13.1 Introduction

The potential of satellites for communications was first realised by A.C. Clarke, who published a paper in 1945 proposing a three-satellite system to provide worldwide relay communications from the geostationary orbit. The geostationary orbit is unique since its orbit rate of 24 hours precisely matches the Earth's rotation allowing one satellite to provide fixed coverage over a large region. With the development of launch vehicles in the 1950s permitting accurate injection of satellites into orbit, communications from this natural resource could finally be achieved.

Satellites have been used for communications since the early 1960s when relatively simple systems were used to provide telephony communications. These were spinner satellites with only limited payload capability. During the 1970s and 1980s three-axis-stabilised satellite designs were introduced which were capable of carrying much larger payloads although still using the geostationary orbit. In the 1990s the satellite industry has shown rapid growth, especially with the development of constellations of satellites using the low-earth orbit for mobile communications. Satellites for geostationary orbit have continued to grow in size, matching the increase in launch-vehicle capability and demand for high-power broadcast satellites.

Figure 13.1 shows how the EUROSTAR satellite platform has grown to meet the demand for larger satellites. EUROSTAR 1000 was used for the INMARSAT 2 contract with the first launch in 1990 with a launch mass of just under 1400 kg. The latest variant, the EUROSTAR 3000 is designed for a launch mass > 4000 kg.

Figure 13.1: Growth...