1. Activities in the framework of GSICS CNES GPRC Report
GSICS Annual Meeting 24-28th March 2014, Darmstadt, Germany
Activities in the framework of GSICS
CNES GPRC Report
Bertrand Fougnie, Sophie Lachérade, Denis Jouglet
for CNES Calibration Center
(CNES-DCT/SI/MO + support from CNES-DCT/ME)

2. Summary 1/2 Cross-calibration over Desert
Aerosol climatology over desert sites
Spectral interpolation using realistic spectrum
Cross-calibration LEO/GEO
Calibration over Rayleigh Scattering  dedicated talk 3p
Implementation for several sensors
ATBD writing for LEO – to be extended to GEO
Implementation for GEO – SEVIRI results
Calibration over DCC -> dedicated talk 3g
Derivation of a BRDF observed by PARASOL
Update of computation for the full spectral range

3. Summary 2/2 Calibration over Moon  dedicated talk 3m
Intensive acquisitions with Pleiades – The “POLO” workshop : Pleiades Orbital Lunar Observations
Synergy to improve the lunar calibration Temporal monitoring, Cross-calibration, Interband calibration
Synergic calibration  dedicated talk 3s
The PARASOL reprocessing activity
The MODIS-Aqua calibration
Preparation of Sentinel-3 : Evaluation of MERIS
IASI cross-calibration  dedicated talks 4f
Overview of IASI-B performances
Cross-calibration between IASI-A, AIRS, IASI-B, and CRIS

4. Cross-Calibration over Desert Sites (PICS)

5. Desert sites – What’s new for Methodology ?
Basic methodology = Geometrical matching + Spectral interpolation
Aspect to be improved :
matching : consider only the geometry, not the date
1) within an angular box 2°/2°/5° or wrt a BRDF variation within 0.5% : BRDF modeling
interpolation : from TOA to BOA + interpolation + from BOA to TOA
2) improve the atmospheric contribution : aerosol inputs, radiative transfer code
3) improve the surface spectral interpolation : interpolation function
Bidirectional characterization of sites
use of BRDF to enlarge the matching on a larger geometrical window
interest = largely increase the number of matchup when necessary
continuation of modeling using PARASOL data archive (bidirectional sensor)
automatic procedure have been operated to generate BRDF models for 20 sites
currently not fully satisfying…
prototyped and tested on restricted datasets - to be fully moved toward the operational phase
Aerosol climatology over desert sites
use of MODIS-A, MODIS-T, and PARASOL, validation with Aeronet
moderate to strong seasonal variation of aerosol load AND aerosol type
to be considered on the cross-calibration

6. Desert sites – Geometrical matching
Use of dynamic box (based on BRDF) instead of fixed angular box
1) enlarge number of matchups and 2) reduce uncertainties due to geometry
865 - PARASOL vs MERIS
B3 - PHR1A vs MERIS
Fix angular
box (2°,2°,5°)
865 - PARASOL vs MERIS
B3 - PHR1A vs MERIS
Dynamic
box 0.5%

7. Desert sites – Aerosol Climatology
Algeria-3
Niger-3
AOT(550)
MODIS vs PARASOL
Mali-1
Egypt-1

8. Desert sites – Aerosol Climatology
Algeria-3
Niger-3
Arabia-1
AOT(550)
Validation using EARONET

9. Desert sites – Spectral interpolation
Interpolate the surface reflectance : from the reference sensor to S.T.C.
nominal Spline function : limitation shown in Lachérade et al. (2013) and Henry et al. (2013)
artifacts : +5% for 620nm or -3% for 708nm for MERIS/MODIS
use of a spectrum measured in Lab (ONERA) or from hyperspectral imager (e.g. GOME)
artifacts are reduced to 1%
 On going activity
MERIS versus MODIS-A (preliminary)
Nominal (spline)
Lab spectrum

10. Desert sites – What’s new for Application ?
Update of the MERIS archive for standard and small sites – now Version 3
confirmation of the consistency with MODIS-Aqua within 1-2%
Cross-calibration LEO/GEO through SEVIRI data
prototype phase – first results still under analysis (presented in AM’13)
cross-calibration with MODIS not yet fully available (only preliminary)

11. Desert Calibration - Development Plan
The reference method is Desert Calibration Version 1.1
DEV = study & ATBD first definition [resp. SI/MO]
PROTO = prototype on dedicated test environment on MUSCLE – Final ATBD [resp. SI/MO]
Pre-OPE = test on the operational MUSCLE [resp. ME/EI]
OPE = fully operational method / Traceability guaranteed [resp. ME/EI]
(non exhaustive)

12. Calibration over Rayleigh Scattering

13. Rayleigh Calibration – What’s new for Methodology ?
Optimization of cloud mask, subsampling and selection for high-resolution sensors
Based on Pleiades data : processing at full resolution not relevant  1km resolution
Climatology for aerosol
Revision of the aerosol model to be considered for oceanic (desert) sites
Based on Aeronet observations and MODIS retrieval analysis
Maritim-98% probably not the best : angstrom 0.2 to 0.4  impact about 1%
Error budget : Continuity of efforts  see presentation 3p about Rayleigh cal.
construction of the error tree
construction of the error factors
first version of the budget based on a first assumption for input contributors
The GSICS-ATBD construction  see presentation 3p about Rayleigh cal.
first outlines for LEO sensors
Rayleigh scattering results for synergic use  see presentation 3s
validation of the temporal monitoring, multi-angular calibration, absolute calibration
See coming presentation 3p
See coming presentation 3s

14. Implementation – What’s new for Application ?
Historically developed with POLDER and Végétation sensors
definition, prototyping and improvements between
now stabilized on the reference Version 3.5
Implementation of Version 3.5 for several sensors
ocean color sensor considered as radiometric reference
SeaWiFS : prototype step
MERIS (operational, reprocessed for data V3) also to prepare OLCI/SLSTR (Sentinel-3)
MODIS : prototype step – to be investigated
high-resolution sensors : limited geographical coverage
SPOT6
Pleiades 1A and 1B
geostationary sensor
SEVIRI : prototype – to be developed
in preparation
SPOT 7
Sentinel-2 : MSI
Sentinel-3 : OLCI and SLSTR
VENUS

15. Rayleigh Calibration - Development Plan
The reference method is Rayleigh Calibration Version 3.5
DEV = study & ATBD first definition [resp. SI/MO]
PROTO = prototype on dedicated test environment on MUSCLE – Final ATBD [resp. SI/MO]
Pre-OPE = test on the operational MUSCLE [resp. ME/EI]
OPE = fully operational method / Traceability guaranteed [resp. ME/EI]

16. Calibration over Deep-Convective Clouds

17. BRDF estimation using PARASOL
DCC are used for cross-calibration and temporal monitoring
also used at CNES for interband and calibration within the field-of-view
in this context a knowledge of their bidirectional properties is useful
Hu et al. (2004) model has been adopted by GSICS to help cross-calibration
PARASOL provides measurements of Earth’s bidirectional reflectances
DCC observations were collected at CNES for the PARASOL monitoring
a mean DCC was elaborated compiling all measurements -> covers a wide range of geometries
its BRDF was derived
 presented at WebMeetings + provided to GSICS (Tech Note + files)
These observations can be compared to computation or prediction (on-going)
DCC computed with Discrete Ordinate Code and hypothesis on particle types
confronted to the Hu et al. reference
See coming presentation 3g

18. Calibration over Moon

19. “POLO”, ROLO, and lunar activity
It has been demonstrated that the Moon is a very precious way to provide accurate in-orbit monitoring of the radiometric drift
Activity under “big” development at CNES
Method implemented in the operational MUSCLE/SADE environment, based on the normalization by the ROLO lunar albedo
Pleiades Orbital Lunar Observations – “POLO”
Starting with Pleiades 1A and 1B commissioning phases in Jan’12 and Jan’13
Strong ability to “catch” the moon
Intensive in-orbit acquisitions have been performed (recom phase = 40°)
1 moon / day during several lunar cycles
several moons / day : every orbit, 2 successively, half an orbit
several configurations
moon simultaneously by PH1A and PH1B
Goals are
to better understand the ROLO model on its operational form
to quantify the potential impact of configuration of acquisition (orientation), spatial sampling and resampling
to derive recommendations
to contribute to improve the use of lunar acquisitions ; phase angle dependency
to develop the use for cross-calibration, inter-band calibration, absolute calibration
See coming presentation 3m

20. Synergic Calibration

21. Indicative behavior – may vary sensitively
What does it mean ?
Indicative behavior – may vary sensitively
Several calibration methods are operational
Statistical approach over natural targets
Desert, Rayleigh, Sunglint, Cloud-DCC, Antarctica, Moon
Each one has its own
behavior : magnitude, spectral, angular, polarized,
l.t. and s.t. stability…
efficiency range
Different aspects of the calibration
Indicative cartography – range of efficiency for each method

22. What does it mean ? See coming presentation 3s
Basic idea = develop the synergic use of several method in order to :
Take advantage of the complementarities of all method
ex : PARASOL for trending and calibration of the entire field-of-view
ex : same for Végétation
Improve the “system calibration” when integrating various results
ex : MODIS-A for absolute calibration
ex: SEVIRI for absolute calibration
Document the confidence from consistency between methods
ex : MERIS for the validation of the calibration
Assess radiometric aspects others that the absolute calibration
ex : SPOT6 & Pleiades for variation of the spectral response within field-of-view
In all cases, accordance between all results is not perfect. Investigate and explain the remaining discrepancies can help
the identification of a radiometric behavior : straylight, spectral response, linearity, mistake…
the improvement of each calibration methods
See coming presentation 3s

23. IASI Cross-calibrations

24. IASI-B Performances IASI-B MetOp-B launch: 17th Sept 2012
IASI-B end of commissioning (RQI): 15th April 2013
Instrument & interferogram acquisition are very stable and work perfectly.
Performances are very good and at the same level as IASI-A
IASI-A
IASI-A is performing very well after >7 years in orbit
No performance degradation or instrument ageing detected
All mission requirements are met : both instrument and processing
The instrument is extremely stable : radiometry, spectral, geometry

25. Massive Cross-calibration
Tool for inter-comparison:
Based on common observations (SNOs or quasi-SNOs)
Operational for the 5 couples of sensors:
IASI-A / IASI-B, IASI-A / AIRS, IASI-A / CRIS, IASI-B / AIRS, IASI-B / CRIS
New outputs for 2014:
Increased size of the dataset (> 1 year for IASI-B)
IASI / CRIS also at high spectral resolution
Spectral inter-calibration of IASI-B / IASI-A
Additional method: IASI-A global mean vs IASI-B global mean
Major result: very accurate cross-calibration!
IASI-B / IASI-A : very close (bias < 0.1K)  continuity of the IASI mission
IASI / AIRS & CRIS : very close (bias < 0.2K)
All are very stable with time
The tool should be operational for a long time (decades for climatic studies)
 Inclusion of future sensors (IASI-C, IASI-NG, etc.)
See presentation 4f