Infrared Atmospheric Sounding Interferometer
IASI FM2 on METOP A
In-Flight Calibration
International TOVS Study Conference 15
4-10, October 2006
Maratea Italy
D. Blumstein1, B.Tournier2, C.Buil1, T.Phulpin1, R.Fjortoft1, F.Bernard1,
T.Carlier1, G.Chalon1 , G.Ponce1, I.Gaudel1, F.Cayla3,
(1) Centre National d'Etudes Spatiales (CNES), Toulouse, France
(2) NOVELTIS, Toulouse, France
(3) SISCLE, France
ITSC-15 – Maratea, 4-10 October 2006
D. Blumstein – CNES DCT/PO/EV
1
Outline
‰IASI Project status
‰Overview of the IASI L1 Cal/Val
‰Implementation
¾ Partnerships
¾ Planning
ITSC-15 – Maratea, 4-10 October 2006
D. Blumstein – CNES DCT/PO/EV
2
IASI Project Status
Since last ITSC conference
‰ Instruments
¾ IASI FM2 on METOP A : ready for launch
¾ FM3 Vacuum Test completed in October 2005 (see results synthesis)
¾ PFM Refurbishment (PFM is the first IASI model Æ tested in 2003)
ƒ Anti-contamination bellow, detectors
¾ PFM-Refurbished Vacuum Test on-going
ƒ Beginning of pumping : 6th of October 2006
ƒ First optical measurement awaited on 14th of October
‰ System
¾ Validation as part of the EPS system validation : start in October 2005
ƒ Reception and processing of IASI L0 data (Eumetcast terminal) : OK
ƒ Participation to SSVT (end-to-end tests with the satellite) : OK
¾ Rehearsal for in-flight commissioning activities : OK
¾ System : ready for launch
ITSC-15 – Maratea, 4-10 October 2006
D. Blumstein – CNES DCT/PO/EV
3
IASI FM3 OV Test results
¾ Better than FM2
especially in B1
‰ Calibration
¾ Spectral and
¾ Radiometric
very good (as FM2)
sm0510241525
NOISE SPECTRUM LN [40..146]
1.1
P1
P2
P3
P4
1
NedT at 280 K in Kelvin
‰ Radiometic noise
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
‰ Low rate of ice
contamination
¾ As for FM2
ITSC-15 – Maratea, 4-10 October 2006
0.1
0
800
31-10-05 14:32
1000 1200 1400 1600 1800 2000 2200 2400
wave numbers (cm-1)
IASI FM3 Optical Vacuum Test
CNES DCT/PO/EV
D. Blumstein – CNES DCT/PO/EV
4
Overview of the IASI L1 Cal/Val (1/3)
‰ The IASI L1 CalVal Plan describes the process, methods and data
that will allow
¾ To obtain the ultimate performances of Level 1 IASI products (calibration),
¾ To demonstrate these performances (validation)
during flight operations
‰ General goal of the Level 1 Cal/Val activities is to ensure that
¾ after the commissioning and thereafter during the mission lifetime,
¾ the IASI Level 1 products are compliant with their specifications
ƒ radiometric, spectral and geometric performances
‰ IASI Level 1 Cal/Val performed under CNES responsibility
¾ In close cooperation with EUMETSAT
¾ IASI TEC
ITSC-15 – Maratea, 4-10 October 2006
D. Blumstein – CNES DCT/PO/EV
5
Overview of the IASI L1 Cal/Val (2/3)
‰ Use of already developed, state-of-the-art methods applicable to
every infrared sounder of the same class of performance
‰ Cal/Val activities will begin when first goal of the commissioning
phase will be achieved : to establish a stable and nominal behavior
of the system
ƒ Health parameters of the instrument monitored by the EPS/CGS
ƒ All the needed products verified and available in the IASI TEC
ƒ Problems, if any, either from hardware or processing clearly identified and flagged
‰ IASI Level 1 Cal/Val activities and performance monitoring will be
mostly performed in the IASI TEC using
ƒ Products obtained via a Eumetcast terminal (PFS format)
ƒ Reference version (latest update) of the Level 1 processing software
‰ In-flight Cal/Val activities broken in 3 (approx.) independent classes
ƒ Geometry, spectral and radiometry (see next slides)
ITSC-15 – Maratea, 4-10 October 2006
D. Blumstein – CNES DCT/PO/EV
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Overview of the IASI L1 Cal/Val (3/3)
0
1
2
3
4
5
6
7
8
Month
IIOV
L1 Cal/Val A
L1 Cal/Val B
L1 Cal/Val C
L2 Validation
Metop A
launch
‰ Accuracy of the validation and diversity of the conditions in which the validations
are performed increase with time
¾ Type of reference measurements and their accuracy evolve accordingly
ƒ stand alone IASI measurements
ƒ comparison with other spaceborne instruments
ƒ meteorological soundings and dedicated correlative measurements
• balloon, aircraft TBC in // with L2 validation
ITSC-15 – Maratea, 4-10 October 2006
D. Blumstein – CNES DCT/PO/EV
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Instrument features supporting Cal/Val activities (1/2)
¾ Normal Operation mode : 30 ground footprints (4 pixels each) every cycle (8 sec)
‰ 2 features of the instrument will be used intensively for Cal/Val activities
¾ External Calibration Mode Î Viewing dir. (i.e. Scan Position : SP) remains fixed
ƒ On-board radiometric calibration is performed as in N.Op mode
ƒ Fixed position can be changed at each cycle : SP=1..30 (30 Earth Views), BB, CS1, CS2 or SM
¾ Verification Data Selection (in N.OP mode and in E.Cal mode)
ƒ 1 raw interferogram (over 408) is available in scientific telemetry every 8 sec
ƒ Pixel Number, Step Number and Spectral Band (PN, SN, SB) which define this interferogram
can be modified every 8 sec (periodic pattern modified by TC VDS)
ITSC-15 – Maratea, 4-10 October 2006
D. Blumstein – CNES DCT/PO/EV
8
Instrument features supporting Cal/Val activities (2/2)
‰ Raw interferograms transmitted to the ground (sampled : 1/408)
¾ Including continuous part of the signal (for NL correction)
‰ Synthesis of imaginary part of the on-board calibrated spectra
‰ Spectral Overlaps B1/B2, B2/B3 (under sampled : 1/120)
¾ Direct comparison of the calibrated spectra measured by 2 different detectors
ƒ Spectral
ƒ Radiometric
‰ 2 Cold Space Calibration Views : CS1, CS2
‰ External Calibration Mode with Earth View Target
¾ Spatial Oversampling
¾ (Quasi) Simultaneous measurement of the same scene by 2 different pixels
‰ IASI Integrated Imager (IIS)
ITSC-15 – Maratea, 4-10 October 2006
D. Blumstein – CNES DCT/PO/EV
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IIOV Phase
‰ Objective
¾ Putting IASI into functional mode
¾ Functional verification of instrument behavior
¾ Commandability/Observability
‰ Instrument performance not necessarily optimal
¾ Instrument state as seen during ground testing (as close as possible)
ƒ Detectors temperature
ƒ On-board processing parameters
¾ Transition to optimal detectors temperature at the end of IIOV phase
‰ Overlap between Cal/Val Phase A and IIOV
¾ Assessing some instrument performances with preliminary measurements
¾ On board processing parameter optimization (uploaded at the end of IIOV)
ƒ Mainly : NL corrections, Band Limits, Coding Tables
ITSC-15 – Maratea, 4-10 October 2006
D. Blumstein – CNES DCT/PO/EV
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Geometrical performances assessment
Activation & Evaluation
Geometry
Early validation
Localisation - co-registration
IIS/AVHRR
- co-registration
IIS/sounder
- validation of navigation
- validation of radiance
spatial distribution in
sounder IFOV
- line of sight short term
stability
- co-registration
IIS/AVHRR
Æ stability check
- co-registration
IIS/sounderÆ stability
check
IPSF
- sounder inter band
co-registration
- approximate check
in depth validation
- validation of radiance
spatial distribution in
sounder IFOV (from Level
2 feedback)
- sounder inter band
co-registration
Æ stability check
‰ Navigation of IASI products based on co-registration of IIS images and soundings
with AVHRR products (Level 1B AVHRR full resolution, fully navigated)
‰ First version of IIS-sounder co-registration offset available from on-ground
calibration
‰ Validation done wrt to highly contrasted scenes (e.g. coastlines)
ITSC-15 – Maratea, 4-10 October 2006
D. Blumstein – CNES DCT/PO/EV
11
Spectral performances assessment
Spectral
Activation & Evaluation
Early validation
in depth validation
calibration
- verify operational calibration
(B3)
- approximate validation
in B1, B2 using synthetic
spectra (climatology)
- validation of spectral
calibration in
B1,B2,B3
(use of NWP profiles)
- validation w.r.t. IASI
balloon spectra
ISRF
- Cube Corner Offset
Æ stability check
- validation of ISRF not
considered as part of
“early validation”
- analysis of residuals
w.r.t. IASI balloon
spectra
‰ Use of off-axis detectors induces possible spectral calibration defects
¾ Correction achieved by using the atmosphere itself (CO2 2350-2380 cm-1 in B3 band)
¾ This correction is extrapolated to the whole IASI spectral band (very few parameters
are needed to model the Michelson interferometer)
‰ GEISA/IASI used as the reference spectroscopic database
‰ It is expected that validation can be achieved using a Line by line radiative
transfert model (4A will be used for validation at 3 wavenumbers in each 3
bands)
¾ Selection of scenes with very good spatial uniformity (clear sky on sea) is necessary
ƒ AVHRR images analysis and subsequent selection of the corresponding IASI products
ITSC-15 – Maratea, 4-10 October 2006
D. Blumstein – CNES DCT/PO/EV
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Radiometric performances assessment
Activation & Evaluation
Radiometry - non-linearity in-flight
estimation
- noise (sounder & IIS)
- residual analysis of
the on-board radiometric
calibration
- inter pixel calibration
- inter band calibration
Early validation
in depth validation
- Cold Space views CS1 /CS2
verification
- approximate validation of calibration
w.r.t. AVHRR (B1 & B3).
- limited validation of B2 through
interband B1/B2 & B2/B3 overlaps
- idem w.r.t. HIRS
- direct comparison w.r.t AIRS radiance
- micro-window analysis
- IIS calib. w.r.t AVHRR
- intercalibration with
AIRS radiances
- statistical analysis of the
residuals from radiance
assimilation in NWP
models
- sounder noise covariance
matrix in-flight
‰ Radiometric calibration of the IASI sounder level 1 products based on
¾ Cold and Hot calibration views measured each 8 sec
¾ Non-Linearity correction performed on the raw interferograms (on-board)
¾ Initial radiometric calibration (on-board) and post-calibration (in level 1 processing)
ƒ First version of lookup tables used to implement these corrections known from the pre-launch
calibration of the instrument Î to be updated in-flight (detectors temperature, etc.)
‰ Early validation of the radiometry based on comparison between IASI and other
instruments on-board METOP + other sounder (AIRS)
ƒ when geometry allows it
‰ In depth validation Îsee slide on analysis of NWP assimilation residuals
ITSC-15 – Maratea, 4-10 October 2006
D. Blumstein – CNES DCT/PO/EV
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How can NWP Centers support L1 Cal/Val activities ?
‰ IASI Radiometric calibration accuracy specifications very stringent
¾ Absolute : 0.5 K
¾ Relative :
ƒ 0.2 K between the 120 soundings of a scan line and all 8500 channels
ƒ 0.15 K short term drift (orbital period)
ƒ 0.15 K long term drift (lifetime)
‰ It is believed that validation at these level of accuracy can be
approached through statistical analysis of NWP residuals
¾ Diversity of geophysical conditions
¾ Diversity of models and radiative transfer models
‰ Please, consider joining the effort already initiated with ECMWF, UK
MetOffice, Meteo France and EUMETSAT
¾ Thomas Auligne paper will be redistributed on ITWG NWP mailing list
¾ Fiona Hilton presentation
ITSC-15 – Maratea, 4-10 October 2006
D. Blumstein – CNES DCT/PO/EV
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Direct Partnerships
‰ METEO FRANCE (CMS)
¾
¾
¾
¾
Cloud Mask software (MAIA) implemented in TEC
Cloud Mask, expertise for Clear Sky Validation
Radiometric Intercalibration with HIRS, AVHRR
NWP 3D fields
‰ Laboratoire de Physique Moléculaire et Applications (CNRS/LPMAA)
¾ IASI Balloon (mainly spectral validation)
‰ ECMWF, UK MetOffice, METEO FRANCE and others
¾ Daily Monitoring of NWP residuals
¾ Providing if necessary detailed residuals files for investigation
ITSC-15 – Maratea, 4-10 October 2006
D. Blumstein – CNES DCT/PO/EV
15
Planning
Oct
2006
Nov
2007
Dec
Jan
Fev
Mar
Apr
May
June
IIOV
L1 Cal/Val A
L1 Cal/Val B
Balloon
L1 Cal/Val C
L2 Validation
Real time IASI L1 products
Metop A
launch
1 IASI
orbit
off line
L1 products
real timedelivery
(selected users)
¾ IASI Balloon campaign belongs logically to Cal/Val C
ƒ Has been advanced for operational constraints
ƒ Key point planned in January to confirm the flight
ITSC-15 – Maratea, 4-10 October 2006
D. Blumstein – CNES DCT/PO/EV
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End
‰ Visit the CNES IASI Web site
¾ http://smsc.cnes.fr/IASI
Thank you
ITSC-15 – Maratea, 4-10 October 2006
D. Blumstein – CNES DCT/PO/EV
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