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CNES / EUMETSAT
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IASI Project Group
Satellite interface
CNES
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Intrument
development
CNES
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center
CNES
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CNES
Rationale
Requirements
Rationale // Requirements
Meteorology
Meteorology
Chemistry
Chemistry
Climate
Climate
Requirements
GEOPHYSICAL
VARIABLES
ACCURACY
Temperature profile
1K (cloudfree)
Humidity profile
10%(cloudfree)
Ozone total amount
5%(cloudfree)
Ozone vertical distribution
10%(cloudfree)
Fractional cloud cover
10%
Cloud top temperature
Cloud emissivity
2K
CO, CH4, N2O column
SO2, CFCs
10%
VERTICAL
RESOLUTION
HORIZONTAL
SAMPLING
1 km
25 km (cloudfree)
1-2 km troposphere (cloudfree)
N/A
2 or 3 pieces of independant information
N/A
25 km (cloudfree)
25 km (cloudfree)
25 km
100 km
10%-20%
Sea surface temperature
<0.5K (cloudfree)
25 km
Land surface temperature
1K (cloudfree)
25 km
1%
25 km
Land surface emissivity
METOP
METOP 1 - 2006
• Eumetsat Polar System Elements
• 14 years of operation
METOP 2 - 2010
• >95% reliability on 5 years
METOP 3 - 2015
Spacecraft and Instruments
GRAS
GOME-2
AVHRR-3
HIRS-4
METOP 1/2 only
IASI
AMSU-A1
AMSU-A2
MHS
ASCAT
Instrument Scan Patterns
IASI
AMSU-A
MHS
HIRS/4
AVHRR/3
Rationale
Requirements
Rationale // Requirements
Meteorology
Meteorology
Climate
Climate
Chemistry
Chemistry
Spectral Range
These products can be derived from high spectral resolution infrared sounder
280
R1
R2
R
R4
R5
R6
R7
R8
R9
R10
3
270
Température
Brillance (K)
Brightness
Temperature
260
250
240
230
220
210
O3
CO2
CO CO2
N2O
H2O
200
600
800
1000
1200
1400
1600
1800
2000
2200
CH4
CO2
2400
2600
Wavenumber
cm-1
Nombre d'ondes
(cm-1)
Name
Spectral region
Absorption band
IASI application
R1
R2
R3
R4
R5
R6
R7
R8
R9
R10
650 to 770 cm-1
790 to 980 cm-1
1000 to 1070 cm-1
1080 to 1150 cm-1
1210 to 1650 cm-1
2100 to 2150 cm-1
2150 to 2250 cm-1
2350 to 2420 cm-1
2420 to 2700 cm-1
2700 to 2760 cm-1
CO2
Atmospheric window
O3
Atmosphere window
H2O
CO
N2O and CO2
CO2
Atmosphere window
CH4
Temperature profile
Surface and cloud properties
O3 sounding
Surface and cloud properties
Humidity profile CH4 and N2O column amount
CO column amount
Temperature profile
Temperature profile
Surface and cloud properties
CH4 column amount
2800
Requirements
Requirements
Principle
Principle
Design
Design
Spectral : resolution
Development
Development plan
plan
Performances
Performances
Sub
Sub systems
systems
(1/2)
• Spectral resolution (FWHM)
– The spectral resolution specification is based on
the line spacing in the 650 cm-1 CO2 absorption band
– This spacing is about 1.5 cm-1
• Spectral sampling interval = 0.25 cm-1
B1
B2
B3
Spectral resolution
0.45
0.43
0.35
Wavenumber (cm-1)
2700
2500
2300
2100
1900
1700
1500
1300
1100
900
0.33
700
Spectral width (cm-1)
0.53
Requirements
Requirements
Principle
Principle
Design
Design
Functional description
Sub
Sub systems
systems
Performances
Performances
Development
Development plan
plan
Requirements
Requirements
Principle
Principle
Configuration
Design
Design
Sub
Sub systems
systems
Performances
Performances
Development
Development plan
plan
Performances Tests
PFM Optical vacuum test : Oct 2003
PFM test on-board Metop: Feb 2004
Courtesy EADS
FM2 optical vacuum test : Sept. 2004
FM3 optical
vacuum test :
Oct. 2005
Courtesy Alcatel
System radiometric noise for FM2 :
System Noise 1A — T_CBS=91,7 K — FM2, 4 pixel average
1,0
0,9
•Average of 4 pixel
*27scan angle*40
lines
•Noise for each line
and averaged on 40
lines
0,8
0,7
NeDT at 280 K (K)
•Raw inteferograms
processed with DPS
0,6
0,5
0,4
0,3
0,2
0,1
0,0
645
845
1045
1245
1445
1645
1845
2045
2245
Wavenumber (cm-1)
FM2 (preliminary)
Spécification
After cold box design modifications, ice
contamination issue solved
Radiometric calibration
•
Interpixel & interscan calibration
•
Scan mirror characterization verified
–
•
Impact of the incidence on calibration error
–
–
–
•
External HBB temperature : 85 K
Measured for external HBB in SP= 1, 5, 10, 25 positions
Incidence : -56.67, -50, -41.67, -16.67 deg
External HBB temperature : 294 K & 240 K
Precautions
–
–
Measurement repeated twice in order to detect potential thermal drift in the test setup
Effect of Earth Panel temperature verified
Requirements
Requirements
Principle
Principle
Design
Design
Development
Development plan
plan
Performances
Performances
Sub
Sub systems
systems
Radiometric Calibration : Sensitivity to incidence angle, scan mirror reflectivity, or
thermal drifts
0 .5
0 .4
Raw results for Tscene=220300k
Pixel 1
Radiometric Calibration Error in NedT at 280 K (K)
0 .3
H B B c o a tin g e m is s iv ity lo s s
0 .2
B B C c o a tin g e m is s iv ity lo s s
0 .1
0
-0 .1
-0 .2
-0 .3
Nominal configuration, Cold case
-0 .4
300 K
294 K
280 K
260 K
240 K
220 K
-0 .5
64500
114500
164500
214500
264500
W a v e N u m b e r (m ^ -1 )
Interscan radiometric performance
(Spec. 0.1 K)
Interpixel radiometric performance
HBB at 294 K, Pixel 1
0 .5
0 .5
0 .4
0 .3
Radiometric Calibration Error in NedT at 280 K (K)
Radiometric Calibration Error in NedT at 280 K (K)
0 .4
0 .2
0 .1
0
- 0 .1
- 0 .2
- 0 .3
- 0 .4
- 0 .5
64500
(Spec. 0.1 K)
HBB at 294 K, Pixel 1
0 .3
0 .2
0 .1
0
- 0 .1
- 0 .2
- 0 .3
- 0 .4
114500
164500
W a ve N u m b e r (m ^ -1 )
214500
264500
- 0 .5
64500
P1
P2
P3
P4
114500
164500
W a v e N u m b e r (m ^ -1 )
214500
264500
Radiometric calibration
•
Objectives of the Mission Specification on radiometric calibration are expected to be achiev
•
Absolute Calibration error
–
•
Intercalibration errors at a given time for all geophysical conditions
–
–
•
< 0.5 K
< 0.2 K
4 pixels, all scan directions, all channels
Intercalibration errors over time
–
–
–
< 0.3 K
Random variations (over orbit period)
Long term variations
Session SM 06 22h59 — T_HBB about 299 K, no Non-Linearity correction
Non-Linearity correction efficiency
300,2
300,0
Measurements performed with
CBS temperature = 98,3 K
–
–
299,8
299,6
No NL correction : error = 1 K (B1)
NL correction : degree 2 polynom (B1)
299,4
K
•
299,2
299,0
• Computed from interf at 98,2 K
Æ error < 0.2 K
• Computed from interfs at 93,5 K
Æ error < 0.4 K
298,8
298,6
298,4
298,2
645
845
1045
1245
1445
1645
1845
2045
2245
Wave number (cm-1)
Pixel 1
Session SM 06 22h59 — T_HBB about 299 K, CBS 98,3 K
Non-Linearity correction calculated on same session
Pixel 2
Pixel 3
Pixel 4
Session SM 06 22h59 — T_HBB about 299 K, CBS 98,3 K
Non-Linearity correction calculated on session sm0306150454 (CBS 94 K)
300,2
300,2
300,0
300,0
299,8
299,8
299,6
299,6
299,4
K
K
299,4
299,2
299,2
299,0
299,0
298,8
298,8
298,6
298,6
298,4
298,4
298,2
645
845
1045
1245
1445
1645
1845
Wave number (cm-1)
2045
2245
298,2
645
845
1045
1245
1445
1645
1845
Wave number (cm-1)
Pixel 1
Pixel 2
Pixel 3
Pixel 4
Pixel 1
Pixel 2
Pixel 3
Pixel 4
2045
2245
Spectral measurements during FM2 tests
• An integrating sphere is put in front of the instrument with 2 laser beams injected
simultaneously in it for direct measurement of the Instrument Spectral Response Function
(ISRF)
– In B1 band : laser CO2 (10.59 µm)
– In B3 band : laser HFDF (3.76 µm)
– Laser beams are periodically occulted by a shutter for measurement of the sphere background
emission
– Gives also a direct measurement of the Cube Corner trajectory
• Results are computed from raw interferograms processing
• Test performed with instrument either in
– External Calibration mode
– Allows to acquire a lot of data
– Scan motion is limited to beta compensation law (biggest part of the
dynamic disturbance)
– Normal Operation mode
– Nominal operation mode
– But lower amount of data available
• Sounder IPSF measured with a dedicated OGSE (Geometric Collimator)
Requirements
Requirements
Principle
Principle
Design
Design
Sub
Sub systems
systems
Performances
Performances
Development
Development plan
plan
IPSF
Non conformity % peak to valley measurement
B1
B2
B3
Pixel 3
3,7
3,8
3,7
Pixel 4
6,8
10,0
10,0
Pixel 1
4,6
2,3
3,8
Pixel 2
2,6
3,0
4,4
IPSF measurements close to predictions
Alignment of the interferometer :
axis position < 200 µrad
Cube corner offset : 32 µm
Specification : ± 5%
Requirements
Requirements
Principle
Principle
Design
Design
Sub
Sub systems
systems
Performances
Performances
Development
Development plan
plan
• The Instrument Spectral Resolution
Function which was measured during
the optical vacuum test is similar to
the predicted one.
ISRF shape variation
Spectral
ISRF shape variation
ISRF definition
ISRF definition domain
Requirements
Requirements
Principle
Principle
Design
Design
Sub
Sub systems
systems
Performances
Performances
Development
Development plan
plan
Spectral resolution
0,6
0,5
Spec
laser CO2
laser HF/DF
Spectral width (cm-1)
0,4
0,3
0,2
0,1
0
645
1145
1645
2145
2645
Wave number (cm-1)
Spectral resolution within the specifications for the 4 pixels.
Requirements
Requirements
Principle
Principle
Design
Design
Sub
Sub systems
systems
Performances
Performances
Development
Development plan
plan
Spectral resolution
Maximum spectral shift = 10-5 < spec. (2.10-4)
< 8.3.10-8 in B1
< 2.5.10-8 in B3
Spectral stability well in the spec. (1.10-8)
Shape error index ε2: = quality index on the knowledge of the
Instrument Line Shape = difference between modeled ILS and actual
ILS
< 0.014 in B1 ~ spec. (0.026)
< 0.023 in B3 ~ spec. (0.042)
Within the specifications
Shape error index ε1 : = index on the knowledge of the ISRF
ILS knowledge meets the spec. marginally
Spectral stability :
Gas Cell Measurements during TV test on Metop 2
unexpected
"optimized"
coding tables
NH3
CO
Background = IASI emission
reflected by cell windows
ZnSe windows emissions
Spectral
lines
in B1/B2
interband
Requirements
Requirements
Principle
Principle
Design
Design
Sub
Sub systems
systems
Development
Development plan
plan
Performances
Performances
Geometry
• Pixels geometrical characterisation
• Pixel diameter : compliant with the expected values
• with less than 0.1 mrd difference
• Angular distance (in mrd) between pixel radiometric
• centers (nominal value is 21.63 mrd)
P1P2
P2P3
P3P4
P4P1
B1
21,65
21,61
21,67
21,61
B2
21,52
21,68
21,57
21,55
B3
21,55
21,66
21,57
21,57
• Effective pixel centres included within circles of less than 0.15 mrd in
radius centered on the reference square corners (specification is 2 mrd)
Geometric performances well within the spec.
Requirements
Requirements
Principle
Principle
Design
Design
Sub
Sub systems
systems
Performances
Performances
Development
Development plan
plan
Imager
• Radiometric performances
– NEDT = 0.57 K (specified at 0.80 K).
– Calibration accuracy < 1 K
– Dynamic range : noise better than specification from 200 K to 300 K of scene temperature
• Geometrical performance
– 4 blind pixels (2 % specified)
FM3 Optical vacuum tests
• FM3 OVT tests were carried out successfully at Alcaltel in October 2005
• FM3 showed the same behavior than FM2
• Radiometric performances are slightly better (specially in B1) and confirm the
validity of the models.
• Calibration is as good as for the FM2
• Water contamination is weak and could lead to a loss of about 0.2%/day
• Instrument was accepted by the Technical Review board
• It is now stored at Alcalel for integration on a next MetOp platform
IASI FM3 on ground radiometric performances
sm0510241525
NOISE SPECTRUM LN [40..146]
1.1
P1
P2
P3
P4
NedT at 280 K in Kelvin
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
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
Comparison IASI/AIRS
AIRS on AQUA
IASI on MetOp
Overpass time
13:30
9:30 AM
Spectral coverage
2378 channels
650 to 2670 cm-1 with gaps
(1136-1216, 1614-2170)
8461 channels
645 to 2760 cm-1
continuous
Radiometric performances
See plot
See plot
Spectral Performances
From 0.4 to 2.5 cm-1
From 0.32 to 0.46 cm-1
Geometry
3*3 pixels of 15*15 km2
2*2 pixels of 12*12 km2
0,6
0,5
NEDT
0,4
AIRS perf 280 K
0,3
IASI FM2 1c (jan 2005)
IASI FM2 1C Ratio 1 Resol AIRS
IASI FM2 1C Ratio 1570
0,2
0,1
0
600
800
1000
1200
Wavenumber
1400
1600
1800
CO and CH4
CO retrieval from IASI-Like spectra
0.8
IASI-Like
LARA
-1
radiance (10 W/cm .sr.cm )
0.7
0.6
-7
2
CO
column:
0.5
0.4
2150
2155
2150
2155
2160
2165
2170
2165
2170
0.02
0.00
-0.02
10-15%
2160
-1
wavenumber (cm )
Surface temperature : 258.65 ± 3.1 K
Retrieved CO column : (1.88 ± 0.13) 1018 molecule.cm -2
Estimated CO ground VMR : 154 ppbv
Retrieved CH4 columns along the trajectory
-1
C H 4 (w in d o w : 1 2 4 0 -1 3 2 0 c m )
2
CH4
column:
CH4 Column (molecule/cm )
4,10E + 019
4,00E + 019
3,90E + 019
3,80E + 019
3,70E + 019
3%
3,60E + 019
10000 10500 11000 11500 12000 12500 130 00 13500 14000 14500 15000
tim e (s )
ISSWG 17 Darmstadt 01-03/04/2003
Clerbaux et al
Camy Peyret et al
One day CO with IASI in cloud free conditions
(courtesy C. Clerbaux)
Conclusions
• The last on the ground tests show that
– All performances meet their specifications (sounder and imager)
– IASI proved an excellent behavior
– The performance model is good and can be used in the analyses
• IASI will be an tremendous step forward in meteorology and atmospheric
research
THANK YOU FOR YOUR ATTENTION
More information on
http://smsc.cnes.fr/Iasi