Space telescope design to directly image the habitable zone of Alpha Centauri

TL;DR

This paper proposes a specialized small space telescope design with advanced coronagraphy and post-processing techniques to directly image Earth-like planets in the habitable zone of Alpha Centauri, achieving high contrast and detection confidence.

Contribution

It introduces an innovative Silicon Carbide off-axis telescope with integrated coronagraph and multi-star wavefront control, optimized for high-contrast imaging of nearby star systems.

Findings

Achieves contrast ratios of 1e-10 necessary for Earth-like planet imaging.

Utilizes a stable Earth-trailing orbit for effective post-processing.

Enables 90% detection completeness of habitable zone planets.

Abstract

The scientific interest in directly image and identifying Earth-like planets within the Habitable Zone (HZ) around nearby stars is driving the design of specialized direct imaging mission such as ACESAT, EXO-C, EXO-S and AFTA-C. The inner edge of Alpha Cen A and B Habitable Zone is found at exceptionally large angular separations of 0.7 and 0.4 arcseconds respectively. This enables direct imaging of the system with a 0.3m class telescope. Contrast ratios in the order of 1e-10 are needed to image Earth-brightness planets. Low-resolution (5-band) spectra of all planets, will allow establishing the presence and amount of an atmosphere. This star system configuration is optimal for a specialized small, and stable space telescope, that can achieve high-contrast but has limited resolution. This paper describes an innovative instrument design and a mission concept based on a full Silicon Carbide off-axis telescope, which has a Phase Induce Amplitude Apodization coronagraph embedded in the telescope. This architecture maximizes stability and throughput. A Multi-Star Wave Front algorithm is implemented to drive a deformable mirror controlling simultaneously diffracted light from the on-axis and binary companion star. The instrument has a Focal Plane Occulter to reject starlight into a high-precision pointing control camera. Finally we utilize a Orbital Differential Imaging (ODI) post-processing method that takes advantage of a highly stable environment (Earth-trailing orbit) and a continuous sequence of images spanning 2 years, to reduce the final noise floor in post processing to 2e-11 levels, enabling high confidence and at least 90 percent completeness detections of Earth-like planets.