A method of initial orbit determination for long arc data

According to the principles of the unit vector method (UVM), a method of initial orbit determination for long arcs is presented. This method is applicable not only to long arc data but also to short arc data and is suitable for earth satellites with arbitrary orbital eccentricity and inclination. This method has a good accuracy of initial orbit determination and good convergence. It offers a basis for extending the application of the UVM method from initial orbit determination to orbit improvement.