VESPER (Very energetic Electron facility for Space Planetary Exploration missions in harsh Radiative environments) is a high energy electron beamline for radiation testing which is part of the CLEAR (CERN Linear Electron Accelerator for Research) experimental linear electron accelerator at CERN. The main application of the beamline is to characterise electronic components for the operation in a Jovian environment, in which trapped electrons of energies up to several hundred MeVs are present with very large fluxes. In addition, the use of the beam line for the characterisation of devices and detectors in a purely electro-magnetic beam for high-energy accelerator applications is also relevant.