Determination of the orbit of a spacecraft and all the constant and dynamic parameters that affect the orbit is an application of estimation theory. A model of the spacecraft motion as a function of initial conditions and certain constant and dynamic parameters is developed that may be used to predict the flight path and compute the value of measurements that are obtained during the space flight. Orbit determination involves adjusting the value of the independent parameters that need to be determined until the computed measurements are close to the actual measurements. Since there are many more measurements than independent parameters, the solution is found that minimizes the error in the measurements. This solution will also minimize the error in the estimated parameters.