The boom in data communications that started in the 1960s is a long way from abating. The early and mid 1980s will see a new generation of digital data transmission services come into operation that could change the ways business is conducted. "Information management and exploitation will change the fabric of society", according to Nicolas Mokhoff, Associate Editor of IEEE Spectrum Magazine. Manipulated by microelectronic, computer, radio and other electronic disciplines, information has become a vital commodity at the trade exchange. But unlike the prices of most commodities today, the price for exchange of information is decreasing because of electronics. One of the principal contributors to this decrease has been the geosynchronous telecommunications satellite, due to rapid advances in space and communications technology and the resulting cost-effectiveness achieved in applying that technology. Advances in IC technology have made digital telephony an equal partner with analogue. The inherent advantages of digital reliability, low cost and smaller packaging are prompting Telecom to phase out present equipment and expand new services with a digital hierarchy, such as the Digital Data Service being introduced in late 1982. Services employing advanced satellite and microwave technology, and also the existing and upgraded telephone systems, will have at least two things in common: they will transmit and switch data digitally, including coded speech, and the data will be transmitted in bursts. The technology that may expand fastest is the second generation of commercial communications satellites. Pier Bargellini, a senior scientist at Comsat Laboratories, says that "without the use of satellites as reflectors for source and data channels, television signals could not be shared by remote areas, long-distance telephone services would be constricted and the data exchange for the business world would be hampered." Changes in the communications industry have been so dramatic (particularly with regard to satellites) that government bodies (including the Australian Federal Government) have been forced to reexamine long-standing communications practices. In October 1979 the Minister for Post and Telecommunications announced the Governments decision that it would be in the national interest to establish a communications satellite system for Australia. At that time, the Minister also announced that, a Satellite Project Office would be established within the Postal and Telecommunications Department to set in train the planning activities necessary for the introduction of the system. The SPO has been operational within the Department since late 1979, and 2. consultation of system service requirements in particular has involved liaison with a broad spectrum of interests including Commonwealth departments. Figure 1 of Appendix A testifies to the Australian Government's policy of supplying outback communities with improved communications services (including television) by using satellite facilities. Very little is known about the benefits and needs (in Australia) that a data communications satellite system might be able to fulfil, including those needs of the Department of Social Security. This is mainly due to the lack of specific details about the final configurations and costs of the separate satellite services, which wont be known until late 1981. This paper is , therefore, an initial but detailed examination of the hardware and software subsystems which constitute a domestic telecommunications satellite system. More specifically, the paper considers the on-board equipment of a communications satellite (the space segment - including satellite launch and orbit characteristics, and signal propagation delay and attenuation), and the earth stations (the ground segment - including signal modulation, multiple access and computer application considerations); all as dictated by Australian geographical, economic and communications traffic density characteristics. The paper then considers some of the possible methods Australian corporations and government departments may adopt to utilise satellite communications links, particularly for data communications. A second paper will re-examine the situation by applying the specific facilities and costs, when they are known (these will be announced by the Satellite Project Office after contracts for the space and ground segments have been let), to a large, low-traffic, interactive multipoint network such as that of the Department of Social Security.