Hartmann Testing and Vibration for RST (WFIRST)

摘要

An important question in the development of the Roman Space Telescope (RST) is how to optically test it at the highest levels of assembly, after the instruments have been integrated with the telescope. Our current strategy is double-pass testing using image-based wavefront sensing (phase retrieval). In this paper, we consider alternative strategies based on Hartmann testing, using either a pupil-plane mask or a mirror array. We developed first-order design considerations for the implementation of such Hartmann tests in the context of RST and designed two specific Hartmann tests to evaluate in further simulations. One of the major suggested benefits of Hartmann testing is insensitivity to vibrations that induce either line-of-sight jitter or dynamic changes in wavefront aberration. In order to understand whether this is true (and under what conditions), we developed a physical optics simulation of our two Hartmann tests under both Gaussian line-of-sight jitter and sinusoidal dynamic secondary mirror motion. We then also developed a data reduction process for fitting these Hartmann test images and estimating system wavefronts. We found that, somewhat contrary to expectations, the first-order design trades required to make a relatively high fidelity optical test lead to a Hartmann test design that is in some cases more sensitive to vibration than an equivalent phase retrieval test using short exposures. We will present both our first order design rules, and the Hartmann design vibration sensitivity analysis.