European Space Agency



The Spacecraft Computer Unit (SCU MK1) is the central computer of the ASTRIUM Eurostar E3000 platform. This externally redounded unit (operating in hot redundancy) has demonstrated that it is well dimensioned in terms of interfaces, processing capability and level of configurability to suit various types of Telecom missions. Nevertheless, the constant market pressure forced us to revisit the SCU architecture in order to improve the overall competitiveness. This was also the opportunity to invest in a “durability” of the EEE parts of the SCU.

In order to avoid the issue of parts obsolescence, the development of a new version (SCU MK2) became crucial. It was proposed to take benefit from this mandatory evolution to introduce upgrades consistent with the overall Eurostar evolutions driven by competitiveness and customer needs.


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  • Evolve Hardware design without entailing SW design modification,
  • Complete non regression tests shall validate modification and their side effects,
  • Complete qualification on a SCU MK2 EQM.


The ability to offer an E3000 Spacecraft Computer Mk2 which incorporates these developments had an important impact on the overall competitiveness of the Eurostar E3000 communication satellite. Benefits are identified here after:

  • Mass & recurrent cost saving,
  • SCU Mk1 heritage,
  • European (ITAR free) AES ciphering for TC:
    • Triple computers configuration


The SCU is the computer unit of the Service Module of the Eurostar E3000 platform for telecommunication satellites. It is in charge of carrying out both TM/TC/Data Handling and Altitude and Orbit Control activities.

The Spacecraft Computer Unit (SCU) presently used in the Eurostar E3000 platform had to evolve to better cope with the customer requirements and the evolution of the Eurostar E3000 platform definition.


  • 100V evolution (as well as for the Supply itself than for the management of new units developed in the frame of Alphabus) while keeping compatibility with 50V,
  • Durable design (parts obsolescent management).

Triplication option:

  • Triple computer architecture (new requirement from the customers),

TC security option:

  • TC AES which comes from a will of providing a European encryption option for the telecommand path.

The SCU improvement consisted in the design, the definition and the validation of the SCU Mk2. It was the opportunity to reduce the number of boards by gathering the processing boards (VPM) and Transponder Interface Board (TIF). This integration was made possible by using a single core ASIC embedding the main functions of previous design (use of IP products).



The design and development plan of the SCU Mk2 has covered the following activities:

  • Specification, design definition & qualification of the equipment, and hardware manufacturing (BB, EM, EQM),
  • SCU Mk2 accommodation for E3000 50V & 100V,
  • Avionic Validation of the unit inside its platform environment (Avionic test bench campaign),
  • On-board software development & non-regression tests of SCU evolutions (notably triple computer and ASICs/boards gathering),
  • Specification & definition of the Harness & Database for industrialisation of SCU product in the satellite process,
  • Satellite AIT EGSE & tests procedures upgrades,
  • Flight procedures upgrades.

To run these activities, the development plan was a standard development logic separated in several phases (Kick Off, BDR, MTR, QRR, Final review).

The validation of each phases and the passage to the next phase was made through formal reviews, and consolidated through a risk mitigation action plan. Building and successful testing of an Engineering Qualification Model (EQM) was mandatory to demonstrate the compliance to the unit technical requirements, but also for the functional chain validation and notably the compatibility with E3000 Flight Software


Current status

  • Contract formalised between ESA and Astrium in March 2007,
  • SCU MK2 50V-100V BDR successfully held in June 2007,
  • PTM Breadboard characterisation test done (processor and Transponder I/F board). SW non regression tests on going,
  • SCU MK2 50V-100V MTR successfully held in November 2008,
  • SCU MK2 50V QR successfully held in April 2009,
  • SCU MK2 50V FR successfully held in June 2009,
  • First Proto Flight SCU MK2 50V: Start of manufacturing in April 2009,
  • SCU MK2 100V (Delta)-MTR successfully held in June 2011,
  • First Proto Flight SCU MK2 50V: Launched in September 2011,
  • SCU MK2 100V QR successfully held in September 2012,
  • SCU MK2 100V FR successfully held in December 2012.

Status date

Friday, March 1, 2013 - 15:47