BELA Electronic Unit

For the BepiColombo Laser Altimeter called BELA an electronic box concept was developed to integrate different types of electronics boards (modules). The concept based on separate mechanical frames which host digital processor modules, signal processing modules and power converter modules. Finally all modules will be integrated into a common electronic unit. The Electrical interconnection of the different modules is implemented as dedicated board top layer. High speed differential signaling allows the communication between each module. Also the secondary power bus to power each module is distributed using a common power bus back plane. Both back planes (power and signal) are developed as specific electronic boards to fulfill requirements concerning robustness, EMC behavior, redundancy aspects and signal performance. The concept allows science and housekeeping data transfer on analogue and digital signal domain.

 BELA Electronic Unit
zum Bild BELA Electronic Unit

CCSDS SpaceWire standard was implemented as TC and TM interface to the spacecraft. The box architecture allows the control and science data exchange within the electronic unit. In parallel an inter-harness grants the signal exchange to other units of the BELA instrument.

Performed vibration and thermal tests demonstrate successful the application for a large number of space application. Also EMC performance was tested successfully.

The concept is scalable in terms of PCB size and format, number of modules, mission radiation requirements and redundancy aspects. In compare to a classical box concept the selected concept is lightweight. The clear definition of mechanical and electrical interfaces permits standalone testing and a shared instrument design development.

Key Parameter



# of modules


# of double modules



3320 g

S/C power interface

28V main & red

TC/TM interface

10Mbit SpW main& red


PPS main&red

Temperature range (tested)   

-40°C … +65°C

Vibration level (tested)

16 g rms (random)
50 g (quasi static load)

Internal I/F

10MHz synchronous serial
RS422, asynchronous laser trigger interface

Thomas Behnke
Deutsches Zentrum für Luft- und Raumfahrt (DLR)

Institut für Planetenforschung
, Planetare Sensorsysteme
Tel: +49 30 67055-397

Fax: +49 30 67055-384

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