IASI on METOP On-Ground Calibration of the FM2 Instrument

Transcription

1 Infrared Atmospheric Sounding Interferometer IASI on METOP On-Ground Calibration of the FM2 Instrument International TOVS Study Conference 25-31, May 2005 Beijing China D. Blumstein 1,B.Tournier 2, T.Carlier 1, T.Maciaszek 1, T.Phulpin 1, G.Chalon 1, P.Astruc 3, D.Miras 3, D.Siméoni 3 (1) Centre National d'etudes Spatiales (CNES), Toulouse, France (2) NOVELTIS, Toulouse, France (3) ALCATEL SPACE, Cannes, France ITSC-14 Beijing, 25-31May D. Blumstein CNES DCT/PO/EV 1

2 Outline Key Performance specifications On-ground characterization of IASI FM2 First IASI instrument in flight (on METOP 2) IASI Program Status ITSC-14 Beijing, 25-31May D. Blumstein CNES DCT/PO/EV 2

3 Key performances specifications Radiometric sensitivity Apodized and non-apodized spectra Radiometric accuracy Absolute accuracy Relative accuracy (at a given time) Between pixels, channels, viewing direction Stability Spectral & geometry Spectral calibration Spectral response function Point Spread Function ( & interband registration) ITSC-14 Beijing, 25-31May D. Blumstein CNES DCT/PO/EV 3

4 IASI FM2 testing in vacuum NeDT at 280 K (K) Detectors temperature 91.7 K Measured on blackbody No evolution of noise (ice cont.) Measured radiometric sensitivity Loss of transmission : 1.5 % at 850 cm -1 over a period of 6 days Equivalent to the absorption by a 40 nm thin film of water ice apodized + pseudo-noise Mission radiometric performance in NeDT T_CBS=91,7 K (IASI FM2 OV Test) Wavenumber (cm-1) Spécification FM2 (Delta-QR) NedT at 280 K (K) 1,0 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0,0 non apodized (293 K scene) AVM result IASI FM2 Noise Spectrum (NedT at 280 K) Session SM CBS 91.7 K Wavenumber (m^-1) Measurement SM Pixel 3 Noise Spectrum in NedT at 280 K after drift correction - P4 - c10693_avm_sm Noise Spectrum Effect of in NedT scene at 280 temperature K after drift correction on B3 noise - P1 - c10693_avm_sm (scene at 240 & 280 K) Noise Spectrum in NedT at 280 K after drift correction - P3 - c10693_avm_sm NedT at 280 K Noise Spectrum in NedT at 280 K after drift correction - P2 - c10693_avm_sm NedT at 280 K measurements ITSC-14 Beijing, 25-31May D. Blumstein CNES DCT/PO/EV 4 NeDT at 280 K (K) 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0,0 B1 B2 NeDT in K (at 280 K) B Wavenumber (cm-1) 240 K 280 K spec

5 Measured radiometric accuracy (1/4) IASI FM2 testing in vacuum Need for NL correction in B1 band DT < 0.25 K Target in nadir position Result valid for other incidences Post-calibration done by Level 1 proc. to achieve "differential" requirements Between pixels, scan views or channels Tscene : K Pixel 1, Nominal Conf., Cold Case Brigthness temperature (K) 300,2 300,0 299,8 299,6 299,4 299,2 299,0 298,8 298,6 298, Session SM 06 22h59 T_HBB about 299 K, no Non-Linearity correction B1 300,2 Pixel 1 Pixel 2 Pixel 3 Pixel 4 300,0 298,2 299, ,6 Wave numbers (cm-1) NL (B1) corrected Brigthness temperature (K) 299,4 299,2 299,0 298,8 298,6 298,4 Session SM 06 22h59 T_HBB around 299 K, Non-Linearity correction applied 298, Wave numbers (cm-1) Pixel 1 Pixel 2 Pixel 3 Pixel 4 Tscene : K Pixel 1, Redundant Conf., Hot Case Radiometric Calibration Error in NedT at 280 K (K) 0.3 H B B coating em issivity loss 0.2 BBC coating emissivity loss K K 280 K K 240 K 220 K W ave Num ber (m ^-1) Radiometric Calibration Error in NedT at 280 K (K) 0.3 HBB coating emissivity lo s s BBC coating emissivity loss Wave Number (m^-1) ITSC-14 Beijing, 25-31May D. Blumstein CNES DCT/PO/EV 5

6 Radiometric Calibration Error in NedT at 280 K (K) Measured radiometric accuracy (2/4) Raw measurements versus model comparison Pixel K 294 K 280 K 260 K 240 K 220 K HBB coating emissivity loss W ave Num ber (m ^-1) BBC coating emissivity loss Nominal Conf. Cold Case Radiometric Calibration Error Model Nominal configuration, Cold Case T_env HBB = 280 K, T_env BBC = 275 K, T_env CBB = 230 K DT at 280 K (Kelvin) Wave Number (cm-1) 220 K 240 K 260 K 280 K 294 K 300 K ITSC-14 Beijing, 25-31May D. Blumstein CNES DCT/PO/EV 6

7 Measured radiometric accuracy (3/4) Radiometric Calibration Error in NedT at 280 K (K) Raw measurements versus model comparison Pixel HBB coating em issivity lo ss BBC coating emissivity loss Redundant Conf Hot Case Radiometric Calibration Error Model Redundant configuration, Hot Case T_env HBB = 295 K, T_env BBC = 285 K, T_env CBB = 230 K Wave Number (m^-1) DT at 280 K (Kelvin) Wave Number (cm-1) 240 K 260 K 280 K 294 K 300 K ITSC-14 Beijing, 25-31May D. Blumstein CNES DCT/PO/EV 7

8 Measured radiometric accuracy (4/4) More in-depth verifications performed during the test Scan angle effect verified Interpixel & interscan calibration Sensitivity to thermal drifts Simulation of Entry/Exit of eclipse Mission Objectives on radiometric calibration are expected to be achieved in orbit Absolute Calibration Error : < 0.5 K Intercalibration error at a given time : < 0.2 K All geophysical conditions 4 pixels, all viewing directions, all channels Intercalibration error over time : < 0.3 K Short term (orbital period) Long term ITSC-14 Beijing, 25-31May D. Blumstein CNES DCT/PO/EV 8

9 IASI PFM testing in vacuum Measured Spectral Response Function 2 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 achieved ISRF Model input are precisely measured Instrument Point Spread Function Interferometric axis and shear Corner Cube trajectory Normalised to Surface B1 ISRF (944 cm-1) 4,0 3,5 Measured P1 Model P1 3,0 0,03 2,5 0,02 0,01 0,00 2,0-15,0-14,5-14,0-0,01-13,5-13,0-0,02 1,5-0,03-0,04 1,0 0,5 0,0-0,5-1,0-16,00-12,00-8,00-4,00 0,00 4,00 8,00 12,00 16,00 Wave numbers (cm-1) 3,0 B3 ISRF (2655 cm-1) 2,5 2,0 Measured P1 Model P1 0,20 0,15 0,10 Normalised to Surface 1,5 1,0 0,010 0,005 0,000-15,0-14,5-14,0-13,5-13,0-0,005-0,010-0,015-0,020-0,025 0,05 0, ,05-0,10-0,15-0,20 0,5 0,0-0,5-16,00-12,00-8,00-4,00 0,00 4,00 8,00 12,00 16,00 Wave numbers (cm-1) ITSC-14 Beijing, 25-31May D. Blumstein CNES DCT/PO/EV 9

10 Measured Spatial Response Function Point Spread Function (IPSF) measured for the 3 IASI bands Interband registration verified Integrated absolute difference < km FOV (at nadir) ITSC-14 Beijing, 25-31May D. Blumstein CNES DCT/PO/EV 10

11 Spectral Performances (1/3) First assessment done on few parameters Dν/ν with respect to nominal instrument Spectral resolution (Full Width at Half Maximum) At 944 cm-1 (B1) and 2655 cm-1 (B3) Shape error index Epsilon2 = variations of the ISRF Absolute difference between average and instantaneous Summed over +/- 16 cm-1 Band 1 P1 P2 P3 P4 Specification Dν/ν FWHM cm cd Epsilon cd Band 3 P1 P2 P3 P4 Dν/ν FWHM cm cd Epsilon cd ITSC-14 Beijing, 25-31May D. Blumstein CNES DCT/PO/EV 11

12 Spectral Performances (2/3) Spectral stability over 80 sec. Spec = Standard deviation of the position of the quadratic barycentre of the ISRF Band 1 P1 P2 P3 P4 cd0 8.27E E E E-08 cd1 7.66E E E E-08 Band 3 P1 P2 P3 P4 cd0 1.67E E E E-08 cd1 1.58E E E E-08 + very good long term stability between measurement sessions Observed Dν/ν (average of the 4 pixels) < Hot Case / Cold Case 14 days between first and last measurements ITSC-14 Beijing, 25-31May D. Blumstein CNES DCT/PO/EV 12

13 Spectral Performances (3/3) Shape error index 1 Spec b1 < 0.02, Spec b3 < 0.05 ISRF 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 P4 +/- 13 cm +/- 16 cm cd0 cd cd1 cd Band 3 P1 P2 P3 P4 +/- 13 cm +/- 16 cm cd0 cd cd1 cd ITSC-14 Beijing, 25-31May D. Blumstein CNES DCT/PO/EV 13

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

15 IASI Project Status : instruments (1/2) FM2 On-ground calibration completed (TVAC test in October 2004) Integration & tests on METOP 2 completed Launch planned April 2006 FM3 Subsystem Integration & Test completed Thermal Vacuum Test planned in October 2005 PFM Instrument TVAC test in June 2003 METOP Payload TVAC test in February 2004 Now dismounted from METOP 2 Detectors refurbishment planned end of year 2005 ITSC-14 Beijing, 25-31May D. Blumstein CNES DCT/PO/EV 15

16 IASI Project Status : system (2/2) OPS software (Level 1 processing) Delivered by CNES to EUMETSAT : Sept Now integrated & tested in CGS Delivered to METEO FRANCE for integration in direct readout software TEC (IASI Technical Expertise Center) Acceptance test completed : Feb NRT terminal installed. First tests completed TEC 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 preparation Instrument on-orbit Verification Plan completed Level 1 Cal/Val Plan completed (see poster B20), implementation on-going ITSC-14 Beijing, 25-31May D. Blumstein CNES DCT/PO/EV 16

17 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. ITSC-14 Beijing, 25-31May D. Blumstein CNES DCT/PO/EV 17