The Voyager 1 probe surprised NASA by activating an instrument unused for 40 years

The Voyager 1 space probe was the first man-made object to leave the solar system, traveling at 61,000 km/h for 35 years to accomplish this feat. Launched on September 5, 1977, the probe demonstrated a resilience that seemed foolproof. But Voyager 1 gave NASA engineers a big scare. Last month, the space agency lost track of it for a few days before discovering that the probe had switched to a radio frequency it had not used since the 1980s.

It all started on October 16 when NASA engineers asked Voyager 1 to turn on one of its heaters. The probe should have had enough power to execute this command without issue, but an unknown event caused it to trigger its fault protection system, which turns various instruments on and off to help save power. Since radio transmissions take almost a full day to reach Earth from outside the solar system, the US space agency did not know it had lost contact with Voyager 1 until October 18.

A radio band not used since 1981

At the time, the probe had reduced the power of its X-band radio, forcing it to transmit on a different frequency. NASA was able to reestablish contact by scanning X-band frequencies, but lost contact again on October 19. Engineers discovered that Voyager 1 had completely turned off X-band radio and switched to S-band radio, which it had not used since 1981. NASA sent a test signal to confirm that X-band radio S was well lit and received a response on October 24.

The US space agency said it is leaving the S-band radio on for now while it determines why the fault protection system was triggered.

Voyager 1 and 2 are in power saving mode

Voyager 1 and Voyager 2 had their share of problems. Voyager 1 experienced technical issues in 2023 that were resolved before the probe began sending scientific data again in June 2024. Voyager 2 had to shut down some instruments to save energy in October 2024.

Both probes are in fairly good condition for their age. They are powered by radioisotope thermoelectric generators. They contain plutonium which continually decays and gives off heat which produces energy.

But as the material disintegrates, the amount of heat it generates decreases, gradually reducing the energy available to Voyagers 1 and 2. To combat this effect, NASA has periodically shut down nonessential systems so that both probes can fly and operate for as long as possible.

Currently, both ships have turned off several systems to save power. Some of the science instruments are still online and continuing to transmit valuable data, including about the interstellar gas in which Voyager 1 continues to float to this day.