San Diego Conference 2 August 2001 Meteosat Second Generation: In Flight Calibration of the Imaging Radiometer SEVIRI D. M. A. Aminou and A. Ottenbacher European Space Agency / ESTEC Keplerlan 1, P.O. Box 299 2200 AG Noordwijk, The Netherlands B. Jacquet Alcatel Space Industries 100, Boulevard du Midi, B.P. 99 06156 Cannes La Bocca Cedex, France F. Pasternak and P. Coste Astrium S.A. 31 Avenue des Cosmonautes 31402 Toulouse, France San Diego Conference 2 August 2001

SEVIRI: The Imaging Radiometer of MSG San Diego Conference 2 August 2001

Image acquisition principle San Diego Conference 2 August 2001

Source image acquisition - spin & Scan - Processing and Data MSG-1 First on-ground Image performed during the End to End Test from an external Source image acquisition - spin & Scan - Processing and Data Transmission through RF Link San Diego Conference 2 August 2001

San Diego Conference 2 August 2001 SEVIRI performance status on MSG-1: Radiometry Noise specifications are met for all channels. Concerning Bias & LTD, the specification is met for all channels with margins. San Diego Conference 2 August 2001

MSG-1 optical vacuum results: Radiance response and Non-Linearity of the Radiometer San Diego Conference 2 August 2001

San Diego Conference 2 August 2001 SEVIRI performance status on MSG-1: Radiometry Noise specifications are met for all channels. Concerning Bias & LTD, the specification is met for all channels with margins. San Diego Conference 2 August 2001

San Diego Conference 2 August 2001 SEVIRI Spectral Channels San Diego Conference 2 August 2001

Objectives of the spectral channels San Diego Conference 2 August 2001

IR and WV spectral bands San Diego Conference 2 August 2001

Examples of spectral responses Spectral response of SEVIRI channel IR10.8: blue diamonds for 85K, red dots for 95K Spectral response of SEVIRI channel VIS0.6 San Diego Conference 2 August 2001

Mean weighting functions San Diego Conference 2 August 2001

San Diego Conference 2 August 2001

SEVIRI Calibration particularities: Scan and primary mirror are not in the calibration path when using the on board black body: the instrument gain needs to be corrected A correction factor is necessary to account for the delta background flux that cannot be calibrated out when using the on board blackbody The correction factor is determined by: using a 2nd temperature on the same on board blackbody monitoring the temperatures of the front telescope Tft L deep space and Earth Scan mirror Blackbody Focal plane M1 L black body San Diego Conference 2 August 2001

San Diego Conference 2 August 2001

San Diego Conference 2 August 2001

Expected Performances of the On-Board Blackbody: Extrapolation to End Of Life (7 years) San Diego Conference 2 August 2001

San Diego Conference 2 August 2001

San Diego Conference 2 August 2001 Calibration of the MSG Level 1.5 Image Data San Diego Conference 2 August 2001

Vicarious method for calibration of Solar Channels Mission of solar channels has less stringent calibration requirement than IR Simplify the instrument by achieving the required calibration with vicarious method The solar channels will be calibrated in the EUMETSAT Ground Segment using a vicarious method: radiance over sea, bright desert and clouds targets will be simulated to compute the calibration coefficients. These targets have been selected to cover the full dynamic range of the solar channels to improve the accuracy. San Diego Conference 2 August 2001

Expected performances of vicarious calibration of Solar Channels Expected accuracy of the derived calibration coefficients is better than +/- 10% after commissioning. After the first year of operations the accuracy is expected to improve up to better than +/- 5%. This is expected to be achieved by an improvement of characterisation of target properties and by tuning the quality control mechanism. Due to the high stability of SEVIRI, it is expected to run the calibration algorithm on a monthly time scale. San Diego Conference 2 August 2001

San Diego Conference 2 August 2001 CONCLUSION The header of the MSG images disseminated to the users will contain the calibration coefficients for each SEVIRI channel. The IR channels will be calibrated using the SEVIRI on board calibration device. Vicarious methods will be used to monitor the long term behaviour of the calibration model. Although SEVIRI allows on-board calibration at every repeat cycle, calibration is needed every 10 images (worst case EOL) The Solar channels will be calibrated by using vicarious methods. The method will be tuned during commissioning and during the first year of operations. San Diego Conference 2 August 2001

Focal plane characteristics San Diego Conference 2 August 2001