Cryogenic, infrared, optical beamsplitter wavefront error analysis and test

Mounting large reflective-refractive optical elements for cryogenic space application requires careful engineering. Optical wavefront error performance is balanced with surviving launch environments and cryogenic temperatures. Mounting and ground testing of a 25 cm by 15 cm plano germanium optical beamsplitter element was completed. Cryogenic WFE testing was performed down to 115 K predicting compliance to operational environment performance requirements. This paper discusses the mount engineering including detailed analysis, testing, and results.