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Stephen Clark, Ars Technica

How NASA Repaired Voyager 1 From 15 Billion Miles Away

Engineers have partially restored a 1970s-era computer on NASA's Voyager 1 spacecraft after five months of long-distance troubleshooting , building confidence that humanity's first interstellar probe can eventually resume normal operations.

Several dozen scientists and engineers gathered Saturday in a conference room at NASA's Jet Propulsion Laboratory, or connected virtually, to wait for a new signal from Voyager 1. The ground team sent a command up to Voyager 1 on Thursday to recode part of the memory of the spacecraft's Flight Data Subsystem (FDS) , one of the probe's three computers.

“In the minutes leading up to when we were going to see a signal, you could have heard a pin drop in the room,” said Linda Spilker, project scientist for NASA's two Voyager spacecraft at JPL. “It was quiet. People were looking very serious. They were looking at their computer screens. Each of the subsystem (engineers) had pages up that they were looking at, to watch as they would be populated.”

Finally, a Breakthrough

Launched nearly 47 years ago, Voyager 1 is flying on an outbound trajectory more than 15 billion miles (24 billion kilometers) from Earth, and it takes 22.5 hours for a radio signal to cover that distance at the speed of light. This means it takes nearly two days for engineers to uplink a command to Voyager 1 and get a response.

In November, Voyager 1 suddenly stopped transmitting its usual stream of data containing information about the spacecraft's health and measurements from its scientific instruments. Instead, the spacecraft's datastream was entirely unintelligible. Because the telemetry was unreadable, experts on the ground could not easily tell what went wrong. They hypothesized the source of the problem might be in the memory bank of the FDS.

There was a breakthrough last month when engineers sent up a novel command to “poke” Voyager 1's FDS to send back a readout of its memory. This readout allowed engineers to pinpoint the location of the problem in the FDS memory . The FDS is responsible for packaging engineering and scientific data for transmission to Earth.

After a few weeks, NASA was ready to uplink a solution to get the FDS to resume packing engineering data. This datastream includes information on the status of the spacecraft—things like power levels and temperature measurements. This command went up to Voyager 1 through one of NASA's large Deep Space Network antennae on Thursday.

Then, the wait for a response. Spilker, who started working on Voyager right out of college in 1977, was in the room when Voyager 1's signal reached Earth on Saturday.

“When the time came to get the signal, we could clearly see all of a sudden, boom, we had data, and there were tears and smiles and high fives,” she told Ars. “Everyone was very happy and very excited to see that, hey, we're back in communication again with Voyager 1. We're going to see the status of the spacecraft, the health of the spacecraft, for the first time in five months.”

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Throughout the five months of troubleshooting, Voyager's ground team continued to receive signals indicating the spacecraft was still alive. But until Saturday, they lacked insight into specific details about the status of Voyager 1.

“It’s pretty much just the way we left it,” Spilker said. “We're still in the initial phases of analyzing all of the channels and looking at their trends. Some of the temperatures went down a little bit with this period of time that's gone on, but we're pretty much seeing everything we had hoped for. And that's always good news.”

Relocating Code

Through their investigation, Voyager's ground team discovered that a single chip responsible for storing a portion of the FDS memory had stopped working, probably due to either a cosmic ray hit or a failure of aging hardware. This affected some of the computer's software code.

“That took out a section of memory,” Spilker said. “What they have to do is relocate that code into a different portion of the memory, and then make sure that anything that uses those codes, those subroutines, know to go to the new location of memory, for access and to run it.”

Only about 3 percent of the FDS memory was corrupted by the bad chip, so engineers needed to transplant that code into another part of the memory bank. But no single location is large enough to hold the section of code in its entirety, NASA said.

So the Voyager team divided the code into sections for storage in different places in the FDS. This wasn't just a copy-and-paste job. Engineers needed to modify some of the code to make sure it will all work together. “Any references to the location of that code in other parts of the FDS memory needed to be updated as well,” NASA said in a statement.

Newer NASA missions have hardware and software simulators on the ground, where engineers can test new procedures to make sure they do no harm when they uplink commands to the real spacecraft. Due to its age, Voyager doesn't have any ground simulators, and much of the mission's original design documentation remains in paper form and hasn't been digitized.

“It was really eyes-only to look at the code,” Spilker said. “So we had to triple check. Everybody was looking through and making sure we had all of the links coming together.”

This was just the first step in restoring Voyager 1 to full functionality. “We were pretty sure it would work, but until it actually happened, we didn't know 100 percent for sure,” Spilker said.

“The reason we didn’t do everything in one step is that there was a very limited amount of memory we could find quickly, so we prioritized one data mode (the engineering data mode), and relocated only the code to restore that mode,” said Jeff Mellstrom, a JPL engineer who leads the Voyager 1 “tiger team” tasked with overcoming this problem.

“The next step, to relocate the remaining three actively used science data modes, is essentially the same,” Mellstrom said in a written response to Ars. “The main difference is the available memory constraint is now even tighter. We have ideas where we could relocate the code, but we haven’t yet fully assessed the options or made a decision. These are the first steps we will start this week.”

It could take “a few weeks” to go through the sections of code responsible for packaging Voyager 1's science data in the FDS, Spilker said.

That will be the key payoff, Spilker said. Voyager 1 and its twin spacecraft, Voyager 2, are the only operating probes flying in the interstellar medium, the diffuse gas between the stars. Their prime missions are long over. Voyager 1 flew by Jupiter and Saturn in 1979 and 1980, then got a gravitational boost toward the outer edge of the Solar System. Voyager 2 took a slower trajectory and encountered Jupiter, Saturn, Uranus, and Neptune.

For the past couple of decades, NASA has devoted Voyager's instruments to studying cosmic rays, the magnetic field, and the plasma environment in interstellar space. They're not taking pictures anymore. Both probes have traveled beyond the heliopause, where the flow of particles emanating from the Sun runs into the interstellar medium.

But any scientific data collected by Voyager 1 since November 14 has been lost. The spacecraft does not have the ability to store science data onboard. Voyager 2 has remained operational during the outage of Voyager 1.

Scientists are eager to get their hands on Voyager 1's science data again. “With the results we got on Saturday, we have new confidence that we can put together the pieces we need to now get back the science data,” Spilker said.

“One thing I'm particularly excited about—there's this feature in the Voyager 1 data. We nicknamed it Pressure Front 2,” Spilker said. “Pressure Front 2 is a jump in both the density of the plasma around the spacecraft and the magnetic field. It's lasted for three-and-a-half years.”

“We'd like to see, is this still there?” she continued. “It's different from what we've seen in the past, and we're trying to figure out, is it some influence coming from the Sun, or is it actually something coming from interstellar space that's creating this feature? So we'd like to see it again, get more data, and be able to study it more carefully.”

This story originally appeared on Ars Technica .

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Nasa hears from voyager 1, the most distant spacecraft from earth, after months of quiet.

Marcia Dunn

Associated Press

CAPE CANAVERAL, Fla. – NASA has finally heard back from Voyager 1 again in a way that makes sense.

The most distant spacecraft from Earth stopped sending back understandable data last November. Flight controllers traced the blank communication to a bad computer chip and rearranged the spacecraft’s coding to work around the trouble.

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NASA’s Jet Propulsion Laboratory in Southern California declared success after receiving good engineering updates late last week. The team is still working to restore transmission of the science data.

It takes 22 1/2 hours to send a signal to Voyager 1, more than 15 billion miles (24 billion kilometers) away in interstellar space. The signal travel time is double that for a round trip.

Contact was never lost, rather it was like making a phone call where you can’t hear the person on the other end, a JPL spokeswoman said Tuesday.

Launched in 1977 to study Jupiter and Saturn, Voyager 1 has been exploring interstellar space — the space between star systems — since 2012. Its twin, Voyager 2, is 12.6 billion miles (20 billion kilometers) away and still working fine.

The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Science and Educational Media Group. The AP is solely responsible for all content.

Copyright 2024 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed without permission.

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Man accused of killing woman on L.A. subway is linked to earlier violence on Metro train

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A 45-year-old man suspected of fatally stabbing a woman as she got off a Metro train in Studio City had attacked a passenger once before, leading a judge to order him to keep his distance from the rail system for three years.

Elliot Tramel Nowden was arrested Monday not long after a woman was found mortally wounded on the ground at the Universal Studios train platform, interim Los Angeles Police Chief Dominic Choi announced Tuesday during a Police Commission meeting.

For the record:

1:04 p.m. April 24, 2024 A previous version of this story said that the stabbing took place at a North Hollywood train station. The stabbing took place at Metro’s Universal City train station in Studio City.

The victim, Mirna Soza, was a 66-year-old mother of three who arrived in L.A. from Managua, Nicaragua, several years ago. She was on her way home from work as a night-shift security guard at an Original Tommy’s hamburger restaurant in North Hills when she was killed.

“This incident is extremely, extremely tragic,” Choi said.

In June 2019, Nowden was arrested and charged with attacking a passenger on a Metro train in Los Angeles County. He pleaded no contest, spent five days in jail and received a 36-month probation term, according to court records.

Under the terms of his probation, he was forbidden to possess weapons or use force or threaten violence. He was also ordered to stay away from Metro trains while on probation.

But just a few weeks later, Nowden appeared before a judge on charges of assault with a deadly weapon and battery. He was sentenced to four years in state prison after pleading no contest to the assault charge, according to court records, and was given 179 days of credit for time served.

Nowden was paroled to the Department of State Hospitals on March 18, 2022, during his prison sentence, according to a spokesperson for the California Department of Corrections and Rehabilitation. He was released on parole supervision in August 2022 and discharged from parole in March 2023.

Most recently, Nowden was arrested for trespassing Jan. 31, according to LAPD Officer Norma Eisenman.

Authorities have released few details about what led to Monday’s attack. Police said Soza was stabbed in the throat shortly after 5 a.m. as she got off the train. Her attacker got off at the same stop and ran away.

People in the area found the woman and called 911, authorities said. Paramedics took her to a local hospital, where she died from her injuries, according to the LAPD.

Roughly 30 minutes after the LAPD arrived at the train station, officers spotted a person matching the description of the suspect near the intersection of Ventura Boulevard and Vineland Avenue.

The man, later identified as Nowden, was detained by officers and interviewed by detectives with the Valley Bureau homicide division. Nowden was arrested on suspicion of murder after detectives reviewed the available evidence, according to the LAPD.

He is being held on bail of $2 million.

During Tuesday’s Police Commission meeting, Commissioner Maria Lou Calanche sought Choi’s assurance that there is adequate security on Metro during early morning hours, when riders tend to be of lower income.

Choi responded that the department’s “deployment is strategic based on crime trends and needs.” He did not provide details.

“It’s not just a flat deployment, just to say that we’re deployed, so we take a look at crime trends as we look at ridership. We look at the activity and deploy accordingly,” Choi added.

He said that officers on trains, in train stations and on buses, along with the Metro system’s ambassadors, “are a directed effort to increase our presence as well as the safety on these lines.”

“Again, we can’t be everywhere all the time,” Choi said. The department tries to spread out officers and engage with riders “to create a sense of safety and address crime trends or problems as they occur immediately and swiftly.”

Commissioner Vice President Rasha Gerges Shields said Monday’s stabbing was “a very unfortunate death and what appears to be a very unprovoked attack on a woman.”

The LAPD described Nowden as a transient. Public records show that his last known address was in Little Rock, Ark. He was a wanted fugitive in Texas in November 2008, according to court records, and was previously charged in Bexar County, Texas, with theft and narcotic possession.

Nowden is being held in a Van Nuys jail, records show.

Investigators believe there may be other who have been attacked by Nowden. Anyone with information can contact the LAPD’s Operations Valley Bureau Homicide Detectives at (818) 374-9550.

Staff writers Richard Winton and James Queally contributed to this report.

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Nathan Solis is a Metro reporter covering breaking news at the Los Angeles Times. He previously worked for Courthouse News Service, where he wrote both breaking news and enterprise stories ranging from criminal justice to homelessness and politics. Before that, Solis was at the Redding Record Searchlight as a multimedia journalist, where he anchored coverage of the destructive 2017 fires in Northern California. Earlier in his career, he worked for Eastsider L.A.

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