The previous years have witnessed an introduction of a large number of mobile satellite (MSS) communications systems. These include a global GEO MSS system, Inmarsat, and domestic GEO MSS systems such as North-American AMSC, Japan's N-Star and the Australian Mobilesat. At present, two types of antennas can be used to access GEO MSS services. They include (1) fixed position antennas, which are used with portable transceivers; and (2) fully mobile antennas such as those installed on a land vehicle. The fixed position antennas are relatively easy to design, as they have to meet a moderate (approximately 7%) operational bandwidth and a medium (about 10 dBi) gain. There are a number of complete portable systems in the commercial market that include both a transceiver and an antenna. One inconvenience of portable systems is that they require the user be stationary with respect to the ground. This inconvenience can be overcome with a mobile antenna system. The design of such a system is more challenging as new features associated with mobility have to be incorporated. This paper presents the development and performance of a circular phased array antenna for land vehicle mobile satellite communications. This antenna is specifically aimed for use with the Australian MSS, Mobilesat. However, it can easily be modified for use with the other L-band GEO MSS systems.