Space agency provides exceedingly long-distance tech support
Maintaining legacy hardware isn’t easy when you’re in the same office. It’s a somewhat greater challenge when you’re updating a computer that is literally on the other side of the solar system.
That was the problem facing NASA recently, as the agency was forced to issue a software patch for Voyager 1, an unmanned probe launched in 1977, days after Elvis Presley died. Almost 50 years later, it’s just about functional while speeding through space, a mere 15 billion miles away.
As you might expect, the hardware is creaking. Last year, the team noticed a problem with the thrusters that keep the craft’s antennas pointed towards Earth. After puzzling over corrupted data, they realised that a build-up of propellant residue was preventing them from firing properly – which, if left untreated, could result in Voyager 1 losing touch with us.
Fortunately, the scientists determined that a software update could fix the problem. Modifying how often and how much the thrusters fire would mitigate the residue build-up. The bad news was that applying the software update to both Voyager 1 and its deep space companion, Voyager 2 (which also launched in 1977), would be far from a regular Patch Tuesday, according to Bruce Waggoner, an engineer working on the Voyager programme at NASA’s Jet Propulsion Laboratory (JPL).
“They were built at JPL and the machine language they use is a JPL-specific version that people cooked up here,” said Waggoner. “It looks similar to other 1970s and 80s opcode architectures you see in processors, but it’s a unique set of instructions and the software isn’t necessarily well written. It was written by people who were just learning the code like everybody was in the 70s and 80s.”
Being half a century old, the system is relatively simple compared to modern standards. And this was both a blessing and a curse for the team working on the software.
“Any time we patch, we’re not doing what you envision with the modern computer,” said Waggoner. “We’re literally just writing over the bits we want to change directly. We’re doing a poke command, essentially.”
Poking around
Exactly how the poke command would be issued was a trickier question – one that required NASA to blow the dust off its rolodex. “One of our retired software engineers was pulled back in and worked a lot of overtime an
