arXiv subjects

Matteo Pasinetti

Publications and source records attributed to Matteo Pasinetti.

3 recordsLinked to original sources

arXiv2026

The infrared unmodulated pyramid wavefront sensor: simulations, lab and on sky

Direct imaging of Earth-like exoplanets requires strong suppression of stellar light at small angular separations, achievable with extreme adaptive optics (XAO). The pyramid wavefront sensor (PWFS) is widely used for its sensitivity but suffers from nonlinearities and limited dynamic range. Modulation extends the range but reduces sensitivity and limits loop speed. We investigate an unmodulated infrared PWFS (IR-umPWFS), where the dynamic range scales with wavelength, removing the need for modulation and enabling faster operation. We adopt a 3-sided PWFS, which eliminates the roof defect of the classical 4-sided design. We assess its feasibility and performance through end-to-end simulations, lab tests, and on-sky observations on the PAPYRUS bench at the Observatoire de Haute-Provence (OHP), and compare it with a visible modulated PWFS (VIS-mPWFS). Simulations show reliable operation, reaching Strehl ratios up to ~60% at 1400 nm for seeing up to 4''. Infrared operation improves linearity, reduces optical-gain variations and modal cross-talk. Laboratory results validate the simulations and confirm the pyramid quality. On sky, stable closed-loop operation was achieved over three nights. Compared with the VIS-mPWFS at 500 Hz, the IR-umPWFS at 1000 Hz showed gains of ~1.63 in Strehl ratio and ~1.26 in encircled energy, and a ~2.03-fold reduction in residual wavefront error. The IR-umPWFS remained robust to tip-tilt offsets up to 3 lambda/D at 1400 nm. It is a strong candidate for future XAO systems: operating in the infrared extends the linear range sufficiently to remove the need for modulation, enabling higher loop speeds no longer limited by the modulation mirror, which contributed to the improved on-sky performance. The OHP turbulence (D/r0 ~ 17 at 1400 nm) is comparable to typical VLT conditions (D/r0 ~ 20), supporting the relevance of these results for VLT/RISTRETTO.

astro-ph.IM↗

arXiv2026

Characterization and on-sky testing of photonic, AWG-based astronomical spectrographs

Astrophotonics is a field that intends to meet the needs of next-generation instruments at a small footprint, low cost, and high stability, compared to bulk-optics-based alternatives. Much development effort is driven by the stringent requirements of direct detection and characterization of exoplanets. Our team works in characterizing Arrayed-Waveguide Grating (AWG) chips for photonics-based, high-resolution, near infrared spectro-interferometry. AWG spectrographs allow to test the feasibility of photonic spectro-interferometers for exoplanet characterization, another step towards fully photonic instruments for astronomy. We present the current status of our AWG characterization and a preliminary on-sky qualification campaign at the PAPYRUS AO system. We present the CoLiBRIS-AWG spectrograph prototype built for on-sky testing, and preliminary results using our high-resolution (H band, R~18000) AWG for observations of Arcturus (alpha Boötes) and Betelgeuse (alpha Orionis). This work contributes to assessing the capabilities of photonic spectroscopy for the development of future compact instruments.

astro-ph.IM↗

arXiv2026

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↗