A missile system comprising: (a) a missile; (b) a seeker located at a nose portion of said missile, said seeker comprising an electro-optic imaging sensor; (c) a control arrangement for steering the missile along a flight path to a target, said control arrangement comprising: (i) a tracking subsystem receiving images from said imaging sensor, said tracking system configured to track a target in said images and to determine a tracked target direction; and (ii) a guidance subsystem operable to steer the missile towards the tracked target based on a guidance algorithm on the basis of said tracked target direction; and (d) a navigation subsystem (26 a, 26 b) receiving images from said imaging sensor, characterized in that said electro-optic imaging sensor of said seeker is a narrow field-of-view, NFOV, gimballed image sensor, having a viewing angle of less than 15 degrees, and supported by a gimbal arrangement so as to be movable relative to a body of said missile, and further characterized in that said navigation subsystem is configured to: (i) co-process a plurality of said images from said NFOV gimballed imaging sensor to derive ego-motion of said missile relative to a region viewed by said NFOV gimballed imaging sensor by tracking the apparent motion of stationary features appearing in a plurality of views from different locations and deriving the motion of said NFOV gimballed imaging sensor relative to the tracked features; (ii) derive from said ego-motion a calculated target direction from said missile to a target; and (iii) provide said calculated target direction to said guidance subsystem during at least part of a flight of said missile as a substitute for said tracked target direction for use in the guidance algorithm. (a) a missile; (b) a seeker located at a nose portion of said missile, said seeker comprising an electro-optic imaging sensor; (c) a control arrangement for steering the missile along a flight path to a target, said control arrangement comprising: (i) a tracking subsystem receiving images from said imaging sensor, said tracking system configured to track a target in said images and to determine a tracked target direction; and (ii) a guidance subsystem operable to steer the missile towards the tracked target based on a guidance algorithm on the basis of said tracked target direction; and (i) a tracking subsystem receiving images from said imaging sensor, said tracking system configured to track a target in said images and to determine a tracked target direction; and (ii) a guidance subsystem operable to steer the missile towards the tracked target based on a guidance algorithm on the basis of said tracked target direction; and (d) a navigation subsystem (26 a, 26 b) receiving images from said imaging sensor, characterized in that said electro-optic imaging sensor of said seeker is a narrow field-of-view, NFOV, gimballed image sensor, having a viewing angle of less than 15 degrees, and supported by a gimbal arrangement so as to be movable relative to a body of said missile, and further characterized in that said navigation subsystem is configured to: (i) co-process a plurality of said images from said NFOV gimballed imaging sensor to derive ego-motion of said missile relative to a region viewed by said NFOV gimballed imaging sensor by tracking the apparent motion of stationary features appearing in a plurality of views from different locations and deriving the motion of said NFOV gimballed imaging sensor relative to the tracked features; (ii) derive from said ego-motion a calculated target direction from said missile to a target; and (iii) provide said calculated target direction to said guidance subsystem during at least part of a flight of said missile as a substitute for said tracked target direction for use in the guidance algorithm. (i) co-process a plurality of said images from said NFOV gimballed imaging sensor to derive ego-motion of said missile relative to a region viewed by said NFOV gimballed imaging sensor by tracking the apparent motion of stationary features appearing in a plurality of views from different locations and deriving the motion of said NFOV gimballed imaging sensor relative to the tracked features; (ii) derive from said ego-motion a calculated target direction from said missile to a target; and (iii) provide said calculated target direction to said guidance subsystem during at least part of a flight of said missile as a substitute for said tracked target direction for use in the guidance algorithm.