During five months of troubleshooting, Voyager’s ground team continued to receive signals indicating the spacecraft was still alive. But until Saturday, they lacked insight into specific details about Voyager 1’s status.
“It’s pretty much the same as it is,” Spilker said. “We’re still in the early stages of analyzing all channels and looking at trends. Temperatures have dropped a little bit over this period, but we’re seeing pretty much what we expected. And that’s always been the case. Good news.”
Rearrange the code
Through investigation, Voyager’s ground team discovered that one chip responsible for storing part of the FDS memory had stopped working, perhaps due to a cosmic ray strike or aging hardware failure. This affected some of the computer’s software code.
“It took away some of the memory,” Spilker said. “All they have to do is relocate that code to a different part of memory, and anything that uses those codes or subroutines can access the new location in memory and run it. .”
The bad chip only corrupted about 3% of the FDS memory, so engineers had to port the code to another part of the memory bank. But according to NASA, no single location is large enough to hold an entire section of code.
So the Voyager team split the code into sections and stored them in different locations in FDS. This wasn’t just a copy and paste job. Engineers had to change some parts of the code to make sure everything worked together. “References to that code’s location in other parts of FDS memory must also be updated,” NASA said in a statement.
NASA’s new mission has a hardware and software simulator on the ground where engineers can test new procedures to ensure they do no harm when uplinking commands to the actual spacecraft. Because of its age, Voyager does not have a ground simulator, and much of the mission’s original design documentation remains in paper form and has not been digitized.
“It was really just my eyes that saw the code,” Spilker said. “So we had to triple-check it. Everyone was looking over it and making sure all the links were connected.”
This was just the first step in restoring Voyager 1 to full functionality. “He was pretty confident it was going to work, but he wasn’t 100 percent sure until it actually happened,” Spilker said.
“The reason I didn’t do everything in one step was because the amount of memory I could find right away was very limited. So I prioritized one data mode (engineering data mode) and restored that mode. ,” said Jeff Mellstrom, a JPL engineer who heads Voyager 1’s “tiger team” tasked with overcoming the problem.
“The next step is to rearrange the remaining three scientific data modes that are actively used, but they are essentially the same,” Maelström said in a written response to Ars. “The main difference is that we are now more constrained by the available memory. We have ideas where we can rearrange the code, but we have not yet fully evaluated or decided on the options. is the first step starting this week.”
