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Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) Instrument Preliminary Peer Review Thermal W. Tolson Slide 2 2 Thermal Peer Review MIGHTI Overview Thermal Requirements 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 Outline 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 Slide 3 3 Thermal Peer Review 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 & 557.7 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) MIGHTI Overview (1 of 3) MIGHTI Ahead (A) MIGHTI Behind (B) ICON 630.0nm 557.7nm 762.0nm Slide 4 4 Thermal Peer Review Camera Electronics box with an integral radiator Calibration Lamp Light source for calibration optics on both MIGHTIs Two identical MIGHTI instruments, located at 905 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 MIGHTI Overview (2 of 3) Slide 5 5 Thermal Peer Review MIGHTI Overview (3 of 3) Instrument Layout Optical Bench Transfer Optics Enclosure Entrance Pupil & Shutter Housing Heat Pipe Optics Enclosure Instrument Flexures (2) near side (2) far side Camera Baffle Assembly Stepper Motor Control Calibration Optics Camera/Heat Pipe Interface Radiator One Shot Door Slide 6 6 Thermal Peer Review Thermal Requirements: Level 4 Direct (1 of 3) NumberRequirement M-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: +/- 0.15 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% - 71.25% across the optical path difference interval, decreasing for increasing optical path. Slide 7 7 Thermal Peer Review Thermal Requirements: Level 4 Direct (2 of 3) NumberRequirement M-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. Slide 8 8 Thermal Peer Review Thermal Requirements: Level 4 Direct (3 of 3) NumberRequirement M-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 25C 0.1C. 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 20C 2C. 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 -45C [+0C, -15C]. 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] Slide 9 9 Thermal Peer Review Thermal Requirements: Level 5 Derived (1 of 2) NumberRequirement M-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 exposure M-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 25C 0.1C M-5-9The optical bench shall be controlled to 20C 2C M-5-11All components shall be kept within their survival temperature limits at all times. Slide 10 10 Thermal Peer Review Thermal Requirements: Level 5 Derived (2 of 2) NumberRequirement M-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. Slide 11 11 Thermal Peer Review Thermal Requirements: Temperature Limits Slide 12 12 Thermal Peer Review 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 Design Approach Overall Slide 13 13 Thermal Peer Review Fin Radiator (2) 1/16 thick 6061 Al face-sheets 2.4 PCF Al core A = 2 x 144 in 2 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 h e / h c = 1.5 / 2.5 W/in/ o C In plane Exposed length MLI Embedded in radiator core Bonded to radiator face-sheets (2) 3/8 contact (2 sides) along radiator full length Thermal Design Heat Pipe / Radiator Assembly Slide 14 14 Thermal Peer Review Heat pipe clamp assembly Thermally isolated from bench Thermal design pending TEC hot side interface SDL design need mC p = 119 J/ o C See power dissipation table in thermal model assumptions section Heat pipe evaporator flange A contact = 1.75 x 2.75 thermal gap filler h = 2.5 W/in 2 / o C Heat pipe clamp / saddle Mass to damp orbital transient temperature swings Beryllium m = 0.073 kg (0.016 lb) Material optimized to minimize absolute mass while maximizing thermal mass (mC p ) Thermal Design TEC to Heat Pipe Interface Slide 15 15 Thermal Peer Review Camera Housing Thermally isolated from bench 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. Heat Pipe Slide 42 42 Thermal Peer Review Summary of Results Conclusion Thermal strap not a viable option 3 lb m solid K-Core section does not meet requirements for high beta angle conditions Likely mass required >6 lb m to meet requirements (11 lb m for heat pipe equivalent performance) Heat pipes meet requirements for worst case on orbit conditions 2-3 lb m 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 Trade Studies: Thermal Strap vs. Heat Pipe (2 of 2) Slide 43 43 Thermal Peer Review 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 1 survival cycle 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 1 survival cycle 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 Testing (1 of 2) Slide 44 44 Thermal Peer Review Functional testing 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 GN 2 / 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 90 o rotation window Testing (2 of 2) Slide 45 45 Thermal Peer Review Optical Bench 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) Plan Forward to PDR