Testing the 10 spectrograph units for DESI: approach and results

International audienceThe recently commissioned Dark Energy Spectroscopic Instrument (DESI) will measure the expansion history of theUniverse using the Baryon Acoustic Oscillation technique.The spectraof 35 million galaxies and quasars over 14000 sqdeg will be measuredduring the life of the experiment.A new prime focus corrector for theKPNOMayall telescope delivers light to 5000 fiber optic positioners.The fibers in turn feed ten broad-band spectrographs.A consortium of Aix-Marseille University (AMU) and CNRS laboratories (LAM, OHP and CPPM) together with LPNHE (CNRS, IN2P3, Sorbonne Université and Université de Paris) and the WINLIGHT Systems company based in Pertuis (France), were in charge of integrating and validating the performance requirements of the ten full spectrographs, equipped with their cryostats, shutters and other mechanisms. We present a summary of our activity which allowed an efficient validation of the systems in a short-time schedule. We detail the main results. We emphasize the benefits of our approach and also its limitations