Nearly 50 years after leaving Earth, Voyager 1 is approaching an extraordinary milestone that will demonstrate just how far humanity’s most distant spacecraft has travelled. However, keeping the ageing explorer operational has become increasingly challenging as its power supply continues to decline, Science Daily reported.
NASA engineers have recently made two important developments in their efforts to extend the mission. In September, they completed a complex energy conservation project aimed at preserving the spacecraft’s remaining scientific capabilities. On October 20, also unexpectedly resumed communication with Earth following a mysterious 48-hour interruption.
In early September, the Voyager team successfully replaced three devices aboard Voyager 1 with alternatives that consume less electricity. The carefully coordinated operation, nicknamed the “Big Bang”, took months of preparation and was completed approximately six weeks after engineers carried out an identical procedure on Voyager 2.
The upgrade is expected to extend the operational lives of Voyager 1’s remaining scientific instruments, allowing the spacecraft to continue gathering valuable information from interstellar space for longer than previously anticipated.
Both Voyager spacecraft generate electricity through radioisotope thermoelectric generators. These systems convert heat released by the radioactive decay of plutonium into electrical power. As the process continues, the spacecraft gradually lose their ability to generate electricity, with each probe experiencing an annual decline of approximately 4 watts.
After nearly five decades in space, this steady reduction has left engineers with very little power to spare. To keep the missions running, NASA has progressively switched off equipment that is no longer essential.
The Big Bang operation presented a particularly complex engineering challenge because all three replacements had to be carried out simultaneously. The six devices involved help regulate temperatures inside the spacecraft despite the extreme cold of space. Replacing the three original devices together was necessary to reduce electricity consumption while maintaining the appropriate distribution of heat throughout Voyager 1.
Power constraints have already forced NASA to deactivate two of Voyager 1’s scientific instruments in recent years.
When the spacecraft launched in 1977, it carried 10 instruments designed for scientific research. Several were switched off after Voyager completed its encounters with the outer planets, while others continued operating to investigate increasingly distant regions of space.
One of the key areas studied was the outer heliosphere, an enormous region of particles and magnetic fields generated by the Sun. Both Voyager spacecraft have since crossed beyond this boundary into interstellar space, making them the only spacecraft ever to directly examine the environment beyond the Sun’s heliosphere.
Preserving their remaining scientific instruments is particularly important because no other missions can currently collect measurements from this distant region.
Without the Big Bang upgrade, NASA could have faced the prospect of shutting down another Voyager 1 instrument as early as summer 2027.
Despite the successful power conservation effort, Voyager 1 continues to encounter unexpected technical problems.
NASA temporarily lost contact with the spacecraft on October 18 and 19, after the agency’s Deep Space Network failed to receive its radio signal during two scheduled communication attempts, separated by 24 hours.
The network comprises large radio antennas at three locations around the world, enabling NASA to exchange signals with spacecraft exploring the Moon and more distant destinations.
At the time of the interruption, Voyager 1 was approximately 16 billion miles (24 billion kilometres) from Earth.
After two unsuccessful attempts to detect the spacecraft, its signal unexpectedly returned on October 20, roughly 48 hours after the interruption began. Communication has remained established since then, and engineers subsequently sent commands to investigate the problem.
NASA has not yet established the exact cause of the incident. However, engineers discovered that one set of Voyager 1’s thrusters had stopped operating, prompting the spacecraft to automatically activate its backup thrusters.
This behaviour is part of an onboard safety mechanism known as fault protection. When the spacecraft’s computers identify a potential problem with active equipment, they can switch to backup hardware, place the spacecraft in a stable configuration and suspend normal operations.
This gives mission controllers on Earth an opportunity to investigate the issue and determine the appropriate response.
“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.”
While NASA continues to investigate the communication interruption, Voyager 1 is moving towards another remarkable achievement.
Travelling through interstellar space at approximately 38,000 mph (61,155 kph), the spacecraft is expected to reach a distance of 16.09 billion miles (25.89 billion kilometres) from Earth on November 18.
This distance is equivalent to one light-day, meaning light takes an entire 24 hours to travel between Earth and the spacecraft.
The milestone also highlights the extraordinary challenges involved in communicating with a spacecraft so far away. Since radio waves travel at the speed of light, commands sent from Earth will take a full day to reach Voyager 1. Any response transmitted by the spacecraft will require another 24 hours to return, resulting in a total communication delay of 48 hours.
Crossing the one-light-day threshold will not cause any physical change to Voyager 1 or its surroundings. The spacecraft will continue travelling through the same interstellar environment, unaware that it has crossed a milestone of particular significance to people on Earth.
Instead, the achievement will serve as a reminder of the enormous distances separating objects in the universe and the extraordinary endurance of a spacecraft launched nearly half a century ago.
Despite declining power, ageing equipment and unexpected technical problems, Voyager 1 continues its historic journey farther from Earth than any other human-made object.
