NPP VIIRS M6 Saturation Study Update

NPP VIIRS M6 Saturation StudyUpdate

Chris MoellerUniv. WisconsinMarch 22, 2012

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Background• M6 SDR contains “fold over” events when the signal is pushed into deep

saturation under bright illumination (e.g. water clouds). Fold over events are characterized by decreasing digital signal level under increasing detector illumination. See presentation “NPP VIIRS M6 Earth Scene Saturation Moeller 2012.02.28” for further background https://casanosa.noaa.gov/docman/?group_id=378&open_folder=61027#61027.

• SDR radiometric calibration of initial two cases (Jan 9 and Feb 10, 2012) lagged sensor performance due to RTA mirror degradation anomaly. Recent cases (Feb 26 and March 13, 2012) are based upon “current” SDR radiometric calibration.

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Today’s Review Summary• “fold over” events continue to trend to higher radiances as

expected. • “out of range” radiance is now occurring for some good

quality scene data as well as some fold over events. Out of range radiances are replaced with out of range threshold.

• Reflectance data not consistent with radiance data for out of range occurrences.

• M7 is nearing its out of range radiance threshold.• M8 still has margin in these stressing cases.

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Four cases to date in tropical South America: Jan 9, Feb 10, 26, Mar 13,

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“At-Launch” F LUT

Lmax

M6At-launch out of range threshold

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Dec 13 F LUT

Lmax

M6At-launch out of range threshold

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Feb 20 F LUT Delivery

Lmax

M6At-launch out of range threshold

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March 12 F LUT Delivery

M6At-launch out of range thresholdLmax

M7 At-launch out of range threshold

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March 12 F LUT Delivery

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Radiance “out of range” occurrences

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March 12 F LUT Delivery

M8 At-launch out of range threshold

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Backup

• Earth scene imagery for all cases• Within band, each case is digitally stretched to

same scale for direct comparison.• Red box defines region within which data is

sampled for the plots in this package.• All cases over Tropical South America (~10 deg

S latitude; high sun)• Display is a scaled radiance quantity

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Band M6 (752 nm)2012-01-09, 173441 – 173605 UTC

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Band M7 (865 nm)2012-01-09, 173441 – 173605 UTC

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Band M6 (752 nm)2012-02-10, 173219 – 173344 UTC

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Band M7 (865 nm)2012-02-10, 173219 – 173344 UTC

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Band M6 (752 nm)2012-02-26, 173232 – 173357 UTC

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Band M7 (865 nm)2012-02-26, 173232 – 173357 UTC

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Band M6 (752 nm)2012-03-13, 173246 – 173410 UTC

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Band M7 (865 nm)2012-03-13, 173246 – 173410 UTC

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