hubble

Radiation damage to the Hubble Space Telescope has been several years out of phase with the Solar cycle

Cosmic rays damage CCD sensors at a greater rate at low-earth orbit - the damage can be temporary (which registers as a spot/streak of light in the image) or permanent (dead pixels). The image processing strategies required to salvage useful data include using multiple exposures (eliminate any pixels present in only one exposure), shift the telescope (?) by a few pixels between two exposure (dithering).