All the aberrations not corrected by Adaptive Optics (AO) systems are important limitations for high contrast imaging at large telescopes. Among them, the most relevant ones are called Non-Common Path Aberrations (NCPA): these are present downstream of the separation of the optical paths to Wavefront Sensor and scientific focal plane. The typical approach to mitigate them is to set an offset on the AO system with the opposite sign of this NCPA. It can be obtained with a trial-and-error approach or with sophisticated focal plane Wavefront sensing. There is a need for a fast procedure to measure NCPA in order to limit the telescope downtime and to repeat, if needed, the correction procedure to cope with any temporal variation. Different methods exists to measure and compensate it introducing the correction as offset in the AO control loop. New approaches based on Neural Networks (NNs) have also been proposed. In this work, using simulated images, we test and describe the application of a supervised Multi-layer Perceptron (MLP) NN for the mitigation of NCPA in high contrast imaging at visible wavelengths. As shown in our previous work, we already tested the method on simulated images and showed that this method is robust even in the presence of turbulence-induced dynamic aberrations that are not labelled in the training phase of the NN corresponding to the typical AO residual of the daytime calibration. We tested the method on the GHOST optical test bench at ESO laboratories and preliminary results show the method is very promising, recovering almost completely the SR in an iterative correction process.
SHARK-VIS the Large Binocular Telescope (LBT) forthcoming optical high-contrast imager is completed and will soon see its first light. Thanks to the high performances of SOUL, the new LBT adaptive optics (AO) system, SHARK-VIS will extend the capabilities of one arm of the binocular telescope down to 400 nm, delivering spatial resolutions (≈ 15 mas) that in the infrared bands will be achieved only by future extremely large telescopes (ELTs). This document describes the instrument and its final laboratory test that assessed the expected performances. End to End test, done on a dedicated test-bench resembling on sky conditions, showed the capability to detect faint target with contrast lower than 10−4 at only 50mas away from a magR 12 point like source.
The Exoplanets at LBT with a Visible IFS for SHARK-VIS (ELVIS) is an add-on imaging spectrograph to be integrated in the new LBT high-contrast high-resolution AO-assisted imager SHARK-VIS. ELVIS is optimized for a medium/high spectral resolution of 10-20k with a limited bandwidth around the Hα, and it is planned fed by a small core (10-20 ⊘ µm) multi mode fiber bundle providing about 140 spaxels on a field of view around 300×300 sqmas. This instrument has a very compact design based on a VPH dispersing element to allow its installation within a standard 19” rack mount. As shown in the literature, young accreting sub-stellar and planetary companions are better detected and analyzed by these instruments allowing to reach contrast at least ten times fainter (in their Hα emission) with respect to standard imagers.
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