MAVIS: optical distortions of the NGS WFS channel and their impact on the plate scale variation during tracking

Abstract

Natural Guide Star (NGS) wavefront sensors (WFS) play a crucial role in multi-conjugate adaptive optics systems by detecting low-order aberrations that laser guide stars cannot measure. In the framework of MAVIS, we plan to use the light from three NGSs to correct the tip-tilt and low-order errors of the wavefront. In this work, we conduct the analysis of the distortions caused by mid-spatial frequency figure errors of the optical surfaces in the NGS WFS channel of the adaptive optics module of MAVIS. These distortions, stemming from component imperfections, can significantly impact wavefront measurements and, consequently, the plate scale in the image plane of the entire instrument. We analyse their influence on the plate scale variations during tracking. Our study quantifies the effect, shedding light on the impact of non-common path distortions between the NGS WFS and the scientific instruments on plate scale variations, ultimately contributing to optimising the MAVIS performance.