John A. Dykema, Joe Demusz, Chris Tuozzolo, Norton Allen, James G. Anderson, Harvard

1. CLARREO FTS Design: Achieving Robust On-Orbit SI Traceability for IR - Principles Distilled from NIST John A. Dykema, Joe Demusz, Chris Tuozzolo, Norton Allen, James G. Anderson, Harvard Hank Revercomb, Fred Best, P. Jonathan Gero, Joe Taylor, Bob Knuteson, Dave Tobin, Bob Holz, UW Jerry Fraser, Eric Shirley Sergey Mekhontsev, Leonard Hanssen, Vladimir Khromchenko NIST

2. NRC DS and CLARREO • “a long-term global benchmark record of critical climate variables that are accurate over very long time periods, can be tested forsystematic errors by future generations, are unaffected by interruption, and are pinned to international standards” • CLARREO science team: • High information content • High accuracy, proven on-orbit • Sampling errors in time, angle, space lower than climate noise

3. What is SI Traceability? • SI traceability is conferred by a chain of comparisons, each of stated uncertainty, back to a recognized SI standard • CLARREO needs to: • have uncertainty low enough for decadal science and • needs to prove that biases (systematic error) that specify this uncertainty are within tolerances

4. SI Traceability and CLARREO • Jerry Fraser (NIST) has introduced the idea of strength of SI traceability claim • NIST would recognize that CLARREO requires robust traceability to achieve its ambitious science goals

5. From Jerry Fraser, NIST The National Measurement Institute (NMI) Model for Traceability • Measurements are Based on Well-Defined Physical Quantities • Measurements are Compared among NMIs • Measurements are Compare to Independent Approaches • Uncertainty Claims are Rigorous and Validated • Methods are Documented in Quality Systems and Peer-Reviewed Publications • Research is Undertaken to Lower Uncertainties • Fundamental Scales are Realized Periodically

7. Plan for suggested CLARREO IR Evaluation at NIST

8. Envisioned NIST Infrared Metrology SupportThe case study involved elements in red

9. Case Study: Goals • Characterize Blackbody Spectral Emissivity using AIRI Facility • Infrared spectral radiance measurements compared to Reference Blackbodies • Use controlled background “scene plate”; also characterize spectral radiance uniformity • Characterize Blackbody Cavity Emissivity using Sphere Reflectometer (CHILR) • Lasers used for low divergence, small spot, high power, 1.32 µm & 10.6 µm • Custom sphere for complete measurement of cavity reflected light • Model Blackbody Cavity Emissivity using characterized cavity coating properties: • Spectral directional hemispherical reflectance (FTIS Facility) • Near-normal - Reference Integrating Sphere with Fourier Transform IR Spectrometer • Variable angle - Center Mount Sphere with FTIR B. Cavity Coating BRDF, Bi-directional reflectance distribution function (IR SIRCUS / BRDF) • Laser-based system, 1.55 µm & 10.6 µm C. Monte Carlo Raytrace Modeling of BlackbodyCavity • Custom Cavity Modeling Software Suite, “STEEP3” and upgraded / modified versions • Requires cavity coating properties data

10. Case Study - Involved Facilities - Artifacts Fourier Transform Spectrophotometry (FTS) and IR BRDF Facilities Advanced Infrared Radiometry and Imaging Facility (AIRI) Complete Hemispherical Laser-based Reflectometer (CHILR)

11. Case Study: Results of Cavity Emissivity from Reflectance, Radiance, and Modeling

12. On-orbit Traceability for Blackbody1 On-orbit diagnostics: De: Reflectometer (QCL2, halo) DT: phase change cells3,4 NIST: CBS-3 De: reflectometry, scene plate DT: contact, fixed point • Dykema and Anderson, Metrologia 43 287-293 (2006). • Gero, et al., in press, J.TECH. (2009). • Gero, et al., J.TECH. 25 (2008). • Best et al., GC23A-0753.

13. Emissivity / QC Power Evaluation dT/dt = 5 x 10-5 K/sec Lab result: C(dT/dt)=35 mW PQC(measured)=33mW

14. QCL Laser Primary Demonstration of SI Traceability (Measures instrument line shape) Heated Halo (used in combination with space view for instrument calibration) (Includes Multiple Phase Change Cells for absolute temperature calibration and Heated Halo for spectral reflectance measurement ) (used for blackbody reflectivity and Spectral Response Module)

15. From Joe Rice, NIST How to prove uncertainty is consistent with what is claimed? (NIST perspective)

16. CLARREO solution: two complete, independent test sensors with independent Test/Validation modules 1st Sensor 1st Sensor 1st Sensor 2nd Sensor 2nd Sensor 2nd Sensor

17. Advantages to Dual Interferometers • Testing uncertainty on cold scenes that can’t reliably produced in laboratory • High duty cycle available for systematic error testing without disturbing benchmark • Testing systematic error by perturbing thermal or stray light environment • Optimization of radiometric performance for far- and mid-IR • Testing blackbody knowledge through thermal gradient perturbation • Agreement between two instruments invaluable in proving uncertainty is consistent with claims

18. Lessons Learned • QCL reflectometer paper to peer review: improve laser power normalization • NIST demonstration study: demands different blackbody control design • Iteration/communication between science and engineering: getting dual interferometers into trade space, looking for realistic path

19. The National Measurement Institute (NMI) Model for Traceability • Measurements are Based on Well-Defined Physical Quantities • Measurements are Compared among NMIs • Measurements are Compare to Independent Approaches • Uncertainty Claims are Rigorous and Validated • Methods are Documented in Quality Systems and Peer-Reviewed Publications • Research is Undertaken to Lower Uncertainties • Fundamental Scales are Realized Periodically CLARREO flight designs must be evaluated against the logic of these principles