Design and assembly of a nested imaging X-ray telescope for the Hot Universe Baryon Surveyor mission

The Hot Universe Baryon Surveyor(HUBS)mission will carry a nested X-ray telescope capable of observing an energy range from 0.5 keV to 2 keV to study hot baryon evolution.In this paper,we report the latest progress in the design and construction of nested X-ray telescopes which were designed to use a three-stage conic-approximation type assembly to simplify the manufacturing process.The mirror substrate is made using the thermal glass slumping method,with mirrors characterized by a root-mean-square roughness of 0.3 nm,with expected high reflectivity and good thermal stability.We also discuss methods of telescope construction and conduct a deformation analysis of the manufactured mirror.The in situ measurement system program is developed to guide the telescope assembly process.