Upgrading SPHERE with the second stage AO system SAXO+: RTC preliminary design

Abstract

The Spectro-Polarimetric High-contrast Exoplanet REsearch instrument has now been in operation at the VLT for more than 5 years, demonstrating a high level of performance. SPHERE has produced outstanding results using a variety of operating modes, primarily in the field of direct imaging of exoplanetary systems, focusing on exoplanets as point sources and circumstellar disks as extended objects. The achievements obtained thus far with SPHERE have motivated a large consortium to propose an upgrade: the SPHERE+ project capitalizes on the expertise and lessons learned from SPHERE to push high contrast imaging performance to its limits on the VLT 8m-telescope. The proposed upgrade takes the form of a high-speed adaptive optics second stage, SAXO+, including a deformable mirror, a pyramid wavefront sensor, and a Real-Time Controller (RTC). Paving the way toward PCS, SAXO+ can be seen as a technical demonstrator for advanced AO control strategies, with a fast-track development aiming at the first light in 2027.In this context, the RTC is a core component that must be flexible enough to handle various control strategies, including AI, while ensuring high efficiency to be able to control the AO loop at high framerate. To achieve those goals, COSMIC has been selected to provide the required hard real-time capabilities, supplemented by the ESO RTC Toolkit for the implementation of soft real-time clustering. This paper will focus on the SAXO+ RTC preliminary design, including the main features of the RTC and preliminary benchmark results.