GREOPy: A Python package for solving the emitter-observer problem in general relativity

Many modern methods of observation and long-range communication rely on the exchange of electromagnetic signals to transmit information.To simulate such a signal exchange, the emission and the corresponding observation points in space and time have to be calculated via the signal sent between them, which is called the Emitter-Observer Problem (EOP).A prominent example in astrophysics is the stationary EOP, where all light rays connecting a distant light source to an observer, neither moving in space, are calculated taking into account effects on the light propagation due to gravity, (see e.g.Viergutz, 1993).In this case, the EOP is characterized by the boundary-value problem (BVP) between the emission event at some light source and the observer.However, the EOP is a much more general problem also present in satellite communication, e.g.