Abstract
ESPRESSO, Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations, is now under the assembly, integration and verification phase and will be installed beginning next year at Paranal Observatory on ESO's Very Large Telescopes. The Front End is the modular system in the Combined Coudé Laboratory receiving the light from the four VLT Units, providing the needed connection between the input signal, i.e., object light, sky light, and calibration light, to feed the spectrograph through optical fibers. The modular concept of the FE Units drove the system design and the alignment workflow. We will show the integration method of the single FE modules adopted to guarantee the necessary repeatability between the different Units. The performances of the system in terms of image quality and encircled energy in the observed point spread function are reported. Finally, the strategy followed in the Paranal Combined Coudè Laboratory to define the convergence point of the four UTs is described, along with the procedure used to align the ground plates, the main structure, and the mode selector.
