NASA's Voyager 2 probe has phoned home. The iconic spacecraft has been doing that reliably for decades, but it's tremendously far away from Earth, and that can make communication difficult. Last month, NASA announced Voyager 2 had gone offline after being pointed in the wrong direction. Well, all it took was a "shout," as NASA calls it, to get the probe back online.
Voyager 2 left the solar system in 2018, following in the tracks of Voyager 1, which entered interstellar space in 2012. Voyager 2 is currently 12.4 billion miles (19.9 billion kilometers) from Earth and gets about 9 miles (15 kilometers) farther away every second. At that distance, even a small misalignment of the communication antenna can be disastrous, and that's what happened last month. A series of commands incorrectly adjusted the antenna to point 2 degrees away from Earth.
NASA said that in the worst case, Voyager 2 would automatically reorient itself in October, but this is not the time to lose months of access to one of two interstellar probes. This spacecraft is powered by a radioisotope thermoelectric generator (RTG), which generates a little less power every year as the plutonium core decays. NASA has already had to scavenge power from safety systems to keep the spacecraft operating, but that can only work for so long. Currently, NASA believes Voyager 2 could stay alive until 2026.
Rather than wait for October to roll around, NASA has been trying to reestablish communication with the probe. NASA used the Deep Space Network facility in Canberra, Australia to send a powerful signal (the "shout") in Voyager's direction, hoping the probe would pick it up and adjust its orientation. Because of the distances involved, it took 18.5 hours for the signal to reach Voyager 2 and another 18.5 hours for any reply to come back.
Happily, NASA heard from Voyager 2 37 hours after sending the signal. At 12:29 a.m. on Aug. 4, the spacecraft began transmitting telemetry and science data through the Deep Space Network. NASA has since confirmed that Voyager 2 is fully back online and operating normally.
Voyager 2 was the first of the twin probes to launch, but its exit from the solar system was delayed by the "Grand Tour" that took it to Jupiter, Saturn, Uranus, and Neptune. It remains the only spacecraft to visit Uranus and Neptune, but scientists are increasingly interested in these distant gas giants.
