Wide field of view optical assemblies for severe environments in space

Wide field-of-view (WFOV) lenses covering a full field of view of >120 degrees have been designed and analyzed for spaceborne applications for use in severe environments. The optical designs have been passively athermalized and achromatized over the visible waveband for use during operating conditions and the opto-mechanical designs have been ruggedized for survivability in severe environmental conditions with random vibration levels exceeding 2000 Grms and cryogenic temperature conditions reaching -175 degrees C. To characterize the performance and survivability of the lens assembly for such environments, image quality and random vibration testing was performed on representative optical assemblies, with previous flight experience, before and after exposure to cryogenic liquid nitrogen temperatures. The dynamic test environment consists of low-level random vibration testing in each of the three orthogonal axes (X, Y & Z) and the image quality testing performed includes resolution (MTF), distortion, and effective focal (EFL). Finite element analysis (FEA) was performed to verify survivability to full random vibration spectrums and shock levels; external testing was performed with flight hardware and results were validated. High correlation of characterization measurements before and after cryogenic exposure indicate the optical assemblies' ability to withstand severe temperature environments without any impact to functionality or performance. This document provides an overview of the optical and opto-mechanical lens designs for severe space environments, a comprehensive look into component material characteristics over temperature for various space-grade adhesives used to mechanically retain lens elements, and detailed explanations of the cryogenic test methodology using a custom laboratory test setup to characterize the performance and survivability of lens assemblies and their various components.