Possible Applications of Communications Satellites to Offshore Communications Systems

Abstract

ABSTRACT Expanding offshore operations have generated an increased need for communications in both international and domestic areas. The capabilities of communications satellites are presented both as currently existing and as envisioned in the future. The possibilities of using these capabilities in offshore communications systems are discussed especially with regard to the potential of new services brought about by the latest generation of satellites currently under production. Two potentially new types of services are hypothesized. Lastly, progress on the development of a small earth station of low cost suitable for such services is reported. It is concluded that communications satellites hold potential both currently and in the future for various offshore operations. INTRODUCTION Communications satellite development is now almost a decade old. A commercial communications satellite system has been in operation for several years providing voice, data and video channels on a global basis. This system is called INTELSAT and uses so-called stationary satellites, these being in synchronous, near-equatorial orbits. The communications capability of these satellites has been growing exponentially with time, as will be described subsequently. Also, the point has been reached where it appears technically and economically feasible to use derivitives of the latest generation of satellites for providing regional and/or domestic communications services. The purpose of this paper is to describe the present and future satellite capabilities and to indicate possible uses of these in offshore communications systems. SATELLITE CAPABILITY The development of satellite capability is shown in Figure 1. The first generation satellite, INTELSAT I (commonly known as "Early Bird"), is still in operating condition after 5 years in orbit. Currently, all commercial satellite communications services are provided through the four in-orbit INTELSAT III satellites. The capacities shown in Figure 1 are in terms of voice circuits; however, television capability can also be provided simultaneously. The capacities indicated in Figure I are achieved between earth stations having large antennas and specially designed electronics equipment. A typical one is shown in Figure 2. - Figure 3 shows the present and planned locations of such earth stations. The next generation of satellites is the INTELSAT IV series, the first satellite being scheduled for launch in about seven months. It is most interesting to note that, within six years, four generations of satellites (each several times more capable than the previous one) have evolved. Similarly, each successive generation of satellites has been designed with better lifetime expectancy. The achieved service reliability of the INTELSAT satellites over the past five years has been outstanding with only one significant communications outage occurring during this period. FUTURE SATELLITE CAPABILITY Technical work is proceeding now on the following generation of satellites. These may take several forms. The first is towards larger, more efficient satellites; the result would be further improvement in economics for existing types of services plus the possible economical provision of additional types of services. The second form is towards satellites used to meet regional and domestic needs. The Soviet Union has a domestic satellite system in operation called "Orbita"(l) and the Canadians are planning to build one through their TELESAT organization (2).