All through the 5 months of troubleshooting, Voyager’s floor workforce continued to obtain alerts indicating the spacecraft was nonetheless alive. However till Saturday, they lacked perception into particular particulars concerning the standing of Voyager 1.
“It’s just about simply the way in which we left it,” Spilker stated. “We’re nonetheless within the preliminary phases of analyzing the entire channels and taking a look at their tendencies. A few of the temperatures went down just a little bit with this time period that is gone on, however we’re just about seeing every part we had hoped for. And that is all the time excellent news.”
Relocating Code
By their investigation, Voyager’s floor workforce found {that a} single chip answerable for storing a portion of the FDS reminiscence had stopped working, most likely because of both a cosmic ray hit or a failure of getting older {hardware}. This affected a few of the laptop’s software program code.
“That took out a bit of reminiscence,” Spilker stated. “What they need to do is relocate that code into a special portion of the reminiscence, after which be sure that something that makes use of these codes, these subroutines, know to go to the brand new location of reminiscence, for entry and to run it.”
Solely about 3 p.c of the FDS reminiscence was corrupted by the dangerous chip, so engineers wanted to transplant that code into one other a part of the reminiscence financial institution. However no single location is giant sufficient to carry the part of code in its entirety, NASA stated.
So the Voyager workforce divided the code into sections for storage elsewhere within the FDS. This wasn’t only a copy-and-paste job. Engineers wanted to change a few of the code to verify it would all work collectively. “Any references to the placement of that code in different elements of the FDS reminiscence wanted to be up to date as nicely,” NASA stated in a press release.
Newer NASA missions have {hardware} and software program simulators on the bottom, the place engineers can check new procedures to verify they do no hurt after they uplink instructions to the true spacecraft. Resulting from its age, Voyager would not have any floor simulators, and far of the mission’s authentic design documentation stays in paper kind and hasn’t been digitized.
“It was actually eyes-only to take a look at the code,” Spilker stated. “So we needed to triple examine. Everyone was trying by way of and ensuring we had the entire hyperlinks coming collectively.”
This was simply step one in restoring Voyager 1 to full performance. “We had been fairly positive it will work, however till it really occurred, we did not know 100% for positive,” Spilker stated.
“The explanation we didn’t do every part in a single step is that there was a really restricted quantity of reminiscence we may discover rapidly, so we prioritized one information mode (the engineering information mode), and relocated solely the code to revive that mode,” stated Jeff Mellstrom, a JPL engineer who leads the Voyager 1 “tiger workforce” tasked with overcoming this downside.
“The subsequent step, to relocate the remaining three actively used science information modes, is basically the identical,” Mellstrom stated in a written response to Ars. “The principle distinction is the accessible reminiscence constraint is now even tighter. We’ve got concepts the place we may relocate the code, however we haven’t but absolutely assessed the choices or decided. These are the primary steps we’ll begin this week.”