Charged particle-induced noise in camera systems

When a camera system is operated in a flux of charged particles, it will generate transient signals. The charged particles will impinge on the focal plane array and generate tracks of ionized electron-hole pairs. The charge tracks will diffuse, and some of the charge will be collected as signal and the rest will recombine. Bremsstrahlung radiation will be generated in the structure around the camera, and the Bremsstrahlung photons will generate secondary electrons in the focal plane array. The radiation hits will look like small stars. The charged particles will also make the optics "glow" due to luminescence and Cerenkov radiation. This paper utilizes a charged particle flux found in the open literature for a future spacecraft called Europa Orbiter to show the effects of charged particles on a camera system. A simple focal plane model is constructed based on typical values, and simulations of the transient noise will be discussed. In this specific simulation, the radiation will generate average values of 3600 photoelectrons for impinging electrons, 6000 photoelectrons for Bremsstrahlung-generated secondary electrons in the focal plane, and 15000 photoelectrons for impinging protons. These transient signals mill make it difficult for the camera system to operate under low light conditions.