Exodus: A mission proposal to explore exoplanet evolution through understanding atmospheric escape

Understanding the variety of system architectures and formation histories of planetary systems remains a major challenge. Current detection methods are strongly biased towards short-period bodies, leaving a gap in the exoplanet population demographics. This paper outlines Exodus, a mission proposal to study the largely unexplored range of sub-Neptune to Jupiter-sized exoplanets with orbital periods greater than 100 days. The focus of the mission lies in the detection of these planets and characterisation of atmospheric escape to constrain their evolutionary pathways. For this, Exodus will directly image exoplanets with radii above
and measure signatures of the helium triplet at 1083 nm. Furthermore, the activity of the host star is monitored in the ultraviolet (UV) wavelengths to distinguish between two mechanisms of atmospheric escape: UV-driven mass loss and core-powered mass loss. The proposed mission design consists of a space telescope which requires a Lissajous orbit around
. The primary instrument uses an Integral Field Unit (IFU) optimised for direct imaging of exoplanetary systems in the near-infrared (NIR) domain. Simultaneous monitoring of the parent star is conducted via photometric observations of the Hα emission. In addition to the necessary instrumentation, we present a comprehensive spacecraft design considering important budgets like mass, power, and propulsion, as well as a thermal design. The mission described in this paper was developed during the Alpbach Summer School 2023, which focused on the theme ”Exoplanets: Understanding alien worlds in diverse environments.”.