What are the two main structural components of a satellite?

• A. The thermal control system and the mission payload.
• B. The bus and the communications package.
• C. The payload and the apogee kick motor.
• D. The bus and the mission payload.

Answer: (D)

The two main structural components are the bus and the payload. The bus is the spacecraft’s backbone—it's the platform that carries and supports all the systems needed to keep the satellite alive and controllable in space. It includes power generation and storage, attitude determination and control, propulsion, thermal management, and the communications infrastructure. The payload is the equipment that actually carries out the mission—sensors, cameras, scientific instruments, or communications hardware—that uses the bus’s resources to achieve the mission objectives. Other items like a dedicated thermal control system sit within the bus, and propulsion hardware such as an apogee kick motor is mission-specific hardware rather than a universal structural component.