The Inmarsat-A system

Abstract

The Inmarsat-A system has been the workhorse of maritime mobile communications since February 1982 when Inmarsat started to provide satellite communications for the marine user. Prior to that date a similar service was provided by the US COMSAT organization and was known as Marisat. The number of ship earth station fittings has massively increased since 1976. Demand for satellite channels has increased as a consequence, leading to the launch of newer, more powerful satellites with increased channel capacity. At the same time, electronic design technology has moved ahead to meet consumer demands for better, cheaper and more compact equipment. The net result is that an Inmarsat-A SES of 1994 is but a fraction of the size, weight and cost of those of 1982. The above decks equipment (ADE), including the radome of an SES, has shrunk in size and weight over the last decade to about a third of its original bulk. Owing to high volume sales and mass production techniques, the cost of a 1994 SES has also reduced to a fraction of what it was ten years previously, whilst the facilities it is able to offer have been greatly improved. A decade of development in the field of electronic design is equivalent to several decades in some other disciplines.