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UW-SSEC IR Calibration Experience and CLARREO Requirements

UW-SSEC IR Calibration Experience and CLARREO Requirements. Hank Revercomb , Fred A. Best, Robert O. Knuteson, David C. Tobin, Joe K. Taylor, Bob Holz University of Wisconsin-Madison, Space Science and Engineering Center. NIST IR Radiometry for CLARREO NIST, Gaithersburg 12 June 2008.

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UW-SSEC IR Calibration Experience and CLARREO Requirements

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  1. UW-SSEC IR Calibration Experience and CLARREO Requirements Hank Revercomb, Fred A. Best, Robert O. Knuteson, David C. Tobin, Joe K. Taylor, Bob Holz University of Wisconsin-Madison, Space Science and Engineering Center NIST IR Radiometry for CLARREO NIST, Gaithersburg12 June 2008 UW-SSEC IR Experience and CLARREO

  2. Topics • UW Scanning HIS calibration and inter-calibration experience as background for CLARREO • CLARREO IR requirements traceability from science drivers • Required NIST Capabilities for CLARREO UW-SSEC IR Experience and CLARREO

  3. Scanning HIS Aircraft Instrument Data Storage Computer Ambient Blackbody Hot Blackbody Electronics Interferometer & Optics N2O CH4 O3 CO CO2 CO2 H2O Scene Mirror Motor N2O Longwave Midwave Shortwave H2O UW-SSEC IR Experience and CLARREO

  4. S-HIS Aircraft Platforms S-HIS on the Proteus S-HIS on the WB-57 S-HIS on the DC-8 S-HIS on the ER-2 UW-SSEC IR Experience and CLARREO

  5. S-HIS Flight Experience Map imagery courtesy NASA visible earth UW-SSEC IR Experience and CLARREO

  6. Atmospheric Spectral Calibration: S-HIS Atmospheric CO2 linesWavenumber Scale chosen to minimize difference Estimated accuracy =1.2 ppm(1 sigma) With many samples,the 3-sigma accuracy is < 1 ppm UW-SSEC IR Experience and CLARREO

  7. S-HIS Absolute Radiometric Uncertaintyfor typical Earth scene spectrum TABB= 260 K THBB= 310 K TBB = 0.10 K BB = 0.0010 Trefl = 5 K 10% nonlinearity **Formal 3-sigma absolute uncertainties, similar to that detailed for AERI in Best et al. CALCON 2003 1.0 Wavenumber Tb Uncertainty (K) 0.2 K 0 200 Brightness T (K) 300 UW-SSEC IR Experience and CLARREO

  8. UW-SSEC AERI Blackbody Predicted Radiance Uncertainty Uncertainty for TBB = 293K, TRefl = 230K 3-sigma Tb Error (K) wavenumber (cm-1) 3 Uncertainties: 3TBB = 0.05 K 3TRefl = 5 K 3BB = 0.001 Total (RSS) UW-SSEC IR Experience and CLARREO

  9. SSEC Spectrometer Ties to NIST Spaceflight High-altitude Aircraft Ground-based AERI S-HIS GIFTS NIST TXR NIST Waterbath Blackbody < 0.06 K error (293 to 333 K) < 0.06 K error (220 to 333 K)  > 0.9994 (within estimated uncertainty) UW-SSEC IR Experience and CLARREO

  10. UW S-HIS & AERI Blackbody Absolute Accuracy: The NIST Connection for SI Traceability AERI BB NIST TXR S-HIS chamber AERI blackbody TXR Ch2 TXR Ch1 Scanning-HIS spectra UW/SSECJanuary 2007 End-to-end radiance evaluations conductedunder S-HIS flight-like conditions with NIST transfer sensor (TXR) such that S-HIS satellite validation & AERI observations are traceable to the NIST radiance scale 227 – 294 K AERI Blackbody 10 & 5 m NIST TXR Channels UW-SSEC IR Experience and CLARREO

  11. NIST TXR Validation of S-HIS RadiancesNIST TXR Channel 2 (10m) AERI minus TXR AERI minus S-HIS mean = -22 mK mean = -60 ± 90 mK BT Diff (K) TXR operations and data c/o Joe Rice and Joe O’Connell AERI BT (K) • mean difference between TXR & S-HIS = 38 mK, well less than propagated 3-sigma uncertainties UW-SSEC IR Experience and CLARREO

  12. NIST TXR Validation of S-HIS RadiancesNIST TXR Channel 1 (5m) AERI minus S-HIS mean = -40±85 mK BT Diff (K) TXR operations and data c/o Joe Rice and Joe O’Connell AERI BT (K) • mean difference between AERI BB & S-HIS = 40 mK • TXR Ch1 analysis requires refinement at this time UW-SSEC IR Experience and CLARREO

  13. AERI Blackbody Reflectivity Test with NIST TXR Confirms Emissivity Estimates NIST Transfer Radiometer(TXR) used to detectreflection from heated tube(up to background +100 ºC)surrounding direct FOV TXR Preliminary Analysis:5 & 10 m emissivitywithin <0.0003of expected value(and closer to 1) January 2007 UW-SSEC IR Experience and CLARREO

  14. Updated August 07 5 microns 10 microns 0.001  =0.999 Measurements confirm estimated emissivity within uncertainty (3-sigma estimates) UW-SSEC IR Experience and CLARREO

  15. Radiance Validation of AIRS with S-HIS UW-SSEC IR Experience and CLARREO

  16. AIRS SHIS • AIRS / SHIS Comparisons • A detailed comparison should account for: • instrumental noise and scene variations • Different observation altitudes (AIRS is 705km, SHIS is ~20km on ER2, ~14km on Proteus) • Different view angles (AIRS is near nadir, SHIS is ~±35deg from nadir) • Different spatial footprints (AIRS is ~15km at nadir, SHIS is ~2km at nadir) • Different spectral response (AIRS Dn=n/1200, SHIS Dn=~0.5 cm-1) and sampling SHIS and AIRS SRFs

  17. MODIS 12 m Band Tbs(K) & near-nadir AIRS FOVs

  18. AIRS minus MODIS 36, 35, 34, 33 32 31 30 AIRS Compared to S-HIS, 21 Nov 2002 Black is Calculation AIRS & S-HIS Obs-Calc “Comparison 2” wavenumber

  19. 28 27 AIRS Compared to S-HIS, 21 Nov 2002 Black is Calculation AIRS & S-HIS Obs-Calc “Comparison 2” wavenumber

  20. Gulf of Mexico Validation case: 2002.11.21 UW-SSEC IR Experience and CLARREO

  21. Gulf of Mexico Validation case: 2002.11.21 (AIRSobs-AIRScalc)- (SHISobs-SHIScalc) (K) UW-SSEC IR Experience and CLARREO

  22. AIRS-SHIS Summary: SW (2004.09.07) Excellent agreement for night-time comparison from Adriex in Italy UW-SSEC IR Experience and CLARREO

  23. Radiance Validation of IASI with S-HIS UW-SSEC IR Experience and CLARREO

  24. IASI on Metop19 October 2006 launch- full cross-track scan - 2x2 12 km pixels sample 50x50 km UW-SSEC IR Experience and CLARREO

  25. Joint Airborne IASI Validation Experiment (JAIVEx) • What:Metop and Aqua satellite under-flights for radiance and retrieval validation • Who:NPOESS Airborne Sounder Testbed team (NAST-I/M & S-HIS on NASA WB57) & UK team (ARIES on Facility for Airborne Atmospheric Measurements BAe146-301) • When:14 April to 4 May 2007 • Where:Comparisons over the Gulf of Mexico and Oklahoma ARM site reached from Houston airbase UW-SSEC IR Experience and CLARREO

  26. IASI L1C GaussianApodization Deapodized NAST-I CLARREO S-HIS 1cm MaxOPD AIRS CrIS CrIS AIRS wavenumber IASI Tb Spectrum: Processed to represent NAST-I, S-HIS (CLARREO), AIRS & CrIS UW-SSEC IR Experience and CLARREO

  27. MetOp overpass of Oklahoma ARM CF19 April 2007 290 285 280 ARM site + S-HIS FOVs o NAST-I FOVs IASI NAST-I S-HIS IASI 900 cm-1 BT(K) BT (K) Imager Data BT (K) BT (K) wavenumber (cm-1) UW-SSEC IR Experience and CLARREO

  28. IASI Longwave Validation IASI, NAST-I, SHIS Mean spectra BT (K) IASI minus NAST-I, IASI minus SHIS (using double obs-calc method) Diff (K) NAST-I: S-HIS: 0.00 K 0.02 K 0.08 K 0.12 K 0.03 K 0.00 K 0.16 K 0.14 K UW-SSEC IR Experience and CLARREO wavenumber

  29. IASI Midwave Validation BT (K) IASI, NAST-I, SHIS Mean spectra IASI minus NAST-I, IASI minus SHIS (using double obs-calc method) Diff (K) NAST-I: S-HIS: 0.12 K 0.20 K 0.04 K 0.03 K -0.19 K -0.08 K UW-SSEC IR Experience and CLARREO wavenumber

  30. IASI Shortwave Validation BT (K) IASI, NAST-I, SHIS Mean spectra IASI minus NAST-I, IASI minus SHIS (using double obs-calc method) Diff (K) NAST-I S-HIS 0.09 K 0.16 K 0.07 K 0.12 K UW-SSEC IR Experience and CLARREO wavenumber

  31. IASI, NASTI, and SHIS BT (K) wavenumber UW-SSEC IR Experience and CLARREO

  32. Aircraft Radiance Validation Results Summary • Aircraft Validation (of high resolution spectra): New, highly accurate capability proven 2002-2007 • AIRS: Differences from Scanning HIS generally <0.2 K with small standard deviations [Tobin et al., JGR, 2006] • TES: Better than 0.5 K agreement in most regions (also characterized small, spectrally correlated noise from variable sample-position-errors)[Shephard et al., JGR, submitted April 2007] • IASI: These preliminary results are comparable to AIRS validation results with higher spectral resolution & contiguous spectral coverage UW-SSEC IR Experience and CLARREO

  33. CLARREO Perspective It is time to apply spectrally resolved IR radiances as a new paradigm for observing climate change High spectral resolution has been successfully demonstrated over the last 20 years, setting the stageAircraft—HIS/Scanning HIS(1985/1998-), ARIES(1996-), NAST-I(1998-), INTESA(1998-)Ground-based—AERI/MAERI(1990-)Spaceborne—IR Sounders: AIRS(2002-), IASI(2006-), CrIS(2009)Very High Res: IMG(1996/97), MIPAS(2002-), ACE(2003-), TES(2004-) UW-SSEC IR Experience and CLARREO

  34. CLARREO: New Paradigms for Benchmark Climate Measurements • High information content, rather than just monitoring total radiative energy budget (i.e. spectrally resolved radiances covering large parts of the spectrum as a product, rather than total IR or Solar fluxes—can separate IR & Solar obs.) • Very high absolute accuracy, with measurement accuracy proven on orbit (stability not sufficient) a) minimizes climate change detection time and b) relieves the need for mission overlap (Must consider Total Accuracy = RSS of Spatial/ Temporal biases and measurement accuracy) • Commitment to ongoing Benchmark Missions planned with 5-8 year lifetime every 8-10 years (Data for Model trend evaluation is needed for the foreseeable future, certainly the next century—therefore, affordability is a key ingredient) UW-SSEC IR Experience and CLARREO

  35. CLARREO: Flow-down Corollaries • Primary products are direct observables, not derived fluxes or retrieved properties(paradigms 1, 2)[e.g.spectrally resolved, IR, nadir radiances (broadband, including far IR), averaged over regions and time of day to control spatial and temporal biases] • Minimize complexity (paradigms 2-3)(do one thing very well—e.g. no cross-track scanning, design for low biases, noise can be relatively high, keep non-linearity and polarization artifacts small) UW-SSEC IR Experience and CLARREO

  36. CLARREO: Flow-down Corollaries (2) 3) Deploy an orbital configurationoptimized for global coverage and to minimize sampling bias(paradigm 2)[e.g. equally spaced, truly polar orbits (90º inclination) giving global coverage and equal time of day sampling every 2 months—explicit diurnal cycle measurement] 4) Depend on other science and operational observations for process studies(paradigm 3)(Cross calibration improves the consistency and value for process studies. However, radiance observations from other sensors do not have the spectral coverage or absolute accuracy to be relied on for providing a fundamental component of the benchmark product) UW-SSEC IR Experience and CLARREO

  37. CLARREO General IR Science Drivers • Information Content: Capture the spectral signatures of regional and seasonal climate change that can be associated with physical climate forcing and response mechanisms (to unequivocally detect change and refine climate models) • Absolute Accuracy: <0.1 K 2-sigma brightness T for combined measurement and sampling uncertainty (each <0.1 K 3-sigma) for annual averages of 15ºx30º lat/long regions (to approach goal of resolving a climate change signal in the decadal time frame) • Calibration transfer to other spaceborne IR sensors:Accuracy approaching the measurement accuracy of CLARREO using Simultaneous Nadir Overpasses(to enhance value of sounders for climate process studies-actually drives few requirements) UW-SSEC IR Experience and CLARREO

  38. Flow-Down IR Requirements (1) • Spectral Coverage: 3-50 m or 200-3000 cm-1(includes Far IR to capture most of the information content and emitted energy) • Spectral Resolution:~0.5 cm-1 (1 cm max OPD)(to capture atmospheric stability, aid in achieving high radiometric accuracy, and allow accurate spectral calibration from atmospheric lines) • Spectral Sampling: Nyquist sampled (to achieve standard spectral scale for multiple instruments) UW-SSEC IR Experience and CLARREO

  39. Flow-Down IR Requirements (2) • Spatial Footprint & Angular Sampling:Order 100 km or less, nadir only(no strong sensitivity to footprint size, nadir only captures information content) • Spatial Coverage: Complete global sampling(to not miss critical high latitude regions) • Orbits: 3 90º inclination orbits spaced 60º apart (to minimize sampling biases that RSS with measurement uncertainty) • Temporal Resolution and Sampling:< 15 sec resolution and < 15 sec intervals (adequate to reduce sampling errors and noise) UW-SSEC IR Experience and CLARREO

  40. Flow-Down IR Requirements (3) • Spectrometer Approach: 2 Fourier Transform Spectrometers(dual FTS sensors to detect unexpected drifts and give full spectral coverage with noise performance needed for calibration transfer and on-orbit characterization testing) • Noise: NEdT(10 sec) < 1.5 K for climate record, < 1.3 K for cal transfer(not very demanding) • Detectors: Pyroelectric for one FTS and cryogenic PV MCT and/or InSb for the other UW-SSEC IR Experience and CLARREO

  41. Flow-Down IR Requirements (4) Space Beamsplitterpolarization axis OptionalSpace Views CalibrationBlackbody(ambient or single T) ValidationBlackbody(widely variable T) Earth • On-orbit characterization: provide non-linearity and polarization test capability • Non-linearity from Out-of-band Harmonics and variable temperature blackbody • Polarization from multiple space view directions (design also minimizes effects of gold scene mirror induced polarization) UW-SSEC IR Experience and CLARREO

  42. Flow-Down IR Requirements (5) • Pre-launch Calibration/Validation:Characterization against NIST primary infrared standards and evaluation of flight blackbodies with NIST facilities (recent “best practice”) • On-orbit Calibration:Onboard warm blackbody reference (~300K), with phase change temperature calibration, plus space view, supplemented with characterization testing(to detect any slow changes) • Validation, On-orbit:Variable-temperature Standard Blackbody, with on-orbit absolute T calibration and reflectivity measurement(to maintain SI measurements on orbit) UW-SSEC IR Experience and CLARREO

  43. CLARREO Expected Calibration Uncertainty:Based on GIFTS Spaceflight Calibration Blackbody Design TBB=300K, TBB=0.045K, BB= 0.999, BB= 0.0006, TStructure=285K, TTelescope=0.02K UW-SSEC IR Experience and CLARREO

  44. Separate SI Validation Standard Blackbody • Provides capability to validate or correct SI measurement on-orbit • New On-orbit Temperature Calibration technique is based on fundamental phase change principles • Normal Reflectivity/Emissivity is measured on-orbit UW-SSEC IR Experience and CLARREO

  45. Required NIST Capabilities UW-SSEC IR Experience and CLARREO

  46. CLARREO Viewing Targets Developed under IIP Used for Ground Testing Only UW-SSEC IR Experience and CLARREO

  47. Required NIST Capabilities Blackbody Paint Reflectivity Measurements Blackbody Temperature Calibration Cavity Emissivity Calc. Using Monte-Carlo Ray-traceing • Directional Hemispheric Reflectance • - near-normal reflectance integrating sphere • - variable angle-center mount sphere • BRDF Blackbody Reflectivity • Complete Hemispherical Laser-based Reflectometer NIST Traceable Temp. Probe Calibration Blackbody Radiance • Controlled-Background Spectrocomparator(CBS3) (vacuum environmemt allowing far IR and low- end atmospheric scene temperature tests) • Hart Scientific • - NIST Themometry Check • STEEP4 Blackbodies • On-orbit Absolute Radiance Standard (OCEM) • Ambient Calibration Blackbody • Earth Scene Target • Space Target UW-SSEC IR Experience and CLARREO

  48. Required NIST Capabilities - Post Launch NIST Temperature, Reflectivity, and Spectral Traceability as needed Scanning HIS Radiance & Linearity Check Using NIST TXR & Transfer BB Ground Witness Measurement Program Aircraft Flight Validations • Periodic Underflights • Phase Change Temperatures • Thermistor Drift • Blackbody Paint Change • Blackbody Radiance UW-SSEC IR Experience and CLARREO

  49. CLARREO Comparison to Existing Sounders UW-SSEC IR Experience and CLARREO

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