SNPP VIIRS SDR RSR LUT Update ADR 4971

SNPP VIIRS SDR RSR LUT Update: ADR 4971, CCR 13 -0888 U. Wisconsin: NASA VCST: Aerospace: Chris Moeller Ning Lei, Shihyan Lee, Zhipeng Wang, Sam Anderson, Chengbo Sun, Sergey Gusev, Vincent Chiang, Hassan Oudrari, and Jon Fulbright Kameron Rausch and Frank De. Luccia April 3, 2013 AERB

SDR RSR Update Background • Ongoing spectral degradation in the SNPP VIIRS RTA mirror reflectance on-orbit (due to tungsten contaminant) is modulating the spectral response of VIIRS RSB (Vis. NIR and SWIR bands I 1 -I 3, M 1 – M 11, DNB). • The spectral nature of the degradation is changing the relative contribution of OOB light to the total signal in all RSB as well as modifying the in-band spectral shape of most RSB. • Modulated RSR are based largely upon on-orbit F factors. – F factors are used to train a VCST thin layer physical absorption model. – The VCST model provides a throughput degradation spectrum which is then convolved with the baseline RSR to produce the modulated RSR. UWisc-RSR, 2013 -04 -03 2

Objective/Rationale for Update • Modulated RSR represent the best on-orbit spectral characterization for SNPP VIIRS RSB. • Modulated RSR have been updated for a snapshot of “current” (orbit 6557, Feb 1 2013) performance. This RSR snapshot is used to populate the SDR RSR LUT. • ~75% of expected 5 yr RTA mirror darkening has already occurred. Darkening will continue to slowly accrue over the lifetime of SNPP VIIRS. • The SDR RSR LUT update will mitigate small systematic biases that have accumulated in VIIRS SDR and EDR operational products. • Fast-track change (no change to LUT format). UWisc-RSR, 2013 -04 -03 3

NASA Thin Layer Degradation Model: V 5 RTA throughput degradation spectrum M 1 -M 4 M 11 I 1 M 5 I 3 M 10 M 6 M 9 M 8 I 2 M 7 • • • Model Version 5 Based upon operational F factors thru orbit 6557 (Feb 1, 2013) Close match to TWM witness sample projection for 4 degraded mirrors (shown as “UW end of life” in plot) V 3 (June 2012), V 4 (August 2012), V 5 (Feb, 2013) degradation models very consistent. UWisc-RSR, 2013 -04 -03 4

Degradation Model Fitting Results dashed lines: modeled solid lines: measured Model fit to on-orbit observations is excellent UWisc-RSR, 2013 -04 -03 5

Degradation Model Fitting Results RTA degradation additional degradation for SWIR bands UWisc-RSR, 2013 -04 -03 degradation not affecting RSR 6

A Few RSR Examples (balance contained in Backup) • Comparison of band averaged baseline RSR (NG Oct 2011 release) to V 5 modulated RSR (Feb 1 2013) used to update VIIRS SDR RSR LUT. • Two plots per band: In-Band Out-of-Band. • Differences exhibit influence of RTA spectral degradation on VIIRS RSR. UWisc-RSR, 2013 -04 -03 7

Examples of Modulated RSR. . . I 1 In-band response shifts to shorter wavelengths UWisc-RSR, 2013 -04 -03 8

Examples of Modulated RSR. . . I 1 Out-of-band response diminished UWisc-RSR, 2013 -04 -03 9

Examples of Modulated RSR. . . M 1 Very minor change UWisc-RSR, 2013 -04 -03 10

Examples of Modulated RSR. . . M 1 Out-of-band response diminished UWisc-RSR, 2013 -04 -03 11

Examples of Modulated RSR. . . M 7 In-band response shifts to shorter wavelengths UWisc-RSR, 2013 -04 -03 12

Examples of Modulated RSR. . . M 7 Out-of-band response enhanced UWisc-RSR, 2013 -04 -03 13

Examples of Modulated RSR. . . M 8 In-band response shifts to longer wavelengths UWisc-RSR, 2013 -04 -03 14

Examples of Modulated RSR. . . M 8 Out-of-band response enhanced UWisc-RSR, 2013 -04 -03 15

Science Test Strategy • Populated SDR RSR PC LUT with V 5 Modulated RSR. • Modify F factor calculation to use Modulated RSR for consistency and populated VIIRS SDR F PREDICTED LUT and VIIRS SDR DNB F PREDICTED LUT. * • Run VCST’s IDPS mock SDR production code using baseline and updated SDR RSR PC LUT (and F factors) for 5 VIIRS granules. • Compare baseline and updated SDR output. Radiance and reflectance impact found to be small (< 0. 2%). • Repeated this process for one granule, running ADL at GRAVITE. Results agree with VCST test. *Note: F LUTs of this package are for test purposes only and not part of the LUT update into 16 IDPS UWisc-RSR, 2013 -04 -03

Sample VIIRS Test Granules Thick cloud Snow Desert Dust/Aerosol UWisc-RSR, 2013 -04 -03 Ocean Forest 17

Earth Scene Reflectance Profile Reflectance Impact Profile Impact < 1 part in 1000 I 1 I 2 I 3 Radiance Impact Profile Earth Scene Radiance Profile Impact < 1 part in 500 I 1 UWisc-RSR, 2013 -04 -03 I 2 I 3 I 1 I 2 I 3 18

Recommendation/Summary • Update RSR (M 1 -M 11, I 1 -I 3) contained in VIIRS SDR RSR PC LUT using VCST V 5 (Feb 1 2013) Modulated RSR (DR-4971). • Incorporates the majority of anticipated lifetime RTA mirror degradation anomaly influence on VIIRS RSR. • Establishes new RSR baseline forward operational processing. • Functionality and impact has been demonstrated by ADL and by VCST SDR algorithm runs. Science test results reveal small impact on SDR. • RTA mirror throughput degradation will continue on-orbit and will be monitored over the SNPP VIIRS lifetime. Further updates to SNPP VIIRS RSR will be considered but are not anticipated at this time. NOTE: Offline processing of RSB F factors planned to incorporate Modulated RSR concurrent with the SDR RSR LUT update. UWisc-RSR, 2013 -04 -03 19

Backup Slides 20

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