The calibration module and radial velocity reference unit are used to provide the instrument with the spectrum of well known laboratory lamps and optical devices (e.g., hollow-cathode lamp, thermalized Fabry-Perot etalon) to correct and calibrate spectra with the highest possible precision. These facilities ensure in particular that any spurious drifts of the spectrum of the observed star with respect to the detector on both short and long timescales can be tracked at a radial velocity precision better than 1 billionth of the speed of light.