Engineers report progress in restoring proper communications with Voyager-1

According to a NASA update yesterday, software engineers for the Voyager-1 spacecraft now beyond the edge of the solar system have managed to decipher the garbled data the spacecraft’s computers have been sending back to Earth since November 2023, and are in the process of analyzing that data with the hope of restoring full understandable communications.

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.

This new readable data was the result of a command sent two days before, suggesting that engineers are on the right track. Because Voyager-1 is so far away, 15 billion miles, it takes 22.5 hours for any command to be sent to the spacecraft, and another 22.5 hours for ground controllers to get a response. This long lag time has slowed the effort to fix the problem, but this new success suggests that a full recovery is possible.

That recovery is going to be relatively short-lived, no matter what. The nuclear-powered power sources for both Voyager spacecraft, flying since 1977, are expected to finally run out of power sometime in 2026, after almost a half century of operation. Moreover, the computers on both Voyagers are the longest continuously running computers in history.

The engineering achievement of both is astonishing.

Computer problem on Voyager-1 remains unsolved

Engineers remain baffled over a computer issue that has prevented the receipt of any data since November 2023 from Voyager-1, floating some 15 billion miles away just outside the solar system in interstellar space.

In November, the data packages transmitted by Voyager 1 manifested a repeating pattern of ones and zeros as if it were stuck, according to NASA. Dodd said engineers at JPL have spent the better part of three months trying to diagnose the cause of the problem. She said the engineering team is “99.9 percent sure” the problem originated in the FDS [Flight Data Subsystem], which appears to be having trouble “frame syncing” data.

So far, the ground team believes the most likely explanation for the problem is a bit of corrupted memory in the FDS. However, because of the computer hangup, engineers lack detailed data from Voyager 1 that might lead them to the root of the issue. “It’s likely somewhere in the FDS memory,” Dodd said. “A bit got flipped or corrupted. But without the telemetry, we can’t see where that FDS memory corruption is.”

Since November the only signal received from Voyager-1 is a carrier signal that simply tells engineers the spacecraft is alive. Though the effort continues to try to fix the spacecraft, the odds of bringing it back to life are becoming slim, especially because its power supply will run out in 2026 at the very latest. Even if they manage to fix the issue now, the spacecraft has only a short time left regardless.

Considering the computers on this spacecraft, as well as its twin Voyager-2, have been operating continuously for almost a half century since their launch in 1977, their failure now is nothing to be ashamed of. The engineers that built both did well, to put it mildly.

As for Voyager-1’s future, even dead it will fly on into interstellar space, eventually getting within 1.5 light years of a star in the constellation Camelopardalis.

Voyager-1 has computer issues

According to the Voyager-1 science team, the probe has developed a problem with one of its three onboard computers, called the flight data system (FDS), that is preventing it from sending back useable data.

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.

Engineers are trouble-shooting the problem, and expect it will take several weeks at best to identify and then fix the issue. The 22-hour travel time for communications to reach the spacecraft, now beyond the edge of the solar system more than 15 billion miles away, means that it will at minimum take about two days to find out if a transmitted fix works.

As the spacecraft was launched in 1977, most of the engineers now working on it were not even born then, and must deal with a technology that was designed before personal computers, no less smart phones, even existed. Like the entire 1960s space race, the two Voyager craft now beyond the solar system were built by engineers using slide rules.

Voyager-2 also had problems in August that engineers were able to fix, so the prognosis here is not bad.

The same region on Ganymede, as seen by Voyager-1 in 1979 and Juno in 2021

Ganymede compared between Voyager-1 and Juno
Click for full image.

When the Jupiter orbiter Juno did a close pass of the moon Ganymede on June 7, 2021, it took four pictures, covering regions mostly photographed for the first time by Voyager-1 in its close fly-by in 1979.

Scientists have now published the data from this new fly-by. Though Juno’s higher resolution pictures revealed many new details when compared with the Voyager-1 images from four decades earlier, the scientists found no changes. The comparison image, figure 2 of their paper, is to the right, reduced and sharpened to post here.

A flicker comparison between the registered JunoCam and Voyager reprojected mosaics revealed no apparent new impact features. Given the high albedo of fresh craters on Ganymede, with high albedo ejecta deposits two or three times the diameter of the craters themselves, we argue that new craters as small as 250 m diameter would be detectable in images at these 1 km per pixel scales. Extrapolating Ganymede cratering rates from Zahnle et al. (2003) below 1 km, the probability of JunoCam observing a new crater over 12.2 million km2 in 42 years is 1 in 1500, consistent with none being observed.

In other words, at these resolutions finding no new impacts is not a surprise.

Of the new features detected, the Juno images could see more details in the bright rays emanating from the crater Tros (in the lower center of both images), and thus found “…terrain boundaries previously mapped as ‘undivided’ or as ‘approximate’, several large craters, and 12 paterae newly identified in this region.”

Paterae resemble craters but are thought to be a some form of volcanic caldera. Their geological origin however is not yet completely understood.

The paper’s conclusion is actually the most exciting:

The insight gained from this handful of images makes it likely in our opinion that new observations from the upcoming JUICE and Europa Clipper missions will revolutionize our understanding of Ganymede.

After 50 years Edward Stone retires as the project scientist for Voyagers 1 and 2

Edward Stone, the only project scientist the interstellar spacecraft Voyagers 1 and 2 have ever known, has now retired after 50 years service.

Stone accepted scientific leadership of the historic mission in 1972, five years before the launch of its two spacecraft, Voyager 1 and Voyager 2. Under his guidance, the Voyagers explored the four giant planets and became the first human-made objects to reach interstellar space, the region between the stars containing material generated by the death of nearby stars.

Until now, Stone was the only person to have served as project scientist for Voyager, maintaining his position even while serving as director of NASA’s Jet Propulsion Laboratory in Southern California from 1991 to 2001. JPL manages the Voyager mission for NASA. Stone retired from JPL in 2001 but continued to serve as the mission’s project scientist.

The new Voyager project scientist however is not new to the project.

Linda Spilker will succeed Stone as Voyager’s project scientist as the twin probes continue to explore interstellar space. Spilker was a member of the Voyager science team during the mission’s flybys of Jupiter, Saturn, Uranus, and Neptune. She later became project scientist for NASA’s now-retired Cassini mission to Saturn, and rejoined Voyager as deputy project scientist in 2021.

Engineers fix problem that caused data to arrive garbled from Voyager-1

By switching computers on Voyager-1 — now in interstellar space and having recently celebrated its 45th anniversary since launch — engineers were able to prevent data from coming back garbled from the spacecraft.

Earlier this year, the probe’s attitude articulation and control system (AACS), which keeps Voyager 1’s antenna pointed at Earth, began sending garbled information about its health and activities to mission controllers, despite operating normally. The rest of the probe also appeared healthy as it continued to gather and return science data.

The team has since located the source of the garbled information: The AACS had started sending the telemetry data through an onboard computer known to have stopped working years ago, and the computer corrupted the information.

Suzanne Dodd, Voyager’s project manager, said that when they suspected this was the issue, they opted to try a low-risk solution: commanding the AACS to resume sending the data to the right computer.

The switch worked. The mystery now is figuring out why the AACS started using that long-decommissioned computer, which could indicate another computer or software issue elsewhere in the spacecraft.

Puzzling telemetry from Voyager-1 suggests problem

Engineers are puzzling over strange operational data coming from Voyager-1, launched in 1977 and now in interstellar space more than 14 billion miles away, that suggests a technical problem but also makes no sense.

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.

Figuring out what has happened is made more difficult by distance. It takes about 20 hours for signals to get from Voyager-1 to Earth, even at the speed of light. Thus, any attempted fix will arrive almost two days after it first occurred, at the soonest.

Both Voyager-1 and Voyager-2 are still operating, though at significantly reduced power. It is expected that sometime in the next few years their nuclear power sources will finally be unable to produce enough power to keep them functioning. If so, both spacecraft will have survived the maximum time predicted when launched.

Interstellar space, as seen by both Voyager spacecraft

Today a suite of new science papers were published outlining what scientists learned when Voyager 2 joined Voyager 1 in interstellar space last November.

The Sun’s heliosphere is like a ship sailing through interstellar space. Both the heliosphere and interstellar space are filled with plasma, a gas that has had some of its atoms stripped of their electrons. The plasma inside the heliosphere is hot and sparse, while the plasma in interstellar space is colder and denser. The space between stars also contains cosmic rays, or particles accelerated by exploding stars. Voyager 1 discovered that the heliosphere protects Earth and the other planets from more than 70% of that radiation.

The data also shows that Voyager 2, which exited the heliosphere somewhat perpendicular to its direction of travel, is still in the transitional zone between the heliosphere and interstellar space. Voyager 1 exited out the head of the heliosphere, so its transitional zone was compressed and shorter.

The real achievement of these results however is that they were obtainable at all. For both spacecraft to be functioning so well after forty years in space, and able to get their data back to Earth from distances more than 11 billion miles, is a true testament to the grand engineering that went into their design and construction.

They built well in the mid-twentieth century.

Engineers adjust Voyagers 1 & 2 because of steadily dropping power

In recognition that the available power on both Voyager 1 and Voyager 2 continues to drop due to the age of the spacecraft, engineers have decided to make some major changes in how they operate both spacecraft.

For example, to save power on Voyager 2 they have turned off the heaters for the instrument that confirmed last year that the spacecraft had entered interstellar space. Even so, the instrument is still functioning and sending back data. It is expected it will continue to work for some time before finally succumbing to the cold of deep space.

They have also decided to reactivate the back-up thrusters on Voyager 2, just as they did with Voyager 1 in 2017.

Another challenge that engineers have faced is managing the degradation of some of the spacecraft thrusters, which fire in tiny pulses, or puffs, to subtly rotate the spacecraft. This became an issue in 2017, when mission controllers noticed that a set of thrusters on Voyager 1 needed to give off more puffs to keep the spacecraft’s antenna pointed at Earth. To make sure the spacecraft could continue to maintain proper orientation, the team fired up another set of thrusters on Voyager 1 that hadn’t been used in 37 years.

Voyager 2’s current thrusters have started to degrade, too. Mission managers have decided to make the same thruster switch on that probe this month. Voyager 2 last used these thrusters (known as trajectory correction maneuver thrusters) during its encounter with Neptune in 1989.

It is thirty years since those thusters on Voyager 2’s were used. If they work it will be an incredible testament to the engineers who designed both spacecraft.

Voyager 1 fires thrusters not used in 37 years

Because Voyager 1’s primary attitude thrusters are beginning to show wear (after forty years in space), engineers decided to experiment using a different set of thrusters not used since the spacecraft flew past Saturn in 1980, and found that they worked!

In the early days of the mission, Voyager 1 flew by Jupiter, Saturn, and important moons of each. To accurately fly by and point the spacecraft’s instruments at a smorgasbord of targets, engineers used “trajectory correction maneuver,” or TCM, thrusters that are identical in size and functionality to the attitude control thrusters, and are located on the back side of the spacecraft. But because Voyager 1’s last planetary encounter was Saturn, the Voyager team hadn’t needed to use the TCM thrusters since November 8, 1980. Back then, the TCM thrusters were used in a more continuous firing mode; they had never been used in the brief bursts necessary to orient the spacecraft.

…On Tuesday, Nov. 28, 2017, Voyager engineers fired up the four TCM thrusters for the first time in 37 years and tested their ability to orient the spacecraft using 10-millisecond pulses. The team waited eagerly as the test results traveled through space, taking 19 hours and 35 minutes to reach an antenna in Goldstone, California, that is part of NASA’s Deep Space Network.

Lo and behold, on Wednesday, Nov. 29, they learned the TCM thrusters worked perfectly — and just as well as the attitude control thrusters.

They figure these back-up thrusters will allow them to extend the mission by two or three years. The test also went so well that they now plan to do the same test on Voyager 2, which has still not entered interstellar space.

Hubble takes a look at both Voyagers’ interstellar path

Using the Hubble Space Telescope astronomers have taken a peek at the interstellar material that the two Voyager spacecraft will travel through as they move out and leave the solar system in the coming decades.

Voyager 1 is 13 billion miles from Earth, making it the farthest human-made object ever built. In about 40,000 years, after the spacecraft will no longer be operational and will not be able to gather new data, it will pass within 1.6 light-years of the star Gliese 445, in the constellation Camelopardalis. Its twin, Voyager 2, is 10.5 billion miles from Earth, and will pass 1.7 light-years from the star Ross 248 in about 40,000 years.

For the next 10 years, the Voyagers will be making measurements of interstellar material, magnetic fields, and cosmic rays along their trajectories. Hubble complements the Voyagers’ observations by gazing at two sight lines along each spacecraft’s path to map interstellar structure along their star-bound routes. Each sight line stretches several light-years to nearby stars. Sampling the light from those stars, Hubble’s Space Telescope Imaging Spectrograph measured how interstellar material absorbed some of the starlight, leaving telltale spectral fingerprints.

Hubble found that Voyager 2 will move out of the interstellar cloud that surrounds the solar system in a couple thousand years. The astronomers, based on Hubble data, predict that the spacecraft will spend 90,000 years in a second cloud before passing into a third interstellar cloud.

This is very clever science. It allows data from Hubble to complement the data from the two Voyager spacecraft to better understand the interstellar regions that surround our solar system.

Voyager 1 might not have left the solar system

The uncertainty of science: Two scientists dispute the finding this year that Voyager 1 has entered interstellar space.

Voyager has yet to detect what scientists long predicted would be the calling card of interstellar space: a shift in the direction of the magnetic field. Scientists had expected the probe to encounter particles under the influence of the interstellar magnetic field draped over the outer shell of the heliosphere, inducing an abrupt shift. But the direction has remained stubbornly constant, and researchers can’t explain why. “This whole region is a lot messier than anyone dreamed of,” Christian says.

It’s a bit too messy for George Gloeckler and Lennard Fisk, Voyager scientists at the University of Michigan in Ann Arbor. They wondered whether the magnetic field and particle density conditions measured by Voyager could exist within the heliosphere. In a paper accepted for publication in Geophysical Research Letters, Gloeckler and Fisk argue that the outer heliosphere could allow an influx of galactic particles from beyond the bubble that would explain the density measurements.

The researchers’ analysis includes a way to definitively test the idea: If Voyager 1 is within the heliosphere, Gloeckler and Fisk note, then it should still be at the mercy of the sun’s magnetic field. If that were the case, within a year or so, Voyager should detect a 180-degree flip in the field’s direction, a regular occurrence caused by the sun’s rotation. “If that happens,” Gloeckler says, “Len and I will have a big celebration.”

I suspect that both sides are right, and that the transition into interstellar space is simply very complex. Some data will say the spacecraft is outside the solar system, while other data will say it is inside.

Voyager 1’s future.

Voyager 1’s future.

Voyager 1 has enough nuclear fuel to keep doing science through to 2025, and then it will be dead, adrift. On its current trajectory, the probe should eventually end up within 1.5 light years of a star in Camelopardalis, a northern constellation that looks like a cross between a giraffe and a camel. No one knows if there are any planets around that star, nor if aliens will be in residence by the time the probe arrives. “But if they are there, maybe they will capture Voyager 1,” says mission scientist Tom Krimigis of Johns Hopkins University in Baltimore, Maryland.

In addition to the above silliness, the article gives a good summary of the real data that Voyager 1 is sending back about interstellar space.

NASA has announced a press conference for later today about the Voyager spacecraft.

NASA has announced a press conference for later today about the Voyager spacecraft.

The rumors are that all the scientists involved with this data from this spacecraft now finally agree that Voyager has left the solar system. More to come.

The rumors were true: NASA has confirmed that Voyager 1 is out of the solar system and in interstellar space, and has been since last summer.

Scientists today published a new model that suggests that Voyager 1 actually entered interstellar space in July of last year.

Ad astra: Scientists today published a new model that suggests that Voyager 1 actually left the solar system and entered interstellar space in July of last year.

In describing on a fine scale how magnetic field lines from the sun and magnetic field lines from interstellar space can connect to each other, they conclude Voyager 1 has been detecting the interstellar magnetic field since July 27, 2012. Their model would mean that the interstellar magnetic field direction is the same as that which originates from our sun.

Other models envision the interstellar magnetic field draped around our solar bubble and predict that the direction of the interstellar magnetic field is different from the solar magnetic field inside. By that interpretation, Voyager 1 would still be inside our solar bubble.

This new model might very well explain the conflicting data received from the spacecraft, some of which said it was out of the solar system and some of which said it was not.

Voyager 1 has found the edge of the solar system to be far more complex than predicted by scientists.

The uncertainty of science: Voyager 1 has found the edge of the solar system to be far more complex than predicted by scientists.

Scientists had assumed that Voyager 1, launched in 1977, would have exited the solar system by now. That would mean crossing the heliopause and leaving behind the vast bubble known as the heliosphere, which is characterized by particles flung by the sun and by a powerful magnetic field.

The scientists’ assumption turned out to be half-right. On Aug. 25, Voyager 1 saw a sharp drop-off in the solar particles, also known as the solar wind. At the same time, there was a spike in galactic particles coming from all points of the compass. But the sun’s magnetic field still registers, somewhat diminished, on the spacecraft’s magnetometer. So it’s still in the sun’s magnetic embrace, in a sense.

The discovery of volcanoes on Io

discovery image

On March 8, 1979, as Voyager 1 was speeding away from Jupiter after its historic flyby of the gas giant three days earlier, it looked back at the planet and took some navigational images. Linda Morabito, one of the engineers in charge of using these navigational images to make sure the spacecraft was on its planned course, took one look at the image on the right, an overexposed image of the moon Io, and decided that it had captured something very unusual. On the limb of the moon was this strange shape that at first glance looked like another moon partly hidden behind Io. She and her fellow engineers immediately realized that this was not possible, and that the object was probably a plume coming up from the surface of Io. To their glee, they had taken the first image of an eruption of active volcano on another world!

Today, on the astro-ph preprint website, Morabito has published a minute-by-minute account of that discovery. It makes for fascinating reading, partly because the discovery was so exciting and unique, partly because it illustrated starkly the human nature of science research, and partly because of the amazing circumstances of that discovery. Only one week before, scientists has predicted active volcanism on Io in a paper published in the journal Science. To quote her abstract:
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On August 13, 2012, Voyager 2 became the longest-operating spacecraft in history, finally topping Pioneer 6, which was launched on Dec. 16, 1965, and sent its last signal back on Dec. 8, 2000.

On August 13, 2012, Voyager 2 became the longest-operating spacecraft in history, finally topping Pioneer 6, which was launched on Dec. 16, 1965, and sent its last signal back to Earth on Dec. 8, 2000.

And Voyager 2, along with its partner Voyager 1, are still working, and engineers hope they will still be working for another eight to twelve years, enough time for them to leave the solar system and enter interstellar space.

More signs that the Voyager 1 spacecraft is about to enter interstellar space.

More signs that the Voyager 1 spacecraft is about to enter interstellar space.

For the last seven years, Voyager 1 has been exploring the outer layer of the bubble of charged particles the sun blows around itself. In one day, on July 28, data from Voyager 1’s cosmic ray instrument showed the level of high-energy cosmic rays originating from outside our solar system jumped by five percent. During the last half of that same day, the level of lower-energy particles originating from inside our solar system dropped by half. However, in three days, the levels had recovered to near their previous levels.

A third key sign is the direction of the magnetic field, and scientists are eagerly analyzing the data to see whether that has, indeed, changed direction. Scientists expect that all three of these signs will have changed when Voyager 1 has crossed into interstellar space. A preliminary analysis of the latest magnetic field data is expected to be available in the next month.

Based on this report, expect scientists to announce that Voyager 1 has left the solar system sometime before the end of the year.

Voyager 1 at the edge

This week the American Geophysical Union (AGU) is having its annual fall meeting in San Francisco. Due to the wonders of technology, they are now making their press conferences available to reporters on line. Thus, I will be posting periodic updates after each conference. This will allow my readers to get a heads up on stories they will be seeing in the mainstream press in the next few hours.

Right now they are wrapping up a press conference from the team of the Voyager 1 spacecraft, in which they have described the spacecraft’s status.
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