Characterisation of a new Laser Guide Star Wavefront Sensor

Adaptive Optics (AO) is a technology that improves the resolution of large telescopes by correcting aberrations introduced by the Earth’s atmosphere, enabling them to capture sharper astronomical images. Traditional AO relies on bright natural stars close to the science target for reference, limiting its use to specific areas of the sky. To overcome this limitation, scientists introduced the concept of Laser Guide Stars (LGS), such as sodium LGS. These artificial stars are created using lasers fired from the telescope position to excite the atomic sodium atmospheric layer, creating an elongated source in the sky. This unique nature of sodium LGS presented challenges for existing wavefront sensors used in AO systems. This thesis focuses on the Ingot Wavefront Sensor (I-WFS), a novel concept initially proposed by Ragazzoni and refined by the Adaptive Optics Group at the INAF-Osservatorio Astronomico di Padova. The I-WFS is designed to address the challenges posed by Sodium LGS and other LGS. It leverages the Scheimpflug principle to sense the full 3D volume of the elongated LGS. This innovative sensor is suitable for use in large telescopes. Currently it is designed to match the specifications of the European Extremely Large Telescope (E-ELT). My work has included the development of advanced algorithms for manipulating the LGS source on a screen, improving alignment procedures, and correcting systematic errors. I have also implemented a quasi closed-loop algorithm for autonomous monitoring and realignment. Ongoing research includes the development of a search algorithm and the integration of real sodium profiles using a new OLED screen. Our ultimate goal is to gain a comprehensive understanding of the I-WFS’s performance and its potential implementation in future Extremely Large Telescopes (ELTs) equipped with AO.