Throughout 5 months of troubleshooting, Voyager’s floor crew continued to obtain indicators indicating that the spacecraft was nonetheless alive. However till Saturday, they lacked concrete particulars about Voyager 1’s standing.
“All the pieces is just about the identical as we left it,” Spilker mentioned. “We’re nonetheless within the early levels of analyzing all of the channels and learning their tendencies. Temperatures have dropped a bit in some locations over the previous interval, however we’re just about seeing all the things we hoped for. And that is at all times excellent news.”
Transferring Code
In the course of the investigation, Voyager’s floor group found that the only chip liable for storing a part of the FDS reminiscence had stopped working, seemingly as a consequence of cosmic rays or outdated {hardware} failure. This affected a few of the laptop’s programming code.
“It destroyed a few of the reminiscence,” Spilker mentioned. “What they should do is transfer that code to a distinct a part of reminiscence after which ensure that no matter is utilizing these codes, these routines, is aware of to go to the brand new reminiscence location in an effort to entry and run it.”
Solely about 3 % of the FDS reminiscence was broken by the defective chip, so engineers needed to transplant that code to a different a part of the reminiscence financial institution. Nonetheless, in keeping with NASA, no single location is massive sufficient to include this complete part of code.
So the Voyager group divided the code into sections for storage in numerous places on the FDS. This wasn’t only a copy-and-paste job. Engineers needed to change a few of the code to ensure all the things would work collectively. “Any references to the placement of this code in different elements of FDS reminiscence additionally should be up to date,” NASA mentioned in an announcement.
New NASA missions have {hardware} and software program simulators on the bottom the place engineers can check new procedures to ensure they will not trigger hurt when transmitting instructions to the precise spacecraft. Resulting from its age, Voyager doesn’t have floor simulators, and far of the unique mission design documentation stays in paper type and has not been digitized.
“It was actually simply to take a look at the code,” Spilker mentioned. “So we needed to triple test. They regarded over all the things and made certain we had all of the connections.”
This was simply step one towards restoring Voyager 1 to full performance. “We had been fairly certain it might work, however till it truly occurred, we weren’t one hundred pc certain,” Spilker mentioned.
“The rationale we did not do all the things in a single step is as a result of we might shortly discover very restricted reminiscence, so we prioritized one information mode (engineering information mode) and moved solely the code to get better that mode. mentioned Jeff Mellstrom, an engineer on the Jet Propulsion Laboratory who leads Voyager 1’s “tiger group” tasked with overcoming this downside.
“The subsequent step is to maneuver the remaining three actively used scientific information modes—basically the identical,” Mellström mentioned in a written response to Ars. “The primary distinction is that the accessible reminiscence restrict is now even tighter. We’ve got concepts the place we might transfer the code, however we have not absolutely evaluated the choices or decided but. These are the primary steps we’ll start this week.”