Posted on by John Williams

Fly Along With Voyager

Fly along with NASA's Voyager spacecraft as the twin probes head towards interstellar space. In this artist's concept, a regularly updated gauge using data from the two spacecraft will indicate the levels of particles that originate from far outside our solar system and those that originate from inside our solar bubble. Those are two of the three signs scientists expect to see in interstellar space. The other sign is a change in the direction of the magnetic field. Image credit: NASA/JPL-Caltech

Far away, deep in the dark, near the edge of interstellar space, Voyager 1 and 2 are hurtling near the tenuous edge of the magnetic bubble surrounding the Sun known as the heliosphere and NASA wants you to ride along.

The Voyager website sports a new feature showing cosmic ray data. NASA’s Eyes on the Solar System, a popular Web-based interactive tool, contains a new Voyager module, that not only lets you ride along for the Voyagers’ journeys but also shows important scientific data flowing from the spacecraft.

[Warning:Play with this tool at your own risk. Interacting with this online feature can seriously impact your time; in an educational way, of course!]

As Voyager 1 explores the outer limits of the heliosphere, where the breath from our Sun is just a whisper, scientists are looking for three key signs that the spacecraft has left our solar system and entered interstellar space, or the space between stars. Voyager 1 began heading for the outer Solar System after zipping through the Saturn system in 1980.

The new module contains three gauges, updated every six hours from real data from Voyager 1 and 2, that indicate the level of fast-moving particles, slower-moving particles and the direction of the magnetic field. Fast-moving charged particles, mainly protons, come from distant stars and originate from outside the heliosphere. Slower-moving particles, also mainly protons, come from within the heliosphere. Scientists are looking for the levels of outside particles to jump dramatically while inside particles dip. If these levels hold steady, it means the Voyager spacecraft no longer feel the wind from our Sun and the gulf between stars awaits.

Over the past couple of years, data from Voyager 1, the most distant man-made object, show a steady increase of high-powered cosmic radiation indicating the edge is near, scientists say. Voyager 1 appears to have reached the last region before interstellar space. Scientists dubbed the region the “magnetic highway.” Particles from outside are streaming in while particles from inside are streaming out. Voyager 2’s instruments detect slight drops in inside particles but scientists don’t think the probe has entered the area yet.

Scientists also expect a change in the direction of the magnetic field. While particle data is updated every six hours, analyses of the magnetic field data usually takes a few months to prepare.

A snapshot riding along with Voyager 1's looking back at the Sun and inner solar system. The positions of Voyager 2 and Pioneers 10 and 11 show within the viewport as well.
A snapshot riding along with Voyager 1’s looking back at the Sun and inner solar system. The positions of Voyager 2 and Pioneers 10 and 11 show within the viewport as well.

Although launched first, Voyager 2 lags behind its twin Voyager 1 by more than 20 times the distance between the Earth and the Sun. Voyager 2 blasted off August 20, 1977 aboard a Titan-Centaur rocket from Cape Canaveral, Florida. The nuclear-powered craft visited Jupiter and Saturn with an additional mission, called the Grand Tour, to study Uranus and Neptune. Voyager 1 launched two weeks later on September 5, 1977. With a faster flight path, Voyager 1 arrived at Jupiter four months before its sister craft. Voyager 1 went on to study Saturn before using the ringed planet’s gravity field to slingshot it up and out of the plane of the solar system toward the constellation Ophiuchus, the Serpent Bearer.

NASA’s Eyes on the Solar System allows viewers to hitch a ride with any of NASA’s spacecraft as they explore the solar system. Time can be slowed for a near approach of a moon or asteroid or sped up to coast between the planets. Watch close at just the right moment and you can witness one of the spacecrafts roll maneuvers. All spacecraft movements are based on actual spacecraft navigation data.

Check out the Voyager module here, and check out the rest of the the Solar System here at Eyes on the Solar System.

Posted on by Nancy Atkinson

Scientists Say Voyager 1 Has Left the Solar System, But Has It Really?

The edge of the solar system. Image Credit: NASA/JPL-Caltech

A new paper out today reports that the Voyager 1 spacecraft appears to have traveled beyond the influence of the Sun and exited the heliosphere. However, the data they cite is the same as what NASA Voyager scientists claimed in December 2012 was just a new region at the edge of the solar system that scientists previously didn’t know was there. They called it a “highway” of magnetic particles, shepherding Voyager 1 out into interstellar space, whereas the new paper put out by the American Geophysical Union says Voyager 1 has crossed a “heliocliff” and into interstellar space.

JPL spokesperson Jia-Rui Cook had just heard of the paper when Universe Today called this morning to verify the findings of the new paper. “Our last statement about this was the critical thing we were looking for was a change in the magnetic field data,” she said via phone. “This paper does not appear to address the magnetic field data.”

UPDATE: NASA has issued a statement regarding this issue:

“The Voyager team is aware of reports today that NASA’s Voyager 1 has left the solar system,” said Edward Stone, Voyager project scientist based at the California Institute of Technology, Pasadena, Calif. “It is the consensus of the Voyager science team that Voyager 1 has not yet left the solar system or reached interstellar space. In December 2012, the Voyager science team reported that Voyager 1 is within a new region called ‘the magnetic highway’ where energetic particles changed dramatically. A change in the direction of the magnetic field is the last critical indicator of reaching interstellar space and that change of direction has not yet been observed.”

Cook told Universe Today that Voyager Project Scientist Ed Stone was out of the country, and she was trying to get in touch with him to verify the paper’s claims that Voyager has left the solar system, and he obviously wasted no time in setting the record straight.

In another update, the AGU reissued the press release with a different title to “to better represent the findings reported in the study.” The initial headline was “Voyager 1 Has Left the Solar System, Sudden Changes in Cosmic Rays Indicate,” and the new headline is “Voyager 1 has entered a new region of space, sudden changes in cosmic rays indicate.” So, basically, the new paper was just iterating the previous findings.

(End of updates)

The authors of the new paper, William Webber and F.B. McDonald, cite the events of last summer when Voyager 1 measured drastic changes in radiation levels, more than 18 billion km (11 billion miles) from the Sun. On July 28, 2012 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. But then the bottom dropped out at the end of August, where anomalous cosmic rays (cosmic rays trapped in the outer heliosphere) all but vanished, dropping to less than 1 percent of previous amounts. At the same time, galactic cosmic rays – cosmic radiation from outside of the solar system – spiked to levels not seen since Voyager’s launch, with intensities as much as twice previous levels.

“Within just a few days, the heliospheric intensity of trapped radiation decreased, and the cosmic ray intensity went up as you would expect if it exited the heliosphere,” said Webber in an AGU press release. Webber is a professor emeritus of astronomy at New Mexico State University in Las Cruces. He called this transition boundary the “heliocliff.”

In the Geophysical Research Letters article, the authors say, “It appears that [Voyager 1] has exited the main solar modulation region, revealing [hydrogen] and [helium] spectra characteristic of those to be expected in the local interstellar medium.”

However, last December in a NASA press conference, the Voyager team said they infered this region is still inside our solar bubble because the direction of the magnetic field lines has not changed. The direction of these magnetic field lines is predicted to change when Voyager breaks through to interstellar space.

“We believe this is the last leg of our journey to interstellar space,” Stone said during the press conference. “Our best guess is it’s likely just a few months to a couple years away. The new region isn’t what we expected, but we’ve come to expect the unexpected from Voyager.”

We’ll provide more information on this discrepancy between the interpretations of the events when we hear more from the Jet Propulsion Laboratory.

Posted on by Nancy Atkinson

Voyager 1 May Have Left the Solar System

Number of particles from the Sun hitting Voyager 1. Credit: NASA

While there’s no official word from NASA on this, the buzz around the blogosphere is that Voyager 1 has left the Solar System. The evidence comes from this graph, above, which shows the number of particles, mainly protons, from the Sun hitting Voyager 1 across time. A huge drop at the end of August hints that Voyager 1 may now be in interstellar space. The last we heard from the Voyager team was early August, and they indicated that on July 28, 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. But then the bottom dropped out at the end of August.

The Voyager team has said they have been seeing two of three key signs of changes expected to occur at the boundary of interstellar space. In addition to the drop in particles from the Sun, they’ve also seen a jump in the level of high-energy cosmic rays originating from outside our Solar System.

The third key sign would be the direction of the magnetic field. No word on that yet, but 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.

“These are thrilling times for the Voyager team as we try to understand the quickening pace of changes as Voyager 1 approaches the edge of interstellar space,” said Edward Stone, the Voyager project scientist for the entire mission, who was quoted in early August. “We are certainly in a new region at the edge of the solar system where things are changing rapidly. But we are not yet able to say that Voyager 1 has entered interstellar space.”

Stone added that the data are changing in ways that the team didn’t expect, “but Voyager has always surprised us with new discoveries.”

Voyager 1 launched on Sept. 5, 1977, is approximately 18 billion kilometers (11 billion miles) from the Sun. Voyager 2, which launched on Aug. 20, 1977, is close behind, at 15 billion km (9.3 billion miles) from the Sun.

Sources: NASA, Eric Berger/ Houston Chronicle, Scientific American

Posted on by Tammy Plotner

Voyager Mission Is Cooling Its Jets

Artist's concept of NASA's Voyager spacecraft. Image credit: NASA/JPL-Caltech

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Or, more appropriately, Voyager 1 is cooling its instruments. To help conserve power, the mission managers at NASA have decided to cut the electricity to a heating element – one that’s part of the nearby infrared spectrometer that’s not been in operation for some 14 years. This power cut will lower the temperature of the ultraviolet spectrometer by about 23 degrees Celsius (41 degrees Fahrenheit)… a temperature that’s mild compared to the below minus 79 degrees Celsius (minus 110 degrees Fahrenheit) that the instrument has dropped to in previous times. It’s not a drastic measure, however, but all part of a crucial plan to manage electrical power to keep the spacecraft operational and transmitting data for another 13 years.

Just because the power is cut back doesn’t mean the instrument quit working. At the present, the spectrometer is continuing to gather and transmit data. The resilient system was designed to work in temperatures as frosty as minus 35 degrees Celsius (minus 31 degrees Fahrenheit) and has even operated beyond the call of duty when heaters were switched off over the last 17 years. While it was taking a chance that the equipment might malfunction, the engineering team was confident since the spectrometer has worked at minus 56 degrees Celsius (minus 69 degrees Fahrenheit.) since 2005. “The spectrometer is likely operating at a temperature somewhat lower than minus 79 degrees Celsius, or minus 110 degrees Fahrenheit,” says the team. “But the temperature detector does not go any lower.”

While it has been awhile since Voyager 1’s encounter with Jupiter and Saturn which made the spectrometer busy, that doesn’t mean its data will be disregarded. Both scientists and mission management specialists will continue to monitor performance levels and an international team of scientists will further review spectrometer data.

Live long and prosper, Voyager!

Original Story Source: JPL News Release.

Posted on by Nancy Atkinson

New Movie Revives Old Voyager Data of Jupiter’s Clouds

I remember, some time after Voyager 1 flew past Jupiter, of seeing a television show that played a movie of Jupiter’s bands of rolling clouds. I was mesmerized. Now, UnmannedSpaceflight.com member Bjorn Jonsson has re-mastered that data into a crisp, clear video. I find it just as mesmerizing! In his description, Jonsson says, “The movie is based on 58 orange-green-blue color composites obtained on every Jovian rotation from January 6 to January 29, 1979. Over this period Voyager 1’s distance from Jupiter dropped from 58 to 36 million km so the resolution and sharpness of the frames increases from start to finish. The 58 frames were tweened, increasing the number of frames by a factor of 8 (that is, 7 synthetic frames are inserted between each real frame).”

You can see more of Jonsson’s work at his website.

Credit: NASA/JPL/Processed by Bjorn Jonsson

Posted on by Nancy Atkinson

Voyager Spacecraft Will Soon Enter Interstellar Space

After 33 years, NASA’s twin Voyager spacecraft are still actively working – gathering information, communicating with Earth, (and Tweeting!), and they are about to go where no space probe has gone before: into interstellar space. Because of the unfamiliar nature of the heliosphere, and especially its outermost layer, the heliosheath, it is not known exactly when the Voyagers will actually reach the “great beyond.”

“The heliosheath is 3 to 4 billion miles (4.8 to 6 billion km) in thickness,” said Voyager Project Scientist, Ed Stone. “That means we’ll be out within five years or so.” The V’ger’s Plutonium 238 heat source will keep the critical subsystems running through at least 2020, but after that, Stone says, “Voyager will become our silent ambassador to the stars.”

This video features highlights of the Voyager journeys to the outer planets and the discoveries they have made, and shows where they are now and where they are headed.

More info on the Voyagers, and here, too.

Posted on by Nancy Atkinson

Aged Voyager 1 Does In-flight Gymnastics for Science

Voyager 1 Mission
Artist impression of Voyager 1, the first probe to traverse the heliosheath (NASA)

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She might be old, but she’s still got it where it counts. The 33-year old Voyager 1 probe, flying out near the edge of the solar system conducted a roll program, spinning 70 degrees counterclockwise, and held the position by spinning gyroscopes for two hours, 33 minutes. Voyager performed its in-flight gymnastics on March 7, 2011 and scientists hope the maneuver will help answer the question of which direction is the sun’s stream of charged particles turns when it nears the edge of the solar system.

“Even though Voyager 1 has been traveling through the solar system for 33 years, it is still a limber enough gymnast to do acrobatics we haven’t asked it to do in 21 years,” said Suzanne Dodd, Voyager project manager, based at NASA’s Jet Propulsion Laboratory. “It executed the maneuver without a hitch, and we look forward to doing it a few more times to allow the scientists to gather the data they need.”

Voyager needed to get in the right orientation to enable its Low Energy Charged Particle instrument to gather data.

The last time either of the two Voyager spacecraft rolled and stopped in a gyro-controlled orientation was Feb. 14, 1990, when Voyager 1 snapped a family portrait of the planets. See the image here.

The two Voyager spacecraft are traveling through a turbulent area known as the heliosheath,the outer shell of a bubble around our solar system created by the solar wind. The solar wind is traveling outward from the sun at a million miles per hour. Scientists think the wind must turn as it approaches the heliosheath where it makes contact with the interstellar wind — , which originates in the region between stars.

In June 2010, when Voyager 1 was about 17 billion kilometers (about 11 billion miles) away from the sun, data from the Low Energy Charged Particle instrument began to show that the net outward flow of the solar wind was zero. That zero reading has continued since. The Voyager science team doesn’t think the wind has disappeared in that area, but perhaps has just turned a corner. But where does it go from there: up, down or to the side?

“Because the direction of the solar wind has changed and its radial speed has dropped to zero, we have to change the orientation of Voyager 1 so the Low Energy Charged Particle instrument can act like a kind of weather vane to see which way the wind is now blowing,” said Edward Stone, Voyager project manager. “Knowing the strength and direction of the wind is critical to understanding the shape of our solar bubble and estimating how much farther it is to the edge of interstellar space.”

Voyager engineers performed a test roll and hold back on Feb. 2, just to make sure the spacecraft was still capable. No problems for the old girl, and spacecraft had no problem in reorienting itself and locking back onto its guide star, Alpha Centauri.

This artist's concept shows NASA's two Voyager spacecraft exploring a turbulent region of space known as the heliosheath, the outer shell of the bubble of charged particles around our sun. Image credit: NASA/JPL-Caltech

There will be five more of these maneuvers over the next seven days, with the longest hold lasting three hours 50 minutes. The Voyager team plans to execute a series of weekly rolls for this purpose every three months.

Over the next few months, scientists will analyze the data.

“We do whatever we can to make sure the scientists get exactly the kinds of data they need, because only the Voyager spacecraft are still active in this exotic region of space,” said Jefferson Hall, Voyager mission operations manager at JPL. “We were delighted to see Voyager still has the capability to acquire unique science data in an area that won’t likely be traveled by other spacecraft for decades to come.”

Voyager 2 was launched on Aug. 20, 1977. Voyager 1 was launched on Sept. 5, 1977. On March 7, Voyager 1 was 17.4 billion kilometers (10.8 billion miles) away from the sun. Voyager 2 was 14.2 billion kilometers (8.8 billion miles) away from the sun, on a different trajectory.

The solar wind’s outward flow has not yet diminished to zero where Voyager 2 is exploring, but that may happen as the spacecraft approaches the edge of the bubble in the years ahead.

Voyager is just another good old girl.

Source: JPL

Posted on by Nancy Atkinson

Voyager 1 Has Outdistanced the Solar Wind

Voyager 1 Mission
Artist impression of Voyager 1, the first probe to traverse the heliosheath (NASA)

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The venerable Voyager spacecraft are truly going where no one has gone before. Voyager 1 has now reached a distant point at the edge of our solar system where it is no longer detecting the solar wind. At a distance of about 17.3 billion km (10.8 billion miles) from the Sun, Voyager 1 has crossed into an area where the velocity of the hot ionized gas, or plasma, emanating directly outward from the sun has slowed to zero. Scientists suspect the solar wind has been turned sideways by the pressure from the interstellar wind in the region between stars.

“The solar wind has turned the corner,” said Ed Stone, Voyager project scientist based at the California Institute of Technology in Pasadena, Calif. “Voyager 1 is getting close to interstellar space.”


The event is a major milestone in Voyager 1’s passage through the heliosheath, the turbulent outer shell of the sun’s sphere of influence, and the spacecraft’s upcoming departure from our solar system.

Since its launch on Sept. 5, 1977, Voyager 1’s Low-Energy Charged Particle Instrument has been used to measure the solar wind’s velocity.

When the speed of the charged particles hitting the outward face of Voyager 1 matched the spacecraft’s speed, researchers knew that the net outward speed of the solar wind was zero. This occurred in June, when Voyager 1 was about 10.6 billion miles from the sun.

However, velocities can fluctuate, so the scientists watched four more monthly readings before they were convinced the solar wind’s outward speed actually had slowed to zero. Analysis of the data shows the velocity of the solar wind has steadily slowed at a rate of about 45,000 mph each year since August 2007, when the solar wind was speeding outward at about 130,000 mph. The outward speed has remained at zero since June.

“When I realized that we were getting solid zeroes, I was amazed,” said Rob Decker, a Voyager Low-Energy Charged Particle Instrument co-investigator and senior staff scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. “Here was Voyager, a spacecraft that has been a workhorse for 33 years, showing us something completely new again.”

Scientists believe Voyager 1 has not crossed the heliosheath into interstellar space. Crossing into interstellar space would mean a sudden drop in the density of hot particles and an increase in the density of cold particles. Scientists are putting the data into their models of the heliosphere’s structure and should be able to better estimate when Voyager 1 will reach interstellar space. Researchers currently estimate Voyager 1 will cross that frontier in about four years.

Our sun gives off a stream of charged particles that form a bubble known as the heliosphere around our solar system. The solar wind travels at supersonic speed until it crosses a shockwave called the termination shock. At this point, the solar wind dramatically slows down and heats up in the heliosheath.

A sister spacecraft, Voyager 2, was launched in Aug. 20, 1977 and has reached a position 8.8 billion miles from the sun. Both spacecraft have been traveling along different trajectories and at different speeds. Voyager 1 is traveling faster, at a speed of about 38,000 mph, compared to Voyager 2’s velocity of 35,000 mph. In the next few years, scientists expect Voyager 2 to encounter the same kind of phenomenon as Voyager 1.

The results were presented at the American Geophysical Union meeting in San Francisco.

Source: NASA