DEFINITION:
It includes:

• On board data systems : Addresses both spacecraft data management and payload data processing and covers the hardware and software required for data acquisition, data processing, storage for both payload and spacecraft data, on board networking and the space link network layer and above.
• On board software : Addresses only space segment (ground segment software is included in 1 K). All basic techniques and technologies in the fields of software and Information Technology with respect to their application to space missions.
• EEE components : Covers technologies related to the design, production and testing of EEE components which meet the performance and reliability requirements for use in on board electric/electronic systems. (Note: This technology domain is concerned with quality issues).
  (Source: ESA TD 1 (on board data systems), TD 2A and 2B (on board software) and TD 23A and 23B modified by PAE (components)).