Maritime satellites - Possible systems for future INMARSAT use

The paper presents a brief recapitulation of the space segment options available to INMARSAT, and reviews additional services and requirements for maritime communications that may need to be progressively introduced after a basic initial satellite service, using the current type of comparatively complicated shipboard terminals, has been established. It is shown that new mission requirements can be met by a logical extension of existing technology, noting that the corresponding increase in necessary payload mass and power will lead to an eventual requirement for larger spacecraft. In addition two concepts for advanced maritime satellites are surveyed: (1) a payload concept based on fixed spotbeam antennas, and (2) one based on a phased array antenna. Finally, it is noted that the flexibility inherent in the MARECS satellites will enable them to provide service to less sophisticated shipborne equipment if necessary.