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 instruments 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
• Overview of AERI and Top Level Radiometric
Performance Requirements
• Instrument Calibration Model and Predicted
Radiometric Performance
• Blackbody Design and Calibration
• 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
H2O
CLOUD
R
adian ce
Radiance
140
120
100
80
60
40
20
0
CO2
850
CLEAR
800
1000
Wavenumber
1200
1400
AERI
Accurate
Provides
HighContinuous
ResolutionAccurate
Radiometry
High
Resolution Radiometry in the Infrared
AERI is used to improve our understanding of atmospheric
radiation transfer and cloud properties for climate studies,
and for weather applications.
Slide 5
900
O3
600
Operational at DOE ARM
800
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
ATMOSPHERIC
RADIATION
SCAN MIRROR
DRIVE
INITIALIZATION
FRINGE
COUNTING
LASER POWER
& CONTROL
R S
RAIN &
SUN
SENSORS
STIRLING
COOLER
Interferometer
Assembly
PREAMPS
PREAMPS
*
HBB
DEWAR
2 DETECTORS
SCENE
MOTOR
BOMEM
INTERFEROMETER
AFT
OPTICS
ABB
ANALOG
FILTERING
TO SCENE
MOTOR
CONTROLLER
*
OPTICS BENCH
OUTSIDE AMBIENT TEMPERATURE
A/D
CONVERTERS
T
TO DSP'S
P
H
• • • •
RACK MOUNTED ELECTRONICS
HOUSEKEEPING
SIGNAL CONDITIONING
R
S
HOUSEKEEPING A/D
Support
Electronics
TO SCENE MOTOR
TO HEATERS
TO STIRLING
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
(115 VAC @ 60 HZ)
Slide 10
ENCODER
CALCON 2003
Radiometric Calibration of AERI
MULTIPLE AERI
DISPLAY SYSTEM
(MADS)
HBB
ABB
INTERFEROMETER
POWER
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
q Top Level Requirements
– Absolute Accuracy: < 1.0% of ambient radiance
– Reproducibility:
< 0.2% of ambient radiance
q 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
Ê CS - C A ˆ
˜ + BA
N = ( BH - BA ) Re Á
Ë 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
AERI Calibration Error Estimates
1.0
1.0
0.8
0.8
0.6
∆Thbb
0.4
∆Tabb
∆Ehbb
0.2
∆Eabb
∆Tstr
0.0
Trss
-0.2
-0.4
% Ambient Radiance
% Ambient Radiance
AERI Calibration Error Estimates
0.6
∆Thbb
0.4
∆Tabb
∆Ehbb
0.2
∆Eabb
∆Tstr
0.0
Trss
-0.2
-0.4
-0.6
-0.6
150
200
250
300
350
150
200
Scene Temperature (K)
Input Parameters
wn
Thbb
Tcbb
Tstr
Ehbb
Ecbb
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, [-]
∆Thbb
∆Tcbb
∆Tstr
∆Ehbb
∆Ehbb
0.10
0.10
5
0.001
0.001
[K]
[K]
[K]
[-]
[-]
wn
Thbb
Tcbb
Tstr
Ehbb
Ecbb
Longwave: 770 cm-1
Slide 16
300
Input Parameters
Uncertainties (3 sigma)
770
333
300
305
0.999
0.999
250
350
Scene Temperature (K)
CALCON 2003
Radiometric Calibration of AERI
Uncertainties (3 sigma)
2200
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, [-]
∆Thbb
∆Tcbb
∆Tstr
∆Ehbb
∆Ehbb
0.10
0.10
5
0.001
0.001
Shortwave: 2200 cm-1
[K]
[K]
[K]
[-]
[-]
AERI Reproducibility Error Estimates
Radiometric Requirement is 0.18% of Ambient Radiance
AERI Calibration Error Estimates
0.20
0.20
0.15
0.15
0.10
∆Thbb
0.05
∆Tabb
∆Ehbb
0.00
∆Eabb
∆Tstr
-0.05
Trss
% Ambient Radiance
% Ambient Radiance
AERI Calibration Error Estimates
0.10
∆Thbb
0.05
∆Tabb
∆Ehbb
0.00
∆Eabb
∆Tstr
-0.05
-0.10
-0.10
-0.15
-0.15
Trss
-0.20
-0.20
150
200
250
300
150
350
200
Scene Temperature (K)
Input Parameters
wn
Thbb
Tcbb
Tstr
Ehbb
Ecbb
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, [-]
∆Thbb
∆Tcbb
∆Tstr
∆Ehbb
∆Ehbb
0.02
0.02
5
0.0005
0.0005
[K]
[K]
[K]
[-]
[-]
wn
Thbb
Tcbb
Tstr
Ehbb
Ecbb
Longwave: 770 cm-1
Slide 17
300
Input Parameters
Uncertainties (3 sigma)
770
333
300
305
0.999
0.999
250
350
Scene Temperature (K)
CALCON 2003
Radiometric Calibration of AERI
Uncertainties (3 sigma)
2200
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, [-]
∆Thbb
∆Tcbb
∆Tstr
∆Ehbb
∆Ehbb
0.02
0.02
5
0.0005
0.0005
Shortwave: 2200 cm-1
[K]
[K]
[K]
[-]
[-]
Blackbody Design and Calibration
Slide 18
CALCON 2003
Radiometric Calibration of AERI
Blackbody Requirements
qBlackbody System Requirements
ÿ Temperature knowledge:
ÿ Temp. gradient knowledge:
ÿ Emissivity:
ÿ Emissivity knowledge:
± 0.10 K
better than 0.10 K
> 0.998
better than ± 0.1%
qInstrument Imposed Requirements
ÿ BB Aperture:
ÿ Envelope:
ÿ Operating Temperature:
ÿ 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
q Cavity Approach
ÿ Provides high emissivity (cavity factor near 40)
ÿ Emissivity enhancement due to cavity is well characterized
ÿ Cavity walls provide good conduction (low gradients)
ÿ Easy to manufacture
q Chemglaze Z306 Black Paint
ÿ Provides high emissivity that is well characterized and stable
ÿ Provides a hardy diffuse surface
q YSI 46041 Super-stable Thermistors
ÿ Very stable (< 0.01°C drift after 100 months at 70°C)
ÿ Easy to couple thermally to blackbody cavity
ÿ 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 Blackbody Calibration Roadmap
Slide 23
CALCON 2003
Radiometric Calibration of AERI
AERI Blackbody Temperature Calibration
Overview
AERI BB 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
3
T = 1 / [ A + B * Ln (R) + C * (Ln(R)) ]
Temperature Uncertainty Budget
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 Traceability & 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
034a
YSI 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
350
Calibration Temperature [K]
Residual Error From Fitting Equations < 3 mK
Ê1ˆ
3
Á ˜ = A + Bln(R) + C(ln(R))
ËT ¯
Data from BB S/N 24
Slide 28
†
CALCON 2003
Radiometric Calibration of AERI
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 Temperatures [C]
40
60
Long-term
Thermistor Drift
< 0.05 K
Error [C]
ABB Bottom Thermistor Drift
After 39 months After 57 months
0.06
0.05
0.04
0.03
0.02
0.01
0.00
-20
0
20
Calibration Temperatures [C]
40
60
Data from AERI
Blackbody S/N 24
Slide 30
Error [C]
ABB Apex Thermistor Drift
After 39 months After 57 months
0.06
0.05
0.04
0.03
0.02
0.01
0.00
-20
0
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 Traceability & Uncertainty
Uncertainty in Calibration Resistor Measurements Expressed as Equivalent
Temperature Errors
Calibration of AERI
thermistor
resistance
measurement
electronics uses
precision resistors
0.012
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 Budget
Uncertainty
(3 sigma)
Note
for Ep=0.94
f=39
∆Ec
∆Ec
(3 sigma)
36
Paint Witness Sample Measurement
1.5% Ep
[1]
∆Ep=0.0141
(1/f)*∆Ep
0.00036
36
Paint Application Variation
1.0% Ep
[2]
∆Ep=0.0094
(1/f)*∆Ep
0.00024
36
Long-term Paint Stability
2.0% Ep
[3]
∆Ep=0.0188
(1/f)*∆Ep
0.00048
39
Cavity Factor
30% f
[4]
∆f=11.7
(1-Ep)/f^2*∆f
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
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
Uncertainty in emissivity
measurement is <0.015*
0.94
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 36
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 37
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 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 Normal Emissivity
Cavity Emissivity > 0.998
± 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
Deviations from the diffuse paint assumption equivalent to 20%
specularity are within the cavity factor uncertainty of 30%.
Slide 39
CALCON 2003
Radiometric Calibration of AERI
AERI Radiometric FOV at Blackbody
Radiometric Field-of-view is
verified at the position of the
blackbody aperture
Slide 40
CALCON 2003
Radiometric Calibration of AERI
Instrument End-to-end Performance
Slide 41
CALCON 2003
Radiometric Calibration of AERI
AERI / NIST 3rd Generation Water-bath
Based Blackbody Intercomparison - LW
Max Error @ 333 K <0.055K
Max Error @ 303 K <0.050K
Max Error @ 293 K <0.050K
Slide 42
CALCON 2003
Radiometric Calibration of AERI
AERI / NIST 3rd Generation Water-bath
Based Blackbody Intercomparison - SW
Max Error @ 333 K <0.035K
Max Error @ 303 K <0.025K
Max Error @ 293 K <0.035K
Slide 43
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 44
CALCON 2003
Radiometric Calibration of AERI
AERI Instrument End-to-end Radiometric
Calibration
General
Agreement
Better Than 0.1 K
Slide 45
CALCON 2003
Radiometric Calibration of AERI
Calibration Variability Among 6 AERIs
Sky Data
Lab
Ice BB
Lab
40 C BB
AERI Radiometric
Model Accurately
Predicts
Performance
Sky Data
Slide 46
Lab
Ice BB
Lab
40 C BB
CALCON 2003
Radiometric Calibration of AERI
1% Specification
Calibration Model
AERI Short Term Reproducability
AERI stability
better than 5 mK
over a period of
4 hours
Slide 47
CALCON 2003
Radiometric Calibration of AERI
AERI Spectra Showing Reproducibility
15 mm
8mm
Wavenumbers (cm-1)
Brightness
Temp Overlay of
2 Observations
900
Slide 48
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 ∆ [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
Track of the R/V Roger Revelle
28 Sept. - 14 Oct. 1997
Slide 49
Largest Daily Mean Difference: 0.020 K
Ten Day Mean Difference:
0.005 K
CALCON 2003
Radiometric Calibration of AERI
Summary
Slide 50
CALCON 2003
Radiometric Calibration of AERI
Summary
q 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.
q The AERI Calibration Blackbody performance and
calibration methodology with Traceability to NIST
have been verified.
q 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 51
CALCON 2003
Radiometric Calibration of AERI