From more than 15 billion miles away, NASA engineers began repairing a space probe headed toward the constellation Ophiucus in April, though it will take another 38,000 years to arrive. NASA launched Voyager 1 in 1977, and it has already exceeded expectations, but the space agency hopes to continue receiving data from the probe until at least 2030. But after Voyager 1 suffered a computer glitch in November and began sending incomprehensible data (a not entirely unusual occurrence), prompting NASA to begin the repairs from afar.
After some uncertainty about whether it would all work, the repairs were successful. Even better, when Salon spoke to NASA about the problem of repairing spacecraft remotely, the experts were optimistic about the future and what it says about space exploration in general.
To understand why, it is first necessary to explain what happened to Voyager 1 in the first place. In November, the spacecraft sent a signal that contained no data. Engineers determined that the problem was with either the flight data subsystem (FDS) or the telemetry modulation unit (TMU). In the last week of February, NASA sent a “poke” to Voyager 1 to prompt the FDS to send a memory readout with data; not only did it succeed, but NASA soon uploaded a separate command that caused Voyager 1 to respond with a full memory readout that helped them identify the specific problem with the FDS.
“The team confirmed that the problem is with the FDS,” Calla Cofield, a media relations specialist at NASA’s Jet Propulsion Laboratory, told Salon. “A chip that stores 256 words of FDS memory has a stuck bit (the code gets stuck on a 0 or a 1), indicating that the component is defective, either due to age or damage from external particles. This section represents about 3% of FDS memory. The team would need to relocate the portion of software code stored on the damaged chip.”
During the April mission, NASA sent a command to Voyager 1 to relocate the portion of the affected FDS software code and redirect references to that code to other places in the spacecraft’s software.
“On April 20, the team received technical data from the spacecraft indicating that the command was successful,” Cofield said. “All indications are that the spacecraft is fine after five months of no contact.”
The team began receiving science data from Voyager 1 again on May 19, and by June all of the science instruments on Voyager 1 had begun sending usable data again. However, Cofield added that “housekeeping [is] “The spacecraft is still under investigation.”
Of course, this is not the end of the story; Voyager 1 is not the only spacecraft that will ever need repair. There are currently two other spacecraft that have left the solar system and are still operational, Voyager 2 and New Horizons. In addition, NASA sent two other spacecraft that are no longer in service, Pioneer 10 and Pioneer 11. Can the lessons that allowed NASA to repair Voyager 1 be applied to these and other distant spacecraft?
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“All indications are that the spacecraft is doing fine after five months without contact.”
“The future is less about repairs and more about finding ways around problems,” said Bob Rasmussen, a member of the Voyager flight team. “We know of several factors that limit life and have strategies to maintain capability as long as possible. But we can’t predict when something will go wrong, so we have to deal with it when it does.”
That’s not to say Rasmussen is entirely confident that NASA can salvage the failed probes. In 2019, the agency had to turn off a heater for Voyager 2’s cosmic-ray subsystem instrument to conserve the probe’s power. In April, NASA kept Voyager 2 running by tapping into a small reservoir of backup power that is used to fuel the spacecraft’s safety mechanism. NASA believes this will keep the spacecraft powered enough that it won’t have to turn off a science instrument until 2026.
Voyager 1 and 2, meanwhile, are always on the brink of a longer-term collapse. Even if all their systems remain optimal, the spacecraft are still not expected to survive past the 2030s. The fact that they have survived this long is a testament to the skill and dedication of the engineers who built them in the 1970s. Unfortunately, the day may come when more than one of their vital systems simply fails.
“The worst case is that both can fail at any time,” Rasmussen said. “Not all failures are recoverable. For many, we would never be able to tell what happened because the contact would simply stop.”
Rasmussen added that the best-case scenario is that Voyager 1 will continue operating for another five to 10 years. “We have a long-term strategy to gradually reduce operations as energy decreases and to use degraded operating modes,” Rasmussen said. “But we also know what happens with the best-laid plans.”
Tragically, June was also the month that Ed Stone, the man who pioneered the Voyager missions and led their missions for half a century, passed away. In its obituary for the former director of the Jet Propulsion Laboratory, NASA wrote that Stone was “a pioneer who dared to do mighty things in space” and “took humanity on a planetary tour of our solar system and beyond, sending NASA where no spacecraft had gone before.”
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