The thrusters are an essential component to maintain the probe's communications, as they're used to reorient the direction of its antennae back toward the Earth.
The thrusts lasted a mere 10-milliseconds, but due to the colossal distance between the probe and its home planet the commands took 19 hours and 35 minutes to reach Voyager.
Voyager 1, NASA's farthest and fastest spacecraft, is the only human-made object in interstellar space, the environment between the stars.
Being able to use the backup thrusters means the lifespan of Voyager 1 has been extended by two or three years, added Suzanne Dodd, project manager for Voyager.
Voyager 1 was initially launched to investigate Jupiter, Saturn, and its neighboring moon Titan via flybys. The JPL will also test out the TCM thrusters on Voyager 1's twin, Voyager 2, although NASA says that that spacecraft's attitude control thrusters are in better shape.
Canada Adds 79500 Jobs in November; Unemployment Rate Falls to 5.9%
For the September-to-November period, Canada added roughly 230,000 full-time jobs, or the strongest three-month gain in over a decade.
The Voyager team gathered a group of momentum specialist at NASA's Jet Propulsion Lab, Pasadena, California, to investigate the puzzle.
"The Voyager flight team dug up decades-old data and examined the software that was coded in an outdated assembler language, to make sure we could safely test the thrusters", Nasa Jet Propulsion Laboratory (JPL) chief engineer Chris Jones said. Over the past four decades, as it flew past Jupiter and Saturn and eventually out into the vast reaches of space, it's been using tiny thrusters to position its antenna so it can communicate with Earth.
So, to recap: these thrusters have sat in disuse since Jimmy Carter was president, they aren't designed for this sort of task, and they're a baker's dozen billion miles away. The mission celebrated its 40th anniversary this year, but it's not just a lump of metal floating through interstellar space: that baby still runs.
The MR-103 thrusters, provided by Aerojet Rocketdyne, are created to fire in pulses to rotate the spacecraft and keep its 12-foot (3.7-metre) antenna pointed at Earth, but engineers have noticed more firings were needed recently, indicating the jets were losing some of their performance. "The mood was one of relief, joy, and incredulity after witnessing these well-rested thrusters pick up the baton as if no time had passed at all", said Barber, a JPL propulsion engineer.
The Voyager team now wants to change over to the TCM thrusters in January, during a process where the spacecraft has to switch on a heater for each thruster, which needs power - a scarce resource for this aging mission.
Illustration of the paths of Voyager 1 and 2.