Techniques operated for the realization of the IERS reference systems make use of electromagnetic signals received on the surface of the Earth. During their transit of the atmosphere, the signals experience delays which must be modeled in the analysis software. This chapter presents models for the propagation of optical signals in the troposphere (9.1), for radio signals in the troposphere (9.2) and for radio signals in the ionosphere (9.4). For Doppler techniques which use time- di erenced phases as observables, the models presented in this chapter should be time-di erenced as well.

Peer Reviewed