On January 25, interstellar spacecraft Voyager 2 encountered a problem during a maneuver that led to some of its science instruments being turned off. Now the engineering team has restored its operation – despite it being the most distant human-made object in space – and this veteran of space exploration is back collecting science data.
The mishap happened when Voyager 2 failed to do a barrel roll. This 360-degree rotation is used regularly to recalibrate the magnetic field instrument on board but for some reason, the maneuver did not start. This delay left two systems to consume a high level of power, causing the craft to overdraw its power supply, so the fault protection software kicked in and shut down the science instruments to make sure nothing would be damaged.
Voyager 2 is located 18.5 billion kilometers (11 billion miles) away. It takes light 17 hours to reach the spacecraft, so any communication back and forth has a delay of almost a day and a half. But thanks to the prompt intervention of the mission team, by January 28 one of the high-power systems was shut off, and regular work had resumed by February 5.
Voyager 2 was launched in 1977 on a trip that took it to visit Jupiter, Saturn, Uranus, and Neptune. After that, it continued to travel faster and faster towards the edge of the Solar System, finally crossing the boundary into interstellar space in December 2018, becoming only the second spacecraft ever to do so after its twin Voyager 1.
The Voyager probes' power supply comes from a radioisotope thermoelectric generator (RTG). When a radioactive element decays, it releases heat and this can be turned into electricity to power a spacecraft, or a rover like NASA’s Curiosity on Mars. And while it is a pretty durable power source, it is not designed to last forever.
The RTG is used to power instruments and keep the craft warm enough that it can continue to maneuver and communicate with Earth, but every year it loses a bit more power – roughly 4 watts per year. As the power begins to dwindle, sacrifices have been made to keep the mission going. Last year, the primary heater for the cosmic ray subsystem instrument was turned off to compensate for this power loss, although the instrument continues to operate. The same goes for the ultraviolet spectrometer, the heater of which was turned off in 2012 to reduce power consumption, and yet it is still extremely sturdy.
Although it's thought the Voyagers' power sources will run out by the mid-2020s, Voyager 2 wasn't going to let a little setback like this glitch stop it from continuing to explore the space between the stars until then.