# Observing Exoplanets with High Dispersion Coronagraphy. I. The scientific potential of current and next-generation large ground and space telescopes

## TL;DR

This paper evaluates the potential of High Dispersion Coronagraphy (HDC) for directly imaging exoplanets, analyzing instrument configurations, and predicting performance for current and future ground and space telescopes, highlighting its advantages and limitations.

## Contribution

It introduces a simulation framework for HDC observations, compares ground and space telescope capabilities, and identifies optimal configurations for detecting Earth-like exoplanets.

## Key findings

- Ground-based ELTs are more suitable than space telescopes for Earth-like planet detection.
- HDC relaxes starlight suppression requirements by factors of 10^3 to 10^2.
- Optimal spectral resolutions are R=400 for HabEx and R=1600 for LUVOIR.

## Abstract

Direct imaging of exoplanets presents a formidable technical challenge owing to the small angular separation and high contrast between exoplanets and their host stars. High Dispersion Coronagraphy (HDC) is a pathway to achieve unprecedented sensitivity to Earth-like planets in the habitable zone. Here, we present a framework to simulate HDC observations and data analyses. The goal of these simulations is to perform a detailed analysis of the trade-off between raw star light suppression and spectral resolution for various instrument configurations, target types, and science cases. We predict the performance of an HDC instrument at Keck observatory for characterizing directly imaged gas-giant planets in near infrared bands. We also simulate HDC observations of an Earth-like planet using next-generation ground-based (TMT) and spaced-base telescopes (HabEx and LUVOIR). We conclude that ground-based ELTs are more suitable for HDC observations of an Earth-like planet than future space-based missions owing to the considerable difference in collecting area. For ground-based telescopes, HDC observations can detect an Earth-like planet in the habitable zone around an M dwarf star at 10$^{-4}$ starlight suppression level. Compared to the 10$^{-7}$ planet/star contrast, HDC relaxes the starlight suppression requirement by a factor of 10$^3$. For space-based telescopes, detector noise will be a major limitation at spectral resolutions higher than 10$^4$. Considering detector noise and speckle chromatic noise, R=400 (1600) is the optimal spectral resolutions for HabEx(LUVOIR). The corresponding starlight suppression requirement to detect a planet with planet/star contrast=$6.1\times10^{-11}$ is relaxed by a factor of 10 (100) for HabEx (LUVOIR).