slide 1 uw-ssec ir experience and clarreo uw-ssec ir calibration experience and clarreo requirements...

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


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


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


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


Slide 5

S-HIS Flight Experience

Map imagery courtesy NASA visible earth


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


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


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


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)


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


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


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)


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


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


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


Slide 20

Gulf of Mexico Validation case: 2002.11.21 Gulf of Mexico Validation case: 2002.11.21


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


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


Slide 23

Radiance Validation of IASI with S-HIS


Slide 24

IASI on Metop 19 October 2006 launch

- full cross-track scan - 2x2 12 km pixels

sample 50x50 km


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


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


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)


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


Slide 29


wavenumber

BT

(K

)D

iff (

K)


0.12 K0.20 K

NAST-I: S-HIS:

0.04 K0.03 K

-0.19 K-0.08 K

IASI Midwave Validation


Slide 30


wavenumber

BT

(K

)D

iff (

K)


0.09 K0.16 K

NAST-IS-HIS

0.07 K0.12 K

IASI Shortwave Validation


Slide 31

IASI, NASTI, and SHIS

wavenumber

BT

(K

)


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


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-)


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)


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)


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)


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)


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)


Slide 39


• 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)


Slide 40


• 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


Slide 41


• 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


Slide 42


• 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)


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


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


Slide 45

Required NIST Capabilities


Slide 46

CLARREO Viewing Targets

Developed under IIP

Used for Ground Testing Only


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


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


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 spectrometer/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 instrument 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 spectrometer/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 instrument 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

slide 1 uw-ssec ir experience and clarreo uw-ssec ir calibration experience and clarreo requirements...

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