The disturbing influence of solar radiation pressure must be taken into account in modeling GPS orbits. The mathematical description of this disturbing force is complicated. There exist several models with distinct complexity. In the special case of GPS satellites there arise difficulties because of the irregular shape and surface of the satellites and by accounting for the alignment of the solar panels. These problems will be considered here. In connection with the alignment of the solar panels the orientation of the spacecraft coordinate system during the satellite's revolution will be examined under consideration of different positions of the Sun. In addition, possibilities to represent the irregular shape of the GPS satellites by parameters, which can be determined via orbit improvement, will be discussed.