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The two Voyager probes launched in 1977 to study Jupiter, Saturn, Uranus and Pluto, and remain in contact with Earth as they move into interstellar space.
The probes have identical designs, with six computers apiece in three roles. Each has a duplicate Computer Command System (CCS) — 18-bit word, interrupt-type processors with 4,096 words each of plated wire, non-volatile memory; a duplicate Flight Data System (FDS) — a 16-bit word machine with modular memories and 8,198 words each; and a duplicate Attitude and Articulation Control System (AACS) — 18-bit word machines with 4,096 words each. That's a total of around 88 Kbytes of memory.
Each computer is a custom design by the Jet Propulsion Laboratory (JPL), which runs the project, and is built by General Electric. The CCS runs the spacecraft and reports problems back to base; the FDS manages the scientific instruments and prepares data for transmission back to Earth; while the AACS performs thruster and instrument platform manoeuvres.
Both Voyager probes have suffered a variety of hardware failures during their lives. Most of their experiments are now turned off, following the last planetary encounters, but with reprogramming and about eight years of life left in the nuclear generators, both have some distance left to run.