SPICA infrared coronagraph for the direct observation of exo-planets

TL;DR

This paper proposes a mid-infrared coronagraph for the SPICA space telescope to enable direct imaging of exoplanets, demonstrating laboratory success in achieving high contrast and discussing technological advancements for future implementation.

Contribution

The paper introduces a feasible binary-shaped pupil coronagraph for SPICA, with laboratory demonstrations achieving high contrast, and discusses technological progress for space-based exoplanet observation.

Findings

Achieved a contrast of 6.7x10^{-8} with binary-shaped pupil coronagraphs.

Demonstrated a contrast of 6.5x10^{-7} with hybrid coronagraphs using active wavefront control.

Developed key technologies including binary masks, PSF subtraction, and cryogenic deformable mirrors.

Abstract

We present a MIR coronagraph to target the direct observation of extrasolar planets for SPICA, in which a coronagraph is currently regarded as an option of the focal plane instruments. The primary target of the SPICA coronagraph is the direct observation of Jovian exo-planets. A strategy of the baseline survey and the specifications for the coronagraph instrument for the survey are introduced together. The main wavelengths and the contrast required for the observations are 3.5-27um, and 10^{-6}, respectively.Laboratory experiments were performed with a visible laser to demonstrate the principles of the coronagraphs. In an experiment using binary-shaped pupil coronagraphs, a contrast of 6.7x10^{-8} was achieved, as derived from the linear average in the dark region and the core of the PSF. A coronagraph by a binary-shaped pupil mask is a baseline solution for SPICA because of its feasibility and robustness. On the other hand, a laboratory experiment of the phase induced amplitude apodization/binary-mask hybrid coronagraph has been executed to obtain an option of higher performance, and a contrast of 6.5x10^{-7} was achieved with active wavefront control.Potentially important by-product of the instrument, transit monitoring for characteization of exo-planets, is also described. We also present recent progress of technology on a design of a binary-shaped pupil mask for the actual pupil of SPICA, PSF subtraction, the development of free-standing binary masks, a vacuum chamber, and a cryogenic deformable mirror. Considering SPICA to be an essential platform for coronagraphs and the progress of key technologies, we propose to develop a mid-infrared coronagraph instrument for SPICA and to perform the direct observation of exo-planets with it.