snpp viirs sdr rsr lut update: adr 4971, ccr 13-0888 u. wisconsin:chris moeller nasa vcst: ning lei,...
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SNPP VIIRS SDR RSR LUT Update:ADR 4971, CCR 13-0888
U. Wisconsin: Chris MoellerNASA VCST: Ning Lei, Shihyan Lee, Zhipeng Wang, Sam Anderson,
Chengbo Sun, Sergey Gusev, Vincent Chiang, Hassan Oudrari, and Jon FulbrightAerospace: Kameron Rausch and Frank DeLuccia
April 3, 2013AERB
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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 (VisNIR and SWIR bands I1-I3, M1 – M11, 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.
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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).
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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)
M1-M4
I1
I2
M5
M6
M8
M9
M11
I3
M7
M10
NASA Thin Layer Degradation Model: V5RTA throughput degradation spectrum
V3 (June 2012), V4 (August 2012), V5 (Feb, 2013) degradation models very consistent.UWisc-RSR, 2013-04-03
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Degradation Model Fitting Results
dashed lines: modeledsolid lines: measured
Model fit to on-orbit observations is excellent
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Degradation Model Fitting Results
RTA degradation
degradation not affecting RSR
additional degradationfor SWIR bands
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A Few RSR Examples(balance contained in Backup)
• Comparison of band averaged baseline RSR (NG Oct 2011 release) to V5 modulated RSR (Feb 1 2013) used to update VIIRS SDR RSR LUT.
• Two plots per band: In-Band and Out-of-Band.• Differences exhibit influence of RTA spectral
degradation on VIIRS RSR.
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I1
Examples of Modulated RSR...
In-band response shifts to shorter wavelengths
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I1
Examples of Modulated RSR...
Out-of-band response diminished
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M1
Examples of Modulated RSR...
Very minor change
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M1
Examples of Modulated RSR...
Out-of-band response diminished
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M7
Examples of Modulated RSR...
In-band response shifts to shorter wavelengths
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M7
Examples of Modulated RSR...
Out-of-band response enhanced
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M8
Examples of Modulated RSR...
In-band response shifts to longer wavelengths
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M8
Examples of Modulated RSR...
Out-of-band response enhanced
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Science Test Strategy• Populated SDR RSR PC LUT with V5 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 IDPSUWisc-RSR, 2013-04-03
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Sample VIIRS Test Granules
Desert Ocean
ForestDust/Aerosol
Snow
Thick cloud
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Radiance Impact Profile
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Impact < 1 part in 1000
Earth Scene Reflectance Profile
Earth Scene Radiance Profile
Reflectance Impact Profile
I1 I2 I3
I3I2I1
I1 I2 I3
Impact < 1 part in 500
I1 I2 I3
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Recommendation/Summary• Update RSR (M1-M11, I1-I3) contained in VIIRS SDR RSR PC LUT
using VCST V5 (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 for 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.
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Backup Slides
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I1
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I1
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I2
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I2
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I3
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I3
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M1
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M1
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M2
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M2
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M3
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M3
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M4
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M4
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M5
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M5
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M6
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M6
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M7
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M7
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M8
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M8
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M9
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M9
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M10
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M10
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M11
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M11
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