Reference : On-sky performance of the QACITS pointing control technique with the Keck/NIRC2 vorte...
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Space science, astronomy & astrophysics
http://hdl.handle.net/2268/207618
On-sky performance of the QACITS pointing control technique with the Keck/NIRC2 vortex coronagraph
English
Huby, Elsa mailto [Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Astroph. extragalactique et observations spatiales (AEOS) >]
Bottom, Michael [> >]
Femenia, Bruno [> >]
Ngo, Henry [> >]
Mawet, Dimitri [> >]
Serabyn, Eugene [> >]
Absil, Olivier mailto [Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Astroph. extragalactique et observations spatiales (AEOS) >]
28-Mar-2017
Astronomy and Astrophysics
EDP Sciences
600
A46
Yes (verified by ORBi)
International
0004-6361
1432-0746
Les Ulis
France
[en] Astrophysics - Instrumentation and Methods for Astrophysics
[en] A vortex coronagraph is now available for high contrast observations with the Keck/NIRC2 instrument at L band. Reaching the optimal performance of the coronagraph requires fine control of the wavefront incident on the phase mask. In particular, centering errors can lead to significant stellar light leakage that degrades the contrast performance and prevents the observation of faint planetary companions around the observed stars. It is thus critical to correct for the possible slow drift of the star image from the phase mask center, generally due to mechanical flexures induced by temperature and/or gravity field variation, or to misalignment between the optics that rotate in pupil tracking mode. A control loop based on the QACITS algorithm for the vortex coronagraph has thus been developed and deployed for the Keck/NIRC2 instrument. This algorithm executes the entire observing sequence, including the calibration steps, initial centering of the star on the vortex center and stabilisation during the acquisition of science frames. On-sky data show that the QACITS control loop stabilizes the position of the star image down to 2.4 mas rms at a frequency of about 0.02 Hz. However, the accuracy of the estimator is probably limited by a systematic error due to a misalignment of the Lyot stop with respect to the entrance pupil, estimated to be on the order of 4.5 mas. A method to reduce the amplitude of this bias down to 1 mas is proposed. The QACITS control loop has been successfully implemented and provides a robust method to center and stabilize the star image on the vortex mask. In addition, QACITS ensures a repeatable pointing quality and significantly improves the observing efficiency compared to manual operations. It is now routinely used for vortex coronagraph observations at Keck/NIRC2, providing contrast and angular resolution capabilities suited for exoplanet and disk imaging.
VORTEX
Researchers
http://hdl.handle.net/2268/207618
10.1051/0004-6361/201630232
http://adsabs.harvard.edu/abs/2017A%26A...600A..46H
http://www.aanda.org/articles/aa/abs/2017/04/aa30232-16/aa30232-16.html - Copyright ESO 2017, published by EDP Sciences
FP7 ; 337569 - VORTEX - Taking extrasolar planet imaging to a new level with vector vortex coronagraphy

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