1 Bertrand Fougnie Patrice Henry, Sophie Lachérade, Philippe Gamet Processing team CNES-DCT/ME Synergic Calibration Crossing Multiple Methods GSICS Annual Meeting 4-8th March 2013, Williamsburg, VA

Summary 2  Context  CNES Calibration Tool Box  Outlines  advantage / drawbacks or limitations  Application for PARASOL end-of-life reCalibration  Application in the OCR-Virtual Constellation context  Application to SEVIRI Synergic Calibration Crossing Multiple Methods

3 Context  In the past years, several calibration methods were developed using natural targets  various calibration methods, different approaches  operational configuration now available  In the past years, several sensors provided extensive calibration time series  a large experience has been developed on the use of each method  a feedback exists on the real advantage and limitations

4 CNES Calibration Tool Box (MUSCLE)

5 SADE/Muscle – The Operational Arsenal  Several calibration methods are operational  Desert, Rayleigh, Sunglint, Cloud-DCC, Antarctica, Moon Deserts Rayleigh SunglintDomes DCCMoon

6 SADE/Muscle – The Operational Arsenal Muscle / SADE (Tools) (Database)

7 Outlines, strengths, limitations  Some outlines, strengths, limitations Green = a very important advantage

8 Outlines, strength, limitations  Several calibration methods are operational  Desert, Rayleigh, Sunglint, Cloud-DCC, Antarctica, Moon  Each target has its own behavior :  Magnitude: from very dark to very bright  Spectral shape : from white to very pronounced  Angular signature : from nearly uniform to large BRDF  Polarized properties : from non-polarized to nearly fully polarized  Short-term stability : from variable to fully stable  Long-term stability : from seasonal variable to fully stable  So efficiency range … Indicative behavior of targets

9 Synergic : What does it mean ?  So the observation is :  Calibration methods are like “Bordeaux Wines” : every method is good but in fact, all the methods show limitations  it is impossible to address all calibration/radiometric aspects (the so-called “system calibration”) with one single method  Basic idea = develop the synergic use of several method in order to :  take advantage of the complementarities of all method  document the confidence from consistency between methods  improve the “system calibration” when integrating various results  assess radiometric aspects others that the absolute calibration  “Indicative” cartography – range of efficiency for each method

10 Application PARASOL end-of-life reCalibration

11 The PARASOL Context  Recent example#1 = PARASOL :  bidirectional polarimeter : ± 50° wide fov optic + 2D focal plane 1400x2000km²  up to 16 viewing directions  9 channels, and 3 polarized (490, 670, and 865nm)  a “3M” concept Multi-directional + Multi-spectral + Multi-polarization  No on-board calibration device in-flight calibration only based on natural targets (Fougnie et al., IEEE-TGARS, ) Multi-method Synergic Approach  Launched in dec-2004, on A-train up to end-2009 currently drifting, End-of-life in September 2013  3MI follow-on serie of instrument is expected on Post-EPS (~2018) 2000 km along-track 1400 km cross-track Satellite PARASOL image zenith viewing angle ⇒ No on-board calibration device

12 PARASOL end-of-life reCalibration  Synergic calibration for the in field-of-view evolution  Clouds suppose the reference band is stable (765nm)  Desert (reference = POLDER1) suggest it is not the case  Rayleigh (absolute reference) confirm that for 75% of the coverage – sufficient to generalize  Confirmed also for most of other bands Absolute calibration over Rayleigh Interband over DCC (ref=765) Intercalibration over desert (ref=POL1) Band 490nm The black hole from band 765nm Calibration result versus pixel on the CCD matrix Black hole – confirmed by Rayleigh  Instrument-765 Bright banner – not confirmed  method artefact

13 PARASOL end-of-life reCalibration  Synergic calibration for the temporal monitoring  670nm band aging model adjusted using clouds  Validated over Rayleigh, Sunglint, Domes, Desert  Not the same for 1020 nm band Calibration versus month

14 PARASOL end-of-life reCalibration  Synergic calibration for the calibration adjustment  Confidence where consistency is observed : e.g. 865nm  Investigation to be conducted when curious behavior are observed : e.g. 443nm  Explanation to be provided when existing : e.g. 565nm, 765nm  Remaining investigations to improve the results : e.g. 490nm, 670nm  Final adjustment = best compromise (TBC) Still under investigation

15 Application Ocean Color Virtual Constellation

16 Ocean Color Virtual Constellation  Recent example#2 : OCR-VC needs for calibration  OCR-VC = still the same idea : toward a unified and homogeneous longer time series (+ global coverage)  Mostly LEO, but GEO are coming »MODIS-Aqua »MERIS-Envisat »POLDER-PARASOL »SeaWiFS-SeaStar  Apply as much as possible all methods to every sensors Multi-sensor Synergic approach (in addition to Multi-method)  Current status of the implementations Fougnie et al., 2012, In-Flight Calibration of Space Sensors Through Common Statistical Vicarious Methods : Toward an Ocean Color Virtual Constellation, Ocean Optics XXI

17 Ocean Color Virtual Constellation  Recent example#2 : Very rich diagnostic comparisons  Rayleigh/Sunglint/Desert-MODIS  Very powerful validation for MERIS  Behavior to be understood for PARASOL and SeaWiFS instrumental // algorithm parts  To be enriched soon with additional results (methods and sensors)

18 Application SEVIRI/MSG2

19 Application to GEO  Recent example#3 : Same approach for GEO sensor  Rayleigh, Desert, Sunglint  Under investigation »Presentation 4b on SEVIRI Calibration

20 Final comments  Cross different methods =  a powerful diagnostic whatever the nominal calibration method  a coverage of most of the system calibration aspects (absolute, angular, spectral, temporal, cross)  A good consistency between multiple methods =  a good confidence on the final calibration (nominal + validation)  a “realistic” estimation of the final calibration accuracy (as if the theoretical evaluation of the error budget for the nominal cal method is excellent)  no radiometric artifacts remain : such as non-linearity, straylight, offset, polarization, inside the field-of-view…  Differences between results from methods =  need investigation to understand why – radiometric artifact  require a good knowledge of the instrumental characteristics  The state of the art cannot be reached through only 1 method  A good consistency between sensors AND for multiple methods =  a very high level of confidence can be claimed