Spacecraft Antenna Requirements as Perceived by an Operator [Antenna Applications Corner]

Spacecraft antennas tend to be a significant resource on a spacecraft, and are, to a first order, intricately intertwined with mission definition. It is therefore not surprising that the requirements of the antennas implemented on Eutelsat satellites are becoming increasingly varied and challenging. These antennas have to be optimized for the classical parameters such as co-polar gain and cross-polar gain, but the criteria are also becoming more complex. Frequency reuse is increasingly becoming the norm, so that together with the maximization of the required parameters over the required service areas, minimization of the co-polar gain over the required isolation areas is also required. Furthermore, the number of distinct market areas that a single Eutelsat satellite has to address is also increasing. Consequently, careful design of the antenna farm is needed, often presenting challenges for spacecraft accommodation. The advent of the high-throughput satellite (HTS), like KA-SAT, introduces more challenges, as the optimization is pushed to more dimensions by at least an order of magnitude at the starting level. Ku-band satellite systems typically have at most a few intra-system interference entries. In high-throughput satellite systems, this is pushed to tens or even hundreds! In 2010, Eutelsat ordered four satellites: W5A, W6A, EUROBIRD™ 2A/Es´Hail, and W3D. These exhibited coverage of a large number of area with frequency reuse and stringent antenna-isolation requirements. This paper gives a brief overview of W5A, W6A, EUROBIRD™ 2A/Es´Hail, W3D, and KA-SAT. In particular, it gives insight into the antennas on board these satellites. It projects the antenna requirements into the future, attempting to highlight the general tendencies for Ku-band satellites and high-throughput satellite systems.