The Calibration Units of KM3NeT

KM3NeT is a deep-sea infrastructure composed of two neutrino telescopes being deployed in the Mediterranean Sea : ARCA, near Sicily in Italy, designed for neutrino astronomy and ORCA, near Toulon in France, designed for neutrino oscillations. These two telescopes are 3D arrays of optical modules used to detect the Cherenkov radiation, which is a signature of charged particles going faster than light in the sea water. To achieve the best performance for the events reconstruction in the telescopes, the exact location of the optical modules, affected by sea current, must be known at any time and the timing resolution between optical modules must reach the nanosecond. Moreover, the properties of the environment in which the telescopes are deployed, such as temperature and salinity, must be continuously monitored because they affect the timing and positioning calibration. KM3NeT is going to deploy several dedicated Calibration Units to meet these calibration goals. The Calibration Base will host several instruments : a Laser Beacon for time calibration and an acoustic emitter and a hydrophone for positioning of the optical modules. To complete the positioning calibration, some of these Calibration Units will be equipped with an Instrumentation Unit hosting environmental monitoring instruments. Because of the difference in size between ARCA and ORCA, the design of the Calibration Unit is not the same for the two sites. This proceeding describes all the devices, features and purposes of the Calibration Units with a focus on ORCA Calibration Unit and its status.