Alphabus: An Extended European Capability

Last Update: 28 Oct 2010


With the Alphabus product line, European Industry extends its telecommunication satellite range significantly beyond the capabilities of the existing platforms, such as Eurostar 3000 and Spacebus 4000, both with respect to maximum payload power and mass. This development has been initiated, by ESA and CNES, as a coordinated European response to the increased market demand for larger telecommunication payloads for new broadband, broadcasting and mobile communications services.

Based on their extensive experience in this field, EADS Astrium & Thales Alenia Space lead, as co-prime contractors, a European Alphabus industrial team. The Alphabus platform will be marketed by these companies to complement their portfolio into this extended payload range.

Alphabus Product line
This new multi-purpose platform is targeted to the high power payload telecommunication satellite market. In its upper range it will allow customers to take full benefit of the capabilities of the new generation of 5 meter fairing commercial launchers, both with respect to payload volume and launch mass. At the lower end of its range compatibility with a 4 meter fairing remains achievable.
A wide range of commercial payloads to provide TV broadcast, multimedia, internet access, and mobile or fixed telecommunication services can be accommodated on the Alphabus platform.

The Alphabus contract covers the development, and qualification of a complete product line, with the following nominal capabilities:

Life time: 15 years
Payload power 12-18 kW (conditioned power)
Satellite mass: Up to 8.1 tonnes (at launch)
Payload mass: Up to 1200 kg

Typical payload capacity: up to 200 transponders - equivalent to more than 1000 TV channels (SDTV) and more than 200 000 audio channels.

The Alphabus product line is designed for future growth and will be compatible in its extended version with higher payload power (up to 22 Kw), higher payload dissipation and higher payload mass (up to 1400 kg).

Alphabus Product line Key Features

  • Structure: Central tube and Additional Carbon and Aluminium Panels
    • Section 2800 mm x 2490 mm
    • Launcher Interface: 1666 mm
  • Chemical propulsion
    • 500 N Apogee Engine and 16 10N RCT thrusters
    • 2 Propellant tanks (Max 4200 kg of bi-propellant)
    • Helium tanks (2x150 litres)
  • Electrical propulsion
    • Xenon tanks (Max 350 kg)
    • PPS 1350 thrusters on Thruster Orientation Mechanisms)
  • Power generation and distribution
    • 2 GaAs solar array wings with 4 to 6 panels
    • Power supply and power distribution offering both 100V and 50V regulated buses
    • Modular Li Ion Battery
  • Modular concept based comprising an Antenna Module for easier antenna accommodation and efficient assembly and test
  • Attitude and Orbit Control (ADCS)
    • Gyros
    • Star and Sun Sensors
    • Reaction Wheels
  • Data Handling through a 1553 bus for payload

Fig. The Alphabus Service Module


click for larger image

The Alphabus design takes full advantage of the experience gained through the Eurostar and Spacebus product range and complements this with the benefits of several new developments to improve the overall platform design and performances. As a result the Alphabus is a considered mix of heritage and proven innovation. Wherever practicable, the Alphabus product line relies on qualified European technologies.

Successful European Cooperation
The original ESA/CNES preparatory programme for Alphabus was approved by the ESA Member States at the Ministerial Council meeting in Edinburgh in November 2001. Subsequently, in 2003 an industrial and commercial agreement was signed between EADS Astrium and Alcatel Space (now Thales Alenia Space) for a joint Alphabus product line covering 12-18 KW payload power. The current contract, for the design of the product line and production of a first Proto Flight Alphabus, was signed as a four party undertaking in June 2005 with a joint ESA and CNES customer team and the co-prime contractors EADS Astrium and Thales Alenia Space. Delivery of the Proto Flight Model (PFM) Platform took place 26 January 2010.

The Alphabus PFM platform will fly in the frame of the Alphasat Programme with Inmarsat allowing an early in orbit demonstration and validation of the Alphabus product. The Alphasat launch is scheduled in 2012 with Ariane 5. Furthermore Alphabus is being formally introduced into the EADS Astrium and Thales Alenia Space industrial product line, and thus available for commercial bids from the end 2009 onwards.

Looking to the future, the Alphabus Extension programme will further extend the capabilities of the platform in terms of power, mass and thermal rejection. Work is progressing with the industrial team to refine the development plan and implement the extension activities which are essential to prepare a solid European offering entry in the world competition of very large communication satellites.