Contrast performance of an 8m off-axis, segmented space telescope equipped with an adaptive optics system

Abstract

The Astro2020 decadal survey recommended an infrared, optical, ultra-violet (IR/O/UV) telescope with a $\sim$6~m inscribed diameter and equipped with a coronagraph instrument to directly image exoEarths in the habitable zone of their host star. A telescope of such size may need to be segmented to be folded and then carried by current launch vehicles. However, a segmented primary mirror introduces the potential for additional mid spatial frequency optical wavefront instabilities during the science operations that would degrade the coronagraph performance. A coronagraph instrument with a wavefront sensing and control (WS\&C) system can stabilize the wavefront with a picometer precision at high temporal frequencies ($>$1Hz). In this work, we study a realistic set of aberrations based on a finite element model of a slightly larger (8m circumscribed, 6.7m inscribed diameter) segmented telescope with its payload. We model an adaptive optics (AO) system numerically to compute the post-AO residuals. The residuals then feed an end-to-end model of a vortex coronagraph instrument. We report the long exposure contrast and discuss the overall benefits of the adaptive optics system in the flagship mission success.