Optimized photometric aperture for the seismology channel Fabio de Oliveira Fialho Michel Auvergne...
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Optimized photometric aperture for the seismology channel
Fabio de Oliveira FialhoMichel Auvergne
2nd CoRoT-Brazil Workshop
03/11/2005 2nd CoRoT-Brazil Workshop2 2
On-board Software and Ground Segment Corrections (CMC)
03/11/2005 2nd CoRoT-Brazil Workshop3 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 ImagesImages
03/11/2005 2nd CoRoT-Brazil Workshop4 4
Jitter Contribution
Not corrected photometry
Jitter corrected photometry
JitterCorrection
MaskImages
(*)
(*)
03/11/2005 2nd CoRoT-Brazil Workshop5 5
Jitter CorrectionProblem Definition
Goal: to recover flux lost by jitter effect
Initial constraint: fixed photometric aperture
Mask Masked Image Photometry
03/11/2005 2nd CoRoT-Brazil Workshop6 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
ii miic FyxKF ).,(
03/11/2005 2nd CoRoT-Brazil Workshop7 7
Jitter Correction Surface Creation
X Pointing Error
Y Pointing Error
Correction Surface
Mask
PSF Model
03/11/2005 2nd CoRoT-Brazil Workshop8 8
Jitter Correction Photometric Correction
X Pointing Error
Y Pointing Error
Photometric Correction
Not Corrected Photometry
Correction Surface
03/11/2005 2nd CoRoT-Brazil Workshop9 9
Jitter Correction Exemple
Not corrected, corrected and ideal photometry
Fourier spectra for corrected and ideal photometry
03/11/2005 2nd CoRoT-Brazil Workshop10 10
Jitter Correction Statistics – Star MV = 6
MV 6 Teff 5000 - SNR
0,9968010,997185
1,000000
flux de départ flux corrigée flux idéal
MV 6 Teff 5000 - variance
1,0064211,005656
1,000000
flux de départ flux corrigée flux idéal
MV 6 Teff 5000 - moyenne
0,999996
1,0000011,000000
flux de départ flux corrigée flux idéal
Not corrected and corrected photometry
03/11/2005 2nd CoRoT-Brazil Workshop11 11
MaskClassic Solution
...3,2,1,
)(
)()(
1
2
1
k
iN
iNk
N
Sk
inoiseph
k
i
ph
oise
ignal
PSF Model
SNR Curve
03/11/2005 2nd CoRoT-Brazil Workshop12 12
MaskHybrid Method
Analytic solution without jitter
Numeric solution with jitter
Photometry
PhotometricCorrection
Mask Definiton(pixel adding)
SNR’(k)
...3,2,1,
)(
)()(
1
2
1
k
iN
iNk
N
Sk
inoiseph
k
i
ph
oise
ignal
03/11/2005 2nd CoRoT-Brazil Workshop13 13
MaskResults – Star MV = 6
Initial Mask Edge Pixels Final Mask
Candidate Pixels SNR SNR with jitter
03/11/2005 2nd CoRoT-Brazil Workshop14 14
MaskSNR
SNR Gain - Optimal Mask
0,211
0,509
SISMO 6 SISMO 9
(%)
03/11/2005 2nd CoRoT-Brazil Workshop15 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 )01.100656.1( 2
photons