terra/aqua instrument and erbe-like calibration status report · 2007. 12. 7. · terra/aqua...

Terra/Aqua Instrument and ERBE-LikeCalibration Status Report

Kory J. PriestleySusan Thomas, Denise Cooper

Phil Hess, Grant Matthews, Peter Szewczyk,Dale Walikainen, Robert Wilson

CERES Science Team MeetingHampton, VA

November 1-3, 2005

NASA Langley Research Center / Science Directorate

Agenda

CERES Project Status

Engineering/Housekeeping Status

FM-4 SW Channel Anomaly - Aqua Spacecraft

Cal/Val Report

Edition2_Rev1 Review

Preparations for Edition3 BDS & ERBE-like

- Spectral Darkening of CERES SW channels


CERES Terra/Aqua Health & Status

With the exception of the SW channel on the CERES/Aqua FM-4 Instrument,

the CERES Terra/Aqua instruments are functioning nominally…

All temperatures and voltages remain within limits

No discernable or alarming trends.

???FM5?

41 +

68 +

9

Collected Data

(Months)

6/025/02FM3, FM4Aqua

3/0012/99FM1, FM2Terra

1/9811/97PFMTRMM

ScienceInitiation

LaunchInstrumentsSpacecraft


CERES/Aqua FM-4 SW AnomalyHistory & Status

History-

• On March 30, 2005 at 18:42 GMT the CERES/Aqua FM-4 instrument stoppedcollecting valid Shortwave channel radiometric measurements.

• Anomaly was characterized by an immediate railing ‘high’ of the SW channel datastream, which subsequently drove the SW channel bridge balance electronics into areset condition in an attempt to bring the SW channel output on-scale.

• The Total and Atmospheric Window radiometric channels continued to functionnominally.

Current Status-

• All attempts to recover the SW channel measurements have been unsuccessful.

• Modeling has indicated the problem is most likely the result of a failed resistor(possibly a detector) in the SW channel Bridge Balance Circuitry.

•Preparing for upcoming Calipso launch.


CERES/Aqua FM-4 SW AnomalyScience Impacts

Near Term

No impact assuming the CERES/Aqua FM-3 instrument is collecting cross-track data.

Long Term

If anomaly cannot be resolved, longer term science issues include (in order of priority)

- significantly increased risk of a gap from Terra/Aqua climate record to the beginning of NPOESS using FM-5 in 2011/2012.

- the second Aqua CERES instrument for the A-train was to scan along-track for multi- angle views over the lidar/radar track to examine effects like 3-D radiative transfer

- the second Aqua CERES instrument is also used to perform intercalibrations with GERB: but these can be accomplished by the second Terra CERES as long as two CERES instruments are active on Terra

- the second Aqua CERES instrument is also used during cloud/aerosol field experiments to provide multi-angle data that tracks a pre-selected surface site (e.g. ARM site).

Radiometric Performance Summary


Operational Coverage Request

http://asd-www.larc.nasa.gov/Instrument/operations.html


CERES BDS and ERBE-Like Product Status

6/02 - 3/05YesEdition2

6/02 - 3/05YesEdition2

1/98 - 8/98 , 3/00YesEdition2

1/98 - 8/98 , 3/00YesEdition1BDSTRMM

1/98 - 8/98 , 3/00YesEdition1ERBE-Like

6/02 - present

6/02 - present

2/00 - 6/05

2/00 - present

2/00 - 6/05

2/00 - present

Months ProcessedAvailableVersionProductSpacecraft

YesEdition1ERBE-like

YesEdition1BDSAqua

YesEdition2

YesEdition1ERBE-like

YesEdition2

YesEdition1BDSTerra

Note: Red text indicates months are in final validation prior to public release.


BDS and ERBE-Like Release Strategy

Edition1 - Static Algorithms and coefficients - baseline product used in cal/val protocol

Edition2 - Utilizes temporally varying coefficients to correct for traceable radiometric drift. All spectral changes are broadband and ‘gray’.

Edition3 - Release date Fall 2006. Will incorporate temporally varying spectral artifacts in the SW measurements. A complete re-analysis of Ground Calibration with additional component characterization measurements.

Revisions - Advance capabilities to the users prior to the release of the nextEdition.

Edition2 products lag Edition1 by a minimum of 4 months, revisions may lagEdition releases.


Instrument Artifact Removal StrategyRemote sensing instruments generally exhibit time varying artifacts in their

data products. For CERES these artifacts stem from either of 2 physicalentities…..

• Radiometric Gain Change- Wavelength independent change in sensor responsivity- Corrections implemented in Count Conversion algorithm (SS1)

• Spectral Response Change- Wavelength dependent change in sensor optics- Corrections implemented in Spectral Unfiltering algorithms (SS2)

The Edition2 production strategy assumes that spectral response changes are ‘Gray’over broad spectral regions. In other words, we assume uniform spectral responsechanges in these broad regions.

Spectral Region

8-12 um-WN

-<5.0 umSW

>3.0 um<3.0 umTotal

LWSW

Radiometric

Channel


Notification of Revision

CERES BDS (BiDirectional Scan) TerraEdition2Data Quality Summary

Investigation: CERESData Product: BiDirectional Scan [BDS]Data Set: Terra (Instruments: FM1, FM2)Data Set Version: Edition2

The purpose of this document is to inform users of the accuracy of this data product as determined by the CERES Team. This documentbriefly summarizes key validation results, provides cautions where users might easily misinterpret the data, provides links to furtherinformation about the data product, algorithms, and accuracy, gives information about planned data improvements. This document alsoautomates registration in order to keep users informed of new validation results, cautions, or improved data sets as they become available.

This document is a high-level summary and represents the minimum information needed by scientific users of this data product. It is stronglysuggested that authors, researchers, and reviewers of research papers re-check this document for the latest status before publication of anyscientific papers using this data product.

Table of Contents

•Nature of the BDS Product•Updates to Current Edition•User Applied Revisions•Validation and Quality Assurance•Current Estimated Uncertainty of Data•Cautions When Using Data•Expected Reprocesings•References•Web links to Relevant information•Referencing Data in Journal Articles•Giving Data to Other Users


BDS & ERBE-Like Edition2 Summary

•Cal/Val Protocol demonstrates radiometric stability of the Ed2 dataproducts through 11/2004 of….

.125.125<.1<.1WN

~.1~.1.3.2SW

<.1<.1<.1<.1LWnight

<.1<.1.125.125LWday

FM4FM3FM2FM1

AquaTerra

Note: Values apply to all-sky global averages Units are in %/yr


CERES SSF Ed2B SW TOA Flux Anomaly

Clear Ocean

Clear Desert


Direct Comparison of Nadir Radiance Measurements

Two CERES instruments on a common platform allows for a uniquevalidation opportunity…..

Direct Comparison of simultaneous Nadir measurements

Each CERES/Terra instrument views nadir every 3.3 seconds

Thus, we obtain nearly simultaneous measurements of the same geo-location (Δt < 3.3 seconds)….

Spatial, angular, and temporal sampling issues are virtually eliminated.

26,000 co-located (but not independent) measurements in a given day,provides a very rigorous statistical tool.

Results can be discretized by scene type to enhance the analysis.


Edition2 BDS SW Nadir Direct Comparison


RAPS

Whats the difference between RAPS and FAPS?

FAPS


RAPS


FAPS

Ground Track

Scan Plane


RAPS


FAPS


Operations to Characterize Spectral Darkening

EliminatedEliminatedNoXtrackNoXtrackNovember

No

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

FM1 SolarCalibrations

No

No

No

No

No

Yes

Yes

Yes(Daily)

Yes

FM2 SolarCalibrations

Xtrack

Xtrack

Xtrack

Xtrack(note3,5)

Xtrack(note3)

Xtrack

Xtrack

Xtrack

Xtrack

FM1 AzimuthGimbal

Notes:

1. Short-Earth scan profile turn-around reduced 8 degrees on March 31, 2005 to both FM1 and FM2.2. Expanded solar-avoidance region criteria May 13, 2005.

3. Greenland Summer Solstice Terra-Aqua Inter-Calibration, June 6- July 6, 2005

4. GERB Operations, June 9-30, 2005.

5. Nighttime internal calibrations, July 1-7, 2005.

6. Valencia Over-Flights, September 12-17, 2005.

EliminatedEliminatedXtrackOctober

EliminatedEliminatedXtrack(note6)

September

--StowedAugust

--StowedJuly

EliminatedEliminatedXtrack(note4)

June

DarkeningRate Impact

FM2 RAMDirection

FM2 SolarExposure

FM2 AzimuthGimbal

Month

(2005)

NominalNominal(lunar scans)

NominalXtrack,Atrack

February

Reduced(note2)

Eliminated(note2)

Rotating,Atrack

May

No ChangeNominalReduced(note1)

RotatingApril

No ChangeAccelerated(solcal)

AcceleratedXtrackMarch


CERES Onboard Calibration SourcesInternal Calibration Module (ICM)

• ICM Provides 3 unique radiance levels for the SW andLW sources

• Blackbodies for the Total and Window channels

• Temperature knowledge obtained via PlatinumResistance Thermometers

• Quartz-halogen tungsten lamp for the Shortwavechannel (2100, 1900, 1700 K spectrums)

• SiPd independently monitors lamp output

• Acceptance testing for lamps includes burn-in periodof ~80 hours to screen for stability

• Narrow and broadband radiant intensitymeasurements are performed prior to acceptance

• Design specification is +-0.5% stability over 5-yearmission


FM2 In-Flight Internal Calibration Results

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

2/1/

00

6/1/

00

10/1

/00

2/1/

01

6/1/

01

10/1

/01

2/1/

02

6/1/

02

10/1

/02

2/1/

03

6/1/

03

10/1

/03

2/1/

04

6/1/

04

10/1

/04

2/1/

05

6/1/

05

Date

Sen

sor

Res

po

nse

Ch

ang

e, P

erce

nt

TOTAL WN SW-L2 SW-L1 SW-L3

Normalized to Ground Calibration Data

CERES Internal Calibration Results


-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

2/1/

00

6/1/

00

10/1

/00

2/1/

01

6/1/

01

10/1

/01

2/1/

02

6/1/

02

10/1

/02

2/1/

03

6/1/

03

10/1

/03

2/1/

04

6/1/

04

10/1

/04

2/1/

05

6/1/

05

Date

Sen

sor

Res

po

nse

Ch

ang

e, P

erce

nt




-5

-4

-3

-2

-1

0

1

2

3

4

5

6/1/

02

8/1/

02

10/1

/02

12/1

/02

2/1/

03

4/1/

03

6/1/

03

8/1/

03

10/1

/03

12/1

/03

2/1/

04

4/1/

04

6/1/

04

8/1/

04

10/1

/04

12/1

/04

2/1/

05

4/1/

05

6/1/

05

Date

Sen

sor

Res

pons

eC

hang

e, P

erce

nt

TOTAL WN SW-L2 SW-L1



-5-4-3-2-1012345

6/1/

02

8/1/

02

10/1

/02

12/1

/02

2/1/

03

4/1/

03

6/1/

03

8/1/

03

10/1

/03

12/1

/03

2/1/

04

4/1/

04

6/1/

04

8/1/

04

10/1

/04

12/1

/04

2/1/

05

4/1/

05

6/1/

05

Date

Sen

sor

Res

po

nse

Ch

ang

e, P

erce

nt




Terra SW Internal Calibration ResultsFM1 In-Flight Internal Calibration Results

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

2/1/

00

6/1/

00

10/1

/00

2/1/

01

6/1/

01

10/1

/01

2/1/

02

6/1/

02

10/1

/02

2/1/

03

6/1/

03

10/1

/03

2/1/

04

6/1/

04

10/1

/04

2/1/

05

6/1/

05

Date

Sen

sor

Res

po

nse

Ch

ang

e, P

erce

nt SW-L1 SW-L2 SW-L3

Normalized to Start of Mission


-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

2/1/

00

6/1/

00

10/1

/00

2/1/

01

6/1/

01

10/1

/01

2/1/

02

6/1/

02

10/1

/02

2/1/

03

6/1/

03

10/1

/03

2/1/

04

6/1/

04

10/1

/04

2/1/

05

6/1/

05

Date

Sen

sor

Res

po

nse

Ch

ang

e, P

erce

nt SW-L1 SW-L2 SW-L3

Normalized to Start of Mission


CERES Solar Calibration

Mirror Attenuator Mosaic (MAM)

• Solar Diffuser plate attenuates direct solar view

• MAM is a Nickel substrate with Aluminumcoated spherical cavities or divots

• Provides a Relative calibration of the Shortwavechannel and the SW portion of the Total channel

• Solar Cal results to date are suspect due tolarge initial drift in MAM surface reflectances…


CERES Solar Calibration Results

-2

-1

0

1

2

3

4

5

6

7

May-02 Nov-02 May-03 Nov-03 May-04 Nov-04

Date

Sen

sor

Res

po

nse

, Per

cen

tag

e C

han

ge

FM3 SW FM3 TOT

-2

-1

0

1

2

3

4

5

6

7

May-02 Nov-02 May-03 Nov-03 May-04 Nov-04

Date

Sen

sor

Res

po

nse

, Per

cen

tag

e C

han

ge

FM4 SW FM4 TOT

-2

-1

0

1

2

3

4

5

6

7

Feb-00 Aug-00 Feb-01 Aug-01 Feb-02 Aug-02 Feb-03 Aug-03 Feb-04 Aug-04

Date

Sen

sor

Res

po

nse

, Per

cen

tag

e C

han

ge

FM1 SW FM1 TOT

-2

-1

0

1

2

3

4

5

6

7

Feb-00 Aug-00 Feb-01 Aug-01 Feb-02 Aug-02 Feb-03 Aug-03 Feb-04 Aug-04

Date

Sen

sor

Res

po

nse

, Per

cen

tag

e C

han

ge

FM2 SW FM2 TOT


LEO Missions Subject to Spectral Darkening

Bandpasses of Selected Instruments

0

1

2

3

4

5

6

7

8

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Wavelength (Microns)

Ind

ex

Modis SeaWifs LandSat7 Toms SORCE-SIM SORCE SOLSTICE GOME


Spectral Darkening on Similar Missions

Global Ozone Monitoring Experiment (GOME) Spectral Darkening

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Wavelength/Radiometric Channel (um)

Rela

tive R

esp

on

se 1996

1997

1998

1999

2000

2001


Spectral Darkening on Similar Missions

Spare NIMBUS ERB Radiometer flown on LDEFMeasured Transmittance Change of Suprasil W

4mm sample, 5 yr. exposure

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Wavelength (Microns)

Rati

o t

o W

itn

ess

Sam

ple


SD degradation (accumulated at a 6-monthperiod) as a function of wavelength

Faster degradation rate after fixing the SDdoor at “open position”

Yr 1

Yr 2

Yr 3

Yr 4

Yr 5

Modis Solar Diffuser Spectral Degradation


Spectral Degradation : SWICS vs. Earth Spectra


Edition2_Rev1 SW Scaling Factors

Use Xtrack instrument as calibration reference to derive Rev1 Scaling Factors


A table of Rev1 adjustment factors is issued via the qualitysummary, authors then use the description “Edition2_Rev1”

Edition2_Rev1 SW Scaling Factors


Terra ES-8 Edition2_Rev1 Summary

•Cal/Val Protocol demonstrates radiometric stability of the data products through 11/2004 of….

<.1

.4

.125

.6

FM2

<.1

.2

.1

.3

FM1

Edition1

<.1<.1<.1<.1WN

.1.1.3.2SW

<.1<.1<.1<.1LWnight

.125.125.125.125LWday

FM2FM1FM2FM1

Edition2_Rev1Edition2

Note: Values apply to all-sky global averages Units are in %/yr


CERES Gain/Spectral Change Summary

-

-

-

-

LW/TOT

.7

.5

.4

-

SW

TOA Flux

All-Sky

(W/m^2)

1.6

1.6

3.6

1.1

LWDay

.75

1.1

1.0

.65

LWNight

FM4

FM3

FM2

FM1

1.2

1.4

2.6

.45

SW/TOT

-

-

-

-

WN

-

-

.40

-

SW

Channel

Spectral Response(%)

Channel

Gain

(%)

.80-.30

--.35Terra

--.40

.50

SWWNTOTSpacecraft

-.45Aqua

1. All values are maximum on-orbit changes

2. Ground to flight shifts are accounted for separately

3. SW/TOT < 3.0 microns, LW/TOT > 3.0 microns

4. TOA Flux values are all-sky global averages

Cumulative changes incorporated in Edition 2 BDS and ERBE-Like products


Derivation of Edition 3 SWSpectral Response

CERES Instrument Working GroupCERES STM, 1 Nov 05, Hampton, VA


Rev1 adjustment removes the drift assuming the Xtrack instrument is stable. Someunexplained features in direct compare suggest this may not be the case:


• Further stows are planned to directly measure anyXtrack darkening

• New reduced noise full swath direct compare datausing both instruments in Xtrack is underproduction

• A physical model of the contaminant depositionand subsequent darkening is being developed andtuned to internal calibration and direct comparedata. This will incorporate results from furtherstows and noise reduced direct compare

In order to fully compensate for darkening effects in the Edition3 spectral response the following activities are underway:


Photons tend to interact with targets of similar size to theirwavelength, hence contaminant absorption can be modeled

as:

Might expect population density of polymer chain lengthto fall off exponentially:


This fits the basic shape of spectral darkening seen on LDEF,GOME and MODIS:


So 1 um thickness of polymerized contaminant might have atransmission given by:

Plot of normilized Earth spectra compared to fractional transmission of polymerized contaminant transmission (1um thick)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2

wavelength (um)

Fra

cti

on

al

tra

ns

mis

sio

n Fractional Transmission

Clear ocean spectrum

Allsky spectrum


Experience from LDEF suggests that continued exposure ofcontaminants to UV photons increases the polymerization, making

the remaining category ‘A’ solo molecules form more absorbinglong chains (becoming category ‘B’)

If N is the total number of contaminant molecules (A+B), thisequation represents a situation where 40% of molecules

arriving per day of RAPs are already polymerized (categoryB). Every day earth UV also converts 0.8% of the remaining

category A molecules to category B


Read in themodes for eachinstrument anduse them togenerate forcing(dN/dt) for arrivalof contaminant ateach instrumentfilter surface


Model estimate of absorbing molecule 'B' layer thickness on Terra SW filters

0

0.5

1

1.5

2

2.5

Mar

-00

Jun-

00

Sep

-00

Dec

-00

Mar

-01

Jun-

01

Sep

-01

Dec

-01

Mar

-02

Jun-

02

Sep

-02

Dec

-02

Mar

-03

Jun-

03

Sep

-03

Dec

-03

Mar

-04

Jun-

04

Sep

-04

Dec

-04

Mar

-05

Jun-

05

Sep

-05

Co

nta

min

ant

thic

knes

s (u

m)

FM1 thickness

FM2 thickness


Hence the contaminant transmission can now be foundthroughout the mission:


Tune the model so its estimate of changes to filtered radiancematches the internal calibration lamps and direct compare:

Plot of normilized Earth spectra compared to fractional transmission of polymerized contaminant transmission (1um thick)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2

wavelength (um)

Fra

cti

on

al

tra

ns

mis

sio

n Fractional Transmission

Clear ocean spectrum

Allsky spectrum


Fix/Darkening model comparison with TERRA Allsky filtered direct compare

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

Mar

-00

Jun-

00

Sep

-00

Dec

-00

Mar

-01

Jun-

01

Sep

-01

Dec

-01

Mar

-02

Jun-

02

Sep

-02

Dec

-02

Mar

-03

Jun-

03

Sep

-03

Dec

-03

Mar

-04

Jun-

04

Sep

-04

Dec

-04

Mar

-05

Jun-

05

Sep

-05

100*

(FM

2-F

M1)

/FM

1

CV Direct Comp (SW)

Fix/Dark model


Fix/Darkening model comparison with TERRA Clear Ocean filtered direct compare

-1.5

-1

-0.5

0

0.5

1

1.5

2

Mar

-00

Jun-

00

Sep-0

0

Dec-0

0

Mar

-01

Jun-

01

Sep-0

1

Dec-0

1

Mar

-02

Jun-

02

Sep-0

2

Dec-0

2

Mar

-03

Jun-

03

Sep-0

3

Dec-0

3

Mar

-04

Jun-

04

Sep-0

4

Dec-0

4

Mar

-05

Jun-

05

Sep-0

5

100*

(FM

2-F

M1)

/FM

1

CV Direct Comp (SW)

Fix/Dark model


The model can also be tuned to Aqua direct compare andinternal calibration results:


Fix/Darkening model comparison with AQUA Allsky filtered direct compare

1.7

1.8

1.9

2

2.1

2.2

2.3

2.4

2.5

2.6

2.7

Jul-0

2

Sep-0

2

Nov-0

2

Jan-

03

Mar

-03

May

-03

Jul-0

3

Sep-0

3

Nov-0

3

Jan-

04

Mar

-04

May

-04

Jul-0

4

Sep-0

4

Nov-0

4

Jan-

05

Mar

-05

100*

(FM

4-F

M3)

/FM

3

CV Direct Comp (SW)

Fix/Dark model


• Rev 1 adjustments remove the majority of thespurious SW trends in Edition 2 data

• Special operations and modeling currentlyunderway to characterize and compensate forRAPs and any Xtrack darkening in Edition 3SW spectral response

• With SW channel model satisfactorily tuned,existing 3 channel inter-comparison methodcan be modified to derive any spectraldarkening to total channel optics

Summary and Conclusions

terra/aqua instrument and erbe-like calibration status report · 2007. 12. 7. · terra/aqua...

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