HEO spacecraft and launch scenarios

Highly elliptical orbit (HEO) communication satellite missions which have been studied in Europe in the last few years use either 12 hour (Molniya) or 24 hour (Tundra) Earth synchronous orbits inclined at 63.4 degrees. These orbits have the facility to be able to provide land mobile communications services to medium and high latitude countries (e.g. Europe) with a high elevation angle. This reduces multipath fading and signal blocking effects dramatically compared to the service potentially available from geostationary satellites as well as allowing the use of a high gain antenna on the mobile. Continuous service dictates that the use of the Molniya orbits requires 3 satellites and the Tundra orbit 2 satellites. The system and subsystem trade offs for satellite design for the HEO missions as well as the launching and orbit control strategies. The satellite configuration options are Nadir pointing, Sun pointing, or with the yaw axis parallel to the Earth´s pole line. The launch strategy options are either direct injection or by using transfer orbits and either dedicated or shared with another user