Change of angular momentum in the dynamics of the solar system

It is quite often that the calculated trajectories of celestial bodies and spacecraft differ from their actual motion. This difference may be due to deficiencies of the methods used to calculate orbits and trajectories. Three such methods-the Galactica software, the DE406 ephemeris, and the Horizons systems-are tested using the change of angular momentum in motion calculations. The smallest change is obtained using Galactica, and the largest, using Horizons. The dynamics is studied of the angular momentum of the planets. The results can be used to control and improve motion calculation methods.