Traceability of Absolute Radiometric Calibration for the Atmospheric Emitted Radiance Interferometer (AERI) Fred A. Best, Henry E. Revercomb, Robert O. Knuteson, Dave C. Tobin, Ralph G. Dedecker, Tim P. Dirkx, Mark P. Mulligan, Nick N. Ciganovich, Yao Te University of Wisconsin Space Science and Engineering Center fred.best@ssec.wisc.edu USU/SDL CALCON 2003 CALCON 2003 Radiometric Calibration of AERI Abstract The Atmospheric Emitted Radiance Interferometer (AERI) is a ground-based spectroradiometer that was developed at the University of Wisconsin for the DOE Atmospheric Radiation Measurement (ARM) program to measure the downwelling infrared emission from CO2, H2O, and clouds. Twelve continuously operating AERIs are deployed throughout the world, including three marine-based instruments (MAERIs) that are configured to measure sea surface temperature. The AERI i nstruments are used to improve our understanding of atmospheric radiation transfer and cloud properties for climate studies, and for boundary level temperature and water vapor retrieval and water vapor transport for weather applications. During operation, the AERI uses two high emissivity blackbody sources to provide instrument absolute calibration accuracies to better than 1% of the ambient radiance. A calibration methodology with traceability to NIST has been successfully implemented for the blackbodies. Absolute radiometric performance of the AERI was verified using the 3rd generation water-bath based NIST blackbody source, with agreement better than 0.065 K over the temperature range from 293 K to 333 K. Instrument repeatability has been demonstrated during a 14 day cruise where two MAERI instruments operating side-by-side measuring sea surface temperature showed agreement to within 0.02 K. An uncertainty analysis based on the instrument calibration equation was used to allocate the allowable blackbody temperature and emisssivity uncertainties. A detailed budget was developed to account for all contributions to both temperature and emissivity uncertainty, including contributions from the instrument spectral calibration. Both temperature and emissivity measurements have traceability to NIST. Slide 2 CALCON 2003 Radiometric Calibration of AERI Topics • AERI Overview & Radiometric Performance Specification • Instrument Calibration Model and Predicted Instrument Performance • Blackbody Design and Performance • Instrument End-to-end Performance • Summary Slide 3 CALCON 2003 Radiometric Calibration of AERI AERI Overview and Radiometric Performance Specification Slide 4 CALCON 2003 Radiometric Calibration of AERI Atmospheric Emitted Radiance Interferometer (AERI) Clear Sky and Cloud Downwelling Emission H 2O 140 120 CLOUD Radiance Radiance 100 CO2 80 800 60 900 O3 40 20 850 CLEAR 0 600 800 1000 1200 1400 Wavenumber Operational at DOE ARM Slide 5 Accurate AccurateHigh HighResolution ResolutionRadiometry Radiometry CALCON 2003 Radiometric Calibration of AERI AERI Provides Continuous Atmospheric Profiling of Temperature and Water Vapor Altitude [km] 2.5 o Altitude [km] 2.5 o Slide 6 CALCON 2003 Radiometric Calibration of AERI AERI Systems Around The World • UW AERI - 2 (AERIBAGO, SSEC) • DOE AERI - 7 (Kansas/Oklahoma, Alaska, S. Pacific) • U-Miami M-AERI - 3 (Florida) • Bomem AERI - 4 (Italy, California, Maryland, Canada) • U Idaho P-AERI - 1 (Antarctica) Slide 7 CALCON 2003 Radiometric Calibration of AERI AERI Interferometer Assembly ABB Stirling Cooler Compressor HBB Bomem Interferometer Slide 8 IR Detector Dewar with Cooler Cold Finger CALCON 2003 Radiometric Calibration of AERI AERI Front-end Assembly Detector with Stirling Cooler Interferometer Assembly with Blackbodies Front-end Port for Scene Mirror Assembly Scene Mirror Assembly Slide 9 CALCON 2003 Radiometric Calibration of AERI AERI Functional Block Diagram ATM OSPHERIC RADIATION SCAN MIRROR DRIVE INITIALIZATION FRINGE COUNTING LASER POWER & CONTROL R S RAIN & SUN SENSORS STIRLING COOLER PREAMPS PREAMPS * HBB DEWAR 2 DETECTORS SCENE MOTOR BOMEM INTERFEROMETER AFT OPTICS ENCODER ABB ANALOG FILTERING TO SCENE MOT OR CONTROLLER * OPTICS BENCH OUTSIDE AMBIENT TEMPERAT URE A/D CONVERTERS T TO DSP'S P H • • • • RACK MOUNTED EL ECTRONICS HOUSEKEEPING SIGNAL CONDITIONING R S HOUSEKEEPING A/D TO SCENE M OTOR TO HEATERS TO STIRL ING COOLER UN-INTERRUPTABLE POWER SUPPLY SCENE MOTOR CONTROLLER ENVIRONMENTAL CONTROL & SAFING STIRLING COOLER CONTROLLER OPTIONAL LOCAL ARCHIVE DSP's (2) INSTRUMENT CONTROLLER & PROCESSOR & FRONT END PROCESSOR BLACKBODY TEMPERATURE CONTROLLERS (2) POWER DISTRIBUTION MULTIPLE AERI DISPLAY SYSTEM (MADS) HBB ABB INTERFEROMETER POWER (115 VAC @ 6 0 HZ) Slide 10 CALCON 2003 Radiometric Calibration of AERI WIDE AREA NETWORK AERI Radiometric Accuracy Requirements • Absolute Accuracy: • Reproducibility: better than 1%* better than 0.2%* *expressed as % of ambient radiance Slide 11 CALCON 2003 Radiometric Calibration of AERI Radiance Uncertainty Requirements and Budget Top Level Requirements – Absolute Accuracy: < 1.0% of ambient radiance – Reproducibility: < 0.2% of ambient radiance Budget Goals for Key Contributors Absolute Reprod. Detector Non-linearity Correction (addressed briefly here) 0.2% 0.05% Blackbody Calibration (main topic of this talk) 0.9% 0.18% Spectral Calibration (material in Dave Tobin’s talk applies) 0.2% 0.05% 0.95% 0.20% All numbers are 3s (“not to exceed”) Slide 12 CALCON 2003 Radiometric Calibration of AERI AERI Non-linearity Correction and Uncertainty Sky view and ABB radiance spectra Maximum Detector Non-linearity correction is order 1% Uncertainty in correction is estimated to be < 0.10% The non-linearity correction is physically based with one adjustable and one modeled parameter Slide 13 CALCON 2003 Radiometric Calibration of AERI Instrument Calibration Model and Predicted Radiometric Performance Slide 14 CALCON 2003 Radiometric Calibration of AERI AERI Instrument Calibration Equation CS C A BA N BH BA )Re CH C A • • • • • • • N is the calibrated spectral radiance BH is the effective Planck emission for the hot blackbody BA is the effective Planck emission for the ambient blackbody CS is the complex spectrum for the sky view CH is the complex spectrum for the hot blackbody view CA is the complex spectrum for the ambient blackbody view Re() is the real part of the complex ratio Slide 15 CALCON 2003 Radiometric Calibration of AERI AERI Calibration Error Estimates Radiometric Requirement is 0.9% of Ambient Radiance Scene Temperature (K) AERI Calibration Error Estimates 150 200 250 300 350 -0.6 1.0 -0.4 0.8 % Ambient Radiance ²Thbb 0.4 ²Tabb ²Ehbb 0.2 ²Eabb ²Tstr 0.0 Trss ec nai daR t nei bmA % -0.2 0.6 Trss 0.0 ²Tstr ²Eabb 0.2 ²Ehbb ²Tabb 0.4 ²Thbb 0.6 -0.2 0.8 -0.4 1.0 -0.6 150 200 250 300 350 AERI Calibration Error Estimates Scene Temperature (K) Input Parameters wn Thbb Tcbb Tstr Ehbb Ecbb Uncertainties (3 sigma) 770 333 300 305 0.999 0.999 Wavenumber, [cm-1] Temp. of Hot Blackbody, [K] Temp. of Cold Blackbody, [K] Temp. of Structure Reflecting into BB's, [K] Emissivity of HBB, [-] Emissivity of CBB, [-] ²Thbb ²Tcbb ²Tstr ²Ehbb ²Ehbb 0.10 0.10 5 0.001 0.001 [K] [K] [K] [-] [-] Ecbb Ehbb Tstr Tcbb Thbb wn Input Parameters Longwave: 770 cm-1 Slide 16 0.999 0.999 305 300 333 2200 CALCON 2003 Radiometric Calibration of AERI Emissivity of CBB, [-] Emissivity of HBB, [-] Temp. of Structure Reflecting into BB's, [K] Temp. of Cold Blackbody, [K] Temp. of Hot Blackbody, [K] Wavenumber, [cm-1] ²Ehbb ²Ehbb ²Tstr ²Tcbb ²Thbb 0.001 0.001 5 0.10 0.10 Uncertainties (3 sigma) Shortwave: 2200 cm-1 [-] [-] [K] [K] [K] AERI Reproducibility Error Estimates Radiometric Requirement is 0.18% of Ambient Radiance Scene Temperature (K) Scene Temperature (K) 150 200 250 300 150 350 -0.20 -0.20 -0.15 -0.15 250 300 350 -0.10 Trss -0.05 ²Tstr ²Eabb 0.00 ²Ehbb ²Tabb 0.05 ²Thbb ec nai daR t nei bmA % -0.10 ec nai daR t nei bmA % 200 Trss -0.05 ²Tstr ²Eabb 0.00 ²Ehbb ²Tabb 0.05 ²Thbb 0.10 0.10 0.15 0.15 0.20 0.20 AERI Calibration Error Estimates AERI Calibration Error Estimates Ecbb Ehbb Tstr Tcbb Thbb wn 0.999 0.999 305 300 333 770 Emissivity of CBB, [-] Emissivity of HBB, [-] Temp. of Structure Reflecting into BB's, [K] Temp. of Cold Blackbody, [K] Temp. of Hot Blackbody, [K] Wavenumber, [cm-1] Input Parameters ²Ehbb ²Ehbb ²Tstr ²Tcbb ²Thbb 0.0005 0.0005 5 0.02 0.02 Uncertainties (3 sigma) [-] [-] [K] [K] [K] Ecbb Ehbb Tstr Tcbb Thbb wn Input Parameters Longwave: 770 cm-1 Slide 17 0.999 0.999 305 300 333 2200 CALCON 2003 Radiometric Calibration of AERI Emissivity of CBB, [-] Emissivity of HBB, [-] Temp. of Structure Reflecting into BB's, [K] Temp. of Cold Blackbody, [K] Temp. of Hot Blackbody, [K] Wavenumber, [cm-1] ²Ehbb ²Ehbb ²Tstr ²Tcbb ²Thbb 0.0005 0.0005 5 0.02 0.02 Uncertainties (3 sigma) Shortwave: 2200 cm-1 [-] [-] [K] [K] [K] Blackbody Design and Performance Slide 18 CALCON 2003 Radiometric Calibration of AERI Blackbody Requirements Blackbody System Requirements Temperature knowledge: Temp. gradient knowledge: Emissivity: Emissivity knowledge: ± 0.10 K better than 0.10 K > 0.998 better than ± 0.1% Instrument Imposed Requirements BB Aperture: Envelope: Operating Temperature: Period between cal. views: Slide 19 CALCON 2003 Radiometric Calibration of AERI 6.9 cm 18 cm dia. X 30 cm long 213 K to 333 K < 10 minutes Top-level Design Choices Cavity Approach Provides high emissivity (cavity factor near 40) Emissivity enhancement due to cavity is well characterized Cavity walls provide good conduction (low gradients) Easy to manufacture Chemglaze Z306 Black Paint Provides high emissivity that is well characterized and stable Provides a hardy diffuse surface YSI 46041 Super-stable Thermistors Very stable (< 0.01°C drift after 100 months at 70°C) Easy to couple thermally to blackbody cavity Reasonably rugged Slide 20 CALCON 2003 Radiometric Calibration of AERI AERI Blackbody Aperture (6.90 cm) Blackbody Cavity Case Circumferential Heater Thermal Insulation Sense Thermistors (3) Cavity Structural Support (thermal isolator) (dedicated feedback thermistor is located at base of cone section) Electrical Connector Slide 21 Handle CALCON 2003 Radiometric Calibration of AERI AERI Blackbody Heater Winding Thermistor Leads Shrink Tubing 46041 Thermistor Epoxy (3M 2216) Thermal Grease (Wakefield 126) Cavity Aperture (6.9 cm) Slide 22 Cavity Support (Thermal Isolator) CALCON 2003 Radiometric Calibration of AERI Blackbody Cone Thermistor Installation AERI Radiometric FOV at Blackbody Radiometric Field-of-view is verified at the position of the blackbody aperture Slide 23 CALCON 2003 Radiometric Calibration of AERI AERI Blackbody Calibration Overview AERI System Resistance Resistance Calibration Calibration CALIBRATION RESISTORS SIGNAL CONDITIONING ELECTRONICS CAL R RESISTANCE AERI INGEST COMPUTER A/D RESISTANCE CALIBRATION COEFFICIENTS (M, B) Temperature Temperature Calibration Calibration PRT PRT SIGNAL CONDITIONING ELECTRONICS A/D AERI INGEST COMPUTER R CAL. COEF. THERMISTOR RESISTANCE TEMPERATURE CHAMBER TEMPERATURE CALIBRATION COEFFICIENTS (A, B, & C) CALIBRATED PRT TEMPERATURE Slide 24 CALCON 2003 Radiometric Calibration of AERI T = 1 / [ A + B * Ln (R) + C * (Ln(R)) ] 3 Temperature Uncertainty Temperature and Resistance Reference Uncertainty 26 32 33 RSS ± peak error [K] 0.030 0.007 0.007 0.032 RSS 0.020 0.003 0.020 0.020 RSS 0.050 0.030 0.058 0.058 RSS 0.050 0.030 0.058 0.058 0.030 0.030 Temperature Calibration Standard (Guildline PRT) Calibration Resistors Resistor Readout Electronics Residual Error RSS [K] 0.032 Thermistor Temperature Transfer Uncertainty 26 28 Temperature Gradient Between PRT and Thermistors Calibration Fitting Equation Residual Error Cavity Temperature Non-uniformity Uncertainty 37 37 37 29 Azumuthal Gradients Due to Free Convection Longitudinal Gradients Due Primarily to Conduction Radial Gradients Due to Conduction, Convection, and Radiation Paint Gradient Long-term Stability 30 34 Thermistor Resistance Measurement Electronics Effective Radiometric Temperature Weighting Factor Uncertainty 36 Monte Carlo Ray Trace Model Uncertainty in Determining Teff XX Indicates slide number where more detailed information is presented 0.095 Slide 25 CALCON 2003 Radiometric Calibration of AERI AERI Blackbody Temperature CalibrationProbe Configuration Insures Excellent Thermal Coupling Between PRT and Blackbody Thermistors UW SSEC Guildline 9540 PRT is calibrated (with an uncertainty of 30 mK) at the factory using a Rosemont 162CE SPRT Primary Standard Traceable to NIST. Standard Configuration Slide 26 Calibration Configuration CALCON 2003 Radiometric Calibration of AERI AERI Thermistor Calibrations Reduce Uncertainty From YSI Nominal Specification Typical AERI Thermistor Calibration Deviation From YSI Nominal 0.15 Temperature (C) 0.10 0.05 0.00 -0.05 -0.10 Calibration reduces AERI thermistor uncertainty to < 0.038 K -0.15 -0.20 -30 -10 10 Integrated BB Thermistor S/N YSI034a Raw Thermistor Spec. 30 50 Self Heat-Theoretical YSI Raw Thermistor Spec. Data from AERI Blackbody S/N 34 Slide 27 CALCON 2003 Radiometric Calibration of AERI 70 90 Thermistor Calibration Residual Errors From Regression Fit of Steinhart and Hart Equations Calibration Residual Errors From Steinhart and Hart Fitting Equations 0.003 Terror = (Tfit -Tprt) [K] 0.002 0.001 Top Bottom Apex 0.000 -0.001 -0.002 -0.003 250 260 270 280 290 300 310 320 330 340 Calibration Temperature [K] Residual Error From Fitting Equations < 3 mK 1 3 A Bln( R) C(ln( R)) T Data from BB S/N 24 Slide 28 CALCON 2003 Radiometric Calibration of AERI 350 Gradient across paint [K] Tamb = 20 C Thbb = 60 C Paint Conductivity, k [W m-1 K-1] Temperature Gradient Due to Paint Thickness ∆T=0.0075 K results from (Th-Ta)=40 C. ∆T expected to be < 0.03 K for max. expected (Th-Ta)=120 C. Emissivity 0.03 K is carried in the uncertainty budget ∆T=(P/A)*(t/k) Slide 29 CALCON 2003 Radiometric Calibration of AERI Typical Long-term Blackbody Thermistor Drift ABB Top Thermistor Drift 0.06 After 39 months Error [C] 0.05 After 57 months 0.04 0.03 0.02 0.01 0.00 -20 0 20 Calibration Tem peratures [C] 40 60 Long-term Thermistor Drift < 0.05 K Error [C] ABB Bottom Thermistor Drift After 39 months 0.06 0.05 0.04 0.03 0.02 0.01 0.00 -20 0 After 57 months 20 Calibration Temperatures [C] 40 60 Data from AERI Blackbody S/N 24 Slide 30 Error [C] ABB Apex Thermistor Drift After 39 months 0.06 0.05 0.04 0.03 0.02 0.01 0.00 -20 0 After 57 months 20 Calibration Temperatures [C] CALCON 2003 Radiometric Calibration of AERI 40 60 AERI Thermistor Resistance Measurement Electronics Blackbody Temperature Sensing (One Channel Shown) Keithley Metrabyte EXP-GP 8 channel signal conditioning board Keithley Metrabyte DAS-HRES 16-bit A/D ISA-bus card HBB 3 Thermistors Blackbodies ABB 3 Thermistors EXP-GP (1 of 4) Control Output Analog Input DAS-HRES Ancillary Sensors Signal Conditioning Electrionics (Gain = 2.5) Slide 31 CALCON 2003 Radiometric Calibration of AERI Industrial Computer Calibration Resistor Uncertainty Uncertainty in Calibration Resistor Measurements Expressed as Equivalent Temperature Errors 0.012 Calibration of AERI thermistor resistance measurement electronics uses precision resistors Calibration Resistor Uncertainty (Equivalent Temperature) Fluke Meter Uncertainty (Equivalent Temperature) Temperature Uncertainty (K) 0.010 0.008 233 K 337 K 0.006 222 K 323 K 0.004 254 K 359 K 288 K 0.002 0.000 100 1,000 10,000 100,000 1,000,000 10,000,000 Temperature error associated with calibration resistor uncertainty is < 7 mK Resistance Value (Ohms) UW SSEC 8842A Fluke Meter Calibrated at Factory using a Fluke 5700A-W/03 Calibrator Primary Standard Traceable to NIST Slide 32 CALCON 2003 Radiometric Calibration of AERI AERI Electronics Post Calibration Residuals NSA Electronics Error Residuals Post-calibration Temperature Error in K 0.005 Err@360 0.003 Err@337 0.001 Err@323 -0.001 Err@288 -0.003 Err@254 -0.005 Err@233 Er@222 -0.007 -0.009 Ch0 Ch1 Ch2 Ch3 Ch4 Ch5 Ch6 Ch7 Equivalent temperature error following AERI electronics calibration is < 7 mK Residuals arise from linear fit in the Count Domain Transformed to the Temperature Domain Slide 33 CALCON 2003 Radiometric Calibration of AERI AERI Electronics Long-term Drift Equivalent Temp of 336 K Equivalent Temp of 249 K Temperature Error Associated With Long-term Drift of the Electronics is < 0.030 K Slide 34 CALCON 2003 Radiometric Calibration of AERI Emissivity Uncertainty Uncertainty (3 sigma) Note for Ep=0.94 f=39 ²Ec ²Ec (3 sigma) 38 Paint Witness Sample Measurement 1.5% Ep [1] ²Ep=0.0141 (1/f)*²Ep 0.00036 38 Paint Application Variation 1.0% Ep [2] ²Ep=0.0094 (1/f)*²Ep 0.00024 38 Long-term Paint Stability 2.0% Ep [3] ²Ep=0.0188 (1/f)*²Ep 0.00048 39 Cavity Factor 30% f [4] ²f=11.7 (1-Ep)/f^2*²f 0.00046 RSS Notes: [1] [2] [3] [4] 0.00080 Factor of 4 higher than NIST* for 2 sigma. Another factor of 1.5 to get to 3 sigma. Worst case difference between 1 and 3 coats 2 x above Accounts of Cavity Model Uncertainty * NIST Stated accuracy is 4% of Reflectivity (2 sigma) XX Indicates slide number where more detailed information is presented f=(1-Ep)/(1-Ec) f=Cavity Factor Ep=Emissivity of Paint Ec=Emissivity of Cavity Slide 35 CALCON 2003 Radiometric Calibration of AERI Emissivity Characterization From Monte Carlo Modeling • Emissivity better than 0.998 • Emissivity knowledge: better than 0.001 R = e * B(Teff) + (1- e)*B(Trefl) HBB B C D E Teff = w1 * TA + w2 * TB A B(T) = Planck radiance at T e, w1, and w2 are computed using a Monte Carlo based cavity model Slide 36 CALCON 2003 Radiometric Calibration of AERI R Model of Thermal Gradients in Blackbody Tamb = 20 C Thbb = 60 C Temperature distribution used in Monte Carlo raytrace determination of Teff Slide 37 CALCON 2003 Radiometric Calibration of AERI Paint Emissivity Measurement Aeroglaze Z306 Paint Emissivity vs Number of Coats (Paint samples measured by Labsphere in 11/96) 0.98 1 coat 2 coats 3 coats Paint Emissivity 0.97 0.96 Blackbody Paint Witness Sample 0.95 0.94 Uncertainty in emissivity measurement is <0.015* 0.93 500 1,000 1,500 2,000 2,500 3,000 Wavenumber [cm-1] *Labsphere does not state accuracy for high emissivity samples. Stated value is Witness Sample Holder “Mimics” conservative. By comparison, NIST stated accuracy for this measurement is < 0.004. Blackbody Cone Geometry Slide 38 CALCON 2003 Radiometric Calibration of AERI Monte Carlo Predictions of AERI Blackbody Cavity Emissivity (Diffuse Paint) Monte Carlo Prediction for AERI Normal Cavity Emissivity 1.000 Cavity Emissivity > 0.998 Cavity Normal Emissivity ± 30% cavity factor uncertainty 0.999 NEVADA Cavity Diffuse f=39 0.7*f=27 1.3*f=51 0.998 Cavity Factor f=(1-Es)/(1-Ec) Range of Z306 emissivity 0.997 0.92 0.93 0.94 0.95 0.96 0.97 0.98 Intrinsic Emissivity of Paint Other Monte Carlo modeling indicates that a 30% increase in Cavity Factor (f) would account for the emissivity increase resulting from paint specularity up to 50%. Slide 39 CALCON 2003 Radiometric Calibration of AERI Instrument End-to-end Performance Slide 40 CALCON 2003 Radiometric Calibration of AERI AERI/NIST Blackbody Intercomparison - LW Max Error @ 333 K <0.055K Max Error @ 303 K <0.050K Max Error @ 293 K <0.050K Slide 41 CALCON 2003 Radiometric Calibration of AERI AERI/NIST Blackbody Intercomparison - SW Max Error @ 333 K <0.035K Max Error @ 303 K <0.025K Max Error @ 293 K <0.035K Slide 42 CALCON 2003 Radiometric Calibration of AERI AERI Instrument End-to-end Radiometric Calibration Configuration AERI Intermediate Temperature Blackbody in Sky view AERI Ice Blackbody in Down View Slide 43 CALCON 2003 Radiometric Calibration of AERI AERI Instrument End-to-end Radiometric Calibration General Agreement Better Than 0.1 K Slide 44 CALCON 2003 Radiometric Calibration of AERI AERI Calibration Validation (6 AERIs) Radiometric Performance of six different AERIs Meets Top-level Requirement of 1% of Ambient Radiance AERI Radiometric Model Accurately Predicts Performance 1% Specification Calibration Model Slide 45 CALCON 2003 Radiometric Calibration of AERI AERI Short Term Reproducability AERI stability better than 5 mK over a peroid of 4 hours Slide 46 CALCON 2003 Radiometric Calibration of AERI AERI Spectra Showing Reproducibility 15 m 8m Wavenumbers (cm-1) Brightness Temp Overlay of 2 Observations 900 Slide 47 CALCON 2003 Radiometric Calibration of AERI 950 Intercomparison of Two MAERIs Measuring Sea Surface Temperature 16 Day Cruise Hawaii Daily Mean Difference in Measured SST Between MAERI01 and MAERI-02 Temperatrue ² [K] 0.150 0.100 0.050 0.000 -0.050 -0.100 -0.150 10/1/97 10/2/97 10/3/97 10/4/97 10/5/97 10/6/97 10/7/97 10/8/97 10/9/97 10/10/97 Date New Zealand Largest Daily Mean Difference: 0.020 K Ten Day Mean Difference: 0.005 K Track of the R/V Roger Revelle 28 Sept. - 14 Oct. 1997 Slide 48 CALCON 2003 Radiometric Calibration of AERI Summary Slide 49 CALCON 2003 Radiometric Calibration of AERI Summary The AERI is a robust well calibrated spectroradiometer with a demonstrated absolute radiometric accuracy better than 1% of ambient radiance, making it an especially valuable tool for climate and remote sensing applications. The AERI Calibration Blackbody performance and calibration methodology with Traceability to NIST have been verified. Success of the AERI has led to the use of the same concept for aircraft instruments (S-HIS and NAST) and for the advanced geostationary sounder (GIFTS). [see Dave Tobin and John Elwell, CALCON 2003] Slide 50 CALCON 2003 Radiometric Calibration of AERI