1. 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 AG Noordwijk, The Netherlands B. Jacquet Alcatel Space Industries 100, Boulevard du Midi, B.P Cannes La Bocca Cedex, France F. Pasternak and P. Coste Astrium S.A. 31 Avenue des Cosmonautes Toulouse, France
San Diego Conference 2 August 2001

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

3. Image acquisition principle
San Diego Conference 2 August 2001

4. 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

5. 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

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

7. 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

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

9. Objectives of the spectral channels
San Diego Conference 2 August 2001

10. IR and WV spectral bands
San Diego Conference 2 August 2001

11. 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

12. Mean weighting functions
San Diego Conference 2 August 2001

13. San Diego Conference 2 August 2001

14. 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

15. San Diego Conference 2 August 2001

16. San Diego Conference 2 August 2001

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

18. San Diego Conference 2 August 2001

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

20. 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

21. 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

22. 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

23. Focal plane characteristics
San Diego Conference 2 August 2001