# The ARIEL Mission Reference Sample

## TL;DR

The ARIEL mission aims to study the atmospheres of around 1000 diverse exoplanets to understand their formation and evolution, utilizing a carefully estimated sample based on current and expected discoveries.

## Contribution

This paper presents the assumptions and methodology used to estimate an optimal and realistic sample of exoplanets for the ARIEL mission, including known and expected discoveries.

## Key findings

- ARIEL can observe approximately 1000 exoplanets within four years.
- The sample includes gaseous and rocky planets around stars of various types.
- The mission's target list will evolve with new exoplanet discoveries.

## Abstract

The ARIEL (Atmospheric Remote-sensing Exoplanet Large-survey) mission concept is one of the three M4 mission candidates selected by the European Space Agency (ESA) for a Phase A study, competing for a launch in 2026. ARIEL has been designed to study the physical and chemical properties of a large and diverse sample of exoplanets, and through those understand how planets form and evolve in our galaxy. Here we describe the assumptions made to estimate an optimal sample of exoplanets - including both the already known exoplanets and the "expected" ones yet to be discovered - observable by ARIEL and define a realistic mission scenario. To achieve the mission objectives, the sample should include gaseous and rocky planets with a range of temperatures around stars of different spectral type and metallicity. The current ARIEL design enables the observation of ~1000 planets, covering a broad range of planetary and stellar parameters, during its four year mission lifetime. This nominal list of planets is expected to evolve over the years depending on the new exoplanet discoveries.