The Voyager 1 spacecraft, located nearly 25 billion kilometers from Earth, continues to experience issues as its onboard power supply gradually depletes.
NASA engineers successfully restored communication with Voyager 1, and the spacecraft is now operating normally after a dwindling power supply caused a weeks-long signal loss. The issue began in October when the aging probe automatically switched from its X-band radio transmitter to the much weaker S-band transmitter for communication with the mission team on Earth. Currently, Voyager 1, the farthest spacecraft from Earth, is exploring interstellar space at a distance of 24.9 billion kilometers.
The probe switched transmitters automatically after its onboard computer detected critically low power levels following a command to activate one of its heaters. This unexpected change left engineers unable to receive status updates or scientific data from Voyager 1 for nearly a month. Using clever workarounds, the team successfully switched Voyager 1 back to its X-band transmitter and resumed receiving daily data by mid-November.
“The twin probes were never truly designed to operate this long, and the team learns new things every day,” said Kareem Badaruddin, Voyager mission manager at NASA’s Jet Propulsion Laboratory in Pasadena, California. “Fortunately, they were able to resolve this issue.”
However, this is just one of many challenges the mission team has faced in recent years as Voyager 1 and its twin probe, Voyager 2, continue exploring space more than 47 years after their launches. Launched weeks apart in 1977, the probes far outlived their original four-year mission to fly by the largest planets in the Solar System. Now, they are traveling through interstellar space, the only spacecraft operating outside the heliosphere—a magnetic and charged particle bubble surrounding the Sun, extending beyond Pluto’s orbit.
Both spacecraft are powered by heat from decaying plutonium, which is converted into electricity. Each year, they lose approximately 4 watts of power, equivalent to a small energy-efficient light bulb. Five years ago, the mission team began shutting down non-essential systems to conserve power for the probes’ core functions. Some of these systems include heaters that keep scientific instruments operational at appropriate temperatures. Surprisingly, all instruments continue functioning, even at temperatures much lower than they were tested for decades ago.
Occasionally, engineers send commands to Voyager 1 to reactivate certain heaters, warming components damaged by decades of radiation exposure, according to Bruce Waggoner, Voyager mission assurance manager. The heat may help reverse radiation-induced damage, which reduces the efficiency of the spacecraft’s systems. However, a command to turn on a heater on November 16 triggered the probe’s automated fault-protection system. If the spacecraft uses more power than is available, it automatically shuts down non-essential systems to conserve energy. The team discovered the issue on October 18 when they failed to receive a response signal from Voyager 1.
Since both Voyager probes had already shut down all unnecessary systems except their scientific instruments, the fault-protection system disabled the X-band transmitter and switched to the lower-power S-band transmitter. Voyager 1 had relied on its X-band transmitter for decades, while the S-band transmitter had not been used since 1981 due to its significantly weaker signal. The team had to locate the faint S-band signal before re-establishing communication with the spacecraft.
On November 7, engineers successfully sent a command to Voyager 1 to switch back to its X-band transmitter and began collecting scientific data again on November 18. They are now actively reconfiguring the system that synchronizes Voyager’s three onboard computers, one of the final tasks needed to restore the spacecraft to its pre-issue functionality.
The transmitter switch is just one of several initiatives NASA has undertaken this year to overcome communication challenges with the aging spacecraft. These include firing thrusters to keep Voyager’s antenna pointed toward Earth and addressing a computer glitch that disrupted the spacecraft’s data transmissions to Earth for months.
The Voyager team uses a computer model to predict power usage by the spacecraft’s heaters and instruments. However, the recent fault-protection trigger indicates that the probe is nearing the end of its operational life, facing an increasingly uncertain future.
