# Presentation: 193736

## Some Thoughts on Transitioning to NPP

- Paul Menzel (with input from Jeff Myers)
**Issues**
- Continuing MODIS through NPP/NPOESS and beyond
- Preparing for VIIRS
- 	participation in VIIRS OAT
- 	P3I
- Assuring viable Cal/Val
- 	Planning evolution of MAS
- 	VIIRS Airborne Simulator

## NPOESS Products(NPOESS IORD Environmental Data Records by Instrument)

## NPOESS Products(NPOESS IORD Environmental Data Records by Discipline)

## VIIRS, MODIS, FY-1C, AVHRR

- VIIRS, MODIS, FY-1C, AVHRR

- H2O

- H2O

- H2O

- H2O

- O2

- CO2

- CO2

- H2O

- O2

- O3

- H2O

- O2

## Earth emitted spectra overlaid on Planck function envelopes

- H20

- CO2

- O3

- CO2

**Notes:**
This slide shows an observed infrared spectrum of the earth thermal emission of radiance to space.  The earth surface Planck blackbody - like radiation at 295 K is severely attenuated in some spectral regions.  Around the absorbing bands of the constituent gases of the atmosphere (CO2 at 4.3 and 15.0 um, H20 at 6.3 um, and O3 at 9.7 um), vertical profiles of atmospheric parameters can be derived.  Sampling in the spectral region at the center of the absorption band yields radiation from the upper levels of the atmosphere (e.g. radiation from below has already been absorbed by the atmospheric gas); sampling in spectral regions away from the center of the absorption band yields radiation from successively lower levels of the atmosphere.  Away from the absorption band are the windows to the bottom of the atmosphere. Surface temperatures of 296 K are evident in the 11 micron window region of the spectrum and tropopause emissions of 220 K in the 15 micron absorption band.  As the spectral region moves toward the center of the CO2 absorption band, the radiation temperature decreases due to the decrease of temperature with altitude in the lower atmosphere.
IR remote sensing (e.g. HIRS and GOES Sounder) currently covers the portion of the spectrum that extends from around 3 microns out to about 15 microns. Each measurement from a given field of view (spatial element) has a continuous spectrum that may be used to analyze the earth surface and atmosphere.  Until recently, we have used “chunks” of the spectrum (channels over selected wavelengths) for our analysis. In the near future, we will be able to take advantage of the very high spectral resolution information contained within the 3-15 micron portion of the spectrum.  From the polar orbiting satellites, horizontal resolutions on the order of  10 kilometers will be available, and depending on the year, we may see views over the same area as frequently as once every 4 hours (assuming 3 polar satellites with interferometers).  With future geostationary interferometers, it may be possible to view at 4 kilometer resolution with a repeat frequency of once every 5 minutes to once an hour, depending on the area scanned and spectral resolution and signal to noise required for given applications. 

## Planning the VIIRS Airborne Simulator 

**Planning the ****VIIRS Airborne Simulator**** **

## MODIS Airborne Simulator (MAS) Spectral Bands

## VIIRS Airborne Simulator (VAS) Concept

- _Rationale:_
-   Collect high-resolution, calibrated data to validate the on-orbit
-   performance and calibration of the VIIRS instrument
-   Build a feature-rich VIIRS-like data set for the development and test of
-    CDR and EDR product algorithms, prior to NPP/NPOES launch
- _Approach:_
-  Capitalize on the NASA MODIS and ASTER Airborne Simulator
-     Programs (MAS and MASTER) and U.W. S-HIS experience
-  Leverage ongoing development programs for accelerated deployment
-  Apply MAS “lessons-learned” and operational experience for
-    risk reduction.

## MAS Lessons

- Spectral stability is critical for atmospheric bands
- Flat-plate blackbody design not capable of <1 degree accuracy
- Cross-track polarization needs to be addressed
- Onboard calibrator for Vis/SWIR bands highly desirable
- Scattered light inside scan cavity needs to be reduced
- Internal IR background radiation has to be better suppressed
- Replace gratings with bandpass filters for LWIR bands
- Eliminate linear-variable filters (LVFs) from design
- Additional SWIR and LWIR water vapor bands are useful

## Design Features

- Single large dewar for LWIR bands and cold secondary optics to reduce background noise
- Filter-based spectral differentiation in M/LWIR bands
- Added 6.7um (and possible 1.88um) band
- Improved blackbody design, based on S-HIS experience
- Visible/SWIR calibrator
- De-polarization methods to be investigated
- Fully supported by Ames Calibration Lab (NIST-traceable)
- Utilize ground-processing and archive software from MAS
-        (including Level-1B/HDF data production system)

## VAS Spectral Bands

-      _VIIRS #_   _Center____(nm)_  ___(nm)_  _SNR/NE____T__*****_
- M1               412              20             880
- M2               445              18             840
- M3               488              20             800
- M4               555              20             750
- M5               672              20             900
- M6               746              15             580
- M7               865              39             500
- M8             1.240m        20               75
- M9             1.378             15             150
- M10           1.610             60             275
*MAS15      1.880             50               --*
- M11           2.250             50             110
- M12           3.700           180             0.05 NET
- M13           4.050           155             0.07
*MOD27      6.715            360            0.25*
- M14           8.550            300            0.05
- M15         10.763          1000            0.05
- M16         12.013            950            0.05
*MOD33     13.3                                 0.25*
***** Based on the equivalent VIIRS orbital pixel size

## Phased Development Approach

**Phase 1:  Implement VIIRS Bands on the NASA MAS System**
-      Design and build a VIIRS-like Spectrometer, compatible with the exisiting MAS Opto-Mechanical Module (OMM) and data system and begin collecting data.
**Phase 2:  Build a dedicated VIIRS Airborne Simulator Instrument   **
**                  ****(based on an improved  MAS design)**
-      Design and build:
-      --  Dedicated Opto-Mechanical Module (with new-design
-              blackbodies)
-       --  New data system (MAS follow-on design)
**Phase 3:   Advanced technology system**
-      -- Design and build next-generation airborne line-scanner
-      -- Re-use high-value elements (e.g. filters, detector arrays)
-      -- Long-term solution for VIIRS airborne simulation
-      -- UAV-Compatible

## Estimated Development Timeline

- Phase 1 – VAS Spectrometer    16 Months
- Phase 2 – Data System, OMM
-                         & Calibrators            18 Months
- Phase 3 – Advanced System      TBD
- All phases could be conducted in parallel.   (Seed-money for preliminary design work could accelerate schedules.)