Optimized photometric aperture for the seismology channel Fabio de Oliveira Fialho Michel Auvergne 2nd CoRoT-Brazil Workshop

2 03/11/2005 2nd CoRoT-Brazil Workshop 2 On-board Software and Ground Segment Corrections (CMC)

3 03/11/2005 2nd CoRoT-Brazil Workshop 3 Fixed Photometric Aperture Goal: to find the mask with the minimum size in pixels and the lowest sensibility to the jitter effect, i. e., to optimize the SNR (Signal to Noise Ratio) Masked Images Images

4 03/11/2005 2nd CoRoT-Brazil Workshop 4 Jitter Contribution Not corrected photometry Jitter corrected photometry Jitter Correction Mask Images (*)

5 03/11/2005 2nd CoRoT-Brazil Workshop 5 Jitter Correction Problem Definition Goal: to recover flux lost by jitter effect Initial constraint: fixed photometric aperture MaskMasked ImagePhotometry

6 03/11/2005 2nd CoRoT-Brazil Workshop 6 Jitter Correction Method Creation of correlation surface using the PSF model Correction of flux Correlation : – Based on the PSF, identification of correlation surface between the mesured flux in the mask and the pointing error – Correction of flux is performed using this surface and the pointing error

7 03/11/2005 2nd CoRoT-Brazil Workshop 7 Jitter Correction Surface Creation X Pointing Error Y Pointing Error Correction Surface Mask PSF Model

8 03/11/2005 2nd CoRoT-Brazil Workshop 8 Jitter Correction Photometric Correction X Pointing Error Y Pointing Error Photometric Correction Not Corrected Photometry Correction Surface

9 03/11/2005 2nd CoRoT-Brazil Workshop 9 Jitter Correction Exemple Not corrected, corrected and ideal photometry Fourier spectra for corrected and ideal photometry

10 03/11/2005 2nd CoRoT-Brazil Workshop 10 Jitter Correction Statistics – Star MV = 6 Not corrected and corrected photometry

11 03/11/2005 2nd CoRoT-Brazil Workshop 11 Mask Classic Solution PSF Model SNR Curve

12 03/11/2005 2nd CoRoT-Brazil Workshop 12 Mask Hybrid Method Analytic solution without jitter Numeric solution with jitter Photometry Photometric Correction SNR’(k) Mask Definiton (pixel adding)

13 03/11/2005 2nd CoRoT-Brazil Workshop 13 Mask Results – Star MV = 6 Initial Mask Edge Pixels Final Mask Candidate Pixels SNRSNR with jitter

14 03/11/2005 2nd CoRoT-Brazil Workshop 14 Mask SNR

15 03/11/2005 2nd CoRoT-Brazil Workshop 15 Conclusions Jitter noise can be corrected in the SEISMO channel Once pointing error becomes important, our ability to correct it will be taken in account to redefine masks Jitter noise is not a critical issue for stars of magnitude 6 if the pointing error respects the specification