Space Technology for Directly Imaging and Characterizing Exo-Earths

TL;DR

This paper discusses advanced space telescope technologies, including starshades and coronagraphs, for directly imaging Earth-like exoplanets and detecting potential biosignatures, outlining a roadmap for future missions.

Contribution

It provides a comprehensive roadmap for developing the necessary technology to directly image and characterize Earth-like exoplanets in space.

Findings

Starshade technology benefits mission stability requirements.

Coronagraphs require advanced telescope aperture and wavefront control.

Future missions like HabEx and LUVOIR aim to image habitable exoplanets.

Abstract

The detection of Earth-like exoplanets in the habitable zone of their stars, and their spectroscopic characterization in a search for biosignatures, requires starlight suppression that exceeds the current best ground-based performance by orders of magnitude. The required planet/star brightness ratio of order 1e-10 at visible wavelengths can be obtained by blocking stellar photons with an occulter, either externally (a starshade) or internally (a coronagraph) to the telescope system, and managing diffracted starlight, so as to directly image the exoplanet in reected starlight. Coronagraph instruments require advancement in telescope aperture (either monolithic or segmented), aperture obscurations (obscured by secondary mirror and its support struts), and wavefront error sensitivity (e.g. line-of-sight jitter, telescope vibration, polarization). The starshade, which has never been used in a science application, benefits a mission by being decoupled from the telescope, allowing a loosening of telescope stability requirements. In doing so, it transfers the difficult technology from the telescope system to a large deployable structure (tens of meters to greater than 100 m in diameter) that must be positioned precisely at a distance of tens of thousands of kilometers from the telescope. We describe in this paper a roadmap to achieving the technological capability to search for biosignatures on an Earth-like exoplanet from a future space telescope. Two of these studies, HabEx and LUVOIR, include the direct imaging of Earth-sized habitable exoplanets as a central science theme.