Design, manufacturing, and validation of the mirrors for an experimental Korsch telescope

Abstract

From 2015, NSPO (National Space Organization) began to develop off-axis Korsch telescope system for next generation earth observation mission. The experimental Korsch telescope system is consist of five mirrors, including: (1) M1: 550mm diameter clear aperture concave primary mirror, (2) M2: Convex secondary mirror, (3) M3: Off-axis concave tertiary mirror with rectangular aperture, (4) FM1 & FM2: Two folding mirrors with rectangular aperture and flat surface. All the experimental mirrors are designed with lightweight structure and made of fused silica. Since early 2016, we collaborated with Taiwanese domestic company and manufactured all the mirrors for the experimental Korsch telescope. Moreover, we not only accomplished the assembly of M1 but also implemented the form error metrology technique to measure the surface error of M1 with high repeatability in 2017. Recently, in order to validate the structural and athermal design of opto-mechanical structures, several vibration tests and thermal experiments have been accomplished in 2018. The experimental data could not only help us to enhance the analysis accuracy of the finite element model but also benefit to our automated opto-mechanical design system. For next developed phase, the aspheric polishing and reflective coating will be achieved till 2021.