iasi on metop on-ground calibration of the fm2 instrument · itsc-14 – beijing, 25-31may. 2005 d....

ITSC-14 – Beijing, 25-31May. 2005 1D. Blumstein – CNES DCT/PO/EV

Infrared Atmospheric Sounding Interferometer

IASI on METOPOn-Ground Calibration of the FM2 Instrument

International TOVS Study Conference25-31, May 2005

Beijing China

D. Blumstein1, B.Tournier2, T.Carlier1, T.Maciaszek1, T.Phulpin1, G.Chalon1, P.Astruc3, D.Miras3, D.Siméoni3

(1) Centre National d'Etudes Spatiales (CNES), Toulouse, France(2) NOVELTIS, Toulouse, France(3) ALCATEL SPACE, Cannes, France


Outline

Key Performance specifications

On-ground characterization of IASI FM2First IASI instrument in flight (on METOP 2)

IASI Program Status


Key performances specifications

Radiometric sensitivityApodized and non-apodized spectra

Radiometric accuracyAbsolute accuracyRelative accuracy (at a given time)

Between pixels, channels, viewing direction

Stability

Spectral & geometrySpectral calibrationSpectral response functionPoint Spread Function ( & interband registration)


AVM result — IASI FM2 Noise Spectrum (NedT at 280 K) — Session SM0410060647 — CBS 91.7 K

0,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

64500 82500 100500 118500 136500 154500 172500 190500 208500 226500

Wavenumber (m^-1)

Ned

T at

280

K (K

)

Noise Spectrum in NedT at 280 K after drift correction - P4 - c10693_avm_SM0410060647Noise Spectrum in NedT at 280 K after drift correction - P1 - c10693_avm_SM0410060647Noise Spectrum in NedT at 280 K after drift correction - P3 - c10693_avm_SM0410060647NedT at 280 KNoise Spectrum in NedT at 280 K after drift correction - P2 - c10693_avm_SM0410060647NedT at 280 K

Measured radiometric sensitivity

IASI FM2 testing in vacuumDetectors temperature 91.7 KMeasured on blackbodyNo evolution of noise (ice cont.)

Loss of transmission : 1.5 % at 850 cm-1 over a period of 6 daysEquivalent to the absorption by a 40 nm thin film of water ice

non apodized (293 K scene)

measurements

B1 B3B2

Measurement SM0410111609 — Pixel 3Effect of scene temperature on B3 noise (scene at 240 & 280 K)

0,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

1900 1950 2000 2050 2100 2150 2200 2250 2300 2350 2400Wavenumber (cm-1)

NeD

T at

280

K (K

)

240 K 280 K spec

NeDT in K (at 280 K)

Mission radiometric performance in NeDT — T_CBS=91,7 K — (IASI FM2 OV Test)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

645 845 1045 1245 1445 1645 1845 2045 2245Wavenumber (cm-1)

NeD

T at

280

K (K

)

Spécification FM2 (Delta-QR)

apodized + pseudo-noise


- 0 .5

- 0 .4

- 0 .3

- 0 .2

- 0 .1

0

0 .1

0 .2

0 .3

0 .4

0 .5

6 4 5 0 0 1 1 4 5 0 0 1 6 4 5 0 0 2 1 4 5 0 0 2 6 4 5 0 0

W a v e N u m b e r ( m ^ - 1 )

Rad

iom

etric

Cal

ibra

tion

Erro

r in

Ned

T at

280

K (K

)

3 0 0 2 9 4 2 8 0 2 6 0 2 4 0

B B C c o a t in g e m is s iv it y lo s sH B B c o a t in g e m is s iv i t y lo s s

Measured radiometric accuracy (1/4)Session SM 06 22h59 — T_HBB about 299 K, no Non-Linearity correction

298,2

298,4

298,6

298,8

299,0

299,2

299,4

299,6

299,8

300,0

300,2

645 845 1045 1245 1445 1645 1845 2045 2245Wave numbers (cm-1)

Brig

thne

ss te

mpe

ratu

re (K

)

Pixel 1 Pixel 2 Pixel 3 Pixel 4

Session SM 06 22h59 — T_HBB around 299 K, Non-Linearity correction applied

298,2

298,4

298,6

298,8

299,0

299,2

299,4

299,6

299,8

300,0

300,2

645 845 1045 1245 1445 1645 1845 2045 2245Wave numbers (cm-1)

Brig

thne

ss te

mpe

ratu

re (K

)

Pixel 1 Pixel 2 Pixel 3 Pixel 4

IASI FM2 testing in vacuumNeed for NL correction in B1 bandDT < 0.25 KTarget in nadir position

Result valid for other incidencesPost-calibration done by Level 1 proc. to achieve "differential" requirements

Between pixels, scan views or channels

B1

NL (B1)corrected

-0 .5

-0 .4

-0 .3

-0 .2

-0 .1

0

0 .1

0 .2

0 .3

0 .4

0 .5

6 4 5 0 0 1 1 4 5 0 0 1 6 4 5 0 0 2 1 4 5 0 0 2 6 4 5 0 0

W a v e N u m b e r (m ^ -1 )

Rad

iom

etric

Cal

ibra

tion

Erro

r in

Ned

T at

280

K (K

)

3 0 0 K2 9 4 K2 8 0 K2 6 0 K

2 4 0 K2 2 0 K

H B B c o a tin g e m is s iv ity lo s s

B B C c o a t in g e m is s iv i ty lo s s

Tscene : 240 – 300 KPixel 1, Redundant Conf., Hot Case

Tscene : 220 – 300 KPixel 1, Nominal Conf., Cold Case


Measured radiometric accuracy (2/4)

Raw measurements versus model comparison Pixel 1Nominal Conf.Cold Case

-0 .5

-0 .4

-0 .3

-0 .2

-0 .1

0

0 .1

0 .2

0 .3

0 .4

0 .5

6 4 5 0 0 1 1 4 5 0 0 1 6 4 5 0 0 2 1 4 5 0 0 2 6 4 5 0 0

W a v e N u m b e r (m ^ -1 )

Rad

iom

etric

Cal

ibra

tion

Erro

r in

Ned

T at

280

K (K

)

3 0 0 K2 9 4 K2 8 0 K2 6 0 K

2 4 0 K2 2 0 K

H B B c o a t in g e m is s iv ity lo s s

B B C c o a t in g e m is s iv ity lo s s

Radiometric Calibration Error Model — Nominal configuration, Cold CaseT_env HBB = 280 K, T_env BBC = 275 K, T_env CBB = 230 K

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

645 1145 1645 2145 2645

Wave Number (cm-1)

DT

at 2

80 K

(Kel

vin)

220 K 240 K 260 K 280 K 294 K 300 K



- 0 .5

- 0 .4

- 0 .3

- 0 .2

- 0 .1

0

0 .1

0 .2

0 .3

0 .4

0 .5

6 4 5 0 0 1 1 4 5 0 0 1 6 4 5 0 0 2 1 4 5 0 0 2 6 4 5 0 0

W a v e N u m b e r ( m ^ - 1 )

Rad

iom

etric

Cal

ibra

tion

Erro

r in

Ned

T at

280

K (K

)

3 0 0 2 9 4 2 8 0 2 6 0 2 4 0

B B C c o a t in g e m is s iv i t y lo s sH B B c o a t in g e m is s iv i t y lo s s

Raw measurements versus model comparison Pixel 1Redundant ConfHot Case

Radiometric Calibration Error Model — Redundant configuration, Hot CaseT_env HBB = 295 K, T_env BBC = 285 K, T_env CBB = 230 K

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

645 1145 1645 2145 2645

Wave Number (cm-1)

DT

at 2

80 K

(Kel

vin)

240 K 260 K 280 K 294 K 300 K



More in-depth verifications performed during the testScan angle effect verifiedInterpixel & interscan calibrationSensitivity to thermal drifts

Simulation of Entry/Exit of eclipse

Mission Objectives on radiometric calibration are expected to beachieved in orbit

Absolute Calibration Error : < 0.5 KIntercalibration error at a given time : < 0.2 K

All geophysical conditions4 pixels, all viewing directions, all channels

Intercalibration error over time : < 0.3 KShort term (orbital period)Long term


Measured Spectral Response Function

IASI PFM testing in vacuum2 laser beams (B1:CO2, B3:HF/DF)

Field and Aperture illuminated

ISRF measured on +/- 16 cm-1 (+)Resolution (FWHM) compliant (w. margins)ISRF Model accuracy achievedISRF Model input are precisely measured

• Instrument Point Spread Function• Interferometric axis and shear• Corner Cube trajectory

B1 ISRF (944 cm-1)

B3 ISRF (2655 cm-1)

-1,0

-0,5

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

-16,00 -12,00 -8,00 -4,00 0,00 4,00 8,00 12,00 16,00Wave numbers (cm-1)

Nor

mal

ised

to S

urfa

ce

Measured P1 Model P1

-0,04

-0,03

-0,02

-0,01

0,00

0,01

0,02

0,03

-15,0 -14,5 -14,0 -13,5 -13,0

-0,5

0,0

0,5

1,0

1,5

2,0

2,5

3,0

-16,00 -12,00 -8,00 -4,00 0,00 4,00 8,00 12,00 16,00Wave numbers (cm-1)

Nor

mal

ised

to S

urfa

ce

Measured P1 Model P1

-0,20

-0,15

-0,10

-0,05

0,00

0,05

0,10

0,15

0,20

-4 -2 0 2 4

-0,025

-0,020

-0,015

-0,010

-0,005

0,000

0,005

0,010

-15,0 -14,5 -14,0 -13,5 -13,0


Measured Spatial Response Function

Point Spread Function (IPSF) measured for the 3 IASI bandsInterband registration verified

Integrated absolute difference < 0.03

12 km FOV (at nadir)


Spectral Performances (1/3)

First assessment done on few parametersDν/ν with respect to nominal instrumentSpectral resolution (Full Width at Half Maximum)

At 944 cm-1 (B1) and 2655 cm-1 (B3)

Shape error index Epsilon2 = variations of the ISRFAbsolute difference between average and instantaneous Summed over +/- 16 cm-1

Band 1 P1 P2 P3 P4 SpecificationDν/ν 2 10-4

FWHM cm-1 0.32 0.32 0.32 0.32 0.35cd0 0.014 0.014 0.010 0.011cd1 0.015 0.013 0.009 0.012

Band 3 P1 P2 P3 P4Dν/ν 2 10-4

FWHM cm-1 0.43 0.40 0.43 0.42 0.48cd0 0.020 0.025 0.015 0.019cd1 0.020 0.023 0.011 0.014

0.026

1 10-5

1 10-5

0.042

Epsilon2

Epsilon2



Spectral stability over 80 sec. Spec = 1.10-6

Standard deviation of the position of the quadratic barycentre of the ISRF

+ very good long term stability between measurement sessionsObserved Dν/ν (average of the 4 pixels) < 1.10-6

Hot Case / Cold Case

14 days between first and last measurements

Band 1 P1 P2 P3 P4cd0 8.27E-08 8.30E-08 7.70E-08 7.36E-08cd1 7.66E-08 7.46E-08 4.79E-08 8.08E-08

Band 3 P1 P2 P3 P4cd0 1.67E-08 2.29E-08 2.36E-08 1.66E-08cd1 1.58E-08 2.55E-08 2.09E-08 1.49E-08



Shape error index 1 Spec b1 < 0.02, Spec b3 < 0.05ISRF knowledge errors

Shape_index_1 = Σ( abs( Isrf_Model(n) – Isrf_Average(n) ) * dn )Ghost has to be removed from the averaged ISRF (computation on 13 cm-1)

Band 1 P1 P2 P3 P4cd0 0.025 0.023 0.023 0.023cd1 0.029 0.023 0.021 0.022cd0 0.034 0.031 0.026 0.027cd1 0.034 0.028 0.023 0.024

Band 3 P1 P2 P3 P4cd0 0.029 0.042 0.026 0.049cd1 0.032 0.046 0.019 0.050cd0 0.043 0.053 0.030 0.056cd1 0.039 0.056 0.021 0.053

+/- 13 cm

+/- 16 cm

+/- 13 cm

+/- 16 cm


Summary

Excellent performances measured on 2nd IASI model (FM2)

The instrument ran flawlessly for the 3 weeks of test

Design modifications decided after PFM testing (ice contamination) successfully implemented on FM2 & FM3

• PFM model will be refurbished to benefit from these modifications

Big investment put into the on-ground calibration (human & financial)

Excellent stability of the instrument (spectral & radiometric)

Spectral Response Function of the instrument• Accurately measured at 2 wavenumbers (use of 2 laser beams for test)• Model accuracy verified at these 2 wavenumbers


IASI Project Status : instruments (1/2)

FM2On-ground calibration completed (TVAC test in October 2004)Integration & tests on METOP 2 completedLaunch planned April 2006

FM3Subsystem Integration & Test completedThermal Vacuum Test planned in October 2005

PFMInstrument TVAC test in June 2003METOP Payload TVAC test in February 2004 Now dismounted from METOP 2Detectors refurbishment planned end of year 2005


IASI Project Status : system (2/2)

OPS software (Level 1 processing) Delivered by CNES to EUMETSAT : Sept. 2004Now integrated & tested in CGSDelivered to METEO FRANCE for integration in direct readout software

TEC (IASI Technical Expertise Center) Acceptance test completed : Feb. 2005NRT terminal installed. First tests completedTEC ready for system level testing with EPS/CGS

Participation of IASI Instrument team to EPS system level tests with METOP 2 (SSVT4a, May 2005)

In-flight commissioning preparationInstrument on-orbit Verification Plan completedLevel 1 Cal/Val Plan completed (see poster B20), implementation on-going


Aknowledgements

The authors would like to express their thanks to the many people involved in the development, integration and test of the IASI instruments either in the industry, in the space agencies or in the universities for their efforts which made IASI a reality.

A special thought goes to F.R.Cayla who has been so involved with IASI project since the beginning and is still very close from us in spite of his retirement four years ago.

iasi on metop on-ground calibration of the fm2 instrument · itsc-14 – beijing, 25-31may. 2005 d....

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