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 best way we left it,” Spilker stated. “We’re nonetheless within the preliminary phases of analyzing all the channels and their tendencies. A few of the temperatures went down a little bit bit with this time period that is gone on, however we’re just about seeing every thing we had hoped for. And that is all the time excellent news.”
Relocating Code
By means of their investigation, Voyager’s floor workforce found {that a} single chip accountable for storing a portion of the FDS reminiscence had stopped working, most likely as a result of both a cosmic ray hit or a failure of growing older {hardware}. This affected a number of the pc’s software program code.
“That took out a piece of reminiscence,” Spilker stated. “What they must do is relocate that code into a distinct portion of the reminiscence, after which guarantee 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 massive sufficient to carry the part of code in its entirety, NASA stated.
So the Voyager workforce divided the code into sections for storage somewhere else within the FDS. This wasn’t only a copy-and-paste job. Engineers wanted to change a number 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 properly,” NASA stated in a press release.
Newer NASA missions have {hardware} and software program simulators on the bottom, the place engineers can take a look at new procedures to verify they do no hurt after they uplink instructions to the actual spacecraft. Resulting from its age, Voyager would not have any floor simulators, and far of the mission’s authentic design documentation stays in paper type and hasn’t been digitized.
“It was actually eyes-only to have a look at the code,” Spilker stated. “So we needed to triple verify. All people was wanting by way of and ensuring we had all the hyperlinks coming collectively.”
This was simply step one in restoring Voyager 1 to full performance. “We have been fairly positive it could work, however till it truly occurred, we did not know one hundred pc for positive,” Spilker stated.
“The rationale we didn’t do every thing in a single step is that there was a really restricted quantity of reminiscence we might discover shortly, 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 out there reminiscence constraint is now even tighter. We now have concepts the place we might relocate the code, however we haven’t but absolutely assessed the choices or decided. These are the primary steps we are going to begin this week.”