Which term describes the command signals sent from ground to a spacecraft to control its actions?

Which term describes the command signals sent from ground to a spacecraft to control its actions?

• A. Telemetry
• B. Data Link
• C. Telecommand
• D. Payload

Answer: (C)

Commands sent from ground to a spacecraft to make it perform actions are telecommands. This term specifically refers to the instructions that control spacecraft operations—attitude adjustments, power or subsystem mode changes, thruster firings, and other commanded actions. Telemetry, by contrast, is the data the spacecraft sends back to Earth about its state and measurements. The data link describes the communication channel itself, carrying both uplink and downlink signals, while the payload means the onboard instruments and experiments, not the control signals. So telecommand is the precise term for the ground-to-spacecraft command signals.