The design and assembly of a long-focal-length telescope with aluminum mirrors

Three-mirror-anastigmat (TMA) telescopes have been widely used in long-focal length payloads especially in space due to its excellent features for correcting aberrations, wide spectral range and shorter physical requirement. This paper describes the assembly results of the telescope that may be used in the payload of Formosat-5 follow-on mission. The telescope was a pathfinding one that was designed according to the target specifications of National Space Organization. Optical design is of Korsch type with three mirrors in the system, which is different from that in Formosat-5 RSI. Mechanical design and assembly procedures require modification from those of Formosat-5 accordingly. focal length of the telescope was 7714 mm and F-number 14. Diamond-turned aluminum mirrors were adopted due to time and budget constraint. Barrel was selected as structure configuration between primary and secondary mirrors, while struts were designed to support the tertiary mirror. A main plate was used to connect the barrel and struts. Analysis of the structure has been performed.