Dimensional stability in a space telescope is one of the important factors for performing high-resolution observations. The supporting structures between the primary and the secondary mirrors in a space telescope are required to maintain the mirror positions with the proper focus for minimizing the optical alignment error. In orbit, the harsh environment subjects a space telescope to temperature variations that can lead to deformation of those structures and degradation of the telescope’s optical performance. Several approaches are available for achieving high dimensional stability. They include minimizing temperature variations with active thermal control, designing the structure with low thermal expansion materials, and correcting the shape and/or position of the structure with actuators. An optimum combination of these measures is determined based on an accurate evaluation of the dimensional stability of the structures. This paper proposes a displacement measuring interferometer system with a simple, robust, and compact sensor that can monitor the dimensional stability of the precise structure by integrating the sensor into the structure. In this technique, a Fabry–Perot displacement sensor was built into the end of a strut that is a component of a metering truss structure. Two types of truss struts were tested to verify the performance of the proposed technique in measuring thermal expansions. The first one was the prototype that was made of stainless steel (SUS304). The other strut was made of a low thermal expansion ceramic (SiAlON) that is one of the most promising materials for a highly thermo-stable satellite structure. The thermal dimensional stability of these struts was evaluated by using the proposed technique and compared with conventional dilatometers for validating this new technique. The results showed that the technique has similar precision to the conventional measurement system and provide a more convenient and stable measurement system.

空间望远镜的尺寸稳定性是进行高分辨率观测的重要因素之一。在太空望远镜中，需要在主镜和副镜之间的支撑结构来保持镜的位置并具有适当的焦点，以最大程度地减少光学对准误差。在轨道上，恶劣的环境使太空望远镜经受温度变化，这可能导致这些结构变形并降低望远镜的光学性能。有几种方法可以实现高尺寸稳定性。其中包括通过主动热控制将温度变化降至最低，使用低热膨胀材料设计结构以及使用执行器校正结构的形状和/或位置。这些措施的最佳组合是根据对结构尺寸稳定性的准确评估确定的。本文提出了一种位移测量干涉仪系统，该系统具有简单，坚固且紧凑的传感器，可以通过将传感器集成到结构中来监视精确结构的尺寸稳定性。在这项技术中，法布里-珀罗位移传感器内置在支柱的末端，支柱是计量桁架结构的组成部分。测试了两种类型的桁架支柱，以验证所提出技术在测量热膨胀方面的性能。第一个是不锈钢（SUS304）制成的原型。另一个支柱是由低热膨胀陶瓷（SiAlON）制成的，这是用于高度热稳定的卫星结构的最有希望的材料之一。这些支柱的热尺寸稳定性通过使用所提出的技术进行了评估，并与传统的膨胀计进行了比较，以验证该新技术。结果表明，该技术具有与常规测量系统相似的精度，并提供了更加方便，稳定的测量系统。