Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Curs: 2020, Tutors: Carme Jordi, Ignasi Ribas, Guillem Anglada-EscudéFuture instruments (e.g. JWST, ARIEL) will study the atmospheres of transiting exoplanets with an unprecedented level of detail. In this work, the retrievability of atmospheric parameters of exoplanets is studied for hot Jupiters, a warm Neptune and a cool sub-Neptune in the context of the ARIEL mission. Synthetic observations are generated using TauREx III for forward-modelling and retrieval. The results show that ARIEL is able to significantly detect main gaseous species in hot Jupiters and warm Neptunes with a single transit observation. The study of smaller and cooler planets will require several observations. For K2-18 b, I estimate a minimum of 50 observations to distinguish a primary atmosphere from a secondary one. This work outlines the scientific capabilities of ARIEL and provides estimates on the quality of observations for different types of exoplanets
