Abstract

Radio-velocity measurements have reached the 1 m/s precision during the past ten years. The HARPS spectrograph has played a fundamental role as a precursor for other instruments and by discovering most of the super-Earths and Neptune-mass planets known to date. The next natural step is to push for a 10 cm/s precision that would allow to reach also Earth-like planets, i.e. Earth-mass planets in the habitable zone of their parent star. Ideally, the radial-velocity measurement would also be combined with transit measurements. Since however most of the candidates delivered by transits surveys are faint, instrumental precision must be combined with large telescopes and high instrumental throughput. The ESPRESSO instrument at ESO ’s VLT is designed to accomplish both tasks. It will use most of HARPS ’s stability concepts while being adapted for an 8-m telescope. Furthermore, limiting factors had to be identified and removed to reach the desired precision. In my talk I will describe ESPRESSO ’s design, its technical challenges, as well as the observational strategies to optimise the scientific output in the presence of stellar ‘noise’. I will also provide an outlook of the scientific capabilities of this high-resolution, high-efficiency visible spectrograph in both its 1-UT and 4-UT mode, i.e. when used in combination with a 16-m equivalent telescope.