NASA’s furthest spacecraft scared mission control when it inexplicably went silent and missed two days of planned checks. The scathing incident occurred just two weeks ago, when the Deep Space Network did not receive a call from Voyager 1 on either October 18 or 19. But before the agency could send repair commands, the spacecraft, now outside the solar system, sent a signal on October 20. There have been no communication outages since then. Engineers still don’t know what caused the problem. So far, the team has discovered that one set of thrusters shut down, leaving a backup set to take over. Thrusters are small engines that point and stabilize the spacecraft. Voyager 1’s computers do this automatically whenever they detect a problem with the active thrusters to ensure the spacecraft is in safe mode. “This is the first time we’ve seen the spacecraft do something like this, but we’re also at a point in the mission where we have to expect the unexpected,” Kareem Badaruddin, Voyager mission manager at NASA’s Jet Propulsion Laboratory, said in a statement. “We are relieved to be back in contact with Voyager 1 and are eager to understand what happened.” The Voyager 1 problem adds to a growing list of signs that NASA’s longest-running mission is coming to an end. Its plutonium power source loses about four watts each year, forcing engineers to shut down two scientific instruments to conserve power. On November 18, the spacecraft is expected to reach a historic milestone of one “light day” from Earth. That distance, approximately 16.09 billion miles, measures how far light travels in 24 hours. Speed of Light Mashable SEE ALSO: Scientists think they just discovered a new dwarf planet like Pluto. Voyager 1 has traveled further than any other man-made object and is racing through space at 38,000 mph. Launched in 1977 to study the outer planets, the spacecraft and its twin Voyager 2 have explored four planets (Jupiter, Saturn, Neptune and Uranus), 48 moons and a large number of planetary magnetic fields and rings. In August 2012, Voyager 1 was the first to enter interstellar space. The two remain the only spacecraft to ever leave the solar system, although New Horizons is also trying to escape. Both Voyagers are powered by radioisotope thermoelectric generators, which are power units that convert the heat of decaying plutonium into electricity. In September, NASA engineers expanded their dwindling power supplies by shutting down three instruments each and replacing them with three lower-powered alternatives, a plan they dubbed “the Big Bang.” The devices involved in the swap also help keep the spacecraft warm enough to operate in the freezing cold of space, so the swaps had to be done at the same time to distribute heat evenly. According to NASA, that strategy should keep its cosmic ray subsystems, magnetometers, and plasma wave subsystems running for at least another year. The devices measure high-energy particles, the local magnetic field and waves of charged gas around the spacecraft. Once Voyager 1 passes one light day, a radio message from Earth will take 24 hours to arrive and your response will take another 24 hours to arrive. “If you want to say hello to Voyager, you send your message and then you go home and wait two days before you finally get a response,” said Suzanne Dodd, Voyager project manager.
