ISO TR 16158:2021 pdf download – Space systems — Avoiding collisions among orbiting objects. They are derived from past observations of satellites. Ephemerides are time-ordered sets of position and velocity within which one interpolates to estimate the position and velocity at intermediate times. Ephemerides need to span the future time interval of interest, where the equations of motion having been propagated by the provider. Observations are measurements of satellite position and velocity from one or more well-characterized and registered instruments. The recipient can use those observations to estimate the evolution of the trajectory either through direct numerical integration of governing...