Voyager 1 Finally Returns a Clue to How to Restore It

It was back in early December when NASA/JPL released some grim news on the status of Voyager 1, now well beyond the solar system and in interstellar space. The last update I saw was in mid-February and the condition was still grim.  Susan Dodd, Voyager Project Manager had said, "it would be the biggest miracle if we get it back. We certainly haven't given up. There are other things we can try. But this is, by far, the most serious since I’ve been project manager."  

Finally, on March 3rd, the JPL ground team received a downlink from Voyager that was different from every communication since November when the problem first surfaced.  

On March 3, the Voyager mission team saw activity from one section of the FDS that differed from the rest of the computer’s unreadable data stream. The new signal was still not in the format used by Voyager 1 when the FDS is working properly, so the team wasn’t initially sure what to make of it. But an engineer with the agency’s Deep Space Network, which operates the radio antennas that communicate with both Voyagers and other spacecraft traveling to the Moon and beyond, was able to decode the new signal and found that it contains a readout of the entire FDS memory. 

The team has suspected that a piece of corrupted memory inside the Flight Data Subsystem (FDS), one of three main computers on the spacecraft, is the most likely culprit for the interruption in normal communication. They suspect the FDS because the overall communications system seems to be working.  It's transmitting to Earth, pointing this way and essentially doing what it's supposed to, it's just that there's no usable information - no actual Flight Data - being sent back.

On March 1st, controllers sent a new command to Voyager. 

Called a “poke” by the team, the command is meant to gently prompt the FDS to try different sequences in its software package in case the issue could be resolved by going around a corrupted section.

With the one way radio travel time to Voyager 1 takes over 22-1/2 hours, the reply was received on March 3rd. 

On March 7, engineers began working to decode the data, and on March 10, they determined that it contains a memory readout.

The team is working through the memory bit by bit, comparing it to a similar download sent when things were working properly. They hope this will allow them to find the root of the problem. But going through "bit by bit" and being sure of how to fix the problem could well take weeks or months before the Voyager team can make the next step or next test. The adage that I've heard called the first law of medicine applies here, too: "first, do no harm." 

Artist’s illustration of one of the Voyager spacecraft. Credit: Caltech/NASA-JPL