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Francisco Oyarzun

Publications and source records attributed to Francisco Oyarzun.

2 recordsLinked to original sources

RAMA: A new agile AO bench for the telescope FEELINGS

The ground-based observation of extended objects such as satellites suffer from severe atmospheric propagation constraints. Specifically, high tracking velocities and low-elevation lines of sight generate non-stationary turbulence alongside strong scintillation. Developing robust wavefront control strategies is therefore critical to maintain stable observations. In this context, we present RAMA, an adaptive optics (AO) testbench deployed on ONERA's 60\,cm FEELINGS telescope. Designed as a pathfinder for future systems like the PROVIDENCE ground station, RAMA evaluates a visible, non-modulated Pyramid Wavefront Sensor (PWFS). The hardware baseline also includes two pupil-conjugated deformable mirrors (DM97 and DM192) driven by the DAO Real-Time Computer (RTC). Inheriting the modular and evolving philosophy of the PAPYRUS project, the bench provides a flexible environment to test new components on-sky and allows for direct comparisons between classical controllers and advanced, data-driven strategies. By implementing Convolutional Neural Networks (CNN) for phase reconstruction and Reinforcement Learning (RL) for loop control, RAMA aims to overcome the specific limitations associated with scintillation and extended-object observations. This paper details the opto-mechanical design, numerical simulations of the bench expected wavefont control performance, preliminary laboratory closed-loop results and the first on-sky optical coupling with the telescope.

astro-ph.IM↗

Performance comparison of the Shack-Hartmann and pyramid wavefront sensors with a laser guide star for 40 m telescopes

Context. The new giant segmented mirror telescopes will use laser guide stars (LGS) for their adaptive optics (AO) systems. Two options to use as wavefront sensors (WFS) are the Shack-Hartmann wavefront sensor (SHWFS) and the pyramid wavefront sensor (PWFS). Aims. In this paper, we compare the noise performance of the PWFS and the SHWFS. We aim to find which of the two WFS is the best to use in a single or tomographic configuration. Methods. To compute the noise performance we extended a noise model developed for the PWFS to be used with the SHWFS. To do this, we expressed the centroiding algorithm of the SHWFS as a matrix-vector multiplication, which allowed us to use the statistics of noise to compute its propagation through the AO loop. We validated the noise model with end-to-end simulations for telescopes of 8 and 16 m in diameter. Results. For an AO system with only one WFS, we found that, given the same number of subapertures, the PWFS outperforms the SHWFS. For a 40 m telescope, the limiting magnitude of the PWFS is around 1 magnitude higher than the SHWFS. When using multiple WFS and a Generalized least squares estimator to combine the signal, our model predicts that in a tomographic system, the SHWFS performs better than the PWFS having a limiting magnitude 0.3 magnitudes higher. If using sub-electron RON detectors for the PWFS, then the performances are almost identical between the two WFSs Conclusions. We conclude that when using a single WFS with LGS, the PWFS is a better alternative than the SH. However, for a tomographic system, either would have almost the same performance.

astro-ph.IM↗