The Pyramid WFS with extended reference source
Enrico Pinna, Alfio Puglisi, Javier Argomedo, Fernando Quiros-Pacheco, Armando Riccardi, Simone Esposito
Osservatorio di Arcetri
During the LBT FLAO commissioning, the Pyramid Wave-Front Sensor (PWFS) demonstrated on sky its potential as component of a NGS SCAO system. These results confirmed the expected PWFS sensitivity in presence of a point-like guide source. The performances of the PWFS using an extended object as reference in astronomical applications have not yet been deeply investigated. In this work we show some preliminary laboratory result obtained on the LBT FLAO system #2 operated using an extended reference sources of diameter up to 1.6”. During the tests, as expected, the PWFS showed a sensitivity reduction due to the reference source extension. The sensitivity reduction only affects modes below a given radial order, leaving the sensitivity of the higher order modes unaffected. The limiting radial order increases with the reference source diameter. Our result suggests that AO systems, with an actuator pitch FLAO-like (30cm) and using a PWFS, can deliver high contrast images in H and K bands using reference object with diameter less than 1” and integrated Rmag < 9.5. The achieved result will be discussed in the framework of the ELTs AO systems and in context of LGS wavefront sensing.