Voyager 1 Completes Power-Saving Swap and Recovers From Brief Signal Loss: One Light-Day From Earth on November 18
NASA said on October 29 that Voyager 1, the most distant human-made object, completed a power-saving swap nicknamed the “Big Bang” in September, recovered on its own from a brief loss of communication on October 18-19, and will reach a milestone of one light-day from Earth on November 18, at a distance of 16.09 billion miles (25.89 billion kilometers).
The swap was completed in early September: engineers turned off three devices on Voyager 1 and substituted three lower-power alternatives, about six weeks after the mission team performed the same swap on Voyager 2. The six devices help keep the spacecraft warm enough to operate in the frigid expanse of space, and only by swapping all three could the team both reduce power use and ensure heat is properly distributed.
The Voyagers are powered by radioisotope thermoelectric generators that convert heat from decaying plutonium into electricity, losing about 4 watts of power each year. The mission launched in 1977 with 10 dedicated science instruments, and in recent years the dwindling supply has forced the team to turn off two of them. Without the Big Bang, NASA said, the mission would have needed to turn off another instrument on Voyager 1 as early as summer 2027; the swap lets the remaining instruments operate longer than previously anticipated.
The signal loss came on October 18 and 19, when NASA's Deep Space Network was unable to detect a radio signal from the probe, then 16 billion miles (24 billion kilometers) from Earth, during two scheduled communications attempts 24 hours apart. The signal reappeared 24 hours later, on October 20, and the team has maintained communication since then.
Engineers are still investigating the cause. They have determined that one group of thrusters went offline and their backups turned on, an automatic fault-protection response programmed to occur when the spacecraft's computers detect something amiss: the probe puts itself in a safe, stable configuration and pauses normal operations while engineers diagnose the issue.
“This is the first time we've seen the spacecraft do something like this, but we are also at a point in the mission where we have to expect the unexpected,” said Kareem Badaruddin, Voyager mission manager at NASA's Jet Propulsion Laboratory in Southern California. “We're relieved to be back in contact with Voyager 1 and are eager to understand what happened.”
Voyager 1 is speeding at 38,000 mph (61,155 kph). Once it passes one light-day, radio waves will take 24 hours to reach it and another 24 hours to carry its reply back to Earth.
“If you want to say 'hello' to Voyager, you send your message and then you go home and you wait two days before you finally get a response,” said Suzanne Dodd, Voyager project manager at JPL. NASA said the spacecraft will not detect any change when it passes the milestone; its significance lies in demonstrating the vastness of the universe and the endurance of humanity's most distant explorer.
Source: GSM · USA (original Chinese edition)
Photo: 图：旅行者号探测器（资料图）。照片：NASA/JPL-Caltech，公共领域。 / The Voyager spacecraft (file photo). Photo: NASA/JPL-Caltech, public domain.
