radiator Assembly Fin Radiator(2) 1/16” thick 6061 Al face-sheets2.4 PCF Al coreA = 2 x 144 in2Z93 white paint; both sidesThermal isolation at supports (4 places)Titanium flexure supports (2)Heat PipeDual bore 0.75” x 0.375” Al extrusionWorking fluid ammoniahe / hc = 1.5 / 2.5 W/in/oCIn planeExposed length MLIEmbedded in radiator coreBonded 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 assemblyThermally isolated from benchThermal design pendingTEC hot side interfaceSDL designneed mCp = 119 J/oCSee power dissipation table in thermal model assumptions sectionHeat pipe evaporator flangeAcontact = 1.75” x 2.75”thermal gap filler h = 2.5 W/in2/oCHeat pipe clamp / saddleMass to damp orbital transient temperature swingsBerylliumm = 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 analysis560 mW internal electronics dissipationHousing radiator area Z93 white paint or Ag Teflon tapePartial radiator area on 2 sides shownRequired radiator area pending analysisNon-radiator area and cabling MLIMLI light seal at camera / bench interfaceThermostat controlled operational / survival heaters as requiredPartial radiator area 2 sidesTEC hot side interface
16 Thermal Design – Optical Bench Thermally isolated from PIPMachined 6061 AluminumInternal dissipation negligibleActive heater controlUp to 3 operational circuitsOperational heaters software controlledOperational heaters maintain 20oC +/- 2oC; transient & spatialHeaters designed to maintain continuous active control (hot-cold environment range)Design margin 30%Survival heaters thermostat controlledHeater size/location definitions pending ongoing analysisZ93 white paint structure radiatorsRadiator design & analysis ongoingNon-radiating surfaces MLIInterior high emissivityCover (not shown)PassiveDiffuse high emissivity interiorMLI on outside surfacesInterferometer OvenCameraBench
17 Thermal Design – Interferometer Thermally isolated from support structureNo internal dissipationCoverThermally coupled to base plateActive heater control; 3 temperature sensors2 high resolution; 1 low resolution1 heater circuit (multiple heaters)Operational heaters maintain 25oC +/- 0.1oC; transient & spatialOperational heaters designed to maintain continuous active controlDesign margin 30%Heater size/location definitions pending ongoing analysisOutside surface MLIInside surface diffuse / high eBase PlateThermally isolated from benchBottom side facing bench Al tape (low e)Top side facing interferometer diffuse / high eCoverTop PlateFixed Top Interferometer ContactsInterferometerBase PlateSpring Loaded Bottom Interferometer ContactsThermal Isolators
18 Thermal Design – Aft Optics Aft Optics & Shutter HousingThermally coupled to benchThermally isolated from baffleInternal dissipation negligibleSingle temperature sensorActive heater control1 circuit (design pending analysis)Operational heaters software controlledOperational heaters maintain 20oC +/- 2oC; transient & spatialHeaters designed to maintain continuous active control (hot-cold environment range)Design margin 30%Survival heaters thermostat controlledSurvival heater circuit combined with benchHeater size/location definitions pending ongoing analysisZ93 white paint structure radiatorsRadiator design & analysis ongoingNon-radiating surfaces MLIInterior high emissivityEntrance Pupil &Shutter HousingStepper MotorAft Optics Enclosure
19 Thermal Design – Baffle Baffle StructureThermally isolated from Aft OpticsThermally isolated from supportsPassive thermal controlHigh emissivity interiorMLI on outside surfaces
20 Thermal Design – Camera Electronics CEB radiator12 W internal electronics dissipationAssumed dissipation at radiatorZ93 white paint on front and fin backCEB housingThermally isolated from PIPModel assumes no conduction to PIP (conservative)PIP temperature range -20oC to +40oC per SSL/BerkleyInterface conductance requirement TBD by SDL & SSL/BerkleyHousing and cabling MLIThermostat controlled survival heaters as required
21 Thermal Design – Calibration Lamp Lamp Housing8 W internal electronics dissipationAssumed dissipation uniform over housingAg Teflon tape on housingThermally isolated from PIP<0.05 W/oCcabling MLIThermostat controlled survival heaters as required
22 Design Approach – Mechanisms Aperture DoorThermal design & analysis pendingDeployment heater as requiredStepper MotorsThermal analysis pendingAft optics motor MLIBench Motor radiates to OB cavityConduction at mounting interfaceLow power duty cycleBaffle DoorBaffle DoorDoor Pin PullerOptical BenchAft OpticsStepper Motors
23 Thermal Control Hardware ThermistorsManufacturer: Measurement SpecialtiesPart # 311P18-06A1015K Ohm 25oCRTD’sManufacturer: Goodrich Corp.Part # 0118MF-2000-A2K Ohm resistanceHeatersManufacturer: TaycoType: TPC-6002 Flexible KaptonThermostatsManufacturer: HoneywellType: 701 series bi-metallic/mechanicalMLI1 outer Layer: mil Germanium Black Kapton (GBK)13 middle layers: mil Aluminized Mylar (VDA2)14 separators: B4A Dacron mesh1 inner layer: 2 mil Kapton (VDA1)Material Vendors: Sheldahl; Dunmore
24 Thermal Control Hardware Temperature Sensor SpecificationsHeater SpecificationsLocationTypeCountMonitoredCal LampTHM2ICPTEC cold side (A&B)RTDTEC hot side (A&B)Optical Bench (A&B)6Interferometer (A&B)(2 coarse,1 fine per IF)Aperture motors (A&B)(may not need)4Aft Optics (A&B)(likely will need to add)SCCamera Electronics1Door Actuator (A&B)Camera Housing (A&B)Circuit ZoneBusControlNotesOptical Bench (A&B)OPICP1,5Interferometer (A&B)Aft Optics (A&B)Camera Housing (A&B)TSTAT2,5Camera Electronics3,5Calibration LampSVL4,6Software controlledPending analysisCurrent analysis indicates likely not needed4 Pending survival / safe mode analysisOperational bus 28-34VSurvival / Safe Mode bus 24-34V
28 Thermal Model: Giver-Receiver Information Exchange Thermal Model FormatAutocad 2014; Thermal Desktop / SindaFluint -Version 5.6ATK to SSLReduced MIGHTI instrument AssemblyMIGHTI-A; MIGHTI-B; Camera Electronics Box (CEB); Calibration LampInclude geometry; optical properties; thermal masses; conduction network; transient dissipationsSSL to ATKReduced PIP & Instrument Suite (geometry & optical properties only)ATK to SDLPreliminary CEB radiator sizeCEB environmental and IR backload heat loads (transient)SDL to ATKCEB mechanical configuration & internal power dissipationTEC hot side temperature vs. power profile
29 Thermal Model: Assumptions OrbitsBeta = 50oBeta = 0oBeta = -50oAltitudeCircular 576 km (nominal)Evaluation of altitude range 450 km to 665 km pendingVehicle AttitudeOperational: +Z Nadir / +X velocity vectorBeta angle versus Time of Year
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 DissipationTEC hot side parasitic heat load not includedBeta AngleTEC A Orb Avg Dissipation (w)TEC B Orb Avg Dissipation (w)-503.426.462.092.25+503.172.51
37 Thermal Model: Analysis Transient Results – TEC Hot Side Hot – Beta -50° - MIGHTI A/BCold – Beta 0° - MIGHTI A Cold – Beta +50° - MIGHTI B
40 Thermal Model: Analysis Transient Results – Electronics Hot – Beta -50° - Camera Electronics & Calibration LampCold – Beta +50° - Camera Electronics & Calibration Lamp
41 Trade Studies: Thermal Strap vs. Heat Pipe (1 of 2) AdvantagesGravity independent testingReduced complexity and handlingNo freeze protection necessaryAdvantagesLight weight solutionSpreads heat along entire radiator lengthRedundant heat pipes will slightly reduce operating temperatures during lifeFlight heritageNegligible end to end DTConcernsMass (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 performanceLength increases as routing details are introducedSignificantly lower conduction through strap/bar thickness (relative to axial) introduces uncertainty in conductance to radiatorFlex Strap does not meet requirements for extreme beta angle seasonal conditions. Heavy solid bar would be required.ConcernsImposing system level test constraints to keep heat pipes in reflux orientationReflux test configuration will require starter heaters that may affect thermal balanceOperation in 0-g is not possible under acceleration
42 Trade Studies: Thermal Strap vs. Heat Pipe (2 of 2) Summary of ResultsConclusionThermal strap not a viable option3 lbm solid K-Core section does not meet requirements for high beta angle conditionsLikely mass required >6 lbm to meet requirements (11 lbm for heat pipe equivalent performance)Heat pipes meet requirements for worst case on orbit conditions2-3 lbm within practical applicationOrbit average TEC dissipation reduced relative to strapHeat pipe cost comparable to strap: ROM approximately $30-50KTesting 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 LevelTypically done by vendorApplicable to components with power dissipation: camera, CEB, calibration lamp, motors, actuators1 survival cycleMinimum of 8 thermal vacuum operational temperature cyclesMinimum of 4 hours at each extreme of each temperature cycleSubsystem / Instrument LevelMinimum of 4 operational thermal vacuum temperature cyclesMinimum of 12 hours at each extreme of each temperature cycleThermal balance: survival, hot operational, cold operationalPayload/Spacecraft Level4 thermal vacuum operational temperature cycles (2 with project approval; dwell times doubled)Minimum 24 hours at each extreme of each temperature cycleThermal balance as practical
44 Testing (2 of 2) Functional testing Test Margins At each operational temperature plateauTurn on test following recovery from survival plateau (usually combined with functional test)Test MarginsSee notes associated with temperature limits tableConsiderations/limitationsLikely auxiliary GSE required for radiator temperature control; instrument & payload/SC levelGN2 / heater controlled panelsHeat pipes must be oriented to perform in “reflux” modeEvaporator (TEC) must be lower than condenser (radiator) relative to gravityNo limitation for +Z axis verticalFor +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 modelsIncorporate interface conductance effects per previous chartOptimize radiator sizes, locations (NA for interferometer)Define operational heater layoutHeat Pipe Radiator AssemblyComplete feasibility evaluation incorporating a short thermal strap at TEC/pipe interfaceEffort to gain additional mechanical compliance to mitigate camera alignment/distortion issueCameraComplete housing radiator designDetermine if housing needs to be thermally coupled to optical benchCamera ElectronicsGood shape for PDRCalibration LampRefine housing radiator size/locationOtherClarify all temperature limitsSurvival / safe-mode analysis to determine heater requirementsUpdate PIP geometry to include star tracker radiator blockage effects (likely negligible)