Ariel Science Advisory Team UK activities

In November 2020 Ariel was adopted as M4, the fourth medium-sized mission in ESA's Cosmic Vision Plan. Ariel is the first space mission dedicated to measuring the chemical composition and thermal structures of a large, well-constructed sample of exoplanets, enabling planetary science far beyond the boundaries of the Solar System. Ariel will study what planets are made of and how planetary systems form and evolve by surveying a diverse sample of ~ 1000 of exoplanets. For this ambitious scientific programme, Ariel is designed as a dedicated survey mission for transit and eclipse spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10-50 part per million (ppm) relative to the star. Given the brightness of the target host stars more sophisticated techniques, such as eclipse mapping, will also be used to give deeper insights. These observations require a specifically designed, stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range covered by Ariel includes all the expected major atmospheric gases from e.g. H2O, CO2, CH4 NH3, HCN, H2S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Ariel data and data products will be of great interest and utility for the entire exoplanet community, beyond those directly involved in the mission. In response, the data policy has been designed to embrace the astronomy community in general and the exoplanet community in particular. The intention is to provide high quality data in a timely manner and to have a continuous dialogue with the wider community, maximising the science and impact that can be achieved by the mission. The target list will be drawn from a larger list of all potential Ariel targets. This larger list will be made public and maintained publicly. Inputs will be solicited from the general community through formal time-bounded processes such as whitepapers and meetings. Moreover the list will be presented and maintained in an interactive environment enabling direct input from members of the community. The target list will be drawn from the larger list through scientific priorities and other guidelines through scheduling exercises performed under the responsibility of the Ariel Science team. The community will be kept informed about the status of the target list, as will the ESA Advisory Bodies whose feedback will be solicited. Beyond the science community, Ariel's mission to characterise distant worlds offers an immense opportunity to capture the public imagination and inspire the next generation of scientists and engineers. Through the provision of enquiry-based educational programmes and citizen science platforms, school students and members of the public will have the opportunity to participate directly in the analysis of Ariel.