Hα和白光望远镜的热光学试验

Thermo-optical testing of Hα and white telescope

Hα和白光望远镜(HWT)是中国空间太阳望远镜(SST)有效载荷之一,为研究HWT的光学性能受温度环境的影响,在进行地面观测工况下温度场测量和数值模拟的基础上,确定了热光学试验的温度控制工况,建立了一套热真空状态下的光学性能检测系统。该热光学试验系统由被测光学系统、真空系统、温度测量和控制系统以及波前检测系统组成。研究了系统中光楔镜结构、副镜结构、主镜结构、准直镜结构和成像镜结构这5个关键部位在不同温度控制工况下的光学性能。试验结果表明,在副镜结构温度不高(低于40℃)的情况下,HWT望远镜在地面观测工况下的光学性能约为λ/8,可以满足λ/6的设计要求。以HWT为研究对象,实施了Hα和白光望远镜的热光学试验过程,实现了对不同温度控制工况下的HWT系统进行光学性能检测,探索的热光学试验思路和方法也适用于其它太阳观测光学望远镜。

The Hα and White Telescope（HWT） is one of the payloads of the Chinese Space Solar Tele-cope（SST）. To study the impact of the thermal environment on the optical performance of the HWT, the temperature conditions of the thermo-optical testing are designed on the basis of the measurement and numerical simulation of the ground observing condition. A thermo-optical testing system is established to test the optical performance of the HWT under a thermal vacuum condition. The thermo-optical testing system comprises mainly four sub-systems： an optical system to be tested, a vacuum system, a temperature measurement and control system, and a wavefront sensing system. The optical performance of the five important structures in the HWT system at the different temperature conditions is investigated, including the wedges, secondary mirror, primary mirror, collimation lens, and the imaging lens. The results show that when the temperature of the secondary, mirror is lower than 40 ℃, the optical performance of HWT is about λ/8, which satisfies the requirement of λ/6. This paper implements a thermo-optical testing procedure for the HWT under different temperature control conditions. The design ideas and test methods are also applicable in similar optical telescope designs for the solar observation.