Command and Data Handling subsystems are the portion of the satellite that acts on commands from the ground or internal commands generated by the Flight Computer (FC) and collects telemetry from the other subsystems and prepares it for transmission to the ground. This subsystem can be as simple as one Flight Computer processor that controls the entire satellite. In distributed architecture applications there can be a Flight Computer, a processor for each subsystem, a data bus controller that provides data and command transfer between subsystems and a C&DH processor to interface with the TCR subsystem. In the more complex systems there are backup systems to minimize impact due to unit failures. Flight recorders that can also be utilized to store data and memory areas to store command tables for scheduled execution.

This subsystem contains the processor or processors, interface bus, the means to receive, decode, process and execute commands and the ability to collect, process, store and transmit telemetry from the satellite through the TCR system.