DIMAC system layout (left: Control Unit,
top: Magnetometer modules, bottom: Sensor Head)

The DIMAC system developed for the Foton M-3 flight is a modular inertial monitoring system which measures vibrations, quasi-steady accelerations and the Earth magnetic field.
The DIMAC system consists of the following units:
  • DIMAC Control Unit:
    Autonomous data acquisition and data storage device containing tri-axial vibration sensor and magnetometer.
  • DIMAC Sensor Head:
    Experimental quasi-steady acceleration sensor.
  • 3 DIMAC Magnetometer Modules:
    Tri-axial magnetic field sensors

The stored data have been downloaded, post-processed and analysed after the mission (see results summary).
The main features of the DIMAC system are:
  • The DIMAC Control Unit is an enhanced version of the TAS3 device featuring:
    • Autonomous acquisition of internal tri-axial vibration sensor (based on Honeywell QA3000 series sensors). Acquisition of vibration data (resolution 1g, bandwidth 0.01Hz to 200Hz, sample rate 1000Hz) and sensor temperature data.
      Acquisition of magnetometer data from dedicated tri-axial local magnetic field sensor (featuring anti-alias filter). This sensor was implemented in order to correct for the minor magnetic field susceptibility of the acceleration measurements that was detected during the processing of TAS3 measurement data after the Foton M-2 mission.
    • Fully autonomous control, monitoring and data acquisition of several external sensors
      (DIMAC Sensor Head and three magnetometer modules)
    • A flexible telemetry and telecommand interface was implemented using the TeleSupport system. This interface was used extensively on the Foton M-3 mission.
      During the mission subsets of the DIMAC measurement data have been downloaded using the telemetry interface. These data have been processed immediately and preliminary results have been available to the scientists and operators of other Foton M-3 payloads.
      The flexible implementation of the telecommand interface allowed telemetry data bandwidth optimisation and DIMAC system troubleshooting.
  • The DIMAC Sensor Head is a proto-flight version of the experimental quasi-steady acceleration sensor developed during the DIMAC study phase. For the Foton M-3 mission the DIMAC Sensor Head was located at the bottom of the re-entry capsule, close to the center of gravity of the spacecraft.
  • Tri-axial magnetometer modules are measuring the Earth magnetic field (and hence indirectly the spacecraft attitude). Three modules have been placed at different locations inside the Foton M-3 re-entry capsule in order to compensate for any local magnetic field disturbances caused by payloads or spacecraft subsystems.
    However, the flight results show no major disturbances. This indicates that if an appropriate location is selected a single magnetometer module might be sufficient for future missions.
  • Foton M-3 DIMAC system engineering budgets:
    • Mass 7.5kg (including harness)
    • Average power consumption 7W
    • Data storage capacity of 10GByte (sufficient for 14 days of continuous data logging)
The modularity of the DIMAC system allows easy implementation of additional sensor modules. The resulting system could provide full inertial and environmental monitoring of a spacecraft for future missions. The major parts of this system have been qualified on the Foton M-3 mission.
Related pages:
TAS3 project
DIMAC study phase project
RedShift reference projects