Subsystems

The mechanical skeleton of a spacecraft — the load-bearing frame that holds everything together and survives the violence of launch, plus the mechanisms that deploy solar arrays, antennas, and instruments once in space.

The subsystem that keeps every part of a spacecraft within its allowable temperature range, radiating away waste heat and insulating against the extreme cold of space and the heat of the Sun.

The subsystem that generates, stores, and distributes electricity — from solar arrays or radioisotope generators, through batteries, to every instrument and heater on board.

The subsystem that changes a spacecraft's velocity — for orbit insertion, trajectory corrections, and station-keeping — using chemical, electric, or cold-gas thrusters.

The subsystem that determines and controls which way a spacecraft points — sensing its orientation with star trackers and gyroscopes, and turning it with reaction wheels or thrusters.

The spacecraft's onboard computing — the flight computer, software, and memory that execute commands, run the spacecraft autonomously, and manage faults across the long light-time to deep space.

The subsystem that carries commands up and telemetry and science data down — the spacecraft's radios and antennas, working with the ground network.

The subsystem — and the few dramatic minutes — that gets a spacecraft from the top of an atmosphere to a safe landing: a heat shield to survive entry, a parachute or thrusters to slow down, and legs or airbags to touch down.

The robotic arms and manipulators that let spacecraft build, service, sample, and move cargo — from the Space Shuttle and station arms to the sampling arms of planetary landers.

For crewed spacecraft, the systems that keep people alive and let vehicles join up — environmental control and life support (ECLSS) and the docking mechanisms that connect spacecraft.