The VLT/ERIS vortex coronagraph: design, pointing control, and on-sky performance

G. Orban de Xivry; O. Absil; R. J. De Rosa; M. J. Bonse; F. Dannert; J. Hayoz; P. Grani; A. Puglisi; A. Baruffolo; B. Salasnich; R. Davies; A. M. Glauser; E. Huby; M. Kenworthy; S. P. Quanz; W. Taylor; G. Zins

doi:10.1117/12.3018265

27 August 2024 The VLT/ERIS vortex coronagraph: design, pointing control, and on-sky performance

G. Orban de Xivry, O. Absil, R. J. De Rosa, M. J. Bonse, F. Dannert, J. Hayoz, P. Grani, A. Puglisi, A. Baruffolo, B. Salasnich, R. Davies, A. M. Glauser, E. Huby, M. Kenworthy, S. P. Quanz, W. Taylor, G. Zins

Author Affiliations +

Proceedings Volume 13097, Adaptive Optics Systems IX; 1309715 (2024) https://doi.org/10.1117/12.3018265
Event: SPIE Astronomical Telescopes + Instrumentation, 2024, Yokohama, Japan

Abstract

The Enhanced Resolution Imager and Spectrograph (ERIS) is the new near-infrared instrument at the VLT-UT4. ERIS replaces and extends the observational capabilities formerly provided by SINFONI and NACO: integral field spectroscopy at 1 to 2.5μm, imaging at 1 to 5μm with several options for high-contrast imaging, and long-slit spectroscopy. In particular, a vortex coronagraph is now available for high contrast observations at L and M band. It is implemented using annular groove (or vortex) phase masks (one for each of the L and M bands) in a focal plane, and a Lyot stop in a downstream pupil plane. The vortex coronagraph has a discovery space starting already at ∼1λ/D, and works well in broadbands. However, to reach its optimal performance, it is critical to correct for slow pointing errors onto the vortex phase mask, which mandates a dedicated pointing control strategy. To do so, a control loop based on the QACITS algorithm has been developed and commissioned for ERIS. Good pointing stability is now regularly achieved with errors between 0.01 and 0.02 λ/D and a correction rate of 0.2Hz. In this contribution, we first review the design of the ERIS vortex coronagraph. We then detail the implementation of the QACITS algorithm describing the entire observing sequence, including the calibration steps, the initial centering, and the stabilization during the observing template. We then discuss performance based on commissioning data in terms of pointing accuracy and stability. Finally, we present post-processed contrast curves obtained during commissioning and compare them with NACO vortex data, showing a significant improvement of about 1 mag at all separations.

Conference Presentation

(2024) Published by SPIE. Downloading of the abstract is permitted for personal use only.

Citation Download Citation

G. Orban de Xivry, O. Absil, R. J. De Rosa, M. J. Bonse, F. Dannert, J. Hayoz, P. Grani, A. Puglisi, A. Baruffolo, B. Salasnich, R. Davies, A. M. Glauser, E. Huby, M. Kenworthy, S. P. Quanz, W. Taylor, and G. Zins "The VLT/ERIS vortex coronagraph: design, pointing control, and on-sky performance", Proc. SPIE 13097, Adaptive Optics Systems IX, 1309715 (27 August 2024); https://doi.org/10.1117/12.3018265

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