A Study Of Airborne Anti-submarine Sonobuoy Location

Because of good concealment,strong capability of surprise attack and formidable detervent, Submarine has always been the most important component of naval weaponry since it came out. So in naval warfare, an important strategic task is to search for and attack enemy's submarines.Ariborne anti-submarine warefare(ASW) is a major mode of operations. It consists of the stage of searching for submarine and that of attacking the submarine. In order to improve the capability of ASW, Navy has,preliminarily been equipped with modern anti-submarine weapons, among which helcopter serves as the core. Consequently, for the formation of the powerful combat capability, there is an urgent need of building an airborne anti-submarine Tactical Data System(TDS), which carries out comprehensive information processing and fulfils inflight commanding and guiding.Searching for submarine , that is, getting accurate position and motion datas, is an essential prerequiste to hitting the submarine. The primary tactical employment of the aircraft is through the use of active and passive electronic sensors, the most useful of which is the sonobuoy. Sonobuoys are dropped from the aircraft in various geometric patterns in the water. The information picked up is transmitted back to the aircraft.In order to maintain close, accurate tracking and be able to launch an attack, the submarine's position must be accurate. Since sonobuoy position error also contributes significantly to the submarine tracking inaccuracies, there is a critical requirement for determining an accurate relative plot of the sonobuoys with respect to the aircraft.Although accurate location informations can be supplied by using GPS , the reliability of this informations will become incredible in ASW. Therefore, according to the mobility of the aircraft, the present study builts a Multi-static Location System, which uses the measurements detected by active or passive airborne sensors, when the aircraft is at the different positions.This study proposes two methods for locating sonobuoys. The first one is using aircraft-to-buoy slant range information. This method does not use triangulation procedures and attemptes to minimize the restrictions upon the aircraft. The report shows the feasibility of tie preposed methodology and the approximate errors to be encountered.The second method is using the bearing from the aircraft to the buoy, This report develops an algorithm which employs extended Kalman filters to determine estimated position. It includes two cascaded Kalmin filters. The primary two-statefilter estimates sonobuoy position. A secondary filter estimates drift from information obtained from the primary filter. This algorithm successfully estimated sonobuoy position for simulated aircraft data. The effect of aircraft-to-sonobuoy range, the frequency of measurement, and changes in altitude are also analyzed.