Record-Breaking Voyager Spacecraft Begin to Power Down

If the stars hadn't aligned, two of the most amazing spaceships ever launched wouldn't have made it to the ground. The stars were planets in the solar system. 60 years ago, they were slowly wheeling into an array that hadn't happened during the presidency of Thomas Jefferson. The rare planetary set piece was mostly hidden. A graduate student at the California Institute of Technology called attention to it.

The Soviet Union had launched Sputnik 1, the first artificial satellite, eight years earlier. He was tasked with finding the most efficient way to send a space probe to Jupiter or even out to other planets. In the late 1970s and early 1980s, all four giant planets were strung like pearls on a necklace.

It was a coincidence that a space vehicle could get a boost in speed from the pull of each giant planet it passed. The flight time between Earth and Neptune would be cut in half thanks to the repeated gravity assists. It was only once every 176 years that the alignment took place. A spaceship would have to be launched by the mid-1970s to get to the planets.

Two space vehicles would be built by NASA to take advantage of that once-in-more-than-a-lifetime opportunity. In the summer of 1977 the two identical ships were launched. Data is sent back to Earth every day from beyond the solar system's most distant known planets. They have traveled farther and stayed longer than any other craft. The boundary between the sun's sphere of influence and the rest of the galaxy has been understood. They will hold the distinction of being the first human-made objects to do so for a long time. The original plan was for the missions to last four years.

The first close-up views of the moons of Jupiter and Saturn were given to researchers four decades ago. Three years after it flew past Neptune, the first spaceship to fly past Uranus was passed by another craft. It is the only craft to have done this. They're both delighted and baffling theorists with a series of unexpected discoveries about the unexplored region.

Their remarkable journey is coming to an end. NASA plans to turn off some of the Voyagers' systems this year in order to extend their journeys by about 15 years. It is a difficult time for the scientists who have worked on the mission. They are facing the end of a project that exceeded their expectations.

McNutt is a physicist at the APL who has devoted a lot of his career to the Voyagers. We have done ten times the warranty on the darn things.

Congress was not cooperating at first. NASA drew up plans for a Grand Tour that would send probes to the giant planets and dwarf planet. It wasambitious. It cost a lot. It was turned down by congress. A few months before their launch, Linda Spilker, a JPL planetary scientist, started working on the mission. It was reduced because of costs.

A scaled-down version of the Grand Tour was approved by congress. There were to be just two planets. NASA's engineers went about designing vehicles that could stand the test of time. They wanted the twin probes to extend their itinerary to other planets.

The prime mission was four years, says Suzanne Dodd, the project manager who came back in 2010 after 20 years away. If an engineer had a choice to put in a part that was 10 percent more expensive but not needed for a four-year mission, they did that. They wouldn't let management know. She says that it's even more remarkable that the scientists were able to build two spaceships.

This was a new area for both engineering and navigation. At that time, the motto "failure is not an option" would not have been appropriate. NASA attempted to send a series of spaceships to the moon in the 1960's to survey future landing sites for crewed missions. One attempt succeeded after 12 failures.

Donald Gurnett said that in those days the failure rate was so high that they would always launch two spaceships. One of the original scientists on the Voyager team was a veteran of 40 other space missions. He talked to me a few weeks before he died. His only regret was that he wouldn't be around to see the next 10 years of data coming from Voyager.

The only craft that used a gravity assist to get to another planet was the Mariner 10 probe. The margin of error was measured in tens of minutes. Jupiter was ten times farther from Earth than Mercury. The asteroid belt would have to be traveled through to get to the planets. There had been a lot of debate about whether it was possible to get through the asteroid belt without being torn to shreds. He says that in the early 1970s, Pioneer 10 and 11 flew through it without a hitch.

The Voyagers needed some onboard intelligence to handle all these challenges. NASA's engineers used less than a hundred thousandth of the capacity of a typical phone to equip the vehicles' computers. The comparison of the two is not correct. The keys that open your car door have more memory than the computers that do the computations. The data collected by the instruments would be stored on eight-track tape recorders and sent back to Earth via a 23 watt transmitter. The weak transmitter can be compensated by carrying 12-foot wide dish antennas.

It felt like we were on top of the technology at the time, according to Alan. What was amazing was how fast that thing happened. The MJS 77 team built three spaceships within four years. The spaceship was rechristened before it was launched.

There are many scientists who have worked on the Voyagers. He was the last person to touch the spaceship. The two detectors were designed to measure the amount of charged particles in the sky. There was a small window in each detector that contained aluminum foil. It was feared that the technicians might have poked holes in the windows. He says they had to be inspected before launch. One of them was a little loose.

After its launch in March of 1979 the spaceship flew to Jupiter. In July of that year, there was a different trajectory of the ship. The vidicon cameras use red, green and blue filters to produce full-color images. The risk of blurred images is mitigated by the fact that they hardly spin as they speed through space. The crowd at JPL watched as the first pictures of Jupiter were transmitted by the craft.

There were TV monitors in all of the conference rooms. Each picture appeared on a monitor as the data came down. The expectation of what we would see when we got up was very exciting.

The first time he saw Jupiter's third-largest moon, Io, he was so excited he cried. He was on the Caltech campus when they showed a livestream of the images. There is a big picture of Io and it is all orange and black. I thought the Caltech students had pulled a prank and it was a picture of a bad pizza.

Io had a colorful appearance. The assumption had been that all moons in the solar system would be the same size. The diversity of moonscapes was not anticipated by anyone.

The first hint that there might be more than one type of moon in the sky came when the planets were a million miles from Jupiter. The low-energy charged particle detector system picked up some strange signals. Stamatios Krimigis is the former head of the space department at the APL and is the inventor of the LECP. The density of oxygen and sulfur ion went up by three orders of magnitude compared with the levels measured up to that point. His team thought the instrument was malfunctioning. There was nothing wrong with the data.

The mysteries were solved by the cameras of the Voyagers. The small world is the most active in the solar system. The only active volcanoes we knew of at the time were on Earth. There was a moon that was 10 times more active than Earth. Io's colors came from elements blasted from the moon's volcanos. The largest of Io's volcanoes, known as Pele, covers an area the size of France.

More than 30,000 pictures of Jupiter and its satellites were taken by the Voyagers. It felt like every picture brought a new discovery: Jupiter had rings, and one of Jupiter's moons was covered with a cracked icy crust. A kick of 35,700 miles per hour was given to the spaceship as they left the Jupiter system. They wouldn't have been able to reach space without it.

The group parted company at the planet. It took thousands of hits from dust grains for Voyager 1 to hurtle through the rings ofSaturn. There was only one person left to go to Uranus and Neptune. The planet Uranus was added to the list of ringed worlds in 1986. The discoveries were overshadowed when the space shuttle Challenger exploded shortly after launch. Christa McAuliffe, a high school teacher from New Hampshire who would have been the first civilian to travel into space, was one of the seven people killed in Challenger.

The highest wind speeds of any planet in the solar system were measured by Voyager 2. The surface temperature of Neptune's largest moon, Triton, was found to be 235 degrees Celsius, making it one of the most frigid places in the Solar System. Nitrogen gas and particles were released from ice volcanoes on the moon.

The images of Neptune and its moons would have been the last taken by either of the ships had it not been for astronomer Carl Sagan. The cameras on both probes were going to be turned off. There would be no photo ops after Neptune, only the endless void and impossibly distant stars.

NASA was urged to send one last series of images by the author. The probe took 60 final shots after it aimed its cameras back towards the inner solar system. Earth was captured from a distance of 3.8 billion miles by the Pale Blue Dot. The most distant portrait of our planet has been taken. Earth is barely visible in the image because it is obscured by wan sunlight. It doesn't have much of an effect.

The man who died in 1996 worked very hard to convince NASA that it was worth looking back at ourselves.

The one-way radio signal that travels at the speed of light takes 22 hours to reach the first one and 18 to reach the second one. They move away by a small amount of time every day. Their only link to Earth is NASA's Deep Space Network, a trio of tracking complexes located around the globe that enable continuous communication with the ground. The signals from the Voyagers are becoming fainter. Glen Nagle is an outreach and communications manager at the Deep Space Network in Australia. Everything makes noise. It gets harder and harder to hear the whispers from the space program.

As they are, those whispers have upended the expectations of what the astronomer would find. The boundary of space and the solar system are not related. The Oort cloud, a spherical collection of comet-like bodies bound by the sun's gravity, is part of the solar system. It will take at least another 300 years for the Voyagers to reach their full potential. It's much closer to the truth. The solar wind is a phenomenon.

The sun has a constant flow of charged particles and magnetic fields. The wind blows out from the sun like a balloon and forms what is called the heliosphere. The sun's magnetic field is pulled along by the solar wind. The boundary of the heliosphere is created by pressure from interstellar matter. There were different estimates of the distance to the heliopause before the voyagers.

Gurnett said that some of them were guesses. It was thought that the heliopause was as close to Jupiter as possible. The distance from 116 to 177AU was set by Gurnett in 1993. The distance between Earth and the sun is oneAU. He says that those numbers weren't very popular with his coworkers. 50AU was on the odometer by 1993 If the heliopause was at 120AU, we had another 70AU to spare. The Voyagers wouldn't leave the heliosphere for another 20 years if Gurnett was correct.

Is the support of Congress going to last for a long time? The funding was extended because of the expectation that the craft would cross the heliopause at 50AU. The spacecraft did not find any signs of transit. Cosmic rays that are low-energy can't reach the inner solar system because of the magnetic cocoon. It protects us from at least 75% of what's out there.

The ground team was waiting for a shift in the magnetic field to be registered. The magnetic field of the heliosphere is thought to have a different orientation than the interstellar magnetic field. The Voyagers didn't detect a change.

The 1993 estimates were correct. It took almost two decades for one of the Voyagers to make it to the heliopause. The mission narrowly survived threats to its funding and the team shrunk from hundreds of scientists and engineers to a few dozen close-knit lifers The majority of them are still on the job. You begin to regard people like family when you have a long-lived mission. We had our children with us. We would go on vacations together. Some of the younger people on the spaceship were not born when it was launched.

On August 25, 2012 the band of brothers and sisters received a reward for their dedication and perseverance. Some of the data it returned was odd. We didn't announce that we had reached space because we couldn't agree on the facts. There was a lot of discussion for a long time.

There was no sign of a change in the direction of the magnetic field despite the expected jump in plasma density. Shouldn't the switch have been visible if the vehicle had traveled from the sun's magnetic field to a region with a magnetic field from other stars? The person says that it was a big surprise. That continues to bother me. A lot of people are getting used to it.

It didn't detect a magnetic field shift when it reached the shoreline. The heliopause was encountered at 120AU from Earth, the same distance as six years ago. The heliosphere should expand and contract in line with the sun's 11-year cycle according to all of the models. During that time, the sun's wind changes. The heliopause should have been pushed farther out than 120AU if the models were correct. Krimigis says it was unexpected by everyone. The findings of the Voyagers have been found lacking in modeling.

The models of the interaction between the heliosphere and the environment are becoming more complex now that the Voyagers have some field data. The general picture is that our sun emerged from a hot, ionized region and entered a spotty, partly ionized area in the universe. The hot region is thought to have formed after a nearby star exploded at the end of its life and stripped electrons from its atoms. The boundary is similar to the seashore with all the water and the waves mixed up. Magnetic fields turn around in that region. The amount of turbulence seen can vary depending on the type of observation. The data shows little field variation at large scales but a lot of small-scale fluctuations around the heliopause. It is thought that at some point in the future, the spaceship will leave the roiling shoals behind and finally reach the unalloyed magnetic field.

Maybe that picture isn't right. Some researchers think that the Voyagers are still in the heliosphere. There is no reason for the magnetic fields in the heliosphere to have the same orientation. A model of the heliosphere that pushes its edge out by another 40AU has been worked on by Fisk and George.

Most people working in the field have been convinced by the dramatic increase in the amount of solar energy. It's difficult to argue that we're not in the real world. It's not like everythingfits. That is the reason we need a probe.

McNutt has been trying to get such a mission for a long time. Plans for a probe that could reach the heliosphere within 15 years and shave 20 years off the flight time of the first man-made object in the solar system were outlined by him and his colleagues. The outer edge of the heliosphere would be studied by the interstellar probe. The mission will be decided by the National Academies of Sciences, Engineering, and Medicine within the next two years.

One of the most important questions about the heliosphere could be answered by a probe. I want to know what the devil looks like if I'm looking from the outside. McNutt wants to know what's going on. We have no idea. It's like looking at a goldfish from a different perspective. The bowl needs to be seen 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. A computer model developed by astronomer Merav Opher and her colleagues at Boston University predicts that more turbulent dynamics will give the heliosphere a shape similar to a Cosmic Croak.

It's going to take more than one fight at a good science conference to see what's happening. It would be great to know what the area looks like.

Answering machines, VCRs, and pennies outlive their purpose. They use 50-year-old technology instead of the Voyagers. The amount of software on these instruments is very small. There are no chips. Thousands of lines of code were not enough to operate the spaceship. The mission lasted so long because almost everything was hardwired. Engineers don't know how to do this I don't know if it can be done. It's the last one of its type.

It will be difficult to say goodbye to these trail-blazers. It's difficult to see it ending. We achieved an amazing thing. We did get to the heliopause.

There are five remaining functioning instruments in Voyager 2 and 4. The heat from plutonium's decay into electricity is converted into electricity by a device. NASA has been forced into triage mode due to the decreasing power output. The mission's engineers turned off the cosmic-ray detector two years ago, which was crucial in determining the heliopause transit. The instrument was supposed to die.

The temperature dropped so low that the instrument kept working. It was absolutely amazing.

The two instruments that will be turned off are a magnetometer and a science instrument. They are kept in the body of the spaceship, where they are warm by the computers on board. The other instruments are on the ground. Dodd says that the instruments get very cold when the heating is turned off.

The Voyagers might last a while. If everything goes well, we may be able to extend the missions into the2030s. The power is the most important thing. The limit is that.

The journeys will go on even after the Voyagers are quiet. After 16,700 years, our nearest star, Proxima Centauri, will be passed by our next star, Voyager 2. For millions of years, they will circle the universe. After the sun collapses and the heliosphere ceases to exist, they will still be out there, more or less intact. They might be able to convey a final message at some point. If it's received, the recipients won't be humans.

Two records are used to carry the message. It's not your standard plastic version. These are encased in an aluminum cover and coated with gold. Images and sounds arecoded in the grooves of the Golden Records in order to give a sense of the world the Voyagers came from. There are pictures of children, dolphins, dancers and sunsets, as well as the sounds of crickets, falling rain and a mother kissing her child.

There is a message from Jimmy Carter. It says that the message was cast into the universe. Someday, having solved the problems we face, we would like to join a community of galactic civilization. Our hope and determination are represented in this record.