1. Slide 1 UW-SSEC IR Experience and CLARREO UW-SSEC IR Calibration Experience and CLARREO Requirements NIST IR Radiometry for CLARREO NIST, Gaithersburg 12 June 2008 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

2. Slide 2 UW-SSEC IR Experience and CLARREO 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

3. Slide 3 UW-SSEC IR Experience and CLARREO Ambient Blackbody Hot Blackbody Scene Mirror Motor Interferometer & Optics Electronics Data Storage Computer Scanning HIS Aircraft Instrument H2OH2O LongwaveMidwaveShortwave CO N2ON2O H2OH2O N 2 O CH 4 CO 2 O3O3

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

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

6. Slide 6 UW-SSEC IR Experience and CLARREO Atmospheric Spectral Calibration: S-HIS Atmospheric CO 2 lines Wavenumber Scale chosen to minimize difference Estimated accuracy =1.2 ppm (1 sigma) With many samples, the 3-sigma accuracy is < 1 ppm

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

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

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

10. Slide 10 UW-SSEC IR Experience and CLARREO NIST TXRS-HIS AERI BB chamber AERI blackbody TXR Ch1 TXR Ch2 Scanning-HIS spectra End-to-end radiance evaluations conducted under 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 UW/SSEC January 2007 227 – 294 K AERI Blackbody 10 & 5  m NIST TXR Channels UW S-HIS & AERI Blackbody Absolute Accuracy: The NIST Connection for SI Traceability

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

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

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

14. Slide 14 UW-SSEC IR Experience and CLARREO Measurements confirm estimated emissivity within uncertainty (3-sigma estimates) Updated August 07 5 microns10 microns 0.001   =0.999

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

16. 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  = /1200, SHIS  =~0.5 cm -1 ) and sampling SHIS and AIRS SRFs AIRS SHIS

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

18. “Comparison 2” wavenumber AIRS Compared to S-HIS, 21 Nov 2002 AIRS & S-HIS Obs-Calc Black is Calculation 36, 35, 34, 33323130 AIRS minus MODIS

19. “Comparison 2” wavenumber AIRS Compared to S-HIS, 21 Nov 2002 AIRS & S-HIS Obs-Calc Black is Calculation 2827

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

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

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

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

24. Slide 24 UW-SSEC IR Experience and CLARREO IASI on Metop 19 October 2006 launch - full cross-track scan - 2x2 12 km pixels sample 50x50 km

25. Slide 25 UW-SSEC IR Experience and CLARREO 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

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

27. Slide 27 UW-SSEC IR Experience and CLARREO ARM site + S-HIS FOVs o NAST-I FOVs 290 285 280 IASI 900 cm -1 BT(K) Imager Data MetOp overpass of Oklahoma ARM CF 19 April 2007 IASI NAST-I S-HIS BT (K) wavenumber (cm -1 )

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

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

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

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

32. Slide 32 UW-SSEC IR Experience and CLARREO 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

33. Slide 33 UW-SSEC IR Experience and CLARREO 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 stage Aircraft—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-)

34. Slide 34 UW-SSEC IR Experience and CLARREO CLARREO: New Paradigms for Benchmark Climate Measurements 1)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.) 2)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) 3)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)

35. Slide 35 UW-SSEC IR Experience and CLARREO CLARREO: Flow-down Corollaries 1)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] 2)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)

36. Slide 36 UW-SSEC IR Experience and CLARREO CLARREO: Flow-down Corollaries (2) 3)Deploy an orbital configuration optimized 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)

37. Slide 37 UW-SSEC IR Experience and CLARREO 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)

38. Slide 38 UW-SSEC IR Experience and CLARREO 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)

39. Slide 39 UW-SSEC IR Experience and CLARREO 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)

40. Slide 40 UW-SSEC IR Experience and CLARREO 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

41. Slide 41 UW-SSEC IR Experience and CLARREO Flow-Down IR Requirements (4) 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) Space Earth Calibration Blackbody (ambient or single T) Validation Blackbody (widely variable T) Beamsplitter polarization axis Optional Space Views

42. Slide 42 UW-SSEC IR Experience and CLARREO 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)

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

44. Slide 44 UW-SSEC IR Experience and CLARREO 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

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

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

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

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

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