- Voyager still operates using assembly code written nearly half a century ago
- NASA maintains interstellar spacecraft with less memory than a smartphone photo today
- The engineers who built Voyager are disappearing faster than the spacecraft itself
Launched in 1977, NASA’s twin Voyager spacecraft continue to operate with onboard computers that run assembly language written for custom General Electric processors.
Each spacecraft carries three separate computer systems with a combined memory of about 64 to 70 kilobytes across all three—less storage than a single small image file on a modern smartphone today.
NASA’s Suzy Dodd has compared the operation of Voyager to flying an Apple II, capturing how primitive computing resources have become by modern standards.
What the spacecraft is actually driving and why the language matters
Popular shorthand often says Voyager runs on Fortran, but that description conflates two different things.
The spacecraft’s low-level flight operations depend on assembly language programming on highly specialized hardware designed in the early 1970s.
Fortran has been linked to ground systems and legacy mission tools, not to the flight software itself.
When NASA went looking for a replacement engineer in 2015, the job posting covered both assembly language skills and a deep understanding of the spacecraft’s unique hardware architecture.
49 years of continuous operation have created knowledge gaps that mean far more than the programming language itself.
Around the start of the interstellar mission after Voyager 2’s flyby of Neptune in August 1989, the flight software was updated to make each spacecraft more autonomous.
This version, augmented by command sequences that the team uploads every few months, is the basis of what now runs on both probes.
However, the team has shrunk and aged dramatically over the decades, and much of the original paper documentation has been lost or fragmented over time.
Original engineers are no longer available to help
Larry Zottarelli was the last original Voyager engineer still working on the project when he retired in 2016 at the age of 80.
All the other original engineers are dead or over 90, as is Dr. Gary Flandro, an aerospace/railway engineer now living in retirement.
Dodd told Live Science in early 2024, the people who built the spacecraft are no longer alive, leaving a shrinking team to maintain code that no one fully understands.
The Voyager signal now takes more than 23 hours to reach Earth, and when NASA receives the next status check, the spacecraft will already be 1.5 million kilometers further out into interstellar space.
The mission continues, but the institutional memory that built it is fading faster than the plutonium power sources that keep the probes alive.
Each passing year brings with it more of that knowledge, and when the last engineer who understands the assembly code retires or dies, NASA will be left with paper documentation, a fading signal, and a spacecraft that no one alive can truly repair.
Via SpaceDaily
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