posted 04-22-2024 02:26 PM               

NASA's Voyager 1 Resumes Sending Engineering Updates to Earth

After some inventive sleuthing, the mission team can — for the first time in five months — check the health and status of the most distant human-made object in existence.

For the first time since November, NASA's Voyager 1 spacecraft is returning usable data about the health and status of its onboard engineering systems. The next step is to enable the spacecraft to begin returning science data again. The probe and its twin, Voyager 2, are the only spacecraft to ever fly in interstellar space (the space between stars).

Voyager 1 stopped sending readable science and engineering data back to Earth on Nov. 14, 2023, even though mission controllers could tell the spacecraft was still receiving their commands and otherwise operating normally. In March, the Voyager engineering team at NASA's Jet Propulsion Laboratory in Southern California confirmed that the issue was tied to one of the spacecraft's three onboard computers, called the flight data subsystem (FDS). The FDS is responsible for packaging the science and engineering data before it's sent to Earth.

The team discovered that a single chip responsible for storing a portion of the FDS memory — including some of the FDS computer's software code — isn't working. The loss of that code rendered the science and engineering data unusable. Unable to repair the chip, the team decided to place the affected code elsewhere in the FDS memory. But no single location is large enough to hold the section of code in its entirety.

So they devised a plan to divide the affected code into sections and store those sections in different places in the FDS. To make this plan work, they also needed to adjust those code sections to ensure, for example, that they all still function as a whole. Any references to the location of that code in other parts of the FDS memory needed to be updated as well.

The team started by singling out the code responsible for packaging the spacecraft's engineering data. They sent it to its new location in the FDS memory on April 18. A radio signal takes about 22 ½ hours to reach Voyager 1, which is over 15 billion miles (24 billion kilometers) from Earth, and another 22 ½ hours for a signal to come back to Earth. When the mission flight team heard back from the spacecraft on April 20, they saw that the modification worked: For the first time in five months, they have been able to check the health and status of the spacecraft.

During the coming weeks, the team will relocate and adjust the other affected portions of the FDS software. These include the portions that will start returning science data.

Voyager 2 continues to operate normally. Launched over 46 years ago, the twin Voyager spacecraft are the longest-running and most distant spacecraft in history. Before the start of their interstellar exploration, both probes flew by Saturn and Jupiter, and Voyager 2 flew by Uranus and Neptune.

posted 06-16-2024 06:25 PM               

Voyager 1 Returning Science Data From All Four Instruments

NASA's Voyager 1 spacecraft is conducting normal science operations for the first time following a technical issue that arose in November 2023.

The team partially resolved the issue in April when they prompted the spacecraft to begin returning engineering data, which includes information about the health and status of the spacecraft. On May 19, the mission team executed the second step of that repair process and beamed a command to the spacecraft to begin returning science data. Two of the four science instruments returned to their normal operating modes immediately. Two other instruments required some additional work, but now, all four are returning usable science data.

The four instruments study plasma waves, magnetic fields, and particles. Voyager 1 and Voyager 2 are the only spacecraft to directly sample interstellar space, which is the region outside the heliosphere — the protective bubble of magnetic fields and solar wind created by the Sun.

While Voyager 1 is back to conducting science, additional minor work is needed to clean up the effects of the issue. Among other tasks, engineers will resynchronize timekeeping software in the spacecraft's three onboard computers so they can execute commands at the right time. The team will also perform maintenance on the digital tape recorder, which records some data for the plasma wave instrument that is sent to Earth twice per year. (Most of the Voyagers' science data is sent directly to Earth and not recorded.)

Voyager 1 is more than 15 billion miles (24 billion kilometers) from Earth, and Voyager 2 is more than 12 billion miles (20 billion kilometers) from the planet. The probes will mark 47 years of operations later this year. They are NASA's longest-running and most-distant spacecraft. Both spacecraft flew past Jupiter and Saturn, while Voyager 2 also flew past Uranus and Neptune.

posted 10-01-2024 06:13 PM               

NASA Turns Off Science Instrument to Save Voyager 2 Power

Mission engineers at NASA have turned off the plasma science instrument aboard the Voyager 2 spacecraft due to the probe's gradually shrinking electrical power supply.

Traveling more than 12.8 billion miles (20.5 billion kilometers) from Earth, the spacecraft continues to use four science instruments to study the region outside our heliosphere, the protective bubble of particles and magnetic fields created by the Sun. The probe has enough power to continue exploring this region with at least one operational science instrument into the 2030s.

Mission engineers have taken steps to avoid turning off a science instrument for as long as possible because the science data collected by the twin Voyager probes is unique. No other human-made spacecraft has operated in interstellar space, the region outside the heliosphere.

The plasma science instrument measures the amount of plasma (electrically charged atoms) and the direction it is flowing. It has collected limited data in recent years due to its orientation relative to the direction that plasma is flowing in interstellar space.

Both spacecraft are powered by decaying plutonium and lose about 4 watts of power each year. After the twin Voyagers completed their exploration of the giant planets in the 1980s, the mission team turned off several science instruments that would not be used in the study of interstellar space. That gave the spacecraft plenty of extra power until a few years ago. Since then, the team has turned off all onboard systems not essential for keeping the probes working, including some heaters. In order to postpone having to shut off another science instrument, they also adjusted how Voyager 2' voltage is monitored.

Monitoring Results

On Sept. 26, engineers issued the command to turn off the plasma science instrument. Sent by NASA's Deep Space Network, it took 19 hours to reach Voyager 2, and the return signal took another 19 hours to reach Earth.

Mission engineers always carefully monitor changes being made to the 47-year-old spacecraft's operations to ensure they don't generate any unwanted secondary effects. The team has confirmed that the switch-off command was executed without incident and the probe is operating normally.

In 2018, the plasma science instrument proved critical in determining that Voyager 2 left the heliosphere. The boundary between the heliosphere and interstellar space is demarcated by changes in the atoms, particles, and magnetic fields that instruments on the Voyagers can detect. Inside the heliosphere, particles from the Sun flow outward, away from our nearest star. The heliosphere is moving through interstellar space, so at Voyager 2's position near the front of the solar bubble, the plasma flows in almost the opposite direction of the solar particles.

The plasma science instrument consists of four "cups." Three cups point in the direction of the Sun and observed the solar wind while inside the heliosphere. A fourth points at a right angle to the direction of the other three and has observed the plasma in planetary magnetospheres, the heliosphere, and now, interstellar space.

When Voyager 2 exited the heliosphere, the flow of plasma into the three cups facing the Sun dropped off dramatically. The most useful data from the fourth cup comes only once every three months, when the spacecraft does a 360-degree turn on the axis pointed toward the Sun. This factored into the mission's decision to turn this instrument off before others.

The plasma science instrument on Voyager 1 stopped working in 1980 and was turned off in 2007 to save power. Another instrument aboard Voyager 2, called the plasma wave subsystem, can estimate the plasma density when eruptions from the Sun drive shocks through the interstellar medium, producing plasma waves.

The Voyager team continues to monitor the health of the spacecraft and its available resources to make engineering decisions that maximize the mission's science output.

posted 03-06-2025 07:30 AM               

NASA Turns Off Two Voyager Science Instruments to Extend Mission

The farthest-flung human-made objects will be able to take their science-gathering even farther, thanks to these energy-conserving measures.

Mission engineers at NASA's Jet Propulsion Laboratory in Southern California turned off the cosmic ray subsystem experiment aboard Voyager 1 on Feb. 25 and will shut off Voyager 2's low-energy charged particle instrument on March 24. Three science instruments will continue to operate on each spacecraft. The moves are part of an ongoing effort to manage the gradually diminishing power supply of the twin probes.

Launched in 1977, Voyagers 1 and 2 rely on a radioisotope power system that generates electricity from the heat of decaying plutonium. Both lose about 4 watts of power each year.

"The Voyagers have been deep space rock stars since launch, and we want to keep it that way as long as possible," said Suzanne Dodd, Voyager project manager at JPL. "But electrical power is running low. If we don't turn off an instrument on each Voyager now, they would probably have only a few more months of power before we would need to declare end of mission."

The two spacecraft carry identical sets of 10 science instruments. Some of the instruments, geared toward collecting data during planetary flybys, were turned off after both spacecraft completed their exploration of the solar system's gas giants.

The instruments that remained powered on well beyond the last planetary flyby were those the science team considered important for studying the solar system's heliosphere, a protective bubble of solar wind and magnetic fields created by the Sun, and interstellar space, the region outside the heliosphere. Voyager 1 reached the edge of the heliosphere and the beginning of interstellar space in 2012; Voyager 2 reached the boundary in 2018. No other human-made spacecraft has operated in interstellar space.

Last October, to conserve energy, the project turned off Voyager 2's plasma science instrument, which measures the amount of plasma — electrically charged atoms — and the direction it is flowing. The instrument had collected only limited data in recent years due to its orientation relative to the direction that plasma flows in interstellar space. Voyager 1's plasma science instrument had been turned off years ago because of degraded performance.

Interstellar Science Legacy

The cosmic ray subsystem that was shut down on Voyager 1 last week is a suite of three telescopes designed to study cosmic rays, including protons from the galaxy and the Sun, by measuring their energy and flux. Data from those telescopes helped the Voyager science team determine when and where Voyager 1 exited the heliosphere.

Scheduled for deactivation later this month, Voyager 2's low-energy charged particle instrument measures the various ions, electrons, and cosmic rays originating from our solar system and galaxy. The instrument consists of two subsystems: the low-energy particle telescope for broader energy measurements, and the low-energy magnetospheric particle analyzer for more focused magnetospheric studies.

Both systems use a rotating platform so that the field of view is 360 degrees, and the platform is powered by a stepper motor that provides a 15.7-watt pulse every 192 seconds. The motor was tested to 500,000 steps — enough to guarantee continuous operation through the mission's encounters with Saturn, which occurred in August 1980 for Voyager 2. By the time it is deactivated on Voyager 2, the motor will have completed more than 8.5 million steps.

"The Voyager spacecraft have far surpassed their original mission to study the outer planets," said Patrick Koehn, Voyager program scientist at NASA Headquarters in Washington. "Every bit of additional data we have gathered since then is not only valuable bonus science for heliophysics, but also a testament to the exemplary engineering that has gone into the Voyagers — starting nearly 50 years ago and continuing to this day."

Addition Through Subtraction

Mission engineers have taken steps to avoid turning off science instruments for as long as possible because the science data collected by the twin Voyager probes is unique. With these two instruments turned off, the Voyagers should have enough power to operate for about a year before the team needs to shut off another instrument on both spacecraft.

In the meantime, Voyager 1 will continue to operate its magnetometer and plasma wave subsystem. The spacecraft's low-energy charged particle instrument will operate through the remainder of 2025 but will be shut off next year.

Voyager 2 will continue to operate its magnetic field and plasma wave instruments for the foreseeable future. Its cosmic ray subsystem is scheduled to be shut off in 2026.

With the implementation of this power conservation plan, engineers believe the two probes could have enough electricity to continue operating with at least one science instrument into the 2030s. But they are also mindful that the Voyagers have been weathering deep space for 47 years and that unforeseen challenges could shorten that timeline.

Long Distance

Voyager 1 and Voyager 2 remain the most distant human-made objects ever built. Voyager 1 is more than 15 billion miles (25 billion kilometers) away. Voyager 2 is over 13 billion miles (21 billion kilometers) from Earth.

In fact, due to this distance, it takes over 23 hours to get a radio signal from Earth to Voyager 1, and 19½ hours to Voyager 2.

"Every minute of every day, the Voyagers explore a region where no spacecraft has gone before," said Linda Spilker, Voyager project scientist at JPL. "That also means every day could be our last. But that day could also bring another interstellar revelation. So, we're pulling out all the stops, doing what we can to make sure Voyagers 1 and 2 continue their trailblazing for the maximum time possible."

posted 05-15-2025 06:35 PM               

NASA's Voyager 1 Revives Backup Thrusters Before Command Pause

The mission team wanted to fix the thrusters, deemed unusable decades ago, before the radio antenna that sends commands to the probe went offline for upgrades.

Engineers at NASA's Jet Propulsion Laboratory in Southern California have revived a set of thrusters aboard the Voyager 1 spacecraft that had been considered inoperable since 2004. Fixing the thrusters required creativity and risk, but the team wants to have them available as a backup to a set of active thrusters whose fuel tubes are experiencing a buildup of residue that could cause them to stop working as early as this fall.

In addition, the mission needed to ensure the availability of the long-dormant thrusters before May 4, when the Earth-bound antenna that sends commands to Voyager 1 and its twin Voyager 2 went offline for months of upgrades.

Thruster Clogging

The Voyagers launched in 1977 and are hurtling through interstellar space at around 35,000 mph (56,000 kph). Both spacecraft rely on a set of primary thrusters to gently pivot them up and down as well as to the right and left in order to keep their antennas pointed at Earth so they can send back data and receive commands. Within the primary set of thrusters are other thrusters that control the spacecraft's roll motion. Seen from Earth, the roll motion rotates the antenna like a vinyl record to keep each Voyager pointed at a guide star it uses to orient itself. Both spacecraft have a primary and backup set for these roll movements.

(Another set of thrusters, intended to change the spacecrafts' trajectory during the flybys of the outer planets, were revived on the spacecraft in 2018 and 2019, but they can't induce roll motion.)

To manage the clogging tubes in the thrusters, engineers switch between the sets of primary, backup, and trajectory thrusters of both Voyagers. But on Voyager 1, the primary roll thrusters stopped working in 2004 after losing power in two small internal heaters. Engineers determined the broken heaters were likely unfixable and opted to rely solely on Voyager 1's backup roll thrusters to orient the star tracker.

"I think at that time, the team was OK with accepting that the primary roll thrusters didn't work, because they had a perfectly good backup," said Kareem Badaruddin, Voyager mission manager at JPL, which manages the mission for NASA. "And, frankly, they probably didn't think the Voyagers were going to keep going for another 20 years."

But without the ability to control the spacecraft's roll motion, a variety of issues would arise that might threaten the mission, so the engineering team decided to reexamine the 2004 thruster failure. They began to suspect that an unexpected change or disturbance in the circuits that control the heaters' power supply had effectively flipped a switch to the wrong position. If they could turn the switch back to its original position, the heaters might work again, enabling them to reactivate the primary roll thrusters and use them if the backup roll thrusters that have been used since 2004 become completely clogged.

Communications Pause

The solution required some puzzle-solving. The team would have to turn on the dormant roll thrusters, then try fixing and restarting the heaters. If, during that time, the spacecraft's star tracker drifted too far from the guide star, the long-dormant roll thrusters would automatically fire (thanks to the spacecraft's programming). And if the heaters were still off when they fired, it could trigger a small explosion, so the team needed to get the star tracker pointed as precisely as possible.

It would be a race, and the team faced additional time pressure: From May 4, 2025, through February 2026, Deep Space Station 43 (DSS-43), a 230-foot-wide (70-meter-wide) antenna in Canberra, Australia, that's part of NASA's Deep Space Network, would be undergoing upgrades. It would be offline for most of that time, with brief periods of operation in August and December.

Although the Deep Space Network has three complexes equally spaced around the globe (in Goldstone, California, and Madrid, in addition to Australia) to ensure constant contact with spacecraft as Earth rotates, DSS-43 is the only dish with enough signal power to send commands to the Voyagers.

"These antenna upgrades are important for future crewed lunar landings, and they also increase communications capacity for our science missions in deep space, some of which are building on the discoveries Voyager made," said Suzanne Dodd, Voyager project manager and director of the Interplanetary Network at JPL, which manages the Deep Space Network for NASA. "We've been through downtime like this before, so we're just preparing as much as we can."

The team wanted to make sure the long-dormant thrusters would be available when the dish is back online briefly in August, by which time the thrusters currently in use on Voyager 1 might be completely clogged.

The advance work paid off: On March 20, the team watched as the spacecraft executed their commands. Because of Voyager's distance, the radio signal takes over 23 hours to travel from the spacecraft to Earth, meaning everything the team saw happening had occurred almost a day earlier. If the test had failed, Voyager might already have been in danger. But within 20 minutes, the team saw the temperature of the thruster heaters rise dramatically and knew they had succeeded.

"It was such a glorious moment. Team morale was very high that day," said Todd Barber, the mission's propulsion lead at JPL. "These thrusters were considered dead. And that was a legitimate conclusion. It's just that one of our engineers had this insight that maybe there was this other possible cause and it was fixable. It was yet another miracle save for Voyager."