DEFINITION:
It includes:

• Space System Control : Covers the design and implementation of control systems for space applications. Includes AOCS for satellites; GNC for space vehicles and launchers; pointing acquisition and tracking systems for antennas, laser terminals, and line of sight stabilisation equipment.
• Flight Dynamics and GNSS : Comprises the activities related to the analysis and definition of trajectory aspects of space projects, known as mission analysis. It includes all operational ground activities related to the measurement and control of spacecraft orbit and attitude. Furthermore it deals with the provision of precise navigation services to both ground and space based users and also the provision of the geodetic reference frame.
• Radio Navigation Systems / Subsystems: Covers radio navigation techniques and technologies, elements and subsystems capable of generating, receiving, exploiting and analysing the signals from current and upcoming radio navigation systems (GPS, Glonass, EGNOS, Galileo), including system tools and navigation equipment.
• Entry, Descent and Landing Systems: Covers the technologies e nabling heavier payloads travelling at faster velocities to enter and descend through atmospheres and land safely with higher precision than currently possible.

(Source: ESA TD 5 (Space System Control), ESA TD 10 (Flight Dynamics and GNSS) and ESA TD 6B (Radio navigation Systems and Subsystems)
and NASA TA9 (Entry, Descent and Landing Systems))