All through the 5 months of troubleshooting, Voyager’s floor group continued to obtain indicators 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 mentioned. “We’re nonetheless within the preliminary phases of analyzing all the channels and their developments. 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 the whole lot we had hoped for. And that is at all times excellent news.”
Relocating Code
By way of their investigation, Voyager’s floor group found {that a} single chip chargeable for storing a portion of the FDS reminiscence had stopped working, most likely resulting from both a cosmic ray hit or a failure of getting old {hardware}. This affected a few of the laptop’s software program code.
“That took out a bit of reminiscence,” Spilker mentioned. “What they need to do is relocate that code into a special portion of the reminiscence, after which make it possible for 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 % of the FDS reminiscence was corrupted by the unhealthy 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 mentioned.
So the Voyager group divided the code into sections for storage elsewhere within the FDS. This wasn’t only a copy-and-paste job. Engineers wanted to switch a few of the code to verify it’ll all work collectively. “Any references to the placement of that code in different components of the FDS reminiscence wanted to be up to date as nicely,” NASA mentioned in an announcement.
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 true spacecraft. Attributable to its age, Voyager does not have any floor simulators, and far of the mission’s unique design documentation stays in paper type and hasn’t been digitized.
“It was actually eyes-only to take a look at the code,” Spilker mentioned. “So we needed to triple verify. Everyone was wanting by means 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 certain it might work, however till it really occurred, we did not know one hundred pc for certain,” Spilker mentioned.
“The rationale we didn’t do the whole lot 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,” mentioned Jeff Mellstrom, a JPL engineer who leads the Voyager 1 “tiger group” tasked with overcoming this downside.
“The subsequent step, to relocate the remaining three actively used science information modes, is basically the identical,” Mellstrom mentioned 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 might relocate the code, however we haven’t but absolutely assessed the choices or decided. These are the primary steps we’ll begin this week.”
