NASA Reconnects with Voyager, Longest Serving Mission in HistoryNASA has once again restored contact with its Voyager spacecraft, allowing the American space agency's longest-running mission to continue. The twin spacecraft, Voyager 1 and Voyager 2, were launched within weeks of each other in 1977, which means they have now been in operation for more than 47 years. In recent years, NASA officials have reported a number of difficulties with the two craft, most of them related to communication. The latest problems concerned Voyager 1: in a statement in April, NASA said it had been out of touch with the spacecraft for the previous five months. Officials later traced the fault to a chip inside one of Voyager 1's onboard computers, which had rendered the data the spacecraft was sending unreadable. Engineers managed to solve the problem by changing the way the spacecraft stores and reads its data. Then, in October, NASA reported a further communication problem, which briefly delayed the arrival of data from Voyager 1. This time the cause turned out to lie in the spacecraft's radio transmitter system. According to the agency, when NASA sent a command instructing Voyager 1 to switch on one of its heaters, the spacecraft's fault protection system was, for some reason, activated. Designed to conserve power, this system caused Voyager 1 to begin sending signals through a different radio transmitter from the one it normally uses. As a result, NASA had to listen for signals on the S-band rather than the usual X-band. Once it did so, data began to arrive again. Because the S-band is far weaker than the X-band, however, engineers set out to bring the X-band system back online for long-term use. NASA noted that it had not used the S-band since 1981. Voyager 1 and Voyager 2 are the most distant spacecraft NASA still operates. Voyager 1 is currently exploring space about 24 billion kilometers from Earth, while Voyager 2 is working at a distance of about 20.5 billion kilometers. Such enormous distances mean that it takes about a day for data to reach Earth, and another day for information sent from Earth to reach the spacecraft. The two Voyagers were originally designed to explore Jupiter and Saturn, and both successfully carried out studies of those planets. Later, in 1989, Voyager 2 made the first-ever close observations of Uranus and Neptune. The spacecraft then embarked on a new mission to explore distant regions of space. In 2013, NASA announced that Voyager 1 had crossed the boundary separating our solar system from interstellar space, a term meaning "between stars." Scientists say interstellar space begins where the sun's continuous flow of particles and its magnetic field come to an end. Voyager 2 first entered interstellar space in 2018, when, according to NASA, it was more than 17.7 billion kilometers from the sun. To date, the two Voyagers are the only spacecraft to have explored interstellar space. The agency says the Voyagers are studying how the interstellar medium interacts with the solar wind, the continuous flow of charged particles released by the sun. They have also returned data on the heliosphere, a kind of protective bubble that surrounds our solar system. Suzanne Dodd, the current project manager for the Voyager mission at NASA's Jet Propulsion Laboratory in California, recently stated that the agency has no plans to retire the two spacecraft as long as they continue communicating with the mission team on Earth. For now, she said, their work is focused on observing how interstellar space and the heliosphere interact. "We wouldn't be doing Voyager if it wasn't taking science data," she added. In Dodd's view, one reason the Voyagers have lasted so long is that the engineers who built them included multiple backup systems to guard against future problems. She also noted that some of the people who worked on Voyager in its earliest days have come out of retirement to pass on their knowledge to the next generation of scientists and engineers. "From where I sit as a project manager, it's really very exciting to see young engineers be excited to work on Voyager," Dodd said. Taking on the challenges of an old mission and working side by side with the people who built the spacecraft, she explained, both generations want to learn from each other.
