Navigation operations require the refinement of the design trajectory to obtain a high-precision trajectory for flight path control and science operations. The preliminary trajectory design often involves approximate solutions of boundary value problems that provide sufficient accuracy for mission design but are not accurate enough for flight operations. The final precision trajectory is obtained by driving a high-precision trajectory model with targeting and optimization algorithms that yield the final high-precision solution. The preliminary trajectory design provides an initial guess for starting the targeting algorithm. With experience, the preliminary design may sometimes be omitted and the trajectory design obtained directly by targeting.