# Presentation: 473643

## NASA Support for MODIS Direct Broadcast:Level-0 to Standard Ocean Products

- Bryan Franz & Mike MacDonald
- Ocean Biology Processing Group
- NASA Goddard Space Flight Center
- International EOS/NPP Direct Readout Meeting
- 3-6 October 2005
- Benevento, Italy

## The Ocean Biology Processing GroupA Component of NASA’s Missions-to-Measurements Initiative

- Heritage: SeaWiFS, SIMBIOS, SeaBASS, SeaDAS
- Designated NASA team responsible for the processing and distribution of ocean color measurements and SST from various spaceborne instruments.
- Ocean Color: CZCS, SeaWiFS, MODIS/Aqua
- SST: MODIS/Aqua MODIS/Terra
- Designated Product Evaluation & Test Element (PEATE) for ocean color and SST on NPP/VIIRS.
- Ocean Color & SST PEATE: NPP/VIIRS

## Outline

- Status of MODIS Oceans
- Product quality
- Data distribution
- Tools for direct broadcast (Mike MacDonald)

## Recent Developments in MODIS Ocean Color & SST

- Transition from MODAPS / DAAC to OBPG
- Aqua Ocean Color, early 2004
- Aqua & Terra SST, late 2005
- Terra Ocean Color, currently unsupported
- Multi-mission environment
- common code for MODIS, SeaWiFS, OCTS, CZCS
- common Level-2 & Level-3 formats
- no more PGE09 or PGE10, no more radcor files
- Revised MODIS/Aqua OC calibration & processing
- pre-launch analyses, on-orbit temporal cal, vicarious cal
- _x0003__x0016_

## MODIS vs SeaWiFS before OBPG Transition Deep-Water nLw   (global mean > 1000m)

**MODAPS**
**Aqua 003**

**MODAPS**
**Terra 041**

**MODIS / SeaWiFS**

**MODIS on Terra shows significant temporal instability**

**MODIS on Aqua shows large bias, but better temporal stability in ocean color**
**OBPG efforts concentrated on MODIS/Aqua ocean color**

## Recent Developments in MODIS Ocean Color & SST

- Transition from MODAPS / DAAC to OBPG
- Aqua Ocean Color, early 2004
- Aqua & Terra SST, late 2005
- Terra Ocean Color, currently unsupported
- Multi-mission environment
- common code for MODIS, SeaWiFS, OCTS, CZCS
- common Level-2 & Level-3 formats
- no more PGE09 or PGE10, no more radcor files
- Revised MODIS/Aqua OC calibration & processing
- pre-launch analyses, on-orbit temporal cal, vicarious cal
- _x0003__x0016_

## Recent Developments in MODIS Ocean Color & SST

- Transition from MODAPS / DAAC to OBPG
- Aqua Ocean Color, early 2004
- Aqua & Terra SST, late 2005
- Terra Ocean Color, currently unsupported
- Multi-mission environment
- common code for MODIS, SeaWiFS, OCTS, CZCS
- common Level-2 & Level-3 formats
- no more PGE09 or PGE10, no more radcor files
- Revised MODIS/Aqua OC calibration & processing
- pre-launch analyses, on-orbit temporal cal, vicarious cal
- _x0003__x0016_

## Revised Polarization Correction

**Solid line = OBPG,  Dashed line = original correction**

## Added Masking for Straylightdeveloped model based on pre-launch line-spread functions

## In collaboration with MCST

Reanalyzed Onboard Calibration (OBC) Data (solar, lunar)

Removed residual correlations with diffuser screen geometry

Refit solar diffuser trends to double exponential model

Improved LUT extrapolation

**Revised Temporal Calibration ****Reflected Solar Bands**

- In collaboration with MCST
- Reanalyzed Onboard Calibration (OBC) Data (solar, lunar)
- Removed residual correlations with diffuser screen geometry
- Refit solar diffuser trends to double exponential model
- Improved LUT extrapolation

## Added Correction for Residual Detector Striping

**nLw(412) Before Correction**

**nLw(412) After Correction**

## we make special L1B LUTs for oceans !

## Bidirectional Reflectance at Surface

- Each sensor views the same location on earth from different view angle and at different time of day (solar angle).
- The angular distribution of upwelling radiance varies with solar illumination angle and the scattering properties of the water body.
- A. Morel developed a correction for this effect, which was incorporated into the common processing software for both sensors.

**Before BRDF**

**After BRDF**

**Residual Scan Dependence in MODIS nLw(443)**

## nLw: MODIS vs SeaWiFS Deep-Water

**nLw: MODIS vs SeaWiFS ****Deep-Water**

**After OBPG Reprocessing of MODIS/Aqua**
**Significantly improved agreement with **
**SeaWiFS global mean nLw **

**MODIS / SeaWiFS**

**MODIS / SeaWiFS**

**OBPG/MSL12**
**Aqua R1**

**MODAPS/PGE09**
**Aqua 003**

**before**

**after**

## Results from ReprocessingComparison with Field Data

**MODIS/Aqua R1**

**Results from Reprocessing****Comparison with Field Data**

## Seasonal Chlorophyll Images

**Seasonal Chlorophyll Images**

**0.01-64 mg m****-3**

**Summer 2004**

**Winter 2004**

**SeaWiFS**

**MODIS/Aqua**

**Winter 2004**

**Summer 2004**

## OBPG Data Distribution

## Slide 18

## Data Distribution

**Instant access:**	entire archive of Level-1A through Level-3
- 		data for all missions is stored online
**Minimal latency:**	MODIS L1A/GEO/L1B/L2 data available
- 			2-5 hours after satellite observation
**Web-based browser:****	**simple viewing/order/download tool for
- 					the entire multi-mission data set
**Data subscriptions:**	automatic staging of new data products
- 				to user-specific ftp accounts

## virtual ground station concepta back-up for your DB station

**Data subscriptions can be created for a limited geographic region, allowing users to receive Level-1A and Level-2 data for their area(s) of interest within 2-5 hours of satellite observation.**

## Slide 21

## SeaDAS

## SeaDAS Features

- Most widely used ocean color software package in the world
- Process/display/analyse MODIS, SeaWiFS, CZCS, OCTS, MOS
- Will support NPP/VIIRS in the future
- Reproduces identical OBPG standard ocean color & SST products
- Runs on Linux, Macintosh OS X, Sun Solaris, SGI IRIX
- Extremely active user support forums

## msl12

- converts sensor measured radiances (Level-1B) to geophysical products
- processes MODIS, SeaWiFS, OCTS, MOS, OSMI, POLDER, and CZCS
- default products generated are identical to those distributed by the OBPG
- customizable run-time parameters control processing options and determine output products
- source code/build environment allow users to implement custom algorithms
**The flexibility of msl12 allows SeaDAS users to investigate alternative processing options and to generate a host of additional output products beyond the standard suite.**

## msl12:  PGE09, PGE10, etc...

**water-leaving radiances**
**remote sensing reflectance**
**SST (thermal and short-wave IR)**
**chlorophyll (8 algorithms)**
**diffuse attenuation of sea water **
**IOP (GSM01, Carder, QAA):**
**	****   ****-absorption (total, phaeophytin, dissolved & detrital)**
**	****   ****-backscatter (total, particulate)**
**particulate organic carbon**
**total suspended matter**
**calcite concentration**
**fluorescence line height**
**photosynthetically active radiation**
**aerosol products (AOT, Angstrom)**
**intermediate products (Lr, La, anc. fields, etc.)**

## Slide 26

## MODISL1DB

## MODISL1DB

- Direct Broadcast software package for processing MODIS Aqua and Terra Level-0 data to Level-1A and Level-1B
- Unifies SeaDAS, MCST/SDST, IMAPP
- Runs on Linux, Macintosh OS X, Sun Solaris
- Very simple to install and use (and integrate into existing processing systems)
- New ‘MODIS Direct Broadcast Support’ forum as well as direct support from developers

## MODISL1DB 1.0 Features

- processing binaries compiled with MCST Version 5 source
- Code and LUTs will remain synchronized with MCST
- processing mechanism to auto-download latest MCST LUTs (and OBPG Aqua LUTs)
- processing mechanism to auto-download definitive or real-time attitude and ephemeris, or use GBAD-generated att/eph
- MCST source code and build environment (available via SeaDAS) allow users to implement custom features

## MODISL1DB directory structure

**bin/ - - - - - - - - - - Processing and utility binaries **
**data/  - - - - - - - - - Supporting data files**
**     ****modis/**
**           ****atteph/ - - - Attitude and ephemeris files**
**           ****dem/  - - - - Digital elevation maps**
**           ****static/ - - - Common ancillary files**
**     ****modisa/**
**            ****cal/ - - - - Aqua calibration LUTs and ancillary files**
**            ****mcf/ - - - - Aqua metadata configuration files**
**            ****pcf/ - - - - Aqua process control files**
**     ****modist/**
**            ****cal/ - - - - Terra calibration LUTs and ancillary files**
**            ****mcf/ - - - - Terra metadata configuration files**
**            ****pcf/ - - - - Terra process control files**
**scripts/ - - - - - - - - Main wrapper scripts and utility scripts**

## Level-0 to Level-1A wrapper script:

**Usage: modis_L0_to_L1A_GEO.csh MODIS_L0_PDS_file [OPTIONS]**
**Options: **
**  ****-o L1A_file               Output MODIS L1A HDF filename**
**  ****-g GEO_file               Output MODIS GEO HDF filename**
**  ****-a1 attitude_file1        Input attitude file 1 (chronological)**
**  ****-a2 attitude_file2        Input attitude file 2 (chronological)**
**  ****-e1 ephemeris_file1       Input ephemeris file 1 (chronological)**
**  ****-e2 ephemeris_file2       Input ephemeris file 2 (chronological)**
**  ****-disable-definitive       Disable use of definitive attitude/ephemeris**
**  ****-disable-definitive-ftp   Disable auto-downloading of definitive att/eph**
**  ****-disable-predicted        Disable use of real-time attitude/ephemeris**
**  ****-disable-predicted-ftp    Disable auto-downloading of real-time att/eph**
**  ****-verbose-ftp              Enable verbose auto-download messages**
**  ****-disable-dem              Disable terrain elevation correction**
**  ****-startnudge n             Level-0 start-time offset (seconds)**
**  ****-stopnudge n              Level-0 stop-time offset (seconds)**
**  ****-geocheck_threshold n     % of geo pixels required to pass validation test**
**  ****-satellite aqua           Only required if non-standard filename**
**  ****-satellite terra          Only required if non-standard filename**
**  ****-save-log                 Save Level 1A and geolocation processing log files**

## Level-1A to Level-1B wrapper script:

**Usage: modis_L1A_to_L1B.csh L1A_file GEO_file [OPTIONS]**
**Options: **
**  ****-o L1B_1KM_filename       Output MODIS L1B 1KM HDF filename**
**  ****-h L1B_HKM_filename       Output MODIS L1B HKM HDF filename**
**  ****-q L1B_QKM_filename       Output MODIS L1B QKM HDF filename**
**  ****-rlut REFL_LUT_filepath   Full path and filename of Reflective LUT file**
**  ****-elut EMIS_LUT_filepath   Full path and filename of Emissive LUT file**
**  ****-qlut QA_LUT_filepath     Full path and filename of QA LUT file**
**  ****-save-log                 Save the Level 1B processing log file**

## Slide 33

## Ciaaao!!

## Back-up Slides

## Atmospheric Correction Equation

*L**t** = L**r** + L**a** + tL**wc** + TL**g** + t L**w*
*L**w** *is the quantity we wish to retrieve at each wavelength.
*TL**g** *is Sun glint, the direct reflectance of the solar radiance from the sea surface. This effect is avoided through tilting.
*tL**wc** *is the contribution due to "white"-capping, estimated from statistical relationship with wind speed.
*L**r** *is* *the contribution due to molecular (Rayleigh) scattering, which can be accurately computed.
*L**a** *is the contribution due to aerosol and Rayleigh-aerosol scattering, estimated in NIR from measured radiances and extrapolated to visible using aerosol models.

## Multi-Mission Approach

- Common software for Level-1 through Level-3
- reduces potential for algorithm and implementation differences
- sensor-specific issues consolidated in i/o function and external tables
- Mission-independent, distributed processing system
- controls staging/sequencing of processing jobs for max through-put
- 150x global reprocessing for MODIS, 1600x for SeaWiFS
- Standard procedures for calibration and validation
- temporal calibration via On-Board Calibration system (OBC)
- vicarious calibration to MOBY (instrument + algorithm calibration)
- validation against SeaBASS *in situ* archive
- temporal trending analysis of Level-3 products

## Results for ReprocessingConsistency in Annual Cycle of nLw

**MODIS/Aqua R1**

**SeaWiFS R5**

## nLw Ratio: MODIS/Aqua vs SeaWiFS 50N-40N, 150W-170W

**Before Polarization Correction**

**After Polarization Correction**

**improved spectral consistency**

**straylight**

## Effect of BRDF Correction to MODIS/SeaWiFS Ratios

**Deep Water nLw Ratio**
**MODIS/SeaWiFS**

**After BRDF**

**Southern Pacific nLw Ratio**
**MODIS/SeaWiFS**

**Before BRDF**

## Identified and removed a residual detector trend in the reflected solar band calibration.Comparison of TOA analysis (red and blue diamonds for two mirror sides) to lunar analysis of MCST (*):

## Residual Striping

- Global mean residual striping at +/- 2% in nLw
- Consistent over life of mission (problem with SD cal?)

**nLw(412)**

**nLw(551)**

**+10%**

**-10%**

**+5%**

**-5%**

## Added Masking for Straylight

**Added Masking for Straylight**

- SeaWiFS already includes correction & masking for straylight.
- Modeled point-spread function (PSF) for MODIS indicates significant sensitivity to straylight from adjacent sources.
- 7 x 5-pixel masking around bright pixels removes significant contamination.
- Fixes AOT discrepancy (excess NIR radiance) between sensors.

**Before SL Masking**

**After SL Masking**

**MODIS Band 16 PSF**

**Improved Agreement with SeaWiFS AOT**