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Abstract

A new era is expected to arrive around 2030 with a pool of exoplanets amounting to about ten thousand, including mainly small to medium-sized planets, and over a hundred habitable terrestrial rocky planets, thanks to the space-borne transit surveys by the Kepler, TESS and PLATO missions, and ground-based transit and radial-velocity (RV) surveys. The exoplanet community has proposed various missions for detailed characterization of the terrestrial planets, but it is quite technique-demanding and time-consuming especially for those with wide orbits. The currently proposed ESA mission ARIEL is a first step for this purpose, and it is powerful for the characterizations of planets down to warm super-Earths. The NASA HabEx and LUVOIR missions are mega projects to further tackle down to habitable rocky planets, and will be in operation after 2035 if approved. In the meanwhile, China is funding a concept study of a 4-6m space telescope named HABITATS ( HABItable Terrestrial planetary ATmospheric Surveyor). HABITATS will be dedicated for the characterization of habitable rocky planets around nearby stars, which aims to start its operation within the next 10-15 years and last for 5+ years. We describe briefly the preliminary concept study of this mission and propose a baseline telescope and instrument parameter values based on our simulation results. International collaborations from various institutes and research groups are welcome to join this ambitious effort in the aspects of science, instrumentation, platform, funding resources.