Kinematic analysis of imaging seekers with roll-over-nod gimbal and a folded electro-optical layout

Nod-over-roll is a commonly used gimbal configuration especially in air-to-air missile seekers due to its volumetric advantage. It may further scaled down by implementing a folded optical layout and locating the detector off-gimbal. Yet, the concept suffers from an inherent kinematic singularity problem right at the center of its task space, where roll axis and pointing vectors coincide. The phenomenon is called zenith pass problem and has to be solved in real time for proper target tracking. A second drawback of the mentioned seeker structure is image registration problem, which reflects itself as rotation of constructed image on the FPA, and shall be considered while localizing the target. This work focuses on the kinematic analysis of the zenith pass and image registration problems in an air-to-air missile seeker perspective.