NASA’s Voyager team focuses on software repairs and engines
These efforts should help extend the lifespan of NASA’s interstellar explorers.
Engineers on NASA’s Voyager mission are taking steps to ensure that the two spacecraft launched in 1977 will continue to explore interstellar space for years to come.
One of these measurements concerns fuel residue that appears to be accumulating in the narrow tubes of some of the spacecraft’s engines. Thrusters are used to point each spacecraft’s antenna toward Earth. This type of accumulation has been observed on some other spacecraft.
The team is also downloading a software patch to prevent a repeat of a problem that occurred with Voyager 1 last year. Engineers have solved the problem and are aiming to prevent it from occurring again on Voyager 1 or its twin, Voyager 2.
Accumulation of fuels
The Voyager 1 and Voyager 2 engines are used primarily to point spacecraft’s antennas toward Earth for communications. Spaceships can rotate in three directions: up and down, left and right, and around the central axis, like a wheel. When this happens, the engines turn on automatically and realign the spacecraft so that its antennas remain pointed at Earth.
Fuel is routed to the engines via fuel lines and then passes through smaller lines within the engines called fuel inlet tubes, which are 25 times narrower than the external fuel lines. Each fuel firing adds tiny amounts of fuel residue, leading to a gradual accumulation of material over decades. Significant deposits occur in some fuel inlet pipes. To slow this buildup, the mission began by allowing both spacecraft to spin a little further in either direction before firing the engines. This reduces the frequency of engine ignitions.
Commands sent in September and October made adjustments to the engines’ rotation range, allowing the spacecraft to move nearly one degree more in each direction than in the past. The mission will also conduct fewer and longer firings, which will further reduce the total number of firings conducted by each spacecraft.
The adjustments were carefully designed to minimize impact on the mission. Although further spacecraft rotations could occasionally lead to the loss of scientific data – similar to a telephone conversation in which the person on the other end of the line interrupts from time to time – the team concluded that the plan will allow Voyagers to send back more data over time.
Engineers can’t say for sure when the engine’s inlet pipes will be completely blocked, but they expect that with these precautions this won’t happen for at least five years, if not longer.
The team may take additional steps in the coming years to further extend the life of the engines.
“At this point in the mission, the engineering team faces many challenges for which we have no recipe,” said Linda Spilker, mission scientist at NASA’s Jet Propulsion Laboratory in California. “But they continue to find creative solutions.”
Making up for lost time In 2022, the onboard computer pointing the Voyager 1 probe toward Earth began sending back garbled status reports, although it continued to function normally. It took months for mission engineers to identify the problem. The Articulation and Attitude Control System (AACS) sent erroneous commands and wrote them into computer memory instead of executing them. One of these missed commands corrupted the flight status report. The AACS before reaching the engineers on the ground.
The team discovered that the AACS had entered an incorrect mode; However, she was unable to determine the cause and is therefore unsure whether the problem could reoccur. The software fix is intended to prevent this.
“This patch is like an insurance policy to protect us in the future and help us keep these probes active for as long as possible,” said Suzanne Dodd, Voyager project manager at JPL.
They are the only spacecraft ever to operate in interstellar space, and the data they return is invaluable to our understanding of our local universe.
Voyager 1 and Voyager 2 traveled more than 15 and 12 billion kilometers from Earth, respectively.
At these distances, it will take more than 18 hours to reach the spacecraft, according to the patch instructions. Due to the age of the ship and communication time, there is a risk that the patch could overwrite critical code or have other unintended effects on the ship. To reduce these risks, the team spent months writing, reviewing, and verifying the code. As an additional security measure, Voyager 2 will receive the patch first and serve as a testbed for its twin. Voyager 1 is further from Earth than any other spacecraft, making its data more valuable.
The team will download the patch and perform an AACS memory read on Friday, October 20th to ensure it is in the correct location. If there are no immediate issues, the team will issue an order on Saturday, October 28th to verify that the patch is working properly.