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Hope returns —

Nasa knows what knocked voyager 1 offline, but it will take a while to fix, "engineers are optimistic they can find a way for the fds to operate normally.".

Stephen Clark - Apr 6, 2024 12:28 am UTC

Engineers have determined why NASA's Voyager 1 probe has been transmitting gibberish for nearly five months, raising hopes of recovering humanity's most distant spacecraft.

Voyager 1, traveling outbound some 15 billion miles (24 billion km) from Earth, started beaming unreadable data down to ground controllers on November 14. For nearly four months, NASA knew Voyager 1 was still alive—it continued to broadcast a steady signal—but could not decipher anything it was saying.

Confirming their hypothesis, engineers at NASA's Jet Propulsion Laboratory (JPL) in California confirmed a small portion of corrupted memory caused the problem. The faulty memory bank is located in Voyager 1's Flight Data System (FDS), one of three computers on the spacecraft. The FDS operates alongside a command-and-control central computer and another device overseeing attitude control and pointing.

The FDS duties include packaging Voyager 1's science and engineering data for relay to Earth through the craft's Telemetry Modulation Unit and radio transmitter. According to NASA, about 3 percent of the FDS memory has been corrupted, preventing the computer from carrying out normal operations.

Optimism growing

Suzanne Dodd, NASA's project manager for the twin Voyager probes, told Ars in February that this was one of the most serious problems the mission has ever faced. That is saying something because Voyager 1 and 2 are NASA's longest-lived spacecraft. They launched 16 days apart in 1977, and after flying by Jupiter and Saturn, Voyager 1 is flying farther from Earth than any spacecraft in history. Voyager 2 is trailing Voyager 1 by about 2.5 billion miles, although the probes are heading out of the Solar System in different directions.

Normally, engineers would try to diagnose a spacecraft malfunction by analyzing data it sent back to Earth. They couldn't do that in this case because Voyager 1 has been transmitting data packages manifesting a repeating pattern of ones and zeros. Still, Voyager 1's ground team identified the FDS as the likely source of the problem.

The Flight Data Subsystem was an innovation in computing when it was developed five decades ago. It was the first computer on a spacecraft to use volatile memory. Most of NASA's missions operate with redundancy, so each Voyager spacecraft launched with two FDS computers. But the backup FDS on Voyager 1 failed in 1982.

Due to the Voyagers' age, engineers had to reference paper documents, memos, and blueprints to help understand the spacecraft's design details. After months of brainstorming and planning, teams at JPL uplinked a command in early March to prompt the spacecraft to send back a readout of the FDS memory.

The command worked, and Voyager1 responded with a signal different from the code it had been transmitting since November. After several weeks of meticulous examination of the new code, engineers pinpointed the location of the bad memory.

"The team suspects that a single chip responsible for storing part of the affected portion of the FDS memory isn’t working," NASA said in an update posted Thursday. "Engineers can’t determine with certainty what caused the issue. Two possibilities are that the chip could have been hit by an energetic particle from space or that it simply may have worn out after 46 years."

Voyager 1's distance from Earth complicates the troubleshooting effort. The one-way travel time for a radio signal to reach Voyager 1 from Earth is about 22.5 hours, meaning it takes roughly 45 hours for engineers on the ground to learn how the spacecraft responded to their commands.

NASA also must use its largest communications antennas to contact Voyager 1. These 230-foot-diameter (70-meter) antennas are in high demand by many other NASA spacecraft , so the Voyager team has to compete with other missions to secure time for troubleshooting. This means it will take time to get Voyager 1 back to normal operations.

"Although it may take weeks or months, engineers are optimistic they can find a way for the FDS to operate normally without the unusable memory hardware, which would enable Voyager 1 to begin returning science and engineering data again," NASA said.

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How are the Voyager spacecraft able to transmit radio messages so far?

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The two Voyage spacecraft certainly have had an amazing track record. They were sent to photograph planets like Jupiter, Saturn and Neptune and have just kept on going past the outer edge of the solar system. Voyager 1 is currently over 7 billion miles (about 11 billion kilometers) away from Earth and is still transmitting -- it takes about 10 hours for the signal to travel from the spacecraft to Earth!

The Voyager spacecraft use 23-watt radios. This is higher than the 3 watts a typical cell phone uses, but in the grand scheme of things it is still a low-power transmitter. Big radio stations on Earth transmit at tens of thousands of watts and they still fade out fairly quickly.

The key to receiving the signals is therefore not the power of the radio, but a combination of three other things:

• Very large antennas
• Directional antennas that point right at each other
• Radio frequencies without a lot of man-made interference on them

The antennas that the Voyager spacecraft use are big. You may have seen people who have large satellite dish antennas in their yards. These are typically 2 or 3 meters (6 to 10 feet) in diameter. The Voyager spacecraft has an antenna that is 3.7 meters (14 feet) in diameter, and it transmits to a 34 meter (100 feet or so) antenna on Earth. The Voyager antenna and the Earth antenna are pointed right at each other. When you compare your phone's stubby, little omni-directional antenna to a 34 meter directional antenna, you can see the main thing that makes a difference!

The Voyager satellites are also transmitting in the 8 GHz range , and there is not a lot of interference at this frequency. Therefore the antenna on Earth can use an extremely sensitive amplifier and still make sense of the faint signals it receives. Then when the earth antenna transmits back to the spacecraft, it uses extremely high power (tens of thousands of watts) to make sure the spacecraft gets the message.

Frequently Asked Questions

What role do earth's ground stations play in receiving signals from distant spacecraft like voyager, how has technology advanced to maintain communication with voyager as it moves further away.

Please copy/paste the following text to properly cite this HowStuffWorks.com article:

• The Contents
• The Making of
• Where Are They Now

Frequently Asked Questions

• Q & A with Ed Stone

golden record

Where are they now.

• frequently asked questions
• Q&A with Ed Stone

Can the Voyager imaging cameras be turned back on?

What instruments on the spacecraft are still working and what have been turned off?

How long can Voyager 1 and 2 continue to function?

Voyager 1 is expected to keep its current suite of science instruments on through 2021. Voyager 2 is expected to keep its current suite of science instruments on through 2020.

The radioisotope thermoelectric generator on each spacecraft puts out 4 watts less each year. Because of this diminishing electrical power, the Voyager team has had to prioritize which instruments to keep on and which to turn off. Heaters and other spacecraft systems have also been turned off one by one as part of power management.

The Voyager team has chosen to keep operating the instruments that are the most likely to send back key data about the heliosphere and interstellar space -- the fields and particles instruments. Engineers expect to begin turning off fields and particles science instruments one by one, starting in 2020 for Voyager 2. Voyager 2 will have to start turning science instruments off sooner because it is currently operating one more instrument than Voyager 1. Engineers expect each spacecraft to continue operating at least one science instrument until around 2025.

Even if science data won't likely be collected after 2025, engineering data could continue to be returned for several more years. The two Voyager spacecraft could remain in the range of the Deep Space Network through about 2036, depending on how much power the spacecraft still have to transmit a signal back to Earth.

Where are Voyager 1 and 2 today? How do they compare to other spacecraft on an outbound trajectory?

Where is Voyager 1 going? When will it get there? How about Voyager 2?

Where do we consider our solar system to end; Pluto's orbit? Solar apex?

Have any human-made objects ever exited the solar system?

Are the distance counters rolling backwards?

Did either of the Voyagers visit Pluto? Why didn't the Voyagers fly by Pluto?

When we send spacecraft through the asteroid belt to the outer planets, how do we navigate the craft through the belt?

I was reading Dr. Carl Sagan's biography recently and found that he persuaded NASA administrators to turn one of the Voyager space probes around in order to take a last image of the solar system. Is this true? Do the craft send back any images of where they are?

I can not locate a copy of the Murmurs of Earth CD. Would you know of a vendor that might sell copies of it?

Who was on the committee with Dr. Sagan regarding the development of the Golden Record? Both American or foreign scientists?

If there is intelligent life in our universe and they were not a peace loving species, wouldn't the information on the Voyager be enough to destroy human kind?

What were the most important discoveries of the Voyager space probes?

How big is Voyager? How much does it weigh?

Is it true that a sketch by Da Vinci is included in the "Message to the Universe" of Voyagers 1 and 2?

What kind of computers are used on the Voyager spacecraft?

How fast are the Voyager computers?

What is the "direction" (constellation and/or star) both VOYAGER 1 & 2 and the Pioneers are "aimed" for, at present.

Where can I find pictures of what the Voyager spacecraft took?

Is there some sort of plate with pictograms on the Voyager 1 spacecraft? Also is it similar to the Pioneer spacecraft plaque?

The twin Voyager 1 and 2 spacecraft are exploring where nothing from Earth has flown before. Continuing on their more-than-45-year journey since their 1977 launches, they each are much farther away from Earth and the Sun than Pluto.

Quick Facts

Voyager 2 launched on August 20, 1977, from Cape Canaveral, Florida aboard a Titan-Centaur rocket. On September 5, Voyager 1 launched, also from Cape Canaveral aboard a Titan-Centaur rocket.

Between them, Voyager 1 and 2 explored all the giant planets of our outer solar system, Jupiter, Saturn, Uranus and Neptune; 48 of their moons; and the unique system of rings and magnetic fields those planets possess.

The Voyager spacecraft are the third and fourth human spacecraft to fly beyond all the planets in our solar system. Pioneers 10 and 11 preceded Voyager in outstripping the gravitational attraction of the Sun.

Voyager 1 crossed the termination shock in December 2004 at about 94 AU from the Sun while Voyager 2 crossed it in August 2007 at about 84 AU.

Both Voyager spacecrafts carry a greeting to any form of life, should that be encountered. The message is carried by a phonograph record - -a 12-inch gold-plated copper disk containing sounds and images selected to portray the diversity of life and culture on Earth.

In August 2012, Voyager 1 made the historic entry into interstellar space, the region between stars, filled with material ejected by the death of nearby stars millions of years ago. Voyager 2 entered interstellar space on November 5, 2018 and scientists hope to learn more about this region. Both spacecraft are still sending scientific information about their surroundings through the Deep Space Network, or DSN.

The primary mission was the exploration of Jupiter and Saturn. After making a string of discoveries there — such as active volcanoes on Jupiter's moon Io and intricacies of Saturn's rings — the mission was extended. Voyager 2 went on to explore Uranus and Neptune, and is still the only spacecraft to have visited those outer planets. The adventurers' current mission, the Voyager Interstellar Mission (VIM), will explore the outermost edge of the Sun's domain. And beyond.

Learn about Voyagers' mission status: where they are in the space, the time required to communicate with them, and a lot more.

Learn about the five science investigation teams, the four operating instruments on-board and the science data being returned to Earth.

The Voyager spacecraft have been exploring for decades. Dive deep into the journey with this interactive timeline.

Interact in 3D. Take a deeper look at the sophisticated systems and instruments that deliver the stunning science and images.

Interstellar Mission

The mission objective of the Voyager Interstellar Mission (VIM) is to extend the NASA exploration of the solar system beyond the neighborhood of the outer planets to the outer limits of the Sun's sphere of influence, and possibly beyond.

Planetary Voyage

The twin spacecraft Voyager 1 and Voyager 2 were launched by NASA in separate months in the summer of 1977 from Cape Canaveral, Florida. As originally designed, the Voyagers were to conduct closeup studies of Jupiter and Saturn, Saturn's rings, and the larger moons of the two planets.

Questions, answers and interviews that explain the Voyager mission.

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Voyager signal spotted by earth radio telescopes.

The signal of NASA’s Voyager 1 spacecraft — the most distant human-made object — has been spotted from Earth by the National Radio Astronomy Observatory’s 5,000-mile-wide (8,000-kilometer-wide) Very Long Baseline Array (VLBA), which links radio telescopes from Hawaii to St. Croix.

These radio telescopes cannot see Voyager 1 in visible light, but rather “see” the spacecraft signal in radio light. Antennas make up a radio telescope like mirrors and pixels make up an optical one. The telescopes made a special attempt to look for Voyager 1’s signal to test their sensitivity.

Voyager 1’s main transmitter radiates around 22 watts, which is comparable to a typical ham radio or a refrigerator light bulb. Though incredibly weak by the standards of modern wireless communications, Voyager 1’s signal is bright when compared to most natural objects studied by radio telescopes.

The VLBA made this image of Voyager 1’s signal on Feb. 21, 2013. At the time, Voyager 1 was 11.5 billion miles (18.5 billion kilometers) away.

The image is about 0.5 arcseconds on a side. An arcsecond is the apparent size of a penny as seen from 2.5 miles (4 kilometers) away. The slightly oblong shape of the image is a result of the array’s configuration.

NASA’s Jet Propulsion Laboratory, Pasadena, Calif., communicates with Voyager 1 practically every day via NASA’s Deep Space Network. The spacecraft, launched in 1977, is currently nearly 12 billion miles (19 billion kilometers) away from the sun.

The Voyager spacecraft were built and continue to be operated by NASA’s Jet Propulsion Laboratory, in Pasadena, Calif. Caltech manages JPL for NASA. The Voyager missions are a part of NASA’s Heliophysics System Observatory, sponsored by the Heliophysics Division of the Science Mission Directorate at NASA Headquarters in Washington. 

For more information about Voyager, visit: https://www.nasa.gov/voyager and http://voyager.jpl.nasa.gov .

For more on the National Radio Astronomy Observatory’s finding, visit: http://www.nrao.edu .

Image credit: NRAO/AUI/NSF.

Engineers Investigating NASA’s Voyager 1 Telemetry Data

NASA’s Voyager 1 spacecraft, shown in this illustration, has been exploring our solar system since 1977, along with its twin, Voyager 2.

While the spacecraft continues to return science data and otherwise operate as normal, the mission team is searching for the source of a system data issue.

The engineering team with NASA’s Voyager 1 spacecraft is trying to solve a mystery: The interstellar explorer is operating normally, receiving and executing commands from Earth, along with gathering and returning science data. But readouts from the probe’s attitude articulation and control system (AACS) don’t reflect what’s actually happening onboard.

The AACS controls the 45-year-old spacecraft’s orientation. Among other tasks, it keeps Voyager 1’s high-gain antenna pointed precisely at Earth, enabling it to send data home. All signs suggest the AACS is still working, but the telemetry data it’s returning is invalid. For instance, the data may appear to be randomly generated, or does not reflect any possible state the AACS could be in.

The issue hasn’t triggered any onboard fault protection systems, which are designed to put the spacecraft into “safe mode” – a state where only essential operations are carried out, giving engineers time to diagnose an issue. Voyager 1’s signal hasn’t weakened, either, which suggests the high-gain antenna remains in its prescribed orientation with Earth.

Get the Latest JPL News

The team will continue to monitor the signal closely as they continue to determine whether the invalid data is coming directly from the AACS or another system involved in producing and sending telemetry data. Until the nature of the issue is better understood, the team cannot anticipate whether this might affect how long the spacecraft can collect and transmit science data.

Voyager 1 is currently 14.5 billion miles (23.3 billion kilometers) from Earth, and it takes light 20 hours and 33 minutes to travel that difference. That means it takes roughly two days to send a message to Voyager 1 and get a response – a delay the mission team is well accustomed to.

“A mystery like this is sort of par for the course at this stage of the Voyager mission,” said Suzanne Dodd, project manager for Voyager 1 and 2 at NASA’s Jet Propulsion Laboratory in Southern California. “The spacecraft are both almost 45 years old, which is far beyond what the mission planners anticipated. We’re also in interstellar space – a high-radiation environment that no spacecraft have flown in before. So there are some big challenges for the engineering team. But I think if there’s a way to solve this issue with the AACS, our team will find it.”

It’s possible the team may not find the source of the anomaly and will instead adapt to it, Dodd said. If they do find the source, they may be able to solve the issue through software changes or potentially by using one of the spacecraft’s redundant hardware systems.

It wouldn’t be the first time the Voyager team has relied on backup hardware: In 2017, Voyager 1’s primary thrusters showed signs of degradation, so engineers switched to another set of thrusters that had originally been used during the spacecraft’s planetary encounters . Those thrusters worked, despite having been unused for 37 years.

Voyager 1’s twin, Voyager 2 (currently 12.1 billion miles, or 19.5 billion kilometers, from Earth), continues to operate normally.

Launched in 1977, both Voyagers have operated far longer than mission planners expected, and are the only spacecraft to collect data in interstellar space. The information they provide from this region has helped drive a deeper understanding of the heliosphere, the diffuse barrier the Sun creates around the planets in our solar system.

Each spacecraft produces about 4 fewer watts of electrical power a year, limiting the number of systems the craft can run. The mission engineering team has switched off various subsystems and heaters in order to reserve power for science instruments and critical systems. No science instruments have been turned off yet as a result of the diminishing power, and the Voyager team is working to keep the two spacecraft operating and returning unique science beyond 2025.

While the engineers continue to work at solving the mystery that Voyager 1 has presented them, the mission’s scientists will continue to make the most of the data coming down from the spacecraft’s unique vantage point.

More About the Mission

The Voyager spacecraft were built by JPL, which continues to operate both. JPL is a division of Caltech in Pasadena. The Voyager missions are a part of the NASA Heliophysics System Observatory, sponsored by the Heliophysics Division of the Science Mission Directorate in Washington.

For more information about the Voyager spacecraft, visit:

https://www.nasa.gov/voyager

News Media Contact

Calla Cofield

Jet Propulsion Laboratory, Pasadena, Calif.

626-808-2469

[email protected]

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After a 12.3-billion-mile 'shout,' NASA regains full contact with Voyager 2

Emily Olson

Ayana Archie

A NASA image of one of the twin Voyager space probes. The Jet Propulsion Laboratory lost contact with Voyager 2 on July 21 after mistakenly pointing its antenna 2 degrees away from Earth. On Friday, contact was fully restored. NASA/Getty Images hide caption

A NASA image of one of the twin Voyager space probes. The Jet Propulsion Laboratory lost contact with Voyager 2 on July 21 after mistakenly pointing its antenna 2 degrees away from Earth. On Friday, contact was fully restored.

Talk about a long-distance call.

NASA said it resumed full communications with the Voyager 2 on Friday after almost two weeks of silence from the interstellar spacecraft.

The agency's Jet Propulsion Laboratory said a series of ground antennas, part of the Deep Space Network, registered a carrier signal from Voyager 2 on Tuesday. However, the signal was too faint.

A Deep Space Network facility in Australia then sent "the equivalent of an interstellar 'shout' " to the Voyager 2 telling it to turn its antenna back toward Earth. The signal was sent more than 12.3 billion miles away and it took 37 hours to get a response from the spacecraft, NASA said.

Scientists received a response at about 12:30 a.m. ET Friday. Voyager 2 is now operating normally, returning science and telemetry data, and "remains on its expected trajectory," NASA said.

NASA said Friday that it lost contact with Voyager 2 on July 21 after "a series of planned commands" inadvertently caused the craft to turn its antenna 2 degrees away from the direction of its home planet.

NASA is keeping Voyager 2 going until at least 2026 by tapping into backup power

What might seem like a slight error had big consequences: NASA previously said it wouldn't be able to communicate with the craft until October, when the satellite would go through one of its routine repositioning steps.

"That is a long time to wait, so we'll try sending up commands several times" before October, program manager Suzanne Dodd told The Associated Press.

These are the 4 astronauts who'll take a trip around the moon next year

Even if Voyager 2 had failed to reestablish communications until fall, the engineers expected it to stay moving on its planned trajectory on the edge of the solar system.

Voyager 2 entered interstellar space in November 2018 — more than 40 years since it launched from Cape Canaveral, Fla. To this day, Voyager 2 remains one of only two human-made objects to ever operate outside the heliosphere, which NASA defines as "the protective bubble of particles and magnetic fields generated by the Sun."

Its primary mission was to study the outer solar system, and already, Voyager 2 has proved its status as a planetary pioneer . Equipped with several imaging instruments, the spacecraft is credited with documenting the discovery of 16 new moons, six new rings and Neptune's "Great Dark Spot."

Voyager 2 Bids Adieu To The Heliosphere, Entering Interstellar Space

Voyager 2 is also carrying some precious cargo, like a message in a bottle, should it find itself as the subject of another world's discovery: a golden record containing a variety of natural sounds, greetings in 55 languages and a 90-minute selection of music.

Last month's command mix-up foreshadows the craft's inevitable end an estimated three years from now.

"Eventually, there will not be enough electricity to power even one instrument," reads a NASA page documenting the spacecraft's travels . "Then, Voyager 2 will silently continue its eternal journey among the stars."

Meanwhile, Voyager 2's sister spacecraft, Voyager 1, is still broadcasting and transmitting data just fine from a slightly farther vantage point of 15 billion miles away.

Correction Aug. 3, 2023

A previous version of this article implied that Voyager 2 flew past Uranus in 2018 when, in fact, the spacecraft concluded its encounter with the planet and started heading toward Neptune in 1986. Voyager 2 entered interstellar space in November 2018.

• Jet Propulsion Laboratory

July 1, 2022

21 min read

Record-Breaking Voyager Spacecraft Begin to Power Down

The pioneering probes are still running after nearly 45 years in space, but they will soon lose some of their instruments

By Tim Folger

NASA/JPL-Caltech

I f the stars hadn't aligned, two of the most remarkable spacecraft ever launched never would have gotten off the ground. In this case, the stars were actually planets—the four largest in the solar system. Some 60 years ago they were slowly wheeling into an array that had last occurred during the presidency of Thomas Jefferson in the early years of the 19th century. For a while the rare planetary set piece unfolded largely unnoticed. The first person to call attention to it was an aeronautics doctoral student at the California Institute of Technology named Gary Flandro.

It was 1965, and the era of space exploration was barely underway—the Soviet Union had launched Sputnik 1, the first artificial satellite, only eight years earlier. Flandro, who was working part-time at NASA's Jet Propulsion Laboratory in Pasadena, Calif., had been tasked with finding the most efficient way to send a space probe to Jupiter or perhaps even out to Saturn, Uranus or Neptune. Using a favorite precision tool of 20th-century engineers—a pencil—he charted the orbital paths of those giant planets and discovered something intriguing: in the late 1970s and early 1980s, all four would be strung like pearls on a celestial necklace in a long arc with Earth.

This coincidence meant that a space vehicle could get a speed boost from the gravitational pull of each giant planet it passed, as if being tugged along by an invisible cord that snapped at the last second, flinging the probe on its way. Flandro calculated that the repeated gravity assists, as they are called, would cut the flight time between Earth and Neptune from 30 years to 12. There was just one catch: the alignment happened only once every 176 years. To reach the planets while the lineup lasted, a spacecraft would have to be launched by the mid-1970s.

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READY FOR LAUNCH: Voyager 2 undergoes testing at NASA’s Jet Propulsion Laboratory before its flight ( left ). The spacecraft lifted off on August 20, 1977. Credit: NASA/JPL-Caltech

As it turned out, NASA would build two space vehicles to take advantage of that once-in-more-than-a-lifetime opportunity. Voyager 1 and Voyager 2, identical in every detail, were launched within 15 days of each other in the summer of 1977. After nearly 45 years in space, they are still functioning, sending data back to Earth every day from beyond the solar system's most distant known planets. They have traveled farther and lasted longer than any other spacecraft in history. And they have crossed into interstellar space, according to our best understanding of the boundary between the sun's sphere of influence and the rest of the galaxy. They are the first human-made objects to do so, a distinction they will hold for at least another few decades. Not a bad record, all in all, considering that the Voyager missions were originally planned to last just four years.

Early in their travels, four decades ago, the Voyagers gave astonished researchers the first close-up views of the moons of Jupiter and Saturn, revealing the existence of active volcanoes and fissured ice fields on worlds astronomers had thought would be as inert and crater-pocked as our own moon. In 1986 Voyager 2 became the first spacecraft to fly past Uranus; three years later it passed Neptune. So far it is the only spacecraft to have made such journeys. Now, as pioneering interstellar probes more than 12 billion miles from Earth, they're simultaneously delighting and confounding theorists with a series of unexpected discoveries about that uncharted region.

Their remarkable odyssey is finally winding down. Over the past three years NASA has shut down heaters and other nonessential components, eking out the spacecrafts' remaining energy stores to extend their unprecedented journeys to about 2030. For the Voyagers' scientists, many of whom have worked on the mission since its inception, it is a bittersweet time. They are now confronting the end of a project that far exceeded all their expectations.*

“We're at 44 and a half years,” says Ralph McNutt, a physicist at the Johns Hopkins University Applied Physics Laboratory (APL), who has devoted much of his career to the Voyagers. “So we've done 10 times the warranty on the darn things.”

The stars may have been cooperating, but at first, Congress wasn't. After Flandro's report, NASA drew up plans for a so-called Grand Tour that would send as many as five probes to the four giant planets and Pluto. It was ambitious. It was expensive. Congress turned it down. “There was this really grand vision,” says Linda Spilker, a JPL planetary scientist who started working on the Voyager missions in 1977, a few months before their launch. “Because of cost, it was whittled back.”

Congress eventually approved a scaled-down version of the Grand Tour, initially called Mariner Jupiter-Saturn 1977, or MJS 77. Two spacecraft were to be sent to just two planets. Nevertheless, NASA's engineers went about designing, somewhat surreptitiously, vehicles capable of withstanding the rigors of a much longer mission. They hoped that once the twin probes proved themselves, their itinerary would be extended to Uranus, Neptune, and beyond.

“Four years—that was the prime mission,” says Suzanne Dodd, who, after a 20-year hiatus from the Voyager team, returned in 2010 as the project manager. “But if an engineer had a choice to put in a part that was 10 percent more expensive but wasn't something that was needed for a four-year mission, they just went ahead and did that. And they wouldn't necessarily tell management.” The fact that the scientists were able to build two spacecraft, and that both are still working, is even more remarkable, she adds.

In terms of both engineering and deep-space navigation, this was new territory. The motto “Failure is not an option” hadn't yet been coined, and at that time it would not have been apt. In the early 1960s NASA had attempted to send a series of spacecraft to the moon to survey future landing sites for crewed missions. After 12 failures, one such effort finally succeeded.

GOLDEN RECORD: Each Voyager carries a golden record ( left ) of sounds and images from Earth in case the spacecraft are intercepted by an extraterrestrial civilization. Engineers put the cap on Voyager 1’s record before its launch ( right ). Credit: NASA/JPL-Caltech

“In those days we always launched two spacecraft” because the failure rate was so high, said Donald Gurnett, only partly in jest. Gurnett, a physicist at the University of Iowa and one of the original scientists on the Voyager team, was a veteran of 40 other space missions. He spoke with me a few weeks before his death in January. (In an obituary, his daughter Christina said his only regret was that “he would not be around to see the next 10 years of data returning from Voyager.”)

When the Voyagers were being built, only one spacecraft had used a gravity assist to reach another planet—the Mariner 10 probe got one from Venus while en route to Mercury. But the Voyagers would be attempting multiple assists with margins of error measured in tens of minutes. Jupiter, their first stop, was about 10 times farther from Earth than Mercury. Moreover, the Voyagers would have to travel through the asteroid belt along the way. Before Voyager there had been a big debate about whether spacecraft could get through the asteroid belt “without being torn to pieces,” McNutt says. But in the early 1970s Pioneer 10 and 11 flew through it unscathed—the belt turned out to be mostly empty space—paving the way for Voyager, he says.

To handle all these challenges, the Voyagers, each about the size of an old Volkswagen Beetle, needed some onboard intelligence. So NASA's engineers equipped the vehicles' computers with 69 kilobytes of memory, less than a hundred thousandth the capacity of a typical smartphone. In fact, the smartphone comparison is not quite right. “The Voyager computers have less memory than the key fob that opens your car door,” Spilker says. All the data collected by the spacecraft instruments would be stored on eight-track tape recorders and then sent back to Earth by a 23-watt transmitter—about the power level of a refrigerator light bulb. To compensate for the weak transmitter, both Voyagers carry 12-foot-wide dish antennas to send and receive signals.

“It felt then like we were right on top of the technology,” says Alan Cummings, a physicist at Caltech and another Voyager OG. “I'll tell you, what was amazing is how quickly that whole thing happened.” Within four years the MJS 77 team had built three spacecraft, including one full-scale functioning test model. The spacecraft were rechristened Voyager 1 and 2 a few months before launch.

Although many scientists have worked on the Voyagers over the decades, Cummings can make a unique claim. “I was the last person to touch the spacecraft before they launched,” he says. Cummings was responsible for two detectors designed to measure the flux of electrons and other charged particles when the Voyagers encountered the giant planets. Particles would pass through a small “window” in each detector that consisted of aluminum foil just three microns thick. Cummings worried that technicians working on the spacecraft might have accidentally dented or poked holes in the windows. “So they needed to be inspected right before launch,” he says. “Indeed, I found that one of them was a little bit loose.”

Credit: Graphic by Matthew Twombly and Juan Velasco (5W Infographic); Consultants: John Richardson (principal investigator, Voyager Plasma Science, Massachusetts Institute of Technology, Center for Space Research) and Merav Opher (professor, Department of Astronomy, Boston University)

Voyager 1 reached Jupiter in March 1979, 546 days after its launch. Voyager 2, following a different trajectory, arrived in July of that year. Both spacecraft were designed to be stable platforms for their vidicon cameras, which used red, green and blue filters to produce full-color images. They hardly spin at all as they speed through space—their rotational motion is more than 15 times slower than the crawl of a clock's hour hand, minimizing the risk of blurred images. Standing-room crowds at JPL watched as the spacecraft started transmitting the first pictures of Jupiter while still about three or four months away from the planet.

“In all of the main conference rooms and in the hallways, they had these TV monitors set up,” Spilker says. “So as the data came down line by line, each picture would appear on a monitor. The growing anticipation and the expectation of what we were going to see when we got up really, really close—that was tremendously exciting.”

Cummings vividly recalls the day he caught his first glimpse of Jupiter's third-largest moon, Io. “I was going over to a building on the Caltech campus where they were showing a livestream [of Voyager's images],” he says. “I walk in, and there's this big picture of Io, and it's all orange and black. I thought, okay, the Caltech students had pulled a prank, and it's a picture of a poorly made pizza.”

Io's colorful appearance was completely unexpected. Before the Voyagers proved otherwise, the assumption had been that all moons in the solar system would be more or less alike—drab and cratered. No one anticipated the wild diversity of moonscapes the Voyagers would discover around Jupiter and Saturn.

The first hint that there might be more kinds of moons in the heavens than astronomers had dreamed of came while the Voyagers were still about a million miles from Jupiter. One of their instruments—the Low-Energy Charged Particle [LECP] detector system—picked up some unusual signals. “We started seeing oxygen and sulfur ions hitting the detector,” says Stamatios Krimigis, who designed the LECP and is now emeritus head of the space department at Johns Hopkins APL. The density of oxygen and sulfur ions had shot up by three orders of magnitude compared with the levels measured up to that point. At first, his team thought the instrument had malfunctioned. “We scrutinized the data,” Krimigis says, “but there was nothing wrong.”

The Voyagers' cameras soon solved the mystery: Io had active volcanoes. The small world—it is slightly larger than Earth's moon—is now known to be the most volcanically active body in the solar system. “The only active volcanoes we knew of at the time were on Earth,” says Edward Stone, who has been the project scientist for the Voyager missions since 1972. “And here suddenly was a moon that had 10 times as much volcanic activity as Earth.” Io's colors—and the anomalous ions hitting Krimigis's detector—came from elements blasted from the moon's volcanoes. The largest of Io's volcanoes, known as Pele, has blown out plumes 30 times the height of Mount Everest; debris from Pele covers an area about the size of France.

The twin spacecraft took a grand tour through the giant planets of the solar system, passing by Jupiter ( 1 , 2 ) and Saturn ( 5 , 6 ) and taking the first close-up views of those planets’ moons. Jupiter’s satellite Europa ( 3 ), for instance, turned out to be covered with ice, and its moon Io ( 4 ) was littered with volcanoes—discoveries that came as a surprise to scientists who had assumed the moons would be gray and crater-pocked like Earth’s. Voyager 2 went on to fly by Uranus ( 7 ) and Neptune ( 8 ), and it is still the only probe to have visited there. Credit: NASA/JPL ( 1 , 2 , 4 , 5 , 6 , 8 ); NASA/JPL/USGS (3); NASA/JPL-Caltech ( 7 )

Altogether, the Voyagers took more than 33,000 photographs of Jupiter and its satellites. It felt like every image brought a new discovery: Jupiter had rings; Europa, one of Jupiter's 53 named moons, was covered with a cracked icy crust now estimated to be more than 60 miles thick. As the spacecraft left the Jupiter system, they got a farewell kick of 35,700 miles per hour from a gravity assist. Without it they would not have been able to overcome the gravitational pull of the sun and reach interstellar space.

At Saturn, the Voyagers parted company. Voyager 1 hurtled through Saturn's rings (taking thousands of hits from dust grains), flew past Titan, a moon shrouded in orange smog, and then headed “north” out of the plane of the planets. Voyager 2 continued alone to Uranus and Neptune. In 1986 Voyager 2 found 10 new moons around Uranus and added the planet to the growing list of ringed worlds. Just four days after Voyager 2's closest approach to Uranus, however, its discoveries were overshadowed when the space shuttle Challenger exploded shortly after launch. All seven of Challenger 's crew members were killed, including Christa McAuliffe, a high school teacher from New Hampshire who would have been the first civilian to travel into space.

Three years later, passing about 2,980 miles above Neptune's azure methane atmosphere, Voyager 2 measured the highest wind speeds of any planet in the solar system: up to 1,000 mph. Neptune's largest moon, Triton, was found to be one of the coldest places in the solar system, with a surface temperature of −391 degrees Fahrenheit (−235 degrees Celsius). Ice volcanoes on the moon spewed nitrogen gas and powdery particles five miles into its atmosphere.

Voyager 2's images of Neptune and its moons would have been the last taken by either of the spacecraft had it not been for astronomer Carl Sagan, who was a member of the mission's imaging team. With the Grand Tour officially completed, NASA planned to turn off the cameras on both probes. Although the mission had been extended with the hope that the Voyagers would make it to interstellar space—it had been officially renamed the Voyager Interstellar Mission—there would be no photo ops after Neptune, only the endless void and impossibly distant stars.

ERUPTION: The discovery of the volcano Pele, shown in this photograph from Voyager 1, confirmed that Jupiter’s moon hosts active volcanism. Credit: NASA/JPL/USGS

Sagan urged NASA officials to have Voyager 1 transmit one last series of images. So, on Valentine's Day in 1990, the probe aimed its cameras back toward the inner solar system and took 60 final shots. The most haunting of them all, made famous by Sagan as the “Pale Blue Dot,” captured Earth from a distance of 3.8 billion miles. It remains the most distant portrait of our planet ever taken. Veiled by wan sunlight that reflected off the camera's optics, Earth is barely visible in the image. It doesn't occupy even a full pixel.

Sagan, who died in 1996, “worked really hard to convince NASA that it was worth looking back at ourselves,” Spilker says, “and seeing just how tiny that pale blue dot was.”

Both Voyagers are now so far from Earth that a one-way radio signal traveling at the speed of light takes almost 22 hours to reach Voyager 1 and just over 18 to catch up with Voyager 2. Every day they move away by another three to four light-seconds. Their only link to Earth is NASA's Deep Space Network, a trio of tracking complexes spaced around the globe that enables uninterrupted communication with spacecraft as Earth rotates. As the Voyagers recede from us in space and time, their signals are becoming ever fainter. “Earth is a noisy place,” says Glen Nagle, outreach and communications manager at the Deep Space Network's facility in Canberra, Australia. “Radios, televisions, cell phones—everything makes noise. And so it gets harder and harder to hear these tiny whispers from the spacecraft.”

Faint as they are, those whispers have upended astronomers' expectations of what the Voyagers would find as they entered the interstellar phase of the mission. Stone and other Voyager scientists I spoke with cautioned me not to conflate the boundary of interstellar space with that of the solar system. The solar system includes the distant Oort cloud, a spherical collection of cometlike bodies bound by the sun's gravity that may stretch halfway to the closest star. The Voyagers won't reach its near edge for at least another 300 years. But interstellar space lies much closer at hand. It begins where a phenomenon called the solar wind ends.

Like all stars, the sun emits a constant flow of charged particles and magnetic fields—the solar wind. Moving at hypersonic speeds, the wind blows out from the sun like an inflating balloon, forming what astronomers call the heliosphere. As the solar wind billows into space, it pulls the sun's magnetic field along for the ride. Eventually pressure from interstellar matter checks the heliosphere's expansion, creating a boundary—preceded by an enormous shock front, the “termination shock”—with interstellar space. Before the Voyagers' journeys, estimates of the distance to that boundary with interstellar space, known as the heliopause, varied wildly.

“Frankly, some of them were just guesses,” according to Gurnett. One early guesstimate located the heliopause as close as Jupiter. Gurnett's own calculations, made in 1993, set the distance at anywhere from 116 to 177 astronomical units, or AU—about 25 times more distant. (One AU is the distance between Earth and the sun, equal to 93 million miles.) Those numbers, he says, were not very popular with his colleagues. By 1993 Voyager 1 already had 50 AU on its odometer. “If [the heliopause] was at 120 AU, that meant we had another 70 AU to go.” If Gurnett was right, the Voyagers, clipping along at about 3.5 AU a year, wouldn't exit the heliosphere for at least another two decades.

That prediction raised troubling questions: would the Voyagers—or the support of Congress—last that long? The mission's funding had been extended on the expectation that the spacecraft would cross the heliopause at about 50 AU. But the spacecraft left that milestone behind without finding any of the anticipated signs of interstellar transit. Astronomers had expected the Voyagers to detect a sudden surge in galactic cosmic rays—high-energy particles sprayed like shrapnel at nearly the speed of light from supernovae and other deep-space cataclysms. The vast magnetic cocoon formed by the heliosphere deflects most low-energy cosmic rays before they can reach the inner solar system. “[It] shields us from at least 75 percent of what's out there,” Stone says.

The Voyager ground team was also waiting for the spacecraft to register a shift in the prevailing magnetic field. The interstellar magnetic field, thought to be generated by nearby stars and vast clouds of ionized gases, would presumably have a different orientation from the magnetic field of the heliosphere. But the Voyagers had detected no such change.

Gurnett's 1993 estimates were prescient. Almost 20 years passed before one of the Voyagers finally made it to the heliopause. During that time the mission narrowly survived threats to its funding, and the Voyager team shrank from hundreds of scientists and engineers to a few dozen close-knit lifers. Most of them remain on the job today. “When you have such a long-lived mission, you start to regard people like family,” Spilker says. “We had our kids around the same time. We'd take vacations together. We're spanning multiple generations now, and some of the younger people on Voyager were not even born [when the spacecraft] launched.”

The tenacity and commitment of that band of brothers and sisters were rewarded on August 25, 2012, when Voyager 1 finally crossed the heliopause. But some of the data it returned were baffling. “We delayed announcing that we had reached interstellar space because we couldn't come to an agreement on the fact,” Cummings says. “There was lots of debate for about a year.”

Although Voyager 1 had indeed found the expected jump in plasma density—its plasma-wave detector, an instrument designed by Gurnett, inferred an 80-fold increase—there was no sign of a change in the direction of the ambient magnetic field. If the vehicle had crossed from an area permeated by the sun's magnetic field to a region where the magnetic field derived from other stars, shouldn't that switch have been noticeable? “That was a shocker,” Cummings says. “And that still bothers me. But a lot of people are coming to grips with it.”

When Voyager 2 reached the interstellar shoreline in November 2018, it, too, failed to detect a magnetic field shift. And the spacecraft added yet another puzzle: it encountered the heliopause at 120 AU from Earth—the same distance marked by its twin six years earlier. That did not jibe with any theoretical models, all of which said the heliosphere should expand and contract in sync with the sun's 11-year cycle. During that period the solar wind ebbs and surges. Voyager 2 arrived when the solar wind was peaking, which, if the models were correct, should have pushed the heliopause farther out than 120 AU. “It was unexpected by all the theorists,” Krimigis says. “I think the modeling, in terms of the findings of the Voyagers, has been found wanting.”

Now that the Voyagers are giving theorists some real field data, their models of the interaction between the heliosphere and the interstellar environment are becoming more complex. “The sort of general picture is that [our sun] emerged from a hot, ionized region” and entered a spotty, partly ionized area in the galaxy, says Gary Zank, an astrophysicist at the University of Alabama in Huntsville. The hot region likely formed in the aftermath of a supernova—some nearby ancient star, or perhaps a few, exploded at the end of its life and heated up the space, stripping electrons off their atoms in the process. The boundary around that region can be thought of as “kind of like the seashore, with all the water and the waves swirling and mixed up. We're in that kind of turbulent region ... magnetic fields get twisted up, turned around. It's not like the smooth magnetic fields that theorists usually like to draw,” although the amount of turbulence seen can differ depending on the type of observation. The Voyagers' data show little field variation at large scales but many small-scale fluctuations around the heliopause, caused by the heliosphere's influence on the interstellar medium. At some point, it is thought, the spacecraft will leave those roiling shoals behind and at last encounter the unalloyed interstellar magnetic field.

Or maybe that picture is completely wrong. A few researchers believe that the Voyagers have not yet left the heliosphere. “There is no reason for the magnetic fields in the heliosphere and the interstellar medium to have exactly the same orientation,” says Len A. Fisk, a space plasma scientist at the University of Michigan and a former NASA administrator. For the past several years Fisk and George Gloeckler, a colleague at Michigan and a longtime Voyager mission scientist, have been working on a model of the heliosphere that pushes its edge out by another 40 AU.

Most people working in the field, however, have been convinced by the dramatic uptick in galactic cosmic rays and plasma density the Voyagers measured. “Given that,” Cummings says, “it's very difficult to argue that we're not really in interstellar space. But then again, it's not like everything fits. That's why we need an interstellar probe.”

McNutt has been pushing for such a mission for decades. He and his colleagues at Johns Hopkins recently completed a nearly 500-page report outlining plans for an interstellar probe that would launch in 2036 and potentially could reach the heliosphere within 15 years, shaving 20 years off Voyager 1's flight time. And unlike the Voyager missions, the interstellar probe would be designed specifically to study the outer edge of the heliosphere and its environs. Within the next two years the National Academies of Sciences, Engineering, and Medicine will decide whether the mission should be one of NASA's priorities for the next decade.

An interstellar probe could answer one of the most fundamental questions about the heliosphere. “If I'm looking from the outside, what the devil does this structure look like?” McNutt asks. “We really don't know. It's like trying to understand what a goldfish bowl looks like from the point of view of the goldfish. We [need to] be able to see the bowl from the outside.” In some models, as the heliosphere cruises along at 450,000 mph, interstellar matter flows smoothly past it, like water around the bow of a ship, resulting in an overall cometlike shape. One recent computer model, developed by astronomer Merav Opher and her colleagues at Boston University, predicts that more turbulent dynamics give the heliosphere a shape like a cosmic croissant.

“You can start multiple fights at any good science conference about that,” McNutt says, “but it's going to take getting out there and actually making some measurements to be able to see what's going on. It would be nice to know what the neighborhood looks like.”

Some things outlive their purpose—answering machines, VCRs, pennies. Not the Voyagers—they transcended theirs, using 50-year-old technology. “The amount of software on these instruments is slim to none,” Krimigis says. “There are no microprocessors—they didn't exist!” The Voyagers' designers could not rely on thousands of lines of code to help operate the spacecraft. “On the whole,” Krimigis says, “I think the mission lasted so long because almost everything was hardwired. Today's engineers don't know how to do this. I don't know if it's even possible to build such a simple spacecraft [now]. Voyager is the last of its kind.”

It won't be easy to say goodbye to these trailblazing vehicles. “It's hard to see it come to an end,” Cummings says. “But we did achieve something really amazing. It could have been that we never got to the heliopause, but we did.”

Voyager 2 now has five remaining functioning instruments, and Voyager 1 has four. All are powered by a device that converts heat from the radioactive decay of plutonium into electricity. But with the power output decreasing by about four watts a year, NASA has been forced into triage mode. Two years ago the mission's engineers turned off the heater for the cosmic-ray detector, which had been crucial in determining the heliopause transit. Everyone expected the instrument to die.

“The temperature dropped like 60 or 70 degrees C, well outside any tested operating limits,” Spilker says, “and the instrument kept working. It was incredible.”

The last two Voyager instruments to turn off will probably be a magnetometer and the plasma science instrument. They are contained in the body of the spacecraft, where they are warmed by heat emitted from computers. The other instruments are suspended on a 43-foot-long fiberglass boom. “And so when you turn the heaters off,” Dodd says, “those instruments get very, very cold.”

How much longer might the Voyagers last? “If everything goes really well, maybe we can get the missions extended into the 2030s,” Spilker says. “It just depends on the power. That's the limiting point.”

TINY SPECK: Among Voyager 1’s last photographs was this shot of Earth seen from 3.8 billion miles away, dubbed the “Pale Blue Dot” by Voyager scientist Carl Sagan. Credit: NASA/JPL-Caltech

Even after the Voyagers are completely muted, their journeys will continue. In another 16,700 years, Voyager 1 will pass our nearest neighboring star, Proxima Centauri, followed 3,600 years later by Voyager 2. Then they will continue to circle the galaxy for millions of years. They will still be out there, more or less intact, eons after our sun has collapsed and the heliosphere is no more, not to mention one Pale Blue Dot. At some point in their travels, they may manage to convey a final message. It won't be transmitted by radio, and if it's received, the recipients won't be human.

The message is carried on another kind of vintage technology: two records. Not your standard plastic version, though. These are made of copper, coated with gold and sealed in an aluminum cover. Encoded in the grooves of the Golden Records , as they are called, are images and sounds meant to give some sense of the world the Voyagers came from. There are pictures of children, dolphins, dancers and sunsets; the sounds of crickets, falling rain and a mother kissing her child; and 90 minutes of music, including Bach's Brandenburg Concerto No. 2 and Chuck Berry's “Johnny B. Goode.”

And there is a message from Jimmy Carter, who was the U.S. president when the Voyagers were launched. “We cast this message into the cosmos,” it reads in part. “We hope someday, having solved the problems we face, to join a community of galactic civilizations. This record represents our hope and our determination, and our good will in a vast and awesome universe.”

*Editor’ Note (6/22/22): This paragraph was edited after posting to correct the description of when NASA began shutting down nonessential components of the Voyager spacecraft.

Tim Folger is a freelance journalist who writes for National Geographic , Discover , and other national publications.

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NASA’s Voyager 2 Is Out of Contact but Not Lost in Space

By Katrina Miller

Voyager 2, the aging explorer of our solar system, appears to be alive and well, NASA officials said on Tuesday. But they may not be able to communicate with the spacecraft for at least the next two months.

On Friday, scientists at NASA’s Jet Propulsion Laboratory announced that they had lost contact with Voyager 2, which is over 12 billion miles from Earth. Engineers on the ground sent an incorrect command to the spacecraft on July 21 that knocked its antenna two degrees away from the Earth. That made it impossible for the mission team to send or receive signals.

But on Tuesday morning, officials from the Deep Space Network, a global system used to operate numerous active space missions, detected a carrier signal from Voyager 2. That means the spacecraft is still broadcasting, though the signal is too weak for transmitting data.

Background: A long, strange trip through the solar system

Voyager 2 launched to space on Aug. 20, 1977, to take a tour of our solar system’s outer planets . It’s the only spacecraft to have visited Uranus and Neptune, and the second mission to cross the boundary that separates our solar system from the rest of the Milky Way, an area commonly referred to as interstellar space.

This isn’t the first time NASA has lost the ability to talk to the spacecraft. In 2020, scientists managing the Deep Space Network shut down the sole radio dish capable of talking to Voyager 2 for repairs and upgrades. When it came back online in March 2021, the Voyager 2 was still functioning.

A few weeks after Voyager 2 began its journey, NASA launched its twin, Voyager 1, which followed a different trajectory and reached interstellar space first . Mission specialists are still in contact with that spacecraft.

Why It Matters: A mission that just keeps going

While the spacecraft is nearly 46 years into its journey, it continues to produce useful scientific data about how the environment changes outside of our solar system, and how the heliosphere — a bubble of radiation from our sun — interacts with interstellar space.

But if something goes wrong before scientists recover communications with the spacecraft, they have no way of fixing it. That’s a bigger concern than what scientific data might be lost in the near term, a spokeswoman for the Jet Propulsion Laboratory said.

Earlier this year, Voyager 2 switched to running its five instruments on backup power to prolong the life of the mission. Scientists anticipate that one of these instruments will need to be shut down completely in 2026, and others in successive years, to keep the mission functioning for as long as possible.

What’s Next: The people of Earth can wait

The mission’s managers will attempt to use the Deep Space Network on Wednesday to send Voyager 2 a command to reorient the direction of its antenna back toward Earth, according to the laboratory spokeswoman. It will take about 18 hours for the signal to arrive at the spacecraft, and another 18 before scientists on Earth will know if it worked.

If the command fails, scientists will have to wait until Oct. 15. On that day, the mission’s computer is programmed to automatically point the antenna back toward Earth, which they hope will restore communications.

“It’s a 46-year-old spacecraft — we don’t like being out of contact with it,” the spokeswoman said. “On the other hand, it’s 46. It’s done well so far. So we have a lot of confidence that it’ll be OK.”

Katrina Miller is a science reporting fellow for The Times. She recently earned her Ph.D. in particle physics from the University of Chicago. More about Katrina Miller

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NASA's Voyager 1 sends readable message to Earth after 4 nail-biting months of gibberish

After four months of being unable to detect comprehensible data from the Voyager 1 spacecraft, NASA scientists have had fresh luck after sending a "poke."

After a nail-biting four months, NASA has finally received a comprehensible signal from its Voyager 1 spacecraft. 

Since November 2023, the almost-50-year-old spacecraft has been experiencing trouble with its onboard computers. Although Voyager 1, one of NASA's longest-lived space missions, has been sending a steady radio signal to Earth, it hasn't contained any usable data , which has perplexed scientists. 

Now, in response to a command prompt, or "poke," sent from Earth on March 1, NASA has received a new signal from Voyager 1 that engineers have been able to decode. Mission scientists hope this information may help them explain the spacecraft's recent communication problems. 

"The source of the issue appears to be with one of three onboard computers, the flight data subsystem (FDS), which is responsible for packaging the science and engineering data before it's sent to Earth by the telemetry modulation unit," NASA said in a blog post Wednesday (March 13) .

Related: NASA's 46-year-old Voyager 1 probe is no longer transmitting data

On March 1, as part of efforts to find a solution to Voyager 1's computer issues, NASA sent a command to the FDS on the spacecraft, instructing it to use different sequences in its software package, which would effectively mean skirting around any data that may be corrupted. 

Voyager 1 is more than 15 billion miles (24 billion kilometers) from Earth. This means any radio signals sent from our planet take 22.5 hours to reach the spacecraft, with any response taking the same time to be picked up by antennas on Earth. 

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On March 3, NASA detected activity from one section of the FDS that differed from the "unreadable data stream" they'd previously been receiving. Four days later, engineers started the heavy task of trying to decode this signal. By March 10, the team discovered that the signal contained a readout of the entire FDS memory. This included the instructions for what the FDS needed to do, any values in its code that can be changed depending on commands from NASA or the spacecraft's status, and downloadable science or engineering data.  

Voyager 1 has ventured farther from Earth than any other human-made object . It was launched in 1977, within weeks of its twin spacecraft , Voyager 2. The initial aim of the mission was to explore Jupiter and Saturn . Yet after almost five decades, and with countless discoveries under their belts, the mission continues beyond the boundaries of the solar system . 

— NASA hears 'heartbeat' signal from Voyager 2 probe a week after losing contact

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NASA scientists will now "compare this readout to the one that came down before the issue arose and look for discrepancies in the code and the variables to potentially find the source of the ongoing issue," they said in the blog post.  

However, NASA stressed that it will take time to determine if any of the insights gained from this new signal can be used to solve Voyager 1's long-standing communication issues. 

Emily is a health news writer based in London, United Kingdom. She holds a bachelor's degree in biology from Durham University and a master's degree in clinical and therapeutic neuroscience from Oxford University. She has worked in science communication, medical writing and as a local news reporter while undertaking journalism training. In 2018, she was named one of MHP Communications' 30 journalists to watch under 30. ( [email protected] ) 

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• Bruzote I have an inside source who says the message said, "Be sure to drink your Ovaltine." Reply
• Grumpy-DC I love Ovaltine. Both flavors. And I remember "Captain Midnight" sponsored by same. Reply

Grumpy-DC said: I love Ovaltine. Both flavors. And I remember "Captain Midnight" sponsored by same.

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Engineers Pinpoint Cause of Voyager 1 Issue, Are Working on Solution

Engineers have confirmed that a small portion of corrupted memory in one of the computers aboard NASA’s Voyager 1 has been causing the spacecraft to send unreadable science and engineering data to Earth since last November. Called the flight data subsystem (FDS), the computer is responsible for packaging the probe’s science and engineering data before the telemetry modulation unit (TMU) and radio transmitter send the data to Earth.

In early March , the team issued a “poke” command to prompt the spacecraft to send back a readout of the FDS memory, which includes the computer’s software code as well as variables (values used in the code that can change based on commands or the spacecraft’s status). Using the readout, the team has confirmed that about 3% of the FDS memory has been corrupted, preventing the computer from carrying out normal operations.

The team suspects that a single chip responsible for storing part of the affected portion of the FDS memory isn’t working. Engineers can’t determine with certainty what caused the issue. Two possibilities are that the chip could have been hit by an energetic particle from space or that it simply may have worn out after 46 years.

Although it may take weeks or months, engineers are optimistic they can find a way for the FDS to operate normally without the unusable memory hardware, which would enable Voyager 1 to begin returning science and engineering data again.

Launched in 1977 , the twin Voyager spacecraft flew by Saturn and Jupiter, and Voyager 2 flew by Uranus and Neptune. They are both exploring interstellar space, outside the bubble of particles and magnetic fields created by the Sun, called the heliosphere. Voyager 2 continues to operate normally.

News Media Contact Calla Cofield Jet Propulsion Laboratory, Pasadena, Calif. 626-808-2469 [email protected]

NASA Engineers Make Progress Toward Understanding Voyager 1 Issue

Editor’s note: This blog post was originally published March 13, 2024, on NASA’s Sun Spot blog . Future Voyager blog posts will appear here, on NASA’s Voyager blog.

Since November 2023, NASA’s Voyager 1 spacecraft has been sending a steady radio signal to Earth, but the signal does not contain usable data. The source of the issue appears to be with one of three onboard computers, the flight data subsystem (FDS), which is responsible for packaging the science and engineering data before it’s sent to Earth by the telemetry modulation unit.

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 FDS memory includes its code, or instructions for what to do, as well as variables, or values used in the code that can change based on commands or the spacecraft’s status. It also contains science or engineering data for downlink. The team will compare this readout to the one that came down before the issue arose and look for discrepancies in the code and the variables to potentially find the source of the ongoing issue.

This new signal resulted from a command sent to Voyager 1 on March 1. 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.

Because Voyager 1 is more than 15 billion miles (24 billion kilometers) from Earth, it takes 22.5 hours for a radio signal to reach the spacecraft and another 22.5 hours for the probe’s response to reach antennas on the ground. So the team received the results of the command on March 3. 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 analyzing the readout. Using that information to devise a potential solution and attempt to put it into action will take time.

Engineers Working to Resolve Issue With Voyager 1 Computer

Editor’s note: This blog post was originally published Dec. 12, 2023, on NASA’s Sun Spot blog . Future Voyager blog posts will appear here, on NASA’s Voyager blog. A previous version of this post identified the TMU as the telecommunications unit. It is the telemetry modulation unit.

Engineers are working to resolve an issue with one of  Voyager  1’s three onboard computers, called the flight data system (FDS). The spacecraft is receiving and executing commands sent from Earth; however, the FDS is not communicating properly with one of the probe’s subsystems, called the telemetry modulation unit (TMU). As a result, no science or engineering data is being sent back to Earth.

Among other things, the FDS is designed to collect data from the science instruments as well as engineering data about the health and status of the spacecraft. It then combines that information into a single data “package” to be sent back to Earth by the TMU. The data is in the form of ones and zeros, or binary code. Varying combinations of the two numbers are the basis of all computer language.

Recently, the TMU began transmitting a repeating pattern of ones and zeros as if it were “stuck.” After ruling out other possibilities, the Voyager team determined that the source of the issue is the FDS. This past weekend the team tried to restart the FDS and return it to the state it was in before the issue began, but the spacecraft still isn’t returning useable data.

It could take several weeks for engineers to develop a new plan to remedy the issue. Launched in 1977, the spacecraft and its twin, Voyager 2, are the two longest-operating spacecraft in history. Finding solutions to challenges the probes encounter often entails consulting original, decades-old documents written by engineers who didn’t anticipate the issues that are arising today. As a result, it takes time for the team to understand how a new command will affect the spacecraft’s operations in order to avoid unintended consequences.

In addition, commands from mission controllers on Earth take 22.5 hours to reach Voyager 1, which is  exploring the outer regions of our solar system  more than 15 billion miles (24 billion kilometers) from Earth. That means the engineering team has to wait 45 hours to get a response from Voyager 1 and determine whether a command had the intended outcome.

Introducing the Voyager Mission Blog

Launched in 1977, NASA’s twin Voyager spacecraft are the agency’s longest-operating and farthest-flung probes. Voyager 1 visited Jupiter and Saturn, revealing new features of both planets and their moons. Voyager 2 followed its twin to Jupiter and Saturn before changing its trajectory to fly by Uranus and Neptune. It remains the only spacecraft to visit our solar system’s two ice giant planets.

Continuing their legacy as science pioneers, the Voyagers are the only two probes to journey into interstellar space – the space between stars. This region lies outside the heliosphere , the protective bubble of particles and magnetic fields emitted by our Sun. By directly sampling the interstellar environment, the Voyagers are providing data that spacecraft closer to Earth can’t replicate. This helps scientists study both the shape of the heliosphere and its interaction with the ocean of interstellar material that the Sun is traveling through.

Readers of this blog can find occasional updates on mission science, the health of the spacecraft, and the creative solutions engineers have needed to come up with in order to keep the venerable spacecraft operating after nearly 50 years.

For more about Voyager, go to www.nasa.gov/voyager and follow along on X (formerly Twitter) at @NASAVoyager . Take Voyager’s Grand Tour with NASA’s Eyes .

News Media Contact Calla  Cofield Jet Propulsion Laboratory, Pasadena, Calif. 626-808-2469 calla.e. cofield @jpl.nasa.gov

pale blue dot

Voyager 1: How far can it go before we lose contact?

Launched by NASA on September 5, 1977 , to study the outer solar system , the Voyager 1 is the furthest human-made object from Earth. As of October 2022, it is more than 14,749,847,051 miles (23,737,577,852 km) away from our home planet. It is also moving away at a speed of 38,026.77 mph (61,198.15 km/h) relative to the Sun.

Despite that huge distance (even the light covers that distance in almost 22 hours!), thanks to NASA’s Deep Space Network (DSN), we can still communicate with it (also with its sister, Voyager 2). But how far can Voyager 1 go before we lose communication?

How long we can communicate with Voyager 1?

Using the Deep Space Network, NASA transmits a 20 kW radio signal from Earth. It takes almost 22 hours for the signal to reach Voyager 1 (so it is almost 22 light hours away from the Earth).

The Deep Space Network (DSN) is a worldwide network of U.S. spacecraft communication facilities, located in the United States (California), Spain (Madrid), and Australia (Canberra), that supports NASA’s interplanetary spacecraft missions. Each complex has a huge 70-meter antenna along with multiple 34-meter antennae which can be combined to pick up signals that are thousands of times weaker than a standard FM signal.

The space probe’s sensitive antenna picks up the signal transmitted from the DSN and replies using a 20-watt signal. It takes another 22 hours to reach the Earth and as the signal travels through space, it weakens. By the time it reaches Earth, it’s barely detectable – but the DSN is able to detect it.

Related: Five space probes leaving the solar system (for now)

Theoretically, there isn’t really a limit on how far we can communicate with objects in space – as long as they reply back to us. With our current technology, we could reliably communicate with the Voyager 1 for thousands of years, even if it’s many light years away from us.

Despite that, we can continue to communicate with Voyager 1 for only a few years more. The reason is: the probe’s nuclear-powered electrical supply weakens each day.

Voyager 1 does not use a nuclear reactor to power itself. It uses three RTG units – (Radioisotope Thermal Generator), which convert the heat from decaying plutonium into electricity using Peltier devices. It is not very fancy, has no moving parts, and is very reliable, but it produces a lot less power than a nuclear reactor.

Voyager 1 and the “Pale blue dot”

Back in 1990, in order to save power, engineers turned off the spacecraft’s camera. But, before that, it was commanded by NASA to turn its camera around and take a photograph of Earth across a great expanse of space, at the request of Carl Sagan.

Taken from a record distance of about 6 billion kilometers (3.7 billion miles, 40 AU) from Earth, the photo is known as the  Pale Blue Dot . In the photograph, Earth is shown as a fraction of a pixel (0.12 pixel in size) against the vastness of space.

The “Pale Blue Dot” is still the farthest image of Earth we’ve ever taken (as of January 2019).

But the old probe still amazes us: on November 28, 2017, a set of thrusters aboard it successfully fired up for the first time since November 1980, after 37 years without use.

Today, only 4 out of 11 scientific instruments on Voyager 1 are still active. These instruments are being used to collect data on magnetic fields, solar winds, and cosmic rays outside of our solar system .

On August 25, 2012 , Voyager 1 became the first spacecraft to cross the heliopause (see notes 1) (the vast, bubble-like region of space that surrounds and is created by the Sun) and enter the interstellar medium.

Related: NASA’s Voyager 1 spacecraft has technical problems, it is generating random-looking telemetry data, and as a result, the spacecraft doesn’t know where it is

We can continue to communicate with Voyager 1 until 2025

Voyager 1’s extended mission is expected to continue until around 2025 when its radioisotope thermoelectric generators will no longer supply enough electric power to operate its scientific instruments. At that time, it will be more than 15.5 billion miles (25 billion km) away from the Earth.

Scientists will communicate with Voyager 1 and receive the important information it gathers until it eventually sends its last bit of data and disappears silently into space, never to be heard from again.

Video: How far can Voyager 1 go before we lose contact?

The video published by the Primal Space channel below looks at how we communicate with Voyager and when it will eventually stop receiving our signals.

• The heliosphere is the vast, bubble-like region of space that surrounds and is created by the Sun. In plasma physics terms, this is the cavity formed by the Sun in the surrounding interstellar medium. The “bubble” of the heliosphere is continuously “inflated” by plasma originating from the Sun, known as the solar wind. Outside the heliosphere, this solar plasma gives way to the interstellar plasma permeating our galaxy. Radiation levels inside and outside the heliosphere differ; in particular, the galactic cosmic rays are less abundant inside the heliosphere, so the planets inside (including Earth) are partly shielded from their impact. The word “heliosphere” is said to have been coined by Alexander J. Dessler, who is credited with the first use of the word in scientific literature.
• Voyager Mission Status page on NASA.gov
• Voyager 1 on Wikipedia
• Voyager 1’s Radioisotope Thermoelectric Generators (RTG) on NASA.gov
• Heliosphere on Wikipedia
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Join the Conversation

I’m looking at the image of the pale blue dot. How did we ascertain that this dot is, in fact, Earth? Where in this image is everything else? ie: the other planets and Sun. What was used as a point of reference? The cosmos is the only thing that truly puzzles me. Great article.

I am an engineer and a Cornell graduate where Carl Sagan and Tommy Gold were on the faculty and helped get the Voyager programs started. The payoff has been unbelievable. We are still getting data from deep in interstellar space, but I don’t know for how much longer.

Thank you enjoyed reading this, fascinating read.

Time and space, the vastness of the universe it all blows my mind but reminds me just how small our planet is in the great scheme of things.

The electrical supply has lasted for many years, why is it we must put up with inferior systems at home?

When you realize just how vast the universe is you know there is other life out there. Even if there is only one planet per galaxy that would mean there are hundreds of thousands of planets with life. It would be an awful big waste of space otherwise.

Doing a quick bit of math if the nearest star is 4 lightyears away that means it is 23 trillion miles from us (((4 x 365 x 24 x 60 x60 x300,000km/sec)/8) x5)= 23.65 followed by 12 noughts. By the time we lose contact with Voyager 1 at 15.5 billion miles from earth it will not have covered even 1% at this distance. We may have left the house but we aren’t even out of the backyard yet….

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Voyager 1 glitch? Strange signals from venerable probe has NASA baffled

It's never too late for a Voyager 1 mystery in deep space.

Spending 45 years traversing the solar system really does a number on a spacecraft.

NASA's Voyager 1 mission launched in 1977, passed into what scientists call interstellar space in 2012 and just kept going — the spacecraft is now 14.5 billion miles (23.3 billion kilometers) away from Earth . And while Voyager 1 is still operating properly, scientists on the mission recently noticed that it appeared confused about its location in space without going into safe mode or otherwise sounding an alarm.

"A mystery like this is sort of par for the course at this stage of the Voyager mission," Suzanne Dodd, project manager for Voyager 1 and its twin, Voyager 2, at NASA's Jet Propulsion Laboratory in California, said in a statement .

Related : Pale Blue Dot at 30: Voyager 1's iconic photo of Earth from space reveals our place in the universe

"The spacecraft are both almost 45 years old, which is far beyond what the mission planners anticipated," Dodd added. "We're also in interstellar space — a high-radiation environment that no spacecraft have flown in before."

The glitch has to do with Voyager 1's attitude articulation and control system, or AACS, which keeps the spacecraft and its antenna in the proper orientation. And the AACS seems to be working just fine, since the spacecraft is receiving commands, acting on them and sending science data back to Earth with the same signal strength as usual. Nevertheless, the AACS is sending the spacecraft's handlers junk telemetry data.

The NASA statement does not specify when the issue began or how long it has lasted.

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The agency says that Voyager personnel will continue to investigate the issue and attempt to either fix or adapt to it. That's a slow process, since a signal from Earth currently takes 20 hours and 33 minutes to reach Voyager 1; receiving the spacecraft's response carries the same delay.

— What Voyager 1 learned at Jupiter 40 years ago — Voyager at 40: 40 photos from NASA's epic 'grand tour' mission — Voyager 1's historic flyby of Jupiter in photos  

The twin Voyager 2 probe, also launched in 1977, is behaving normally, NASA said. The power the twin spacecraft can produce is always falling, and mission team members have turned some components off to save juice — measures they hope will keep the probes working through at least 2025.

"There are some big challenges for the engineering team," Dodd said. "But I think if there's a way to solve this issue with the AACS, our team will find it."

Email Meghan Bartels at [email protected] or follow her on Twitter @ meghanbartels . Follow us on Twitter @ Spacedotcom and on Facebook .

Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at: [email protected].

Meghan is a senior writer at Space.com and has more than five years' experience as a science journalist based in New York City. She joined Space.com in July 2018, with previous writing published in outlets including Newsweek and Audubon. Meghan earned an MA in science journalism from New York University and a BA in classics from Georgetown University, and in her free time she enjoys reading and visiting museums. Follow her on Twitter at @meghanbartels.

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NASA's Voyager 1 is sending mysterious data from beyond our solar system. Scientists are unsure what it means.

• NASA said Voyager 1 is sending data that doesn't match the spacecraft's movements.
• The veteran spacecraft has been exploring our solar system and interstellar space since 1977.
• It is now 14.5 billion miles away from Earth, making it the most distant human-made object.

NASA's Voyager 1 is continuing its journey beyond our solar system, 45 years after it was launched. But now the veteran spacecraft is sending back strange data, puzzling its engineers.

NASA said on Wednesday that while the probe is still operating properly, readouts from its attitude articulation and control system — AACS for short — don't seem to match the spacecraft's movements and orientation, suggesting the craft is confused about its location in space. The AACS is essential for Voyager to send NASA data about its surrounding interstellar environment as it keeps the craft's antenna pointing right at our planet.

"A mystery like this is sort of par for the course at this stage of the Voyager mission," Suzanne Dodd, a project manager for Voyager 1 and 2 at NASA's Jet Propulsion Laboratory, said in a statement . "The spacecraft are both almost 45 years old, which is far beyond what the mission planners anticipated." NASA said Voyager 1's twin, the Voyager 2 probe, is behaving normally.

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Launched in 1977 to explore the outer planets in our solar system, Voyager 1 has remained operational long past expectations and continues to send information about its journeys back to Earth. The trailblazing craft left our solar system and entered interstellar space in 2012 . It is now 14.5 billion miles away from Earth, making it the most distant human-made object.

NASA said that from what its engineers can tell, Voyager 1's AACS is sending randomly generated data that does not "reflect what's actually happening onboard." But even if system data suggests otherwise, the spacecraft's antenna seems to be properly aligned — it is receiving and executing commands from NASA and sending data back to Earth. It said that so far the system issue hasn't triggered the aging spacecraft to go into "safe mode," during which it carries out only essential operations.

"Until the nature of the issue is better understood, the team cannot anticipate whether this might affect how long the spacecraft can collect and transmit science data," NASA said.

Dodd and her team hope to figure out what's prompting the robot emissary from Earth to send junky data. "There are some big challenges for the engineering team," Dodd said. A major one: It takes light 20 hours and 33 minutes to get to Voyager's current interstellar location, so a round-trip message between the space agency and Voyager takes two days.

"But I think if there's a way to solve this issue with the AACS, our team will find it," Dodd added.

Watch: NASA is flying a $1.5 billion spacecraft into the sun — here's why

• Main content

Engineers attempt to fix a computer glitch on Voyager 1

Voyager 1's system that sends data home is malfunctioning, preventing the computer from operating as it should.

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Last November, the Voyager 1 spacecraft began sending gibberish radio signals back to Earth. Engineers have now identified the problem, but trying to repair a 46-year-old device on a craft 24 billion kilometres from Earth is not easy.

Voyager 1 and its twin Voyager 2 were both launched in 1977 on a reconnaissance mission to Jupiter and Saturn. They were designed to fly past the giant planets to obtain closeup images of those distant worlds and their myriad of moons.

Both spacecraft performed beyond expectations, discovering many new moons — some covered in ice , one with active volcanoes , another with a thick atmosphere and closeup details of Saturn's rings .  

Following the Saturn encounter, Voyager 1 was flung upwards by Saturn's gravity on a trajectory northward, above the orbital plane in which most of the planets orbit the Sun, out of our solar system. NASA extended its mission and from there it went on to become the first human-made object to venture into interstellar space in 2012. 

Voyager 2, however, was aimed toward Uranus and Neptune, which were conveniently positioned in a rare alignment with Jupiter and Saturn making it the only spacecraft to visit those distant worlds.

Following the grand tour of the outer solar system, Voyager 2 was also tossed out toward interstellar space in 2018 when its mission was extended and where it continues on its journey today. 

• After a 42-year journey, Voyager 2 goes interstellar
• Voyager 1 picks up the 'hum' of interstellar space

While their primary missions were over, both spacecraft were still in good health, thanks largely to their nuclear power sources or Radioisotope Thermoelectric Generators (RTG). These containers hold small amounts of plutonium which provide heat that is turned directly into electricity with no moving parts. They have an expected lifetime of around 50 years and have kept the Voyagers' instruments running.

Now, as both spacecraft continue their journey through the space between the stars, they are showing signs of their age.

For Voyager 1, the problem seems to be in the flight data subsystem (FDS) that packages data from the scientific instruments for transmission to Earth. The scientists don't know if the faulty module was corrupted by cosmic rays or just worn out, but they say they're optimistic they may be able to work around the problem, although it will take some time.

Engineers have confirmed that corrupted memory aboard my twin <a href="https://twitter.com/hashtag/Voyager1?src=hash&amp;ref_src=twsrc%5Etfw">#Voyager1</a> has been causing it to send unreadable data to Earth. It may take months, but our team is optimistic they can find a way for the FDS to operate normally again: <a href="https://t.co/qe5iQUu4Oj">https://t.co/qe5iQUu4Oj</a> <a href="https://t.co/AGFBZFz53v">https://t.co/AGFBZFz53v</a> &mdash; @NASAVoyager

The challenge is that the computers were built in the 1970s using old code and send data very slowly by today's standards.

In addition, these computers are so deep in space, it takes 22.5 hours for a radio signal from Voyager 1 to reach Earth. That means the controllers on the ground have to wait 45 hours for each two-way communication with the spacecraft.

Given how very, very far they are from home, if something goes wrong with them, it's up to engineers on the ground to fix it by sending radio signals since reaching them for repair missions isn't possible. We're a long way from the fictional warp drive and sub-space communication that made life so easy on the Starship Enterprise of Star Trek fame. 

The twin Voyagers are now the most distant objects ever sent from Earth; a demonstration of how vast space is and how slow our spacecraft are. In 1977, I attended the launch of Voyager 2 when my hair was black and skin was smooth. This one mission with Voyager 1 and 2 has occupied a good chunk of my lifetime.

In another few years, the RTGs on both Voyagers are expected to run down to the point where the spacecraft will no longer be able to communicate with Earth. They will just continue to drift in silence among the stars of the Milky Way for billions of years. 

However, there is one item on both Voyagers that will continue to function, the Golden Record, which carries a message from Earth to anyone out there who may find the spacecraft in the future.

The chances of them being found are astronomically small, but they will become the longest running experiment in human history.

ABOUT THE AUTHOR

Bob McDonald is the host of CBC Radio's award-winning weekly science program, Quirks & Quarks. He is also a science commentator for CBC News Network and CBC TV's The National. He has received 12 honorary degrees and is an Officer of the Order of Canada.

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