A technique to evaluate on-orbit thermal deformation for large precise structures in ASTRO-H

ASTRO-H is a next-generation X-ray observatory satellite planned for launch in fiscal 2015. Because ASTRO-H is a large structure and requires precise and accurate pointing, an understanding of on-orbit thermal deformation behavior is particularly important to the success of the ASTRO-H mission. In the conventional technique for predicting thermal deformation, testing is performed in a thermal vacuum chamber so asto simulate the temperature distribution on orbit. However, when using this conventional technique it is difficult to observe the detailed characteristics of the tested structures due to the limits of the applied temperature distribution cases. To overcome this problem, we propose a new evaluation technique for ASTRO-H. In our technique, on-orbit prediction of thermal deformation is performed thorough numerical simulation using a finite element (FE) model. The validation and correlation of the FE model are carried out by comparing results with thermal deformation test data collected in advance. This technique is especially suitable for satellites that are exposed to various thermal conditions on orbit. Using this technique, we confirmed all of the requirements for on-orbit pointing accuracy and precision in ASTRO-H.