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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

Summary of work on VIIRS task CSE-3

Ed Bicknell, Kelly Wallenstein, & Erin O’Connor

24 October 2012

Suomi NPP SDR Product Review


Outline

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

Task: Calibration System Evaluation (CSE) 3

Charter


Overview of procedure

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

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

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

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

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

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

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

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

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

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

BACKUP CHARTS


M4 sd and ev reflectance cross correlation

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

Summary of SD-EV reflectance zero-lag correlation coefficient


Smoothing filter procedure

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

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

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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