Airbus Defence and Space


Antenna pointing mechanism/equipment

The Antenna Pointing Mechanism was developed and qualified for high precision two -axis pointing of geo-stationary steerable antennas or antenna dishes. The two axes of the mechanism are arranged in one plane so that a stiff and flat configuration is achieved. The APM is driven by stepper motors and can be equipped with high resolution encoders in its rotation axes. A feed-through in the centre of the mechanism allows to rout Flexible Waveguides from the antenna down to the S/C I/F. The APM steering function can be controlled by a dedicated fully redundant APM-Electronics.

Four different assemblies have been developed and qualified for the application:

  • Pointing Mechanism, PM
  • Pointing Mechanism Electronics, PME
  • Hold-Down and Release Mechanism, HRM

The Antenna Pointing Mechanism (APM) was developed to steer complete spot beam antennas or simple reflector dishes in geo-stationary orbits with high precision about two gimbal axes.

The mechanism provides excellent pointing performance, high load carrying capability, long lifetime and was developed as a commercial item. European sub-units and parts modified for space application are used. The APM is a compact self-standing unit with simple interfaces to the satellite and to the antenna as well.

Features / technical details

  • Number of Axes: 2
  • Pointing Range: typical 10 deg halfcone
  • Pointing Velocity: 3 deg / min
  • Pointing Accuracy: +/-0.005
  • Step Resolution: 0.002 deg at full step command
  • Mass: 4 to 6 kg (depending on antenna mass and rotation range)
  • Height: 150 mm (depending on antenna dimensions and rotation range)
  • Operational Temperature Range: max. +/- 90 °C, typical -40/+60°C
  • Orbit Life: 15 years at 4 re-positioning/ day

Space Qualified Stepper Motor Control Electronics available


  • Pointing of Antennas and Antenna Dishes on Geo-Stationary Communication Satellites
  • Potential other applications e.g: Pointing of thrusters

Reference customers

The mechanism was qualified in the frame of an Airbus Defence and Space/DLR development program for a Steerable Antenna. A model is flying on DFH 3 since 2004.

16 similar units have been built and qualified for a telecom application (launch 2007)