Spectroscopic fourth-order coronagraph for the characterization of terrestrial planets at small angular separations from host stars
arXiv:2012.04779 · doi:10.3847/1538-3881/abd248
Abstract
We propose a new approach for high-contrast imaging at the diffraction limit using segmented telescopes in a modest observation bandwidth. This concept, named "spectroscopic fourth-order coronagraphy", is based on a fourth-order coronagraph with a focal-plane mask that modulates the complex amplitude of the Airy disk along one direction. While coronagraphs applying the complex amplitude mask can achieve the theoretical limit performance for any arbitrary pupils, the focal plane mask severely limits the bandwidth. Here, focusing on the fact that the focal-plane mask modulates the complex amplitude along one direction, we noticed that the mask can be optimized for each spectral element generated by a spectrograph. We combine the fourth-order coronagraph with two spectrographs to produce a stellar spectrum on the focal plane and reconstruct a white pupil on the Lyot stop. Based on the wavefront analysis of an optical design applying an Offner-type imaging spectrograph, we found that the achievable contrast of this concept is 10^{-10} at 1.2 - 1.5 times the diffraction limit over the wavelength range of 650 - 750 nm for the entrance pupil of the LUVOIR telescope. Thus, this coronagraph concept could bring new habitable planet candidates not only around G- and K-type stars beyond 20 - 30 pc but also around very nearby M-type stars. This approach potentially promotes the characterization of the atmospheres of nearby terrestrial planets with future on- and off-axis segmented large telescopes.
arXiv comment26 Pages, 12 Figures, Accepted for publication in The Astronomical Journal
References in corpus (15)
- Water Vapor and Clouds on the Habitable-Zone Sub-Neptune Exoplanet K2-18b
- Water vapour in the atmosphere of the habitable-zone eight Earth-mass planet K2-18 b
- How to Characterize Habitable Worlds and Signs of Life
- Exoplanet Biosignatures: Observational Prospects
- Exoplanets imaging with a Phase-Induced Amplitude Apodization Coronagraph - I. Principle
- High Performance Lyot and PIAA Coronagraphy for Arbitrarily shaped Telescope Apertures
- High Contrast Imaging with an Arbitrary Aperture: Active Correction of Aperture Discontinuities
- Improved High Contrast Imaging with On-Axis Telescopes using a Multi-Stage Vortex Coronagraph
- Apodized pupil Lyot coronagraphs for arbitrary apertures. V. Hybrid Shaped Pupil designs for imaging Earth-like planets with future space observatories
- Vortex coronagraphs for the Habitable Exoplanet Imaging Mission (HabEx) concept: theoretical performance and telescope requirements
- Eighth-Order Image Masks for Terrestrial Planet Finding
- Lyot-plane phase masks for improved high-contrast imaging with a vortex coronagraph
- A Family of Phase Masks For Broadband Coronagraphy Example of the Wrapped Vortex Phase Mask Theory and Laboratory demonstration
- Point Spread Function of Hexagonally Segmented Telescopes by New Symmetrical Formulation
- Fourth-order Coronagraph for High-Contrast Imaging of Exoplanets with Off-axis Segmented Telescopes