Alphabus is a family of heavy geostationary communications satellites developed by a joint venture between Thales Alenia Space and EADS Astrium Satellites in France, with support of the Centre national d'études spatiales (CNES), the French space agency and the European Space Agency (ESA). The Alphabus platform is designed for communications satellites with payload power in the range 12-18 kW. Satellites based on Alphabus will have a launch mass in the range 6 to 8 tonnes, 40% more than the most powerful Spacebus 4000. In order to cover the mission range in an optimised way, the platform product line includes several options such as electric propulsion, and features scalable resources (solar array, radiators for thermal dissipation, etc.). The platform will be able to accommodate up to 190 high power transponders and large antenna farms, and will have a significant growth potential (22 kW payload power and 9 tonnes launch mass for the extended range). Product line Development of the new satellite, made in cooperation between the two large European satellite manufacturers, take into account the best lessons learned from previous incarnations of similar satellites: the Spacebus and Eurostar families, respectively from Thales Alenia Space and EADS Astrium Satellites. Structure is based on a central tube (the vertebral column of the satellite), like the Spacebus design, with additional carbon and aluminium panels (Section 2800 mm x 2490 mm, Launcher Interface: 1666 mm) Chemical propulsion with a 500 N Apogee Engine and 16 x 10 N thrusters; Propellant tanks (Max 4200 kg of bipropellant) and Helium tanks (2x150 litres) Electrical propulsion with Xenon tanks (Max 350 kg) ; PPS 1350 thrusters Thruster Orientation Mechanisms Power generation and distribution offering both 100 V and 50 V regulated buses, accommodating two GaAs solar array wings with 4 to 6 panels ; modular Lithium-ion battery Attitude and Orbit Control (ADCS) with Gyros, Star and Sun Sensors, Reaction Wheels Data Handling accommodating a 1553-bus for payload Payload allowing for a modular-concept-based setup, comprising an antenna module for easier antenna accommodation and efficient assembly and testing. Alphasat (Inmarsat-4A F4) Inmarsat awarded a contract to EADS Astrium Satellites for a first use of such a platform. The satellite is named Alphasat (Inmarsat 4A F4), and will augment Inmarsat's Broadband Global Area Network (BGAN) service supporting a new generation of mobile technologies and enable communications across Europe, Asia, Africa and the Middle East. Alphasat was partially funded by ESA and