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vortex-exoplanet / VIP

VIP is a python package/library for angular, reference star and spectral differential imaging for exoplanet/disk detection through high-contrast imaging.
http://vip.readthedocs.io/
MIT License
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Fake companions and reference frame choices #33

Closed rmjc closed 7 years ago

rmjc commented 8 years ago

Hi all,

I'm working with the contrast curve code with the new annular RDI mode. It looks like when the throughput function injects fake companions, the choice of the RDI reference frames are affected relative to the no fake companion case. Is this correct?

It seems that the throughput should use the same reference frames as the no fake companion case.

oabsil commented 8 years ago

Hi Becky,

This is a tough question. I guess you're refering to the fact that the reference frames are selected based on maximum correlation with the science frame? If it's the case, then I think it's a healthy behaviour of VIP. Indeed, if there was a companion in the cube with the characteristics of the injected fake companion, it would indeed affect the selection of the RDI reference frames in the PCA processing. If we want to properly assess the throughput of the RDI-PCA algorithm in presence of companions with various fluxes and positions, I think we need to let the possibility for the RDI reference frames to change as a function of the injected fake companion.

Note that this reasoning would probably not hold any more if we were injecting several fake companions at a time, unless all the companions are treated in separate regions during the RDI-PCA processing (because the other injected companions could also change the choice of the reference frames). Am I right that in the current version of VIP, only one companion is injected at a time?

Let me know if this answers your question, or if I've missed your point...

Cheers, Olivier.

Le 16/02/16 19:47, Rebecca Jensen-Clem a écrit :

Hi all,

I'm working with the contrast curve code with the new annular RDI mode. It looks like when the throughput function injects fake companions, the choice of the RDI reference frames are affected relative to the no fake companion case. Is this correct?

It seems that the throughput should use the same reference frames as the no fake companion case.

— Reply to this email directly or view it on GitHub https://github.com/vortex-exoplanet/VIP/issues/33.

Dr. Olivier ABSIL F.R.S.-FNRS Research Associate Dept. of Astrophysics, Geophysics and Oceanography Université de Liège (ULg), bât. B5c 17 allée du Six Août Tel: +32-(0)4-366.97.24 B-4000 Sart-Tilman Fax: +32-(0)4-366.97.46

Email: absil (at) astro.ulg.ac.be

dmawet commented 8 years ago

Hi Olivier,

Yes to your response but this is not the point (Becky correct me if I am wrong). When injecting FC for throughput calibration VIP goes through the selection of new reference stars, rather than keeping the same ones as for the first step without FC.

Dimitri

On Wednesday, February 17, 2016, Olivier Absil notifications@github.com wrote:

Hi Becky,

This is a tough question. I guess you're refering to the fact that the reference frames are selected based on maximum correlation with the science frame? If it's the case, then I think it's a healthy behaviour of VIP. Indeed, if there was a companion in the cube with the characteristics of the injected fake companion, it would indeed affect the selection of the RDI reference frames in the PCA processing. If we want to properly assess the throughput of the RDI-PCA algorithm in presence of companions with various fluxes and positions, I think we need to let the possibility for the RDI reference frames to change as a function of the injected fake companion.

Note that this reasoning would probably not hold any more if we were injecting several fake companions at a time, unless all the companions are treated in separate regions during the RDI-PCA processing (because the other injected companions could also change the choice of the reference frames). Am I right that in the current version of VIP, only one companion is injected at a time?

Let me know if this answers your question, or if I've missed your point...

Cheers, Olivier.

Le 16/02/16 19:47, Rebecca Jensen-Clem a écrit :

Hi all,

I'm working with the contrast curve code with the new annular RDI mode. It looks like when the throughput function injects fake companions, the choice of the RDI reference frames are affected relative to the no fake companion case. Is this correct?

It seems that the throughput should use the same reference frames as the no fake companion case.

— Reply to this email directly or view it on GitHub https://github.com/vortex-exoplanet/VIP/issues/33.

Dr. Olivier ABSIL F.R.S.-FNRS Research Associate Dept. of Astrophysics, Geophysics and Oceanography Université de Liège (ULg), bât. B5c 17 allée du Six Août Tel: +32-(0)4-366.97.24 B-4000 Sart-Tilman Fax: +32-(0)4-366.97.46

Email: absil (at) astro.ulg.ac.be

— Reply to this email directly or view it on GitHub https://github.com/vortex-exoplanet/VIP/issues/33#issuecomment-185092499 .

Dimitri Mawet Associate Professor of Astronomy JPL Senior Research Scientist

Astronomy Dept. MC 249-17 Caltech, 1200 E. California Blvd. Pasadena, CA 91125 Tel: 626-395-1452 E-mail: dmawet@astro.caltech.edu

rmjc commented 8 years ago

Hi Olivier and Dimitri,

The contrast is ((sigma * noise_samp_sm)/thruput_interp_sm)/starphot, where noise_samp_sm is the interpolated noise from the science frame with no fake companion. My understanding is that the purpose of dividing by the throughput is simply to convert (sigma * noise_samp_sm) into the units of "companion's signal", given that a companion's signal is attenuated by the PCA that we applied in order to get our noise_samp_sm.

When the throughput corresponds to a different set of reference frames (and perhaps a different number of principal components applied), than what we used to get noise_samp_sm, than this conversion doesn't quite make sense to me.

carlos-gg commented 8 years ago

Hi all,

The point of _pca_rdiannular is keeping the best correlated frames (annular patches) so indeed the frames and even the number of frames in the reference library might change. Becky, It makes sense what you say, and the ideal way to compute the noise and to get the attenuation caused by PCA is by keeping the same parameters of the post-processing. But by leaving all the frames (or same set of frames) with annular PCA RDI we might be reducing the improvement we obtain wrt the full-frame PCA RDI version and even full-frame PCA ADI (this needs more testing).

If you still want to keep the same library each time then a simple workaround is to set the _mincorr parameter to 0 (it uses all of them). Another way is just using the full-frame PCA with a set of reference frames (_cuberef). Then the library will be the same no matter how many companions were injected in the cube, because there is no correlation-based rejection. Also set a number of PCs for PCA so this parameter stays constant.

Olivier, the companions are not injected one at a time, but in non-overlaping radial patterns to sample the throughput each FWHM.

One thing that occurs to me, is to include a parameter _percentreject (or something like that) which overrides the _mincorr and just defines a percentage of least correlated frames (patches) to be removed from the library to keep it at least of the same size between runs.

Cheers, Carlos