Illumination analysis tool for preliminary assessment of proximity operations. Interest in graphical simulations to support proximity operations is increasing along with the number of private and public missions involving robotic spacecraft operating close to each other for commercial or scientific (and military) purposes. Using the open-source computer graphics software Blender, a simulation environment was developed to perform a preliminary assessment of lighting conditions for proximity operations in Low Earth Orbit. The main purpose of the simulator is to guide mission requirements in terms of trim, position and payload performance. The instrument created was used to assess the observation and docking conditions of an observe-and-dock mission of a CubeSat near its mothership.