# Presentation: 517477

## VIIRS Performance Status Summary

- H. Oudrari et al.
- NPP PSG/NICST/NICSE/Science Team

**NPP VIIRS Calibration and Characterization (NVCC)**
- May 15th, 2008
- Baltimore, MD

## Content

-  Objective and General Comments
-  VIIRS FU-1 Testing Schedule
-  On-board Calibration System
-  VIIRS Performance Summary
-  NPP Science Team (ST) Risk Items

## Objective - General Comments

**Objective: Present NASA data processing results based on the VIIRS FU1 Ambient testing, and share our assessments with NASA at-large Subject Matter Experts (SMEs) for SDRs and EDRs.**
**These results are not meant to represent VIIRS sensor performance sell-off:**
- NASA NPP L1 Team is still participating in the on-going VIIRS Program Ambient Test Data Reviews (NASA, IPO, NGST and SBRS)
- End of Life performance still needed
- Some specifications sell-off will be determined after TV testing
**Raytheon SBRS has been leading the VIIRS testing program for NGST prime contractor, but program has now transitioned to Raytheon El-Segundo for all forthcoming testing**
**NASA Science interaction with VIIRS sensor team facilitated through IPO Government teams and NGST/SBRS team**

## VIIRS FU-1 Testing Schedule

-    FU-1 Thermal Vacuum (TV) Schedule:
-  Pre-TV testing: 	08/01/08 – 08/17/08
-  TV testing: 	08/20/08 – 12/03/08

**VIIRS FU-1 Testing Schedule**

- FU-1 Ambient Testing Complete:
- Phase I testing:  	06/20/07 – 08/29/07
- Phase II testing: 	08/29/07 – 11/30/07
- Phase III testing:	01/28/08 – 04/18/08

**FU-1 testing complete and  Ready to Ship: 02-24-09**

- Schedule current as of April 23rd

## VIIRS Bands and Products

**Dual gain band**

**VIIRS 22 Bands:**
**16 M_ Band, 5 I_Band and 1 DNB**

**VIIRS 24 EDRs**
**Land, Ocean, Atmosphere, Snow**

*** Product has a Key Performance attribute**

## VIIRS Incorporates Modular Sensor Approach

**All reflective**
**Rotating telescope**

**VIIRS Incorporates Modular ****Sensor Approach**

**Cryoradiator**

**4-Mirror Anastigmat**
**All Reflective**
**Aft Optics Imager**

**Blackbody**

**Solar Diffuser**

**Half-angle Mirror**

**Separately Mounted Electronics Module**

**Solar Diffuser**
**Stability Monitor**

**FPIE**

- OMM configuration

**Cold FPA**
**Dewar Assembly**

**RTMA**

## VIIRS Performance Summary

## Radiometric Response:Dynamic Range, Gain Transition and SNR/NeDT

**All VIIRS bands meet SNR/NeDL/NeDT specifications**
**All of VIIRS bands meet the Dynamic range and Transition requirements, except:**
- M1 High Gain transition:
- M1 and M2 Low Gain early saturation:
- M8 early saturation:
- I1, I2, I3, I4 meet dynamic range, but margin is less than 1%. Need TV testing to determine compliance.

## Response Vs. Scan (RVS)

**Reflective bands RVS:**
**All bands RVS meet uncertainty spec: **
- RSB RVS Spec:  0.3 %
- Uncertainty for fit residual: <0.06 %
- Uncertainty for fit residual + measurement: <0.22 %
- Correction of the illumination response drift led to RVS compliance.
- M9 water absorption correction was applied, improving the RVS uncertainty to meet spec
- Government approach: Uncertainty < 0.1 %
- SBRS approach: Uncertainty < 0.18 %
**Thermal Emissive bands RVS:**
**All bands RVS meet uncertainty spec: **
- TEB RVS Spec:  0.2 % (M14: 0.6 %)
- Fit residuals <0.07%
- Measurement repeatability <0.15%

## Stray Light Rejection (SLR)

**Multiple studio lamp positions (33) were used to simulate Earth radiance for stray light contamination**
- Spec: 1% of Ltyp
- Spec only for reflective bands (M1-M11, I1-I3)
- View angle range:  4 – 28degrees
**SLR testing was performed in 3 telescope positions**
- Nadir, End of Scan, and Space View
**SLR analysis results are showing non compliance for 4 bands: ****M5-**** ****M7**** and ****M11**
**A waiver is proposed to relax the SLR requirements leading to spec compliance at the end-of-life.**
**EDR impact assessments is needed using MODIS and/or synthetic data**
**Need to integrate between lamp positions to reflect Cloud surfaces**

## Near Field Response (NFR)

**Near Field response requirement limit the amount of scattered light into a detector from a bright target.**
**FU1 NFR analysis has shown non compliance for many bands: ****M1-M5, M7-M8, M11-M12, I1**
**A waiver was proposed limiting the radiance values for bright targets, and deletion of I1-I3 bands NFR spec.**
- Simulations based on new proposed spec, and the sensor model calculation have shown** ****margin improvements****. **
- NFR non compliance still observed for many bands: M4,M5, M7, M8, M11, M12, M13.
**Ghosting is observed for many SMWIR and LWIR bands. Impact on EDRs is ongoing (EFR3326).**

## Polarization Sensitivity

**VIIRS Polarization analysis using the polarized sheet is ****still ongoing****.**
- Preliminary results are good and promising, showing compliance for polarization factor.
- Still need to verify compliance for polarization characterization (0.5%)
- Test data analysis has shown detector dependency of VIIRS polarization, not supported by the current model.
**Some light leak issues related to the use of SIS source with polarized sheet are being investigated to determine correction factors (e.g M1).**

## Spatial Characterization

**Band to Band Registration (BBR):**
- All VIIRS band-pairs meet BBR specification for intra M-bands and intra I-bands
- Very low margin for 3 band pairs: I5-I1, I5-I2 and I5-I4
**IFOV/DFOV Characterization**
- Scan DFOV Spec is not met for majority of detectors
- Track IFOV is met for all detectors except 3 detectors.
- Thermal Vac. testing is expected to improve margins for Track IFOV.
**MTF/LSF Characterization**
- Scan MTF Spec is met for majority of M-band detectors
- Track MTF meets spec for all M-bands.
**Pointing characterization:**
- FU1 meets specifications

## Dynamic Crosstalk

**Dynamic crosstalk (VisNIR): **
- No spec for dynamic crosstalk
- General agreement to the expected low dynamic crosstalk level (FU1 bond wire fix).
- Most sender/receiver band pairs have coefficients much smaller than 0.001
- Some band pairs are showing few detectors with crosstalk coefficients little larger than 0.001
- Crosstalk coefficients are showing some detector dependency, especially for most affected band pairs.
- Fixed low gain is showing lower crosstalk coefficients than HG
- Dynamic crosstalk linearity was observed for many VisNIR bands.

**Based on EDU crosstalk analysis, crosstalk specifications are being reviewed to make them consistent, realistic and specific to each crosstalk type. **

## Static Electric Crosstalk

**VisNIR**
- Stringent crosstalk specification (0.2%Ltyp) are not met for all VIIRS bands
- The electric crosstalk levels are much smaller than those observed in optical crosstalk
- Crosstalk map is showing high sender detectors (e.g. det 3, 8 and 13 for M-bands and 6, 16, 26 for I-bands)
- High crosstalk at -/+N detector from the sender, and dependency on the sub-sample for I-bands are shown
- Low gain crosstalk coefficients are higher than those from high gain
**SMWIR**
- Specification not met for all bands, but small crosstalk coefficients. No high sender detectors.
- Low gain is showing M1, M2 and M3 as very high senders into most SMWIR bands and detectors.
- In-band crosstalk is very high for M13 band in fixed low gain
**LWIR**
- Specification not met, but very small electrical crosstalk. No high sender detectors.

**Based on EDU crosstalk analysis, crosstalk specifications are being reviewed to make them consistent, realistic and specific to each crosstalk type. **

## VisNIR Optical Crosstalk

- Stringent optical crosstalk specification (0.2%Ltyp or 0.5NedL) is not met for any VIIRS band (STR406 and STR443)
- Based on ambient test results, FU-1 optical crosstalk is significant for many VisNIR bands.
- Uncertainties associated with test artifacts, the current optical/electronic de-convolution approach, and application to SDR/EDRs (Filter Spread Function) limit our understanding of final crosstalk impacts.
- Current EDR assessments have shown large impact on Ocean Color and high risk for Aerosol products
- Baseline testing of FU1 optical crosstalk is planned in Pre-TV (e.g FP-15, FP16)
- Further EDR impact assessments based on the combined future optical xtalk maps, as well as electric and dynamic crosstalk still to be finalized between NASA, NGST and IPO.

**Based on EDU crosstalk analysis, crosstalk specifications are being reviewed to make them consistent, realistic and specific to each crosstalk type. **

## Four Major VIIRS Issues(EFRs)

**1- Thermal Emissive Calibration (EFR2386)**
- EDU Emissive bands calibration spec is not met for 3 bands (M12, M13 and M14)
- Large quadratic fit residuals and inconsistency between BCS and OBB calibration.
- FU1 TV does now include additional testing to investigate this EFR
**2- Reflective Band Uniformity (EFR2384)**
- EDU bands uniformity has shown non compliance for many bands (M4-M5, M7-M11, and I1-I3)
- NGST team recently provided a new data processing approach currently being reviewed by the government team.
- Verification of this approach is needed for FU1 TV
**3- Ghosting in FU1 Emissive Bands (EFR3326)**
- Root cause identified and characterization is ongoing based on ambient data
- Impact on FU1 EDRs is still to be completed.
**4- Transition Noise and Linearity (EFR2129)**
- EDU data have shown large noise increase (4X) at gain transition for dual gain bands.
- Noise is affecting a limited area of the radiance located at ~10% below HG Lmax
- Non-linearity increase (1%) is leading to non-compliance for calibration
- Need to complete characterization of this artifact for FU1 and assess impact on EDRs
- Land, Aerosol and Cloud pixels will have high probability to be affected

## Other VIIRS Science Issues (Joint Government List) 

**Other VIIRS Science ****Issues ****(Joint Government List) **

**Items not yet in priority order**

**In addition to the four EFRs in the previous slide,** **NASA team is also **
**tracking and updating 10 other FU-1 Risk Items**

**VisNIR IFA Optical Crosstalk****	****	****	****	****Pre-TV**
**VisNIR ROIC Static Electronic Crosstalk****	****	****	****Amb**
**VisNIR Dynamic Crosstalk****	****	****	****	****Amb**
**Stray Light Contamination****	****	****	****	****Amb**
**Relative Spectral Response (RSR) Measurements****	****	****Pre-TV**
**End-to-End Calibration (SD-SAS-SDSM)****	****	****	****Amb**
**Sensor Stability (Temperature, SC voltage, EMI/EMC)****	****TV**
**Response Versus Scan (RVS) Angle Verification****	****	****Amb**
**Polarization Sensitivity characterization****	****	****	****Amb**
**Ambient to T/V to On-orbit Spatial Performance****	****	****TV**

## Backup Slides

## FU1 Sensor Test Flow

**Ambient Phase II Tests**
- FP-11  Polarization Insensitivity
- FP-14  Near Field Response
- FP-10  Response vs. Scan Angle
- FP-9  Operational Modes
- FP-8  Power Profile
- FP-12 Stray Light Rejection
- FP-7  Mechanical Functions
- FP-2  SD Operation SDSM Functional
- FP-5 Pointing Knowledge

**Ambient Phase I Tests**
- SI-4  Commands and Telemetry
- SI-2  Electronics Throughput
- FP-5 Pointing Knowledge
- SI-5  Electronics Self Test
- SI-6  Noise Test
- RC-1 Dynamic Range
- FP-1  BB Functional and DC Restore
- FP-4  Spectral Band Registration
- FP-6  MTF and HSR

**Safe-to-Mate Tests**
- SI1, SI-7 Isolation and Continuity** **

**Opto-Mech**
**Module**
**CTI**

- OMM Mechanical Integration

**Electronics**
**Module**
**CTI**

**EMI Tests in El Segundo**

**Vibe Tests in El Segundo**

**Post Vibe/Pre TV Tests**
- SI1, SI-7 Isolation and Continuity
- SI-4  Commands and Telemetry
- SI-5  Electronics Self Test
- SI-6  Noise Test
- FP-2  SD Operation and SDSM Functional
- FP-5 Pointing Knowledge
- FP-7 Mechanical Functions
- FP-6 MTF and HSR Warm FPAs
- FP-3  Crosstalk Warm FPAs
- FP-15  Relative Spectral Resp Warm FPAs
- FP-16 Out-of-Band Spectral Resp Warm FPAs

**TV Test**
- SI-4  Commands and Telemetry
- SI-5  Electronics Self Test
- SI-6  Noise Test
- FP-3  Crosstalk CFPAs
- FP-4  Spectral Band Registration
- FP-6  MTF and HSR
- FP-7 Mechanical Functions
- FP-9  Operational Modes
- FP-15 Relative Spectral Response CFPAs
- FP-16 Out-of-Band Spectral Resp  CFPAs
- RC-2 Reflective Calibration
- RC-3 Radiometric Stability
- RC-5 Emissive Calibration
- Thermal Cycling, Thermal Balance

**Post TV Tests**
- FP-7 Mechanical Functions
- FP-5 Pointing Knowledge
- FP-17 Mass Properties
- Bench Acceptance Tests (BAT)

**PSR**

**FU1 TRR**

**= Consent to Break/Proceed**

## NPP VIIRS Sensor

_**Purpose:**_  Global observations of land, ocean, & atmosphere parameters at high temporal resolution (~ daily)
_**Predecessor Instruments:**_  AVHRR, OLS, MODIS, SeaWiFS
_**Management**_**:** IPO
_**Status**_**:** Phase C/D (Raytheon)
_**Approach:**_  Multi-spectral scanning radiometer (22 bands between 0.4 μm and 12 μm)   12-bit quantization
_**Swath width:**_  3000 km

**Environmental Data Records (EDRs) are Similar to CEOS/NASA Level 2**
**NPP will provide 25 of 55 NPOESS EDRs**

**Calibration Requirements**
- RSB Calibration: < 2% Uniform scenes
- TEB Calibration: See Table #1 in Back up
- Non-linearity: 1%
- Stability: 0.3%
- Stray Light: <1% Ltyp
- Polarization: M2-6: <2.5% ; M1,M7: <3%
- RVS: Vis/NIR: 0.3% ; SWIR: 0.2%
- Crosstalk: 0.002 Ltyp or 0.5NEDL
**Full Requirement list in the Sensor Spec Document**

**Orbit: 1:30 pm**
**Altitude: 833 km**
**Polar Sun-Synch**
**Launch: 06/2010**

**Dimension: 134x141x85 cm**
**Mass: 275 kg**
**Power: 200 W**
**Data Rate: 10.5 peak/8 Mbps**

## VIIRS Sensor Photons to DN Out

**HAM rotates at half RTA speed in same direction to eliminate image rotation**

**SWIR/MWIR**
**& LWIR Dewar**

**VNIR/DNB FPA**

**FMA Imager**

**Half Angle Mirror (HAM)**

## VIIRS Band/Detector Physical Layout

*Lin et al NASA 20080131*

- This document might contain information subject to the ITAR restrictions on the title page.

**VisNIR FPA**

**LWIR FPA**

**SMWIR FPA**

## NASA L1 Science Team

## Table # 17/18 Emissive Bands RadiometricCalibration Accuracy Requirements

**Equivalent or Better Performance Was Achieved on MODIS**

## TABLE 5.	VIIRS Spectral band optical requirements

- [1] The values given under "OOB Integration Limits" are the specified limits on the 1% relative response points.
- [2] The OOB integration limits will be the 1% response points determined during sensor characterization.

## TABLE 12.	Dynamic range requirements for VIIRS Sensor reflective bands

**TABLE 12.****	****Dynamic range requirements for VIIRS Sensor reflective bands**

## TABLE 13.	Dynamic range requirements VIIRS Sensor emissive bands

## TABLE 14.	Sensitivity requirements for VIIRS Sensor reflective bands

- Notes:
- The units of spectral radiance for Ltyp are watt m-2 sr-1 mm-1.
- The SNR column shows the minimum required (worst-case) SNR that applies at the end-of-scan.

## TABLE 15.	Sensitivity requirements for VIIRS Sensor emissive bands