Rubin Observatory active optics system status

The Vera C. Rubin Observatory is now under construction on Cerro Pachon in Chile. This ground-based facility is designed to conduct the Legacy Survey of Space and Time (LSST), which is a decade-long time-domain optical survey of the night sky. The system aberrations introduced by temperature gradients, hysteresis and other non-predictable errors can prevent the telescope from delivering a consistently high-quality image over its 3.5 degrees field of view, necessary to the LSST scientific goals. Therefore, the active optics system (AOS) uses a combination of an open-loop and a closed-loop correction. The AOS open-loop is planned to correct for typical gravity variations while the AOS closed-loop will correct the real-time (within 30s) system aberrations. The components used for this task consist mainly of: two mirrors with active support systems (M1M3 and M2), two hexapods and curvature wavefront sensors integrated to the focal plane of the science detector. By the beginning of 2019, both M1 and M3 mirrors had been extensively tested using interferometry techniques, providing necessary measurements to refine our Finite Element models. This will help to achieve higher image quality when integrating all mirrors on the telescope. Progress has also been made on the active optics pipeline, which allows for conversion of the wavefront sensor images into corrective data for the mirrors and hexapods. In this paper, we will present the main results from the mirror testing as well as predicted performance of the AOS using these results. Finally, we will discuss the test plan for commissioning the AOS on the telescope.