Danger area when using chaff against anti-ship missiles in naval operations

Normally, an Electronic Warfare suite for a platform, such as a ship, is designed to counter threats coming at the platform. However, in naval operations there is often more than one ship involved. If one of these ship is countering a threat such as one or two incoming radar guided missiles by using decoys (i.e. chaff), it is important to understand the eventual effect for other ships in the unit. If the ship is successful in the seduction of a missile seeker, the missile will go for the decoy. When the missile passes the decoy it will not detonate, and shortly afterwards try to search for the target. This means that other ships may come into harms way, and in the worst scenario get sunk. So the questions that are discussed in this report are shortly as follows: If the deception is successful, where will the danger area be? Are there any own ships in the determined danger area? In order to answer the above given questions a geometric approach has been used. By looking at the geometry for the situation, a solution to find the geometric extension of the danger area has been found. Consideration is also taken into account for uncertainties in direction and range to the incoming missile. The effects on the danger area due to the uncertainties are descibed. After the geometrical analysis, the time interval, in which the danger area is active, is calculated. Finally, by using the position as a function of time for other ships, it can be determined if they are within the danger area or not during the critical time interval.