This is a multi-object instrument that is being deployed on the 4.2 m VISTA telescope of the European Southern Observatory. It can deploy 2436 science fibres on a field of view of 2 degrees of diameters. Some fibres feed low resolving power spectrographs (R 5000) and some a high resolving power spectrograph (R 20000). The instrument is currently being installed at the telescope and shall begin operations at the end of 2025 or early 2026. It shall initially operate for five years operating 10 surveys defined by the 4MOST consortium and 15 community surveys that have been approved, after a call for proposals.
Observatoire de Paris was responsible for designing the high resolution spectrograph in phase A, because of this LIRA has a seat, currently occupied by P. Bonifacio, as non-voting member on the 4MOST executive board. The two members of pôle Etoiles et Galaxies that are also members of the 4MOST consortium have the responsibility of defining the target input catalogues for the S2 survey (Milky Way High Resolution).
