Document Type : Original Article
Department of Guidance, M.T.C.,Cairo,Egypt.
The accuracy of Ballistic Missile (BM) guidance is mainly dependent on the accuracy of the navigation system used. Majority of BM's apply the inertial navigation system (INS) where the inaccuracies of its sensors (accelerometers and gyros) induce errors which may accumulate to intolerable values due to increased flight time. The guidance is restricted only to the powered flight phase of the whole BM trajectory. In the present paper we navigate the BM motion in the free-flight phase (ballistic phase) using the NAVSTAR/GPS model and an implementation of the BM motion in the ballistic phase. The simulation includes several cases of ballistic trajectories applied on the GPS model that includes 24 satellites constellation. pseudo-range and ephemeries data are simulated, and the application of the principle of minimum geometric dilution of precision (GDOP) is performed. The implementation of the BM motion in the free-flight phase is applied on the optimum trajectories using the Keplerian orbit (elliptical section) in which Kepler's equation is solved at each instant on the trajectory by Newton Raphson method.The results of the different algorithms of implementation are evaluated. The solution of GPS equations is executed for BM motion in the ballistic trajectory using the iterative method. Different algorithms for selection of GPS model are given.