A system for engaging hostile air or space threats with a defensive missile, where the defensive missile comprises an antenna for receiving global positioning system (GPS) signals. A global positioning system receiver is coupled to said antenna, for receiving global positioning system signals directly from global positioning system satellites and global positioning system signals reflected from the threat. A processing arrangement processes the direct and reflected global positioning system signals for determining the position and velocity of the threat. Vectoring controls are coupled to the processing arrangement, and are responsive to the location of the threat for directing the defensive missile toward the threat. In a particular embodiment, the antenna of the defensive missile is directionally controllable, and the defensive missile includes an antenna direction controller responsive to the processor for directing at least a beam of the antenna toward the threat.