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CLARREO Infrared Instrument: Overview, Requirements, and Calibration Drivers

This presentation provides an overview of the CLARREO Infrared Instrument, including its requirements, concept, calibration drivers, and more. It also discusses the current radiometric modeling, measured pyroelectric detector performance, and updated noise performance. Additionally, it covers NIST activities and investments, as well as an outline of Phase-A planning and status.

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CLARREO Infrared Instrument: Overview, Requirements, and Calibration Drivers

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  1. Presenter: Marty Mlynczak Infrared Instrument Overview - CLARREO Infrared Team CLARREO IR Science Lead

  2. Outline • IR Requirements, Concept, Calibration Drivers, etc. • Review Instrument Re-Scope Study • Current Radiometric Modeling • Measured Pyroelectric Detector Performance • Updated Noise Performance • Updated Systematic Uncertainty Assessment • NIST Activities • Investments in FY2011 • Overview of Phase-A Planning • Status, Concerns, Summary

  3. Level 1 IR Requirements • Infrared Baseline Science Measurement: CLARREO shall obtain infrared radiance spectra of the Earth and its atmosphere using nadir views from orbiting satellites. The benchmark and reference intercalibration measurements require: • a Broad spectral coverage of the earth emitted spectrum, including the Far-Infrared, that captures climate trend information about atmospheric structure, composition, clouds, and surface properties; • b Spectral resolution chosen for greenhouse gas species separation and for vertical structure information; • c Radiance measurement systematic error that corresponds to < 0.1 K brightness temperature radiometric calibration uncertainty (3-s confidence, excluding random noise) for the range of expected earth scene temperatures and wavelengths relevant to climate; • d Spatial and temporal sampling sufficient to provide global coverage and reduce sampling errors to levels that degrade the measured climate trend accuracy by less than 15%, and that degrade the time to detect climate trends less than 10%.  The degradation of trend accuracy is relative to the limits of accuracy caused by climate natural variability.

  4. Level 2 IR Instrument Requirements • Spectral Range: 200 to 2000 cm-1 (2760 cm-1 goal) • Rationale: • Spectral Range for Climate Benchmark and Fingerprinting • Spectral Range for Reference Intercalibration of Longwave Broadband Sensors (CERES; GERB; Megha-Tropiques) • Spectral Resolution: 0.5 cm-1 unapodized • Rationale: • Ability to resolve effects of temperature and water vapor as functions of altitude • Systematic Uncertainty:0.100 Kelvin (3s, i.e. coverage factor, k=3) • Rationale: • 0.1 K is half of the expected trend in global temperature change per decade • IFOV: No less than 25 km • Rationale: Enables climate record, reference intercalibration • Ground sampling: One calibrated spectrum every 200 km or less • Rationale: Nyquist samples the autocorrelation length of the radiation field • Nadir Viewing within +/- 0.2 deg • Rationale: Keeps temporal bias between satellites < few milli-Kelvin CL.SYS.1.REQ.1001 Level 2 requirements defined

  5. IR Concept Consists of Electro-Optical and Calibration-Verification Modules Unique verification system quantifies calibration uncertainties

  6. Major Terms Driving Calibration • Measurement equation converts sensor output signals into calibrated scene radiance FTS Error Terms Target Radiance Cold Calibration Blackbody Radiance Hot Calibration Blackbody Radiance Signal Gain Term Uncertainty in Linearity Correction Thermometry Space View Used On-Orbit – Not a Significant Contributor Error Drivers FTS Instrument Temperature Changes Between Calibrations Driving error terms defined

  7. Methodology for Measuring Spectral Radiance Enabling SI Traceable measurements of absolute spectral radiance, spectral emissivity and temperature of Blackbody sources Planck Equation Compare to NIST BBs Temperature NIST Approach for Temp Sensor Calibration Emissivity • NIST Approaches for Emissivity Determination • Paint and Cavity Reflectivity Measurements • Monte Carlo • Modeling SI Traceable Fixed Points Provide Known Temperature with Known Uncertainty NIST’s Advanced Infrared Radiometry and Imaging (AIRI) Facility - IR Spectral Radiance and Radiance Temperature at Ambient Conditions Measure spectral radiance with quantified uncertainties

  8. Maintaining Accuracy On-Orbit • High accuracy determination of the time-dependent bias is critical to creating trusted, enduring climate records. • Traditional Approach: • Space-based measurements of emitted thermal radiances are determined using blackbodies that have been well-characterized on the ground. The dominant sources of uncertainties include those in the BB cavity temperature and emissivity. • Challenge: On-orbit sensors generally change/degrade over time. • -- Temperature sensors and electronics drift • -- BB surface coatings are known to change after extended exposure to LEO environment (e.g., atomic oxygen, outgassing) • Solution: SI traceable measurements that quantify the BB T and eon-orbit On-orbit, SI traceable measurements of temperature and emissivity

  9. On-Orbit Verification Melt Material SI (Kelvin)-Based IR Radiance Scale Realization Planck Equation Temperature Emissivity Cavity Emissivity Measurement 3 Phase Change Cells Provide SI Traceable Fixed Points (-40oC, 0oC, 30oC) Quantum Cascade Laser (QCL) Phase Change Cells Heated Baffle SI Traceability: Unbroken chain of comparisons with stated uncertainties

  10. Verification System Overview

  11. Can L1 Accuracy Requirement be Met? • Three initial and independent studies of FTS instruments show that the CLARREO accuracy requirements can be met • University of Wisconsin/Harvard University analysis indicates CLARREO accuracy requirement (total combined uncertainty) will be met over full spectrum • Analysis by Space Dynamics Lab (SDL) indicates requirement will be met at wavelengths > ~ 5.5 mm (280K scene) • Calibration Equation used to quantify > 40 contributors to total uncertainty • Major contributors identified and tolerances assigned • Risk factors identified and mitigation plan prepared • Current analysis at Langley for CLARREO design also indicates requirement can be met

  12. IR Instrument Meets Level 1 Requirements SI Traceability: Unbroken chain of comparisons with stated uncertainties Estimated k=3 uncertainties at 1000 cm-1 for scene temperature of 250K, with calibration BB at 270K Total Combined Uncertainty 54 mK IR Level 1 Requirement 100 mK, 3s (k=3) Annual Type A Uncertainty < 1 mK Combined Type B Uncertainty 54 mK Calibration Blackbody Radiance 31 mK Gain Nonlinearity 29 mK FTS Uncertainty Terms 33 mK Space View Radiance < 1 mK Meet level 1 & level 2 requirements

  13. Random Measurement Uncertainty • CLARREO, with its climate focus, looks to generate accurate radiances on annual to semi-annual time scales, on global average • Random uncertainty is present as noise on the measured radiance • Random uncertainty is reduced by averaging • More than 2 x 106 spectra per year reduce random uncertainty by ~ 1440 • IR FTS noise is dependent on detector type (Pyroelectric vs. Solid State) • Prior analyses indicated single spectrum noise: 0.05 K < NeDT < 10 K • Annual average uncertainty due to random noise: 0.034 mK to 7 mK • Random noise substantially impacts time to calibrate on ground and in-orbit • Examined current off-the-shelf pyroelectric devices to verify performance Random uncertainty is not a science concern

  14. SELEX Pyroelectric Detector Characterization • Acquired 15 pyroelectric detectors from SELEX and their Specifications: • IR waveband range: 15 to 50-micrometer for CLARREO Far-IR • Material: DLATGS (Deuterated L-alanine doped Triglycine Sulfate) • Operating temperature: ~300K • Element active area: 3 mm • Window: CsI • Frequency range of operation: 10 Hz to 1 KHz • Type Number: P5504 (5) • Detectivity: 4.5x108cm-Hz1/2/W@ 100 Hz, 2.5x108 cm-Hz1/2/W@ 1KHz • Type Number: P5546 (5) • Detectivity: 6x108cm-Hz1/2/W@ 100 Hz, 3.2x108cm-Hz1/2/W@1KHz • Type Number: P5550 (5) • Detectivity: 1.8x109cm-Hz1/2/W@10 Hz

  15. SELEX Pyroelectric D* Calculations SELEX P5550-03 DLATGS Pyroelectric Detector Detectivity variation with Chopper Frequency Detector Temperature: 20oC Detector/Monochromator with N2 Purge Vendor Specifications (Spec.): Frequency: 10 Hz D*: 25.0×108Jones Note: This is beginning of life performance. We are looking into flight performance of similar pyroelectrics to estimate end of life performance

  16. SELEX Pyroelectric D* Summary Selected Four SELEX Pyroelectric Detectors

  17. NeDT Comparison, SELEX and Prior Pyro NEdT Comparison of SELEX DLATGS and Old Pyroelectric (200 cm-1 to 700 cm-1 with 25 cm-1 interval, Scene Temperature: 250K) SELEX Detectors: D* (P5546-04): 1.296×109 Jones @100Hz 5.82×108 Jones @1000Hz D* (P5550-03): 1.62×109 Jones @100Hz 4.64×108 Jones @1000Hz Old Pyroelectric Detector: D*: 2.5×108 Jones @100Hz 1.5×108 Jones @1000Hz

  18. Detector NER Summary

  19. Detector NeDT Summary

  20. Total Radiance Uncertainty by Detector and Scene

  21. Total Error (TB) by Detector and Scene Third Independent Study Supports CLARREO IR can meet Accuracy Reqm’t.

  22. Radiometric Modeling Status • Testing at Langley and GSFC of SELEX pyroelectrics will continue • Devices tested at Langley show much improved far-IR noise performance than previously calculated with data from SELEX catalog • Maximum NeDT is ~ 2 K vs. ~ 15 K at 200 cm-1 previous • Three separate modeling efforts (UW; SDL; LaRC) all indicate CLARREO systematic error requirement (0.1 K, k = 3) can be achieved • Integrated Product Team (selection coming soon) will continue to refine and update radiometric model to further guide instrument development

  23. Instrument Mass, Power, Thermal

  24. IR Instrument Suite Metrology Laser Radiator IR Instrument Mount QCL Radiator IR FTS Scan Mechanism IR Scene Select Assembly Mid IR Detector Optical Assembly IR Bench Radiator Cryo-Cooler Radiator Cryo-Cooler Far IR Detector Optical Assembly IR Instrument Mount Blackbody Radiator Verification Assembly Instrument suite is of moderate size and complexity

  25. Infrared Instrument Comparison * Values reflect results of “DAC-5” activity to become compatible with Falcon 1-e IR suite is moderate class

  26. Task: Develop IR Compatible with Falcon 1-e • Vital Stats as of 5/2010 • Mass: 85 kg • Power: 152 W • Falcon 1-e accommodation requires • Mass target: 80 kg • Power target: 140 W • Held IDC session to evaluate alternate instrument configuration • Identify driving requirements and evaluate impact (e.g., risk, science) and benefit (e.g., mass, power, cost reduction) of relaxing the requirement

  27. IDC Potential Trades • Modified or no fore-optics • Smaller blackbodies (emissivity vs. size) • No dedicated instrument controller (i.e., use s/c processor) • Reduce spectral range • Reduce mid-IR detectors from 2 to 1 • Reduce measurement requirements (e.g., resolution, accuracy, etc.) • Methods for reducing and handling non-linearity • Reduce temperature stability/control requirements • Operation of verification system when excess power is available • Use of composite materials • Data rate reduction with compression

  28. Instrument Geometry Trade • Use more “evolved” instrument design • Breadboard-like design, with smaller volume and surface area • Reduced cooling requirements and power • Update mass in cooling system hardware • Mass change: - 3.7 kg • Heater Power change: - 1.1 W • Volume: 0.277 m3 (Prior 0.49 m3)

  29. CLARREO IR Instrument Assembly, 05/01/2010 LaRC Optic Design, Four Port FTS, Pupil Image and Winston Cone Combined SystemBreadboard Version IR Instrument Configuration Zenith 0.76 m 0.560 m 0.65 m Volume 0.277 m³ Nadir

  30. Verification Blackbody Temperature • Knowledge of system response non-linearity in observed scene temperatures on orbit required • More than 98% of earth scenes are between -70C and +50C • Have cold calibration via space view below -70C • Reduce cooling requirement (DAC4: -80C) to -70C • Little impact (-1W) in reducing high (+50C) temperature; retain this for complete non-linearity verification • Heater Power change: - 8W

  31. Mid-IR Cryocooler Temperature • Analysis: Mid-IR MCT detectors with similar spectral ranges and sensitivities • BAE (AIRS-LITE) operates at 60K • Teledyne (CrIS) operates at 80K • Change to higher temperature (80K) Teledyne HgCdTe over prior baselined BAE AIRS-LITE 60K cryocooler temperature • No change in science performance • Cryocooler power change: - 11.1W

  32. Refined Electronics Hardware Definitions • Details now available concerning components sketched out in prior design cycles • Determined specific component and board masses and powers • Assumed cabling is 7% of final instrument mass • Separate survival board electronics removed • Function to be provided by s/c • Mass Change: - 4.1 kg • Power Change: - 7.7W

  33. MEL Scrub • Reviewed MEL in detail to identify areas in need of additional refinement • FTS Assembly and Scanner: - 2.95 kg • Scene Select Components: + 0.6 kg • Thermal Control (Heat Pipes): + 1.5 kg

  34. “Falcon 1-e” Summary • Implemented the following changes • Instrument form factor changed • Raised minimum verification blackbody temperature to -70C • Changed mid-IR detector (increased operating temperature) • Refined MEL definition • Results • Mass Change: - 8.6 kg (- 5 kg target) • Power Change: - 27.9 W • DC-DC converter power reductions with this change: - 6.4 W • Total Power Change: - 34.3 W (- 18 W target) • Current IR Instrument: 76 kg, 124 W Current IR Instrument fits well within envelope for Falcon 1-e

  35. Technology Development Status • NASA has funded, via Instrument Incubator, Advanced Component Technology, and Advanced Technology Initiatives several projects since 2001 • These have addressed fundamental needs for CLARREO IR instrument • FTS Technology • Verification system • Calibration • Component hardware • Detector technology

  36. NASA Technology Investments in CLARREO IR • IIP 2001: FIRST • FTS; Focal planes; Beamsplitters; Far-IR science • IIP 2004: INFLAME • FTS; Calibration; • IIP 2007: CORSAIR • Beamsplitters, Blackbodies, Detectors • IIP 2007: AASI • Blackbodies; Phase Change Cells; QCL; Verification system • ACT 2008: FIREBIB • Far-IR detectors and Calibration • ATI 2008: Melt Cell • Testing of Wisconsin and Utah State/SDL melt cells on the ISS • First launch in January 2011

  37. Technology Development Heritage Melt Material • LaRC has developed technology for CLARREO for nearly one decade • FIRST and INFLAME FTS instruments developed and flown • CORSAIR, FIREBIB, Melt Cell projects in progress • Detectors, beamsplitters, blackbodies in development • UW/Harvard developing CLARREO Technology • Verification system elements in development Phase Change Cells QCL Blackbodies Emissivity Monitoring Key CLARREO technologies in development to TRL 6

  38. September 5 2009 – PWV = 0.75 mm 18

  39. September 5 2009 – PWV = 0.75 mm 19

  40. September 19 2009 – PWV = 0.4 mm 20

  41. Technology Development Plan Leverages Hardware Matured Through Breadboard and IIP Programs IIPs and Breadboard Provide Early Risk Reduction

  42. Technology Assessment Reflects Current TRL Assessment Expect TRL-6 at Completion of IIP

  43. Technology Assessment Reflects Current TRL Assessment Expect TRL-6 at Completion of IIP

  44. NIST-CLARREO (IR-Instrument) Partnership- Activities Funded in Next Few Months - BRDF Integrating Sphere 1. QCL Laser (23 mm) will be purchased this summer. The laser will be used to measure the BRDF of various candidate surface treatments. It will also be used for Reflectometry measurements in CHILR to measure reflections (emissivity) of actual assembled blackbodies 2. STEEP-3 Emissivity Modeling Software will be upgraded to incorporate BRDF for better blackbody modeling and design prior to construction.

  45. Detector Cavity Integrating sphere Sphere rotation & X - Y stage 10.6 µ m µ m 23 CLARREO Calibration Facility Requirements- Activities Under Consideration for Phase A - • CHILR Investments: Complete Hemispherical IR Laser Reflectometerwill provide necessary data to the blackbody designers in order to develop high-fidelity models of emitting surfaces at wavelengths beyond ~15 mm. Currently, there are no facilities that can acquire this data. These data will be fed back into the STEEP-3 upgrade as actual working parameters. • CBS3 Investments: The Controlled Background Spectroradiometry and Spectrophotometer System will serve as NIST’s premier calibration facility for high accuracy (15 mK at 10 mm / 300 K k = 2) investigations of blackbodies and detectors in the near to far IR (Range of operation: 1 mm to 100 mm, 190K to 350 K) This will provide absolute radiometric calibrations of the CLARREO flight blackbodies with high accuracy and confidence CBS 3 CHILR

  46. Climate Absolute Radiance and Refractivity Observatory(CLARREO) IR Instrument Phase A Trades

  47. List of Potential Phase-A Trades • T1: Operating Temperature and Control • T2: Optical Alignment Sensitivity • T3: Detector Frequency Response • T4: Temperature Measurement Electronics • T5: Linearity • Potential Trades discussed on following charts

  48. T1: Operating Temperature and Control • Operating temperature, thermal control, and thermal knowledge • Examines the trade between accurately measuring changes in temperature, reducing sensitivity to temperature changes by reducing the operating temperature, and the difficulty in controlling temperature at different operating temperatures. • Includes scene select mirror and baffles, fore optics and baffles, temperature difference between beamsplitter and compensator, and internal reference blackbody source.

  49. T2: Optical Alignment • Optical alignment Sensitivity • Examine the ability of the optical path (including input and output optical axes, the beamsplitter and corner cube mounts, and FTS scan mechanism) to maintain shear alignment over the 15s calibration cycle. • Derive tolerance for changes in temperature gradients in the optical bench over the calibration period.

  50. T3: Detector Frequency Response • Examine the trade between leveling the frequency response of the pyroelectric detector (by boosting gain for high frequency?), maintaining well-behaved group delay in the signal chain, and maintaining velocity reproducibility in the FTS scan mechanism. • Right now the fact that the pyroelectric response decreases so rapidly with frequency means that slight changes in FTS scan velocity give significant changes in responsivity and decrease calibration accuracy.

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