NASA’s Voyager 1 spacecraft, the most distant human-made object, has resumed sending engineering updates to Earth after a five-month hiatus. The Voyager engineering team at NASA’s Jet Propulsion Laboratory in Southern California discovered an issue with one of the spacecraft’s onboard computers, the flight data subsystem (FDS). The team devised a plan to divide the affected code into sections and store those sections in different places in the FDS. The spacecraft, over 15 billion miles from Earth, is now able to send usable data about its health and status. The team will continue to adjust the FDS software to enable the return of science data.
Voyager 1: Resuming Communication with Earth
NASA’s Voyager 1 spacecraft, the most distant human-made object in existence, has resumed sending engineering data back to Earth after a five-month hiatus. This marks the first time since November 2023 that the spacecraft has returned usable data about the health and status of its onboard engineering systems. The next step for the mission team is to enable Voyager 1 to begin returning science data once again.
Voyager 1, along with its twin Voyager 2, are the only spacecraft to have ever ventured into interstellar space, the space between stars. However, Voyager 1 ceased sending readable science and engineering data back to Earth on November 14, 2023. Despite this, mission controllers were able to ascertain that the spacecraft was still receiving their commands and operating normally.
The Problem: A Faulty Chip in the Flight Data Subsystem
The issue with Voyager 1 was traced back to one of the spacecraft’s three onboard computers, the flight data subsystem (FDS), by the Voyager engineering team at NASA’s Jet Propulsion Laboratory in Southern California. The FDS is responsible for packaging the science and engineering data before it is sent back to Earth.
The team discovered that a single chip responsible for storing a portion of the FDS memory, including some of the FDS computer’s software code, was not functioning. The loss of that code rendered the science and engineering data unusable. Unable to repair the chip, the team decided to relocate the affected code elsewhere in the FDS memory. However, no single location was large enough to hold the entire section of code.
The Solution: Dividing and Relocating the Code
The team devised a plan to divide the affected code into sections and store those sections in different places in the FDS. To ensure that these code sections still function as a whole, they needed to adjust the code sections and update any references to the location of that code in other parts of the FDS memory.
The team began by isolating the code responsible for packaging the spacecraft’s engineering data and sent it to its new location in the FDS memory on April 18. Given that Voyager 1 is over 15 billion miles (24 billion kilometers) from Earth, a radio signal takes about 22 ½ hours to reach the spacecraft and another 22 ½ hours for a signal to return to Earth. When the mission flight team heard back from the spacecraft on April 20, they confirmed that the modification had worked.
The Future: Returning Science Data and Voyager 2’s Status
In the coming weeks, the team will relocate and adjust the other affected portions of the FDS software, including the portions that will start returning science data. Meanwhile, Voyager 2 continues to operate normally. Launched over 46 years ago, the twin Voyager spacecraft are the longest-running and most distant spacecraft in history. Before their interstellar exploration, both probes flew by Saturn and Jupiter, with Voyager 2 also flying by Uranus and Neptune.
The Jet Propulsion Laboratory, which manages the Voyager mission, is managed by Caltech in Pasadena, California, for NASA. The successful resumption of communication with Voyager 1 is a testament to the ingenuity and perseverance of the mission team, and a significant step towards the continuation of this historic exploration of interstellar space.
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