Alphabus: An Extended European Capability

Status date

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.


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.


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.

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.


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

Current status

System and Launch

The Alphabus Qualification Review is currently ongoing and is planned to be closed by end November. This review will confirm the qualification of the service module as a generic product line.

The results of the Shogun shock testing campaign show that Alphabus globally complies with the Ariane 5 launch environment requirement. Using the measurements inside the spacecraft, the prime team reassessed the qualification of each unit by comparing its qualification test at unit level to the level expected in flight. The positive results of this assessment were delivered at a final meeting on 17 September between the Alphabus Prime contractor Astrium and Thales Alenia Space, and ESA/CNES.

Service Module (SM)

Activities on the Service Module integration are progressing nominally; the electric propulsion system gas plate has been delivered to Toulouse, integrated on the SM and the proof test, covering the Xenon high pressure part has been performed in the Astrium bunker facility. Furthermore, thermal control and MLI have been successfully integrated on the SM. In parallel the battery modules have been mounted on the East / West SM walls and full battery level tests have started. The Closed Loop System (CLS) test equipment has been delivered to Toulouse on 8 September. The CLS will be connected to the spacecraft for preparation for the end-to-end system level test campaign.

Remaining activities on the SM include:
• Final CPS completion (last SM thruster integration and functional testing)
• Integration of PSR PFM
• Re-integration of refurbished STRs
• Integration of fourth reaction wheel
• Final electrical and functional testing
• XPS Thruster module assembly (TMA) / SM interface testing prior to TMA integration in the repeater module
These activities are planned to be completed by the end of the year for an SM ready for coupling with the Repeater Module.

Alphabus Extension

The Alphabus Extension will further extend the capability of the platform in terms of power, mass and thermal rejection capabilities. The workplan includes the development of key enabling technologies such as a deployable panel radiator for increased heat dissipation and an ultra stable antenna module for future complex Alphabus satellites. The industrial proposal has been received end of July, evaluated by ESA/CNES and is currently under clarification / negotiation with the objective of placing the industrial contract before the end of the year.