All through the 5 months of troubleshooting, Voyager’s floor staff continued to obtain indicators indicating the spacecraft was nonetheless alive. However till Saturday, they lacked perception into particular particulars in regards to 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 traits. A number of the temperatures went down a bit bit with this time period that is gone on, however we’re just about seeing all the things we had hoped for. And that is at all times excellent news.”
Relocating Code
By their investigation, Voyager’s floor staff found {that a} single chip liable for storing a portion of the FDS reminiscence had stopped working, most likely because of both a cosmic ray hit or a failure of ageing {hardware}. This affected a number of the pc’s software program code.
“That took out a piece of reminiscence,” Spilker mentioned. “What they need to do is relocate that code into a special 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 unhealthy 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 mentioned.
So the Voyager staff 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 number of the code to verify it’ll all work collectively. “Any references to the situation of that code in different elements of the FDS reminiscence wanted to be up to date as nicely,” NASA mentioned 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 true spacecraft. Because of its age, Voyager does 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 mentioned. “So we needed to triple examine. 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 had been fairly certain it might work, however till it truly occurred, we did not know 100% for certain,” Spilker mentioned.
“The rationale we didn’t do all the things 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 staff” tasked with overcoming this drawback.
“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. Now we have concepts the place we might relocate the code, however we haven’t but totally assessed the choices or decided. These are the primary steps we are going to begin this week.”
