Recoding Voyager 1NASA’s interplanetary explorer finally makes sense again

After five long months of troubleshooting, engineers have partially restored a 1970s-era computer aboard NASA’s Voyager 1 spacecraft, building confidence that humanity’s first interstellar probe can finally return to normal operations.

On Saturday, dozens of scientists and engineers gathered in a conference room at NASA’s Jet Propulsion Laboratory or connected virtually, waiting for new signals from Voyager 1. A command that recoded part of Voyager 1’s memory.

You could have heard a pin drop in the room in the minutes before we were going to see the signal,” said Linda, program scientist for the two Voyager spacecraft at NASA’s Jet Propulsion Laboratory. Linda Spilker said. People looked very serious. They are looking at a computer screen. Each subsystem (engineer) has pages they are looking at to see if they will be populated.

Finally a breakthrough

Launched nearly 47 years ago, Voyager 1’s outbound trajectory is more than 15 billion miles (24 billion kilometers) from Earth, with radio signals coming in the form of light. This meant it took engineers nearly two days to upload commands to Voyager 1 and get a response.

In November, Voyager 1 suddenly stopped transmitting its usual stream of data, which contains information about the health of the spacecraft and measurements from scientific instruments. Instead, the spacecraft’s data stream was completely incomprehensible. Because the telemetry data cannot be read, on-site experts cannot easily determine where the problem lies. They speculated that the source of the problem may lie in FDS’s memory bank.

The breakthrough came last month when engineers issued a new command to “poke” Voyager 1’s FDS to transmit back readings from its memory. This reading enables engineers to locate the problem within the FDS memory. FDS is responsible for packaging engineering and scientific data for transmission to Earth.

A few weeks later, NASA is preparing to upload the solution and allow FDS to resume packaging engineering data. This data stream includes information about the spacecraft status, such as power level and temperature measurements. The command was sent to Voyager 1 on Thursday via one of NASA’s large Deep Space Network antennas.

Then, wait for a response. Spilke started working on Voyager right out of college in 1977, and he was in the room when Voyager 1’s signal reached Earth on Saturday.

“When the signal came in, we could suddenly see clearly, boom, we have data, and there were tears and smiles and high-fives,” she told Ars. “Everyone is very happy and excited to see this, hey, we’re in touch with Voyager 1 again. We’re going to see for the first time in five months the status of the spacecraft, the health of the spacecraft.”

During five months of troubleshooting, Voyager’s ground team continued to receive signals indicating that the spacecraft was still present. But until Saturday, they lacked specific details about Voyager 1’s status.

That’s pretty much how we left,” Spilke said. “We’re still in the early stages of analyzing all the pipelines and looking at trends. As this period has gone on, some temperatures have dropped, but we’re seeing pretty much everything we were hoping for. That’s always good news.

Retarget code

Through investigation, Voyager’s ground team discovered that a single chip responsible for storing part of the FDS memory stopped functioning, possibly due to cosmic ray impact or aging hardware failure. This affected some of the computer’s software code.

“This deletes a portion of the memory,” Spilke said. “What they have to do is relocate the code to a different part of memory, and then make sure that anything that uses that code, these subroutines, knows to go to the new location in memory in order to access and run it.”

Only about 3% of FDS memory is damaged by a bad chip, so engineers need to transplant the code to another part of the memory bank. But NASA says no location is large enough to accommodate a complete section of the code.

Therefore, the Voyager team divided the code into multiple parts and stored them in different locations in FDS. This is not just a copy and paste job. Engineers need to modify some codes to make sure they work together. “Any references to the location of this code elsewhere in FDS memory will also need to be updated,” NASA said in a statement.