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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