In this paper, in order to increase system capacity and reduce the transmitting power of the user's equipment, we propose a modified power control scheme consisting of a modified closed-loop power control (CLPC) and open-loop power control (OLPC). The modified CLPC algorithm, combining delay compensation algorithms and pilot diversity, is mainly applied to the ancillary terrestrial component (ATC) link in urban areas, because it is more suitable to the short round-trip delay (RTD). In the case of rural areas, where ATCs are not deployed or where a signal is not received from ATCs, transmit power monitoring equipment and OLPC algorithms using efficient pilot diversity are combined and applied to the link between the user's equipment and the satellite. Two power control algorithms are applied equally to the boundary areas where two kinds of signals are received in order to ensure coverage continuity. Simulation results show that the modified power control scheme has good performance compared to conventional power control schemes in a geostationary earth orbit (GEO) satellite system utilizing ATCs.