NASA’s Voyager 1 and Voyager 2 spacecraft, launched in 1977, are now the farthest human-made objects from Earth, traveling through interstellar space, the region between stars. Engineers at NASA’s Jet Propulsion Laboratory (JPL) are taking steps to help ensure that both spacecraft can continue to explore for years to come.

One challenge is the buildup of fuel residue inside narrow tubes in some of the thrusters on the spacecraft. The thrusters are used to keep each spacecraft’s antenna pointed at Earth, which is essential for communication.

To slow the buildup, the mission team has begun letting the two spacecraft rotate slightly farther in each direction before firing the thrusters. This will reduce the frequency of thruster firings and the amount of residue deposited each time.

The team is also performing fewer, longer firings, which will further reduce the total number of firings done on each spacecraft.

The adjustments to the thruster rotation range were made by commands sent in September and October 2023, and they allow the spacecraft to move almost 1 degree farther in each direction than in the past.

The mission team has carefully devised the adjustments to ensure minimal impact on the mission. While more rotating by the spacecraft could mean bits of science data are occasionally lost, the team concluded the plan will enable the Voyagers to return more data over time.

Engineers can’t know for sure when the thruster propellant inlet tubes will become completely clogged, but they expect that with these precautions, that won’t happen for at least five more years, possibly much longer. The team can take additional steps in the coming years to extend the lifetime of the thrusters even more.

In 2022, the onboard computer that orients the Voyager 1 spacecraft with Earth began to send back garbled status reports, despite otherwise continuing to operate normally. It took mission engineers months to pinpoint the issue.

The attitude articulation and control system (AACS) was misdirecting commands, writing them into the computer memory instead of carrying them out. One of those missed commands wound up garbling the AACS status report before it could reach engineers on the ground.

The team determined the AACS had entered into an incorrect mode; however, they couldn’t determine the cause and thus aren’t sure if the issue could arise again. A software patch should prevent that.

“This patch is like an insurance policy that will protect us in the future and help us keep these probes going as long as possible,” said JPL’s Suzanne Dodd, Voyager project manager. “These are the only spacecraft to ever operate in interstellar space, so the data they’re sending back is uniquely valuable to our understanding of our local universe.”

The team uploaded the patch to Voyager 2 on October 20, 2023, and it’s now operating as it should. The team plans to upload the patch to Voyager 1 on November 10, 2023.

The Voyager mission was originally scheduled to last only four years, sending both probes past Saturn and Jupiter. NASA extended the mission so that Voyager 2 could visit Uranus and Neptune; it is still the only spacecraft ever to have encountered the ice giants. In 1990, NASA extended the mission again, this time with the goal of sending the probes outside the heliosphere, a protective bubble of particles and magnetic fields created by the Sun. Voyager 1 reached the boundary in 2012, while Voyager 2 (traveling slower and in a different direction than its twin) reached it in 2018.

Voyager 1 and Voyager 2 have traveled more than 15 billion and 12 billion miles from Earth, respectively. They are the farthest human-made objects from Earth and the only spacecraft to have entered interstellar space.

The Voyager mission continues to provide scientists with valuable data about the outer solar system and interstellar space. The spacecraft’s instruments are measuring plasma density, temperature, and magnetic fields, as well as the composition of the interstellar medium.

NASA’s Voyager mission is a testament to the ingenuity and dedication of engineers and scientists who have worked to keep these spacecraft operating for over four decades. The Voyager probes are still sending back data from the edge of the solar system, providing us with a glimpse of the vast and mysterious interstellar realm.

©️ Rocky Mountain Dispatch 2023