近地天体望远镜增加卡氏内氏焦点的可行性研究

Feasibility Study on the Addition of Cassegrain Focus and Nasmyth Focus to the China Near Earth Object Survey Telescope

近地天体望远镜是巡天望远镜,具有短焦距、大视场、低空间分辨率的光学特点.望远镜只有一个主焦点,焦距1.8 m,底片比例9μm/″,像斑几何能量集中度EE80≤2″(像斑环绕能量的80%,即80%encircled energy,记为EE80),有效视场直径为4.28°(14.3 deg^2),目前配10 k×10 k的STA1600LN CCD(charge-coupled device)camera,观测视场为9 deg^2.通过光学系统设计,在原光学系统上增加副镜及场改正镜,获得了焦距9m的卡氏焦点和内氏焦点,底片比例43.6μm/″,在直径15′的可用视场内,像斑EE80≤0.5″,为近地天体望远镜实现多终端观测提供了理论依据.

As a typical Schmidt telescope,China Near Earth Object Survey Telescope(CNEOST)has the optical characteristics of short focal length,large field of view,and low spatial resolution.The optical system has a prime focus with a focal length of 1.8 m,the film scale of 9μm/1″,and the geometric encircled energy concentration EE80≤2″.The diameter of the optical FOV(field of view)is 4.28°,and the observational FOV is 9 deg^2 with the equipment of the current 10 k×10 k STA1600LN CCD(chargecoupled device)camera.In order to expand the observation capacity of the telescope,a secondary mirror and a field corrector are added in the original optical system,and the Cassegrain focus and Nasmyth focus with a focal length of 9 m can be obtained.The diameter of the optical FOV of new focus is 15′,and the geometric encircled energy concentration EE80≤0.5″.It provides a prerequisite for high-resolution photography,spectrum,and high-precision multicolor photometry of solar system small bodies.