行星(月球)自转监测望远镜的原理样机地面验证实验

The Ground-based Experiment of the Prototype of Planetary(&Lunar)Rotation Monitor Telescope

类地行星(月球)自转监测望远镜的科学目标是在行星(月球)表面现场测量行星(月球)自转并研究其内部结构和物理性质.为了验证全新的观测原理和资料处理方法,项目团队设计制造了一套原理样机,在一台商用天文望远镜的光路前端增加3面反射镜组,使其具有同时观测3个视场的能力.自2017年起在地面上开展了观测实验,获得了混合有3视场星象的图像.通过计算星象在前后图像上的位移实现了归属视场识别,使得观测效果与分视场独立观测等同,证明了用一台设备同时观测多视场的可行性.处理图像并通过3个视场中心的指向变化归算地球自转轴的空间指向,与理论值比较偏差平均约1′′,证明了观测原理和数据处理方法有效.对各种观测误差来源进行了分析,包含大气折射、仪器热稳定性和光学分辨能力的影响等,指出采用更长焦距的望远镜可以提高空间分辨率,优化形变控制可以提高观测稳定性.改进多视场同时观测中的光学设计也有助于精度的提高.

The scientific objective of the Planetary(&Lunar)Rotation Monitor(PRM)telescope is to study the planet’s(the Moon’s)rotation and their inner structure and physics by in-situ observation.In this work,the prototype of the telescope is designed and manufactured.The prototype’s optical system is a commercial astronomical telescope.A trihedron mirror set is placed at the beginning of its light path to realize observing three fields of view(FOVs)simultaneously.The ground-based validating observation began in 2017.Images containing stars from three FOVs were achieved.Star images from different FOVs initially mix together,and can be categorized into three FOVs respectively,in which motion behavior of star images on CCD plate between adjacent exposures differs with FOVs.The principle,hardware design and image process are demonstrated here.From the observational images,the direction change of three FOVs in space due to the Earth’s rotation are shown,and the mean direction of the rotation axis of the Earth in celestial sphere can be calculated.The deviation of the determined celestial coordinate of the rotation axis from the theoretical values is shown around 1′′.The main errors in observation are discussed,including atmospheric reflection,thermal deformation of the commercial telescope,low optical resolution caused by short focal length,optical aberration in multiple FOVs’observation,etc.All these experience and knowledge will be adopted in the next-generation design of PRM,and help to realize the goal of the final PRM which will be launched to the Moon in future.