# Presentation: 642052

## Level 1 Product Assessment of NPP VIIRS 

**Level 1 Product Assessment of NPP VIIRS**** **

- Paul Menzel (PI)
- Chris Moeller (Co-I)
- Dan LaPorte
- Univ. Wisconsin
**NPP Science Team Kickoff mtg**
**Nov 4-6, 2003**** **

##      Primary focus on Level 1 data RDR/SDR
TEB radiances
RSB radiances/reflectances
Performance evaluation
Spectral characterization influence
Detector and mirror side striping
Crosstalk assessment in various forms

EDR/CDR focus to evaluate importance of Level 1 performance issues, e.g.
Imagery
Cloud Mask (intermediate product)
Cloud Cover (including cloud phase)
SST

**TEB radiances**
**RSB radiances/reflectances**
**Performance evaluation**
**Spectral characterization influence**
**Detector and mirror side striping**
**Crosstalk assessment in various forms**
- EDR/CDR focus to evaluate importance of Level 1 performance issues, e.g.
**Imagery**
**Cloud Mask (intermediate product)**
**Cloud Cover (including cloud phase)**
**SST**

**Level 1 Product Assessment of NPP VIIRS: EDR/CDR List**

## Level 1 Product Assessment of NPP VIIRS: Role of PI, Co-I

- Paul Menzel (PI), Chris Moeller (Co-I), Dan LaPorte
- Menzel, Moeller: collaborate on strategy.
- Moeller: Test data set and forward model analysis, influence on science products, L1B cal/val.
- LaPorte: Test data set acquisition/analysis/strategy. On-site presence desired during prelaunch testing.
- Strengths: 	Sensor design/testing (LaPorte)
- 					TEB calibration (Menzel, Moeller) 				Product validation (Moeller)
- All participated in MODIS pre & postlaunch evaluation.
- **Close working relationship with MCST**

## Level 1 Product Assessment of NPP VIIRS: Approach

- Prelaunch
- Review/analyze test data sets to evaluate quality/information content, esp. when performance anomalies are uncovered.
- Simulate EDRs primarily with aircraft data to evaluate impact of SDR performance.
- Create forward model simulations to investigate radiometric impact of anomalous performance in TEB bands.
- Build corporate knowledge applicable to on-orbit performance investigations.
- Postlaunch
- Review on-orbit data sets for performance anomalies. Propose/generate correction algorithms when useful.
- Conduct field campaigns for L1B validation using aircraft-based observations.  Comparisons with existing on-orbit sensors (e.g. MODIS, GOES)

## Level 1 Product Assessment of NPP VIIRS

***A known optical leak at 11um caused the image of the earth’s surface (in this case, Baja peninsula) to be present in MODIS 14.3um data.  Through testing, the pre-launch correction coefficients were revised, removing the contamination. ***

- Baja

- 11um

- 14.3um

- 14.3um

- Pre launch correction

- Post launch correction

- Terra Experience

**Level 1 Product Assessment of NPP VIIRS**

**Notes:**
The 11um leak into LWIR atmospheric bands meant that out of band surface-based  radiance was contaminating the inband radiance.  While this optical leak was discovered during prelaunch, insufficient test data was available to accurately characterize the amplitude of the leak.  Through use of moon view and earth scene data, post-launch correction coefficients have been devised that greatly reduce the contamination.

## Cirrus Detection in MODIS Band 26 Corrected Reflectances

**Notes:**
This MODIS B26 (1.38um) imagery over Central Asia demonstrates the improvement in cirrus detection potential by correcting for striping and surface influences (out-of-band influence).  The correction improves the reflectance contrast between cirrus cloud and the earth surface background in B26.

The reduction of striping, as shown in lower right chart will allow us to reduce the cirrus reflectance threshold so that more of the existing cirrus around the globe will be detected in the MODIS Cloud Mask, and thus will be incorporated into Global Climate Studies. The data shown in the lower right graphic is an along track profile taken from the vertical yellow lines in the uncorrected and corrected images.  The thin cirrus detection threshold has been lowered from the stripe peaks (in blue) down to near the baseline of the red trace.  Model results suggest that thin cirrus with optical depth of about 0.1 will be detectable after correcting the B26 data.

## MODIS Emissive Band L1B 

- Cal/Val from ER-2 Platform

-  Underfly Terra and Aqua with ER-2
-  Compare MODIS with MAS and S-HIS
-  SAFARI-2000, TX-2001, TX-2002

**Notes:**
This is the only airborne effort to validate EOS MODIS thermal band radiances.  We’ve collected ER-2 data for validating Terra MODIS L1B:
WISC-T2000  (Spring 2000)
SAFARI-2000 (Fall 2000)
TX-2001  (Spring 2001)
We’ll collect ER-2 data for validating Aqua MODIS L1B:
TX-2002 (November 2002)
Hawaii-2003 (Feb. 2003)
Since MAS is basically a 1 K accuracy instrument, the S-HIS plays a very important role by allowing the 0.5 K or better accuracy of S-HIS to be transferred to MAS. The MAS 50 m resolution data allows the MODIS footprint to be accurately mapped over MAS (S-HIS 2 km footprint is bigger than MODIS 1 km).  A forward model (with radiosonde atmospheric characterization) is used to generate spectral (different bandpass) and viewing geometry (altitude difference) corrections.

Comparisons between Terra MODIS and MAS/S-HIS from SAFARI-2000 (lower right) show that most Terra MODIS bands are performing at or near the L1B accuracy specification (i.e. most of the stars fall very near or within the open bars).  Aqua MODIS will also be evaluated in future ER-2 field campaigns.

## Level 1 Product Assessment of NPP VIIRS: Resources and Contributions

- Sensor characterization data set evaluation (e.g. spectral knowledge, crosstalk  impact).
- Forward model based sensitivity studies for insight into performance issues in SDR.
- Close relationship with NCST
- Contributions towards Cal/Val Plan and reports on RDR/SDR performance.

## Questions/thoughts

- How does NPPST impact/influence/monitor prelaunch test data set progress/plan?
- How do validation findings evolve into operational algorithm improvements?