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... When Voyager 1 lifted off to space on September 5, 1977, no one expected that the probe would still be operating today.

As a result of its exceptionally long-lived mission, Voyager 1 experiences issues as its parts age in the frigid outer reaches beyond our solar system. When an issue crops up, engineers at NASA's Jet Propulsion Laboratory in Pasadena, California, have to get creative while still being careful of how the spacecraft will react to any changes.

Currently the farthest spacecraft from Earth, Voyager 1 is about 15 billion miles (24 billion kilometers) away. The probe operates beyond the heliosphere " the sun's bubble of magnetic fields and particles that extends well beyond Pluto's orbit " where its instruments directly sample interstellar space.

Earlier this year, engineers spotted an issue when the fuel tube inside one of Voyager's thrusters became clogged. If the thrusters are clogged, they can't generate as much force to keep the spacecraft steady. Voyager's thrusters keep the spacecraft oriented in a way that it can communicate with Earth.

If Voyager 1 isn't positioned in such a way so that its antenna is pointed at Earth, the spacecraft can't "hear" commands from mission control or send back data, according to Calla Cofield, media relations specialist at JPL.

"If the thrusters that keep the antenna pointed at Earth get clogged, that would be end of mission," she said. ...