One thing that may go unnoticed when you look at static images of IKAROS is that the sail rotates as the spacecraft glides along, collecting photons from sunlight as it goes to keep its forward momentum. IKAROS usually corrects its attitude via onboard thrusters attached to its main body, but if long-term space sailing is to become reality mission handlers need a way to create a disparity between the thrust on one part of the sail's surface versus the rest of the sail.