Realization of the ESO-VLT ESPRESSO instrument control electronics

Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO) is the latest instrument installed at the European Southern Observatory (ESO)-Very Large Telescope (VLT) site in Chile. To fulfill its scientific requirements, ESPRESSO can operate both in 1-UT mode (using any of the four VLT unit telescopes) and in 4-UT mode. In 4-UT mode, the light of the four 8-m telescopes is combined in an incoherent focus to form a 16-m equivalent telescope, thus providing the largest collecting area ever at optical-NIR wavelengths. In ESPRESSO, dedicated front end units (FEUs) allow collection of the light coming from the telescope tunnels conveying it through fibers to the spectrograph. All the functionalities of the FEUs are managed by the instrument control electronics (ICE) and software. We aim to provide the detailed description of the realization of this ICE, based on Beckhoff programmable logic controllers. In particular, we show ESPRESSO ICE functions distribution, the motion control characteristics, and the main validation tests performed during the European and Chilean integration phase, which led to technical acceptance of ESPRESSO by ESO before its first light achieved at the end of 2017.