Post on 31-Dec-2015
UW-SSEC IR Experience and CLARREO
Slide 1
UW-SSEC IR Calibration Experience and CLARREO Requirements
NIST IR Radiometry for CLARREONIST, 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
UW-SSEC IR Experience and CLARREO
Slide 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
Slide 3
Ambient Blackbody
Hot Blackbody
Scene Mirror Motor
Interferometer & Optics
Electronics
Data Storage Computer
Scanning HIS Aircraft Instrument
H2O
LW/MW overlap MW/SW overlapLW/MW overlap MW/SW overlap
Longwave Midwave Shortwave
CO
N2O
H2O
N2O CH4
CO2
O3CO2
UW-SSEC IR Experience and CLARREO
Slide 4
S-HIS Aircraft PlatformsS-HIS on the DC-8S-HIS on the ER-2S-HIS on the ProteusS-HIS on the WB-57
UW-SSEC IR Experience and CLARREO
Slide 5
S-HIS Flight Experience
Map imagery courtesy NASA visible earth
UW-SSEC IR Experience and CLARREO
Slide 6
Atmospheric Spectral Calibration: S-HIS
Atmospheric CO2 lines
Wavenumber 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
Slide 7
200 Brightness T (K) 300
Tb U
nce
rtai
nty
(K
)
Wav
enu
mb
er
**Formal 3-sigma absolute uncertainties, similar to that detailed for AERI in Best et al. CALCON 2003
TABB= 260 K THBB= 310 K
TBB = 0.10 K
BB = 0.0010Trefl = 5 K10% nonlinearity
S-HIS Absolute Radiometric Uncertaintyfor typical Earth scene spectrum
0.2 K
1.0
0
UW-SSEC IR Experience and CLARREO
Slide 8
3 Uncertainties: 3TBB = 0.05 K 3TRefl = 5 K 3BB = 0.001 Total (RSS)
wavenumber (cm-1)
3-si
gma
Tb
Err
or (
K)
Uncertainty for TBB = 293K, TRefl = 230K
UW-SSEC AERI Blackbody Predicted Radiance Uncertainty
UW-SSEC IR Experience and CLARREO
Slide 9
SSEC Spectrometer Ties to NISTGround-based High-altitude Aircraft Spaceflight
AERI S-HIS GIFTS
NISTWaterbathBlackbody
NISTTXR
< 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
Slide 10
NIST TXR S-HIS
AERI BB
chamber AERI blackbody
TXRCh1
TXRCh2
Scanning-HISspectra
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/SSECJanuary 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
UW-SSEC IR Experience and CLARREO
Slide 11
• 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 (10m)
AERI BT (K)
BT
Diff
(K
)
AERI minus TXRAERI minus S-HIS
mean = -22 mK
mean = -60 ± 90 mK
TXR operations and data c/o Joe Rice and Joe O’Connell
UW-SSEC IR Experience and CLARREO
Slide 12
• 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 (5m)
UW-SSEC IR Experience and CLARREO
Slide 13
AERI Blackbody Reflectivity Test with NIST TXR Confirms Emissivity Estimates
TXR
NIST Transfer Radiometer(TXR) used to detectreflection 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
UW-SSEC IR Experience and CLARREO
Slide 14
Measurements confirm estimated emissivity within uncertainty (3-sigma estimates)
AERI Blackbody Reflectance (5µ)
0.00000
0.00020
0.00040
0.00060
0.00080
0.00100
0.00120
0.00140
0.00160
0.00180
UW Predicted UW Analyis-1 UW Analyis-2 NIST Analysis
Refl
ect
an
ce
AERI Blackbody Reflectance (10µ)
0.00000
0.00020
0.00040
0.00060
0.00080
0.00100
0.00120
0.00140
0.00160
0.00180
UW Predicted UW Analyis-1 UW Analyis-2 NIST Analysis
Refl
ect
an
ce
Updated August 07
5 microns 10 microns
0.001 =0.999
UW-SSEC IR Experience and CLARREO
Slide 15
Radiance Validation of AIRS with S-HIS
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 SRFsAIRS
SHIS
MODIS 12 m Band Tbs(K) & near-nadir AIRS FOVs
“Comparison 2”
wavenumber
AIRS Compared to S-HIS, 21 Nov 2002
AIRS & S-HIS Obs-Calc
Black is Calculation
36, 35, 34, 33 32 31 30
AIRS minus MODIS
“Comparison 2”
wavenumber
AIRS Compared to S-HIS, 21 Nov 2002
AIRS & S-HIS Obs-Calc
Black is Calculation
28 27
UW-SSEC IR Experience and CLARREO
Slide 20
Gulf of Mexico Validation case: 2002.11.21 Gulf of Mexico Validation case: 2002.11.21
UW-SSEC IR Experience and CLARREO
Slide 21
(AIR
Sob
s-A
IRS
calc
)-
(S
HIS
obs-
SH
ISca
lc)
(K)
Gulf of Mexico Validation case: 2002.11.21 Gulf of Mexico Validation case: 2002.11.21
UW-SSEC IR Experience and CLARREO
Slide 22
AIRS-SHIS Summary: SW (2004.09.07) AIRS-SHIS Summary: SW (2004.09.07)
Excellent agreement for night-time comparison from Adriex in Italy
UW-SSEC IR Experience and CLARREO
Slide 23
Radiance Validation of IASI with S-HIS
UW-SSEC IR Experience and CLARREO
Slide 24
IASI on Metop 19 October 2006 launch
- full cross-track scan - 2x2 12 km pixels
sample 50x50 km
UW-SSEC IR Experience and CLARREO
Slide 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
Slide 26
IASI Tb Spectrum: Processed to represent
NAST-I, S-HIS (CLARREO), AIRS & CrIS
wavenumber
IASI L1C
Deapodized
1cm MaxOPD
AIRS
CrIS
CLARREO S-HIS
NAST-I
GaussianApodization
AIRS
CrIS
UW-SSEC IR Experience and CLARREO
Slide 27
ARMsite
+ S-HIS FOVso NAST-I FOVs
290
285
280
IASI 900 cm-1 BT(K)
Imager Data
MetOp overpass of Oklahoma ARM CF19 April 2007
IASINAST-IS-HIS
BT
(K
)B
T (
K)
BT
(K
)
wavenumber (cm-1)
UW-SSEC IR Experience and CLARREO
Slide 28
IASI, NAST-I, SHISMean spectra
wavenumber
BT
(K
)D
iff (
K)
IASI minus NAST-I, IASI minus SHIS(using double obs-calc method)
0.00 K0.02 K
NAST-I: S-HIS:
0.08 K0.12 K
0.03 K0.00 K
0.16 K0.14 K
IASI Longwave Validation
UW-SSEC IR Experience and CLARREO
Slide 29
IASI, NAST-I, SHISMean spectra
wavenumber
BT
(K
)D
iff (
K)
IASI minus NAST-I, IASI minus SHIS(using double obs-calc method)
0.12 K0.20 K
NAST-I: S-HIS:
0.04 K0.03 K
-0.19 K-0.08 K
IASI Midwave Validation
UW-SSEC IR Experience and CLARREO
Slide 30
IASI, NAST-I, SHISMean spectra
wavenumber
BT
(K
)D
iff (
K)
IASI minus NAST-I, IASI minus SHIS(using double obs-calc method)
0.09 K0.16 K
NAST-IS-HIS
0.07 K0.12 K
IASI Shortwave Validation
UW-SSEC IR Experience and CLARREO
Slide 31
IASI, NASTI, and SHIS
wavenumber
BT
(K
)
UW-SSEC IR Experience and CLARREO
Slide 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
Slide 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 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-)
UW-SSEC IR Experience and CLARREO
Slide 34
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)
UW-SSEC IR Experience and CLARREO
Slide 35
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)
UW-SSEC IR Experience and CLARREO
Slide 36
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)
UW-SSEC IR Experience and CLARREO
Slide 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
Slide 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
Slide 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
Slide 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
Slide 41
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
CalibrationBlackbody(ambient or single T)
ValidationBlackbody(widely variable T)
Beamsplitterpolarization axis
OptionalSpace Views
UW-SSEC IR Experience and CLARREO
Slide 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
Slide 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
0.00
0.02
0.04
0.06
0.08
0.10
0.12
200 220 240 260 280 300 320
Scene Temperature [K]
Brightn
ess
T E
rror [K
]
200 cm-1 500 cm-1 1000 cm-1 1500 2000 cm-1
CLARREO Requirement
0.00
0.02
0.04
0.06
0.08
0.10
0.12
200 220 240 260 280 300 320
Scene Temperature [K]
Brightn
ess
T E
rror [K
]
200 cm-1 500 cm-1 1000 cm-1 1500 2000 cm-1
CLARREO Requirement
UW-SSEC IR Experience and CLARREO
Slide 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
Slide 45
Required NIST Capabilities
UW-SSEC IR Experience and CLARREO
Slide 46
CLARREO Viewing Targets
Developed under IIP
Used for Ground Testing Only
UW-SSEC IR Experience and CLARREO
Slide 47
Required NIST Capabilities
BlackbodyPaint ReflectivityMeasurements
BlackbodyTemperatureCalibration
Cavity Emissivity Calc. Using Monte-Carlo Ray-traceing
BlackbodyRadiance
BlackbodyReflectivity
NIST TraceableTemp. ProbeCalibration
- 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
UW-SSEC IR Experience and CLARREO
Slide 48
Required NIST Capabilities - Post Launch
Ground WitnessMeasurement
Program
Aircraft FlightValidations
Scanning HISRadiance & Linearity
Check UsingNIST TXR & Transfer BB
NIST Temperature,Reflectivity, and
Spectral Traceabilityas needed
- Phase Change Temperatures- Thermistor Drift- Blackbody Paint Change- Blackbody Radiance
- Periodic Underflights
UW-SSEC IR Experience and CLARREO
Slide 49
CLARREO Comparison to Existing Sounders
Absolute Tb Calibration & Resource ComparisonsProperty AIRS IASI CrIS CLARREO
Radiometric Cal. 1. Absolute Accuracy 2. BB emissivity 3. Blackbody T error
1. < 0.3 K at scene T 2. >0.999 3. <0.05 K
1. < 0.5 K at scene T 2. >0.996 3. <0.08 K
1. < 0.4 K at scene T 2. >0.995 3. <0.08 K
Verified on orbit! 1. < 0.1 K 3- at scene T 2. >0.999 3. <0.045 K 3-
Spectral Calibration 1. Absolute Reference 2. Stability 3. Instrument Line Shape (ILS) knowledge
1. Atmospheric lines 2. T control of spectro- meter/aft optics (2.2% shift/K) 3. Prelaunch tests with FTS source
1. 2. Stable laser controls interferogram sampling (< 1ppm over 6 months) 3. fundamental instru- ment design, verified with laser sources in ground testing
1. (&/or Ne source) 2. 3.
1. 2. 3. On-orbit ILS Source
Linearity <0.3% over much of spectrum, < ~1% peak; error assumed < 0.05 K after correction
< 1% longwave, negli-gible mid- & shortwave error < ~0.15 K after correction stability verifiable in orbit from out of band features
<0.1% longwave & negligible elsewhere error < ~0.07 K even uncorrected stability verifiable in orbit from out of band features
Very small for DTGS and InSb, longwave goal <<0.1 %
Polarization ±worst case 0.4K (9 & 15 m); error assumed < 0.07 K after correction
<0.2% (“paddle wheel” gold scene mirror over- coated) uncorrected error < 0.2 K
<0.05% (45º gold scene mirror with overcoating) error < 0.04 K even uncorrected
Nominally zero (nadir only & 45º gold scene mirror with optimized view angles)
Mass (kg) 166 kg 200 kg 133 kg <35 kg each Power (W) 256 W 200 W 106 W <60 W Far IR FTS
< 80 W Low noise FTS
Absolute Tb Calibration & Resource ComparisonsProperty AIRS IASI CrIS CLARREO
Radiometric Cal. 1. Absolute Accuracy 2. BB emissivity 3. Blackbody T error
1. < 0.3 K at scene T 2. >0.999 3. <0.05 K
1. < 0.5 K at scene T 2. >0.996 3. <0.08 K
1. < 0.4 K at scene T 2. >0.995 3. <0.08 K
Verified on orbit! 1. < 0.1 K 3- at scene T 2. >0.999 3. <0.045 K 3-
Spectral Calibration 1. Absolute Reference 2. Stability 3. Instrument Line Shape (ILS) knowledge
1. Atmospheric lines 2. T control of spectro- meter/aft optics (2.2% shift/K) 3. Prelaunch tests with FTS source
1. 2. Stable laser controls interferogram sampling (< 1ppm over 6 months) 3. fundamental instru- ment design, verified with laser sources in ground testing
1. (&/or Ne source) 2. 3.
1. 2. 3. On-orbit ILS Source
Linearity <0.3% over much of spectrum, < ~1% peak; error assumed < 0.05 K after correction
< 1% longwave, negli-gible mid- & shortwave error < ~0.15 K after correction stability verifiable in orbit from out of band features
<0.1% longwave & negligible elsewhere error < ~0.07 K even uncorrected stability verifiable in orbit from out of band features
Very small for DTGS and InSb, longwave goal <<0.1 %
Polarization ±worst case 0.4K (9 & 15 m); error assumed < 0.07 K after correction
<0.2% (“paddle wheel” gold scene mirror over- coated) uncorrected error < 0.2 K
<0.05% (45º gold scene mirror with overcoating) error < 0.04 K even uncorrected
Nominally zero (nadir only & 45º gold scene mirror with optimized view angles)
Mass (kg) 166 kg 200 kg 133 kg <35 kg each Power (W) 256 W 200 W 106 W <60 W Far IR FTS
< 80 W Low noise FTS