Overview of the main activities performed - · Patrice Henry, Bertrand Fougnie, Sophie Lach érade, Denis ... SADE access through CNES scientific mission website

GSICS – May 2012 Washington

CNES Report

GSICS 12 th Executive Panel Meeting

Patrice Henry, Bertrand Fougnie, Sophie Lachérade, Denis Jouglet, Eric Péquignot

2 GSICS – March 2012 Beijing

Overview of the main activities performed since the last Executive Panel Meeting

■ Crosscalibration of visible channels over stable sites w Improvement of sites characterization (desert + Antarctica)

• BRDF modeling using PARASOL/POLDER • DTM and Structure using Pleiades

w LEO/GEO crosscalibration ■Lunar Calibration w Intensive lunar acquisitions with Pleiades

■Calibration over Rayleigh Scattering w Improvement of calibration zones climatology and application to SeaWiFS calibration w Method adaptation for GEO calibration w Assessment of the error budget

■SADE database w Reprocessing and populating with new data w Opening to calibration community users

■ IASI calibration w Operational IASI/AIRS crosscalibration w Preparation for IASIB calibration


CrossCalibration of Visible Channels

over Stable Sites


Calibration sites characterization

■Whatever the (cross)calibration method, a refined knowledge of the surface reflectance of calibration sites is needed

■ Improve radiometric characterization w Spectral behavior for the full reflective domain (extension to UV or SWIR)

• MODIS or MERIS from SADE database + GOME, Hyperion, Sciamachy

w Bidirectional properties (solar and viewing geometries) • PARASOL data from SADE database

w Seasonal variation and long term stability

• time series from SADE database

w Spatial homogeneity

• MODIS or MERIS full resolution images, SPOT images

w Surface structure

• highresolution images: stereoscopic acquisitions (SPOT), SRTM data, Pléiades


Bidirectional properties of desert sites

■Bidirectional properties w Investigation using PARASOL data w Which BRDF model best fits measurements à Snyder w Derive Snyder model’s parameters for all sites

Algeria3 – Parasol 490nm

Reflectance Difference Measure Model

black dots = measurements


Bidirectional properties of Antarctica sites

Huge amount of PARASOL data (x 2.5 comparing to desert)

PARASOL geometry over Dôme C BRDF model over Dôme C (SZA=60°)

Dôme C – Parasol 565nm


Desert sites seen by PLEIADES

ARABIA1 MODIS

SRTM


Calibration sites ALGERIA5 MODIS

SRTM

Desert sites seen by PLEIADES


DOME C

Antarctica sites seen by PLEIADES


DOME C



DOME 1



■ Crosscalibration over desert sites = operational method for LEO w still improving method w updated results: VGT, MODIS, PARASOL, MERIS… w extension to SeaWiFS: in progress w uncertainty assessment w operational environment SADE database (+ Muscle tools)

■Extension to GEO w SEVIRI data = new type of data (fixed VZA, variable SZA) w Data to be inserted into SADE w Method to be adapted: initiated in 2010 (presented at Eumetsat conf.), ongoing activity

■Crosscalibration LEO/GEO w Method will probably need some optimization (geometrical coupling)

LEO/GEO crosscalibration over desert sites


Lunar Calibration

GSICS – March 2012 Beijing

A new site (for us…)


Starting Moon calibration with Pléiades

380 m resolution


Full Moon

Native PAN + XS acquisitions – no need for geometrical resampling agility + very accurate steering of LOS

Regular acquisition of the Moon – fixed phase of 40° every month 2 views in 50 min – phase step = 0.4°

Experimental acquisitions:

daily acquisitions over one lunar cycle : from 92° to 104° 2 views per day in 50 min – phase step = 0.4° 30 images from 31/01/12 to 15/02/12 à document the error budget for each phase

+ investigate extrapolation slightly over 90° Has been reproduced with the March lunar cycle

stereoscopic acquisition allowed using the 2 views


PLEIADES Acquisitions of the MOON


Lunar calibration: first results

Preliminary Pléiades calibration (blue band) using ROLO model

0.92

0.94

0.96

0.98

1

1.02

1.04

1.06

150 100 50 0 50 100 150 Moon phase angle

Ak(t)/Ak(to)

Feb. cycle April cycle

Relative calibration results normalized by the first Moon acquisition in January 2012


Calibration over

Rayleigh Scattering


Fougnie et al., "Climatology of Oceanic Zones Suitable for In flight Calibration", 2010.

Oceanic sites for calibration


Comparison historical/operational versus updated climatology • Historical-operational = 1999 Recent update = 1999-2007 • SeaWiFS reprocessing (calib. adjustment + algo improvements)

From Fougnie et al., "Climatology of Oceanic Zones Suitable for Inflight Calibration", 2010.

Blue = ope clim 99 Red = new clim 9907

SouthEast Pacific 4 subareas

Surface refle

ctan

ce 443nm

Month

Depending on bands and sites • smoother seasonal variation (more realistic) • small bias (direct impact of

cal update) North Pacific 3 subareas

Climatology updating


510 490

443 412

555 670

Statistics: 3463 points year 2000

band ratio stdev 412 1.003 0.018 443 0.995 0.017 490 1.004 0.011 510 0.990 0.009 555 0.993 0.009 670 0.999 0.008

Calibration results plotted vs measured radiance (year 2000)

Perfect consistency - within 0.5 to 1% - very small dispersion - for all bands

1/ Validation of cal method (part of error budget)

2/ Confirmation of SeaWiFS official calibration

SeaWiFS calibration over Rayleigh Scattering


Absolute Calibration over Rayleigh Scattering • same method can be used

for MODIS and SEVIRI • currently used for MERIS,

PARASOL, VGT, SeaWiFS…

Experimental phase (2009) • from Jolivet et al. from a CNES R&T • Extension to extreme airmass

Processing transferred to SADE (Muscle) • SEVIRI archive into SADE • operational processing • to be completed end 2012

From Jolivet et al., Rayleigh calibration of SEVIRI, Eumetsat conference, 2009.

SEVIRI Red band

SEVIRI calibration over Rayleigh Scattering


Identification of contributors • first, global contributions are quantified for predefined datasets:

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

VGT / B0

VGT / B2

VGT / B3

PARASOL / 443

PARASOL / 490

PARASOL / 565

PARASOL / 670

PARASOL / 765

PARASOL / 865

MERIS / 412

MERIS / 442

MERIS / 490

MERIS / 510

MERIS / 560

MERIS / 620

MERIS / 665

SEVIRI / R

Absorption gazeuse

Contribution marine

Contribution aérosols

Contribution Rayleigh

Gaseous absorption

Marine contribution

Aerosol contribution

Rayleigh contribution

Assessing the error budget


Prelim

inar

y ve

rsion


SADE Database


■ Few feedbacks from betausers but positive…

■ Complete reprocessing of SADE exported files up to end 2011 w VGT1 updated calibration w New sensors (Terra/Modis, Landsat 7, Theos, SeaWiFS) w New MERIS reprocessing (3 rd )

■ SADE access through CNES scientific mission website w http://smsc.cnes.fr/CALIBRATION/ (free access) w Password mandatory (for “SADE data” downloading only) w Password delivery : contact Aimé Meygret (limited to CEOS & GSICS space agencies)

SADE opening to GSICS and CEOS




IASI Calibration


IASI / AIRS : some results

■ Tool operational for systematic download and comparison of data

■ SNO with a large tolerancy on the time delay between IASI & AIRS (< 20min)

■ Monitoring of calibration with time: è IASI and AIRS radiometric calibration

are very close and stable

■ Dependency of ΔT with w Scene temperature (surface or atmo) w Scene temperature heterogeneity w IASI / AIRS temporal delay w …

■ Possibility to focus the studies on an data subset (selection criteria: temperature, heterogeneity, etc.)

Example – Comparison Channels 5 & 32 using broad pseudochannel approach


MetopA/IASI1 MetopB/IASI2

~39°

Common zone

16km

10km

IASIA & IASIB intercalibration

■ MetOpA / MetOpB ■Same orbit but time delay of 50 min


■ Relative location of the tracks :

èIASIA and IASIB have common observations • For each IASIA line, with the IASIB previous and following tracks • Possible for all latitudes • Offnadir observations (except at the poles à Nadir Observations) • 50 min systematic delay between IASIA and IASIB

IASIA / IASIB : method

IASIA IASIB

Nadir IASIA 1

Nadir IASIA 2

Nadir IASIB 1


■ Use of these common observations, focusing on: w The columns of similar viewing absolute angles (same atmospheric thickness) w The most relevant regions (homogeneous and stable surface temperature)

■ Data processing: based on the IASI / AIRS software w IASI 1C data w Zonal mean for IASIA and IASIB spectra w ΔT Comparison for each IASI channel and for broad pseudochannels (avoid any spectral bias) w An atmosphere correction by double differences will be available if necessary, using RT model + meteo profiles

■ Plan to perform ‘circular’ validation w IASIA/IASIB using ‘Common not nadir Observation’ w IASIA/AIRS using SNO w IASIB/AIRS using SNO wAs far as possible: use of the same areas

IASIA / IASIB : method


IASI/2 (dν/ν=10 6 ) Absolute calibration

IASI (1km) Geolocation accuracy Navigation

IASI (25km) Spatial sampling

IASI (12km) Spatial resolution Geometry

IASI/2 (0.25K@280K) Absolute calibration

IASI/2 NedT@280K (α 1/SNR) Radiometry

IASI/2 (0.25 cm1 ) i.e. 16921 channels Spectral sampling

IASI/2 (0.125 cm 1 ) Spectral resolution

IASI ([6452760] cm 1 or [15.53.62] µm) Continuous spectral coverage Spectral

Objective Specification (L1C)

Preparing IASI New Generation

■ Performances improvement for IASING

■ CNES commitment to provide IASING to EUMETSAT ■2 industrial phase A studies in parallel (2 different instrument concept…)


Thank you for your attention

Documents

Overview of the main activities performed - · Patrice Henry, Bertrand Fougnie, Sophie Lach érade, Denis ... SADE access through CNES scientific mission website