sgp4: sgp4 (Satellites Tracking library) sgp4: sgp4: SGP4 is mathematical model used to calculate orbital state vectors of sgp4: satellites and space debris relative to the Earth-centered inertial sgp4: coordinate system. sgp4: sgp4: sgp4: sgp4: sgp4: Homepage: https://github.com/dnwrnr/sgp4/ sgp4: