In Orbit Determination, you have the observations (also known as "Tracking Data"), but you have no idea what orbit the satellite had at the time of observation. In many ways, Orbit Determination is the reverse of Orbit Propagation. Orbit Propagation is to Orbit Determination as differentiation is to integration.

Several methods of initial orbit determination are presented here. Initial orbit determination involves determining the orbit of a satellite without any prior knowledge of the satellite's orbit characteristics. This is especially useful for satellites that have just been placed into their orbits and an initial orbit determination is required quickly using limited tracking data.