An autonomous predictive regulator (Linear Quadratic Gaussian (LQG)) is being developed within the European H2020 ORP project, to be tested on the Gran Telescopio Canarias Adaptive Optics (GTCAO) system (about 400 actuators and 600 SH-WFS measurements). The system can run at 1kHz with 1.65ms loop delay in the predictive case, under DARC real-time computer. This LQG controller is based on a data-driven model identified using both machine learning and parametric identification techniques and automatically updated from telemetry data during operation. The complete procedure under OOMAO simulator is presented here (including calibration). The disturbance is generated thanks to StereoScidar measurements, with in addition turbulence bursts, windshake and vibrations. Specific mechanisms insure regulator stability. Performance in terms of Strehl ratio and stability is evaluated for both LQG and integrator regulators. These developments and results will serve the on-sky tests on GTC foreseen in 2024.
The Adaptive Optics (AO) of the Gran Telescopio Canarias (GTC) is a single conjugate postfocal system, integrated in one of the Nasmyth platforms of the telescope. GTC is located in the Observatory of Roque de Los Muchachos (ORM) in the island of La Palma, Spain. GTCAO is based on a single deformable mirror (DM) with 373 actuators, conjugated to the GTC pupil, and a Shack-Hartmann wavefront sensor (WFS) with 312 useful sub-apertures on an OCAM2 camera. The performance required for GTCAO is 65% Strehl Ratio in K-band under average atmospheric conditions and bright NGS. After finishing its laboratory testing and calibration in 2022, the laboratory acceptance and transport readiness review took place in April 2023. GTCAO integration in the telescope was carried out along June 2023. The GTCAO control software was integrated with the GTC observing software along July, to implement the optical derotation, the WFS positioning in the field and guiding, the WFS atmospheric dispersion compensation, and the tip-tilt correction loop implemented with the GTC secondary mirror. At the end of Summer 2023 started the on-sky commissioning. Since then, the AO loop has been closed on sky in different turbulence and guide star conditions. This paper presents the GTCAO integration results and first on sky commissioning results.
KEYWORDS: Adaptive optics, Wavefront sensors, Telescopes, Linear regression, Data modeling, Control systems, Actuators, Vibration, Matrices, Point spread functions
The Gran Telescopio Canarias (GTC) is being equipped with an Adaptive Optics (AO) system, developed by the Instituto de Astrofísica de Canarias (IAC). The Institut d’Optique Graduate School-Laboratoire Charles Fabry (IOGS-LCF), through a collaboration with the IAC, integrated some high performance control solutions. In this proceeding, we present the first and promising on-sky results on a 10-meter class telescope for such a controller, namely a full Linear Quadratic Gaussian regulator (LQG). We start with a brief description of the GTCAO system, including the data-driven LQG regulator construction. Performance results are then presented with a full LQG regulator in line with the previous on-bench experiments, implemented in DARC, the GTCAO RTC. A comparison is performed with the integrator, the baseline controller, through the comparison of point spread functions acquired on the scientific camera and residual slopes recorded by the wavefront sensor.
The Gran Telescopio Canarias (GTC) will be soon equipped with an Adaptive Optics (AO) system. The GTCAO system is currently at the Instituto de Astrofisica de Canarias (IAC), where tests and performance assessment are ongoing. The Institut d’Optique Graduate School-Laboratoire Charles Fabry (IOGS-LCF), through a collaboration with IAC, is exploring high performance control solutions. In this proceeding, we present first bench results for such a controller, namely a Linear Quadratic Gaussian regulator (LQG). First, we briefly describe the GTCAO bench and the principle of the LQG regulator. Second, an aspect of this development is outlined, namely the wavefront sensor measurement noise variance characterization. It is conveniently based on the use of telemetry data (wavefront sensor closed-loop slopes power spectral densities and subapertures flux) allowing for an easy-to-update and best-tuned controller. Finally, on-bench performance results are presented with an LQG regulator in the line of the previous on-sky experiments with full LQG regulator, implemented in DARC,5 the GTCAO RTC. Comparison is performed with the integrator as baseline controller, through evaluation of the Strehl ratio from point spread functions acquired on the scientific camera, rejection transfer functions and stability margins.
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