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Summary of work on VIIRS task CSE-3. Ed Bicknell, Kelly Wallenstein, & Erin O’Connor 24 October 2012. Suomi NPP SDR Product Review. Outline. CSE-3 charter Selecting non-sun-illuminated SD M4 band orbit signature

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Summary of work on VIIRS task CSE-3

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Summary of work on VIIRS task CSE-3

Ed Bicknell, Kelly Wallenstein, & Erin O’Connor

24 October 2012

Suomi NPP SDR Product Review


Outline

  • CSE-3 charter

  • Selecting non-sun-illuminated SD M4 band orbit signature

  • Cross-correlation between SD signature and EV radiance and reflectance during daytime, non-sun-illuminated SD

  • Predicting SD signature from EV radiance data and observation of sun glint

  • Summary

More comprehensive description of this work can be found in the CSE-3 Task folder in CASANOSA: VIIRS Project Documentation


Task: Calibration System Evaluation (CSE) 3

Charter


Overview of procedure

  • Examine M4 band (555 nm) data

  • Average SD data

    • Average SD 48 samples/scan for each of 16 detectors

    • SD data is ‘calibrated’ into radiance using High and Low gaincoefficients from Orbit 1164*

    • 16 detectors are then averaged into single In-track ‘scan’ record

      • Yields 48 in-track data points per granule

      • In-track swath/scan of ~12 km at nadir

      • In-track swath/scan of ~25 km at cross-track edge

  • 16 detector earth radiance and reflectance data are similarly averaged to give 48 in-track records/granule

  • Standardized correlation variable formed:

  • Use closed-door data to establish non-sun-illuminated SD orbit period

* Coefficients provided by Kameron Rauch. (‘Accurate’ calibration is not a major concern.)


SD signature with doors closed*Orbit 333, 20 November 2011

  • 48 SD scan samples averaged/scan

  • 16 M4 detectors averaged/scan

  • 1 granule = 48 scans

Approximate calibration window

DAY

DAY

NIGHT

SD radiance noise level

Equator

Equator

North Pole

South Pole

Indicates earthshine rejection by the SAS during

non-sun-illuminated SD portion of the orbit

*First closed door SD signature reported by Shihyan Lee, (09/12/2011)


Closed door SD sun-illuminated signature(Orbit 333 over South Pole terminator region)

  • SD returns to non-illuminated status at Solar Declination angleless than about -60 degrees

  • SC latitude varies with season

    • apprx -50o (winter) to -5o (summer)

  • Will use criterion to select non- sun-illuminated SD portion of orbit

Approximate

calibration window

M4 closed door noise level


M4 SD radiance with doors open versus closed(averaged 48 samples & 16 detectors per scan)

Indicates spurious non-sun-illuminated SD signature with doors-open

Observed on all door open orbital SD signatures examined to date

DAY

DAY

NIGHT

SD radiance noise level

Equator

North pole

Equator

South pole


Orbits 569-570 M4 SD and EV radiance cross-correlation

  • 1 lag unit = 11.9 km earth footprint at nadir

  • 1 lag unit = 25.6 km earth footprint at edge of scan

  • SD data averaged 48 detector samples/scan and averaged all 16 M4 detector signatures/scan

  • Earth radiance averages all 16 M4 detector signatures/scan


M4 SD and EV radiance cross correlation

  • 1 in-scan lag unit = 11.9 km earth footprint at nadir

  • 1 in-scan lag unit = 25.6 km earth footprint at edge of scan

Correlation


Summary of SD-EV radiance zero-lag correlation coefficient

For EV reflectance: Zero-lag peak correlation coefficient ~0.6


M4 band SD non-sun-illuminated signature prediction

  • ‘Predict’ SD signature from non-sun-illuminated daytime earth radiance data

  • Procedure:

    • Smooth earth radiance with rectangular kernel

    • On a cross track line-by-line basis, perform linear regression between SD and earth radiance signature.

    • Choose optimal cross track sample number

    • Record regression parameters

  • Results

    • Best fit cross-track scan is ~6.2o West of nadir

    • Kernel size encompasses West side scan angle span of ~0oto 14o

    • Earth radiance image west of nadir shows a faintly detectable satellite “noon-time” glint ‘smudge’ – which may be related to West side best-fit filter kernel?

Testing the Model

Using 13 New Orbit Pairs

*Mean of all Solar Diffuser signatures considered: 1.45 W/m2/sr/μm


Glint observations

  • The glint smudge* appears to follow seasonally-predicted changes in latitude

  • It appears on the West side of the satellite scan

    • Peak satellite “noon time” glint occurs at ~11.4o West scan angle

    • Falls within the 0o to 14o prediction smoothing filter kernel cross-track angle span

  • Glint and associated forward bi-directional scatter could explain why the West scan side more predominately contributes to non-sun-illuminated SD signature than East scan side or the nadir view directly below the instrument

East

East

East

Orbit 3707/3708 (July 2012)

Orbit 1967/1968 (March 2012)

Orbit 569/570 (December 2011)

West

West

West

*“Glint” is enhanced by applying a MATLAB morphological structure element function


Summary

  • Non-sun-illuminated SD signature observed after doors opened

  • Verified SAS design rejects earthshine during portion of daytime orbit

  • M4 band non-sun-illuminated SD signature is correlated with both the earth view radiance and reflectance data

    • 21 orbit pairs examined (8-initial, 13-signature prediction)

    • In-track zero-lag radiance correlation value typically >~0.8

    • In-track zero-lag reflectance correlation value typically >~0.6

    • Correlation extends throughout cross-track swath near in-track zero lag

  • Average non-sun-illuminated diffuser M4 band radiance ~ 1.5 W/m2-sr-mm

  • Can predict SD signature from smoothed earth radiance data

    • Best fit for cross-track location on West scan side

    • Possibly explained by susceptibility of West side earth radiance to forward bi-directional scatter and sun glint

More comprehensive description of this work can be found in the CSE-3 Task folder in CASANOSA: VIIRS Project Documentation


BACKUP CHARTS


M4 SD and EV reflectance cross correlation

  • 1 in-scan lag unit = 11.9 km earth footprint at nadir

  • 1 in-scan lag unit = 25.6 km earth footprint at edge of scan

Correlation


Summary of SD-EV reflectance zero-lag correlation coefficient


Smoothing filter procedure

Inputs to process:

Orbit 569-570 ERad and SD

ERad smoothed by

top-hat kernel (31x501)

Linear Regression

R2 = 0.9935

Cross Track Sample 1796

  • Smoothing window = 31 x 501 samples (In Track x Cross Track)

  • Smoothed cross track sample useful for ‘predicting’ SD signature


Smoothing filter results

For 31x501 kernel size,

R2 as a function of cross-track sample

this peak value…

Map of peak R2 value for all kernel sizes

…is recorded for the kernel size

Path Forward: Use these parameters on new data sets to judge predictive capability of model


Satellite “noon time” glint

  • A seasonally varying “glint smudge” was observed for west-side scan angles within latitudes + 23.5o of the equator

  • “Glint smudge” appears as a lighter, “glow-like” region in the radiance and reflectance images

  • Signature is enhanced by applying a MATLAB morphological structure element function*

  • The appearance of the smudge mightbe tracedto a sun glint angle**

  • When the solar vector

  • declination angle is 90o

  • the satellite-sun vector

  • lies in the YZ scan plane

disk, r=35

*A mathematical operation qualitatively viewed as ‘accentuating’ objects in an image by sequential ‘erosion’ (thinning) and ‘dilation’ (thickening) logic operations on the image with a ‘morphological structuring element’ (pattern).

**L. M. Mailhe, C. Schiff, and J. H. Stadler, “Calipso’s mission design: Sun-glint avoidance strategies”, 14th Space Mechanics Meeting, Feb. 2004, AIAA, paper AAS 04-114


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