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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. 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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  1. Summary of work on VIIRS task CSE-3 Ed Bicknell, Kelly Wallenstein, & Erin O’Connor 24 October 2012 Suomi NPP SDR Product Review

  2. 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

  3. Task: Calibration System Evaluation (CSE) 3 Charter

  4. 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.)

  5. 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)

  6. 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

  7. 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

  8. 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

  9. 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

  10. Summary of SD-EV radiance zero-lag correlation coefficient For EV reflectance: Zero-lag peak correlation coefficient ~0.6

  11. 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

  12. 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

  13. 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

  14. BACKUP CHARTS

  15. 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

  16. Summary of SD-EV reflectance zero-lag correlation coefficient

  17. 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

  18. 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

  19. 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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