Mechanical deformations of space mirrors under thermal stress and their effect on wavefront errors: measurements by ESPI and comparison with multiphysics modeling

Numerical modeling tools are widely used in space science, but are usually limited to the thermomechanical steps. However, many payloads are equipped with high performance optical systems with tight tolerances. Therefore, experimental testing of space optics in very realistic conditions is a mandatory process. This experimental step is both time consuming and expensive. A multiphysics modeling tool that also takes into account the optical performances would therefore be an elegant solution to avoid these drawbacks. In this paper we compare some experimental results with numerical results obtained from a multiphysics suite. The local displacements of two space mirrors have been measured by use of electronic speckle pattern interferometry (ESPI) and the deformation itself has been calculated by subtracting the rigid body motion. After validation of the thermo-mechanical model, experimental and numerical wavefront errors are compared.