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Voyager 2’s Discoveries From Interstellar Space

In its journey beyond the boundary of the solar wind’s bubble, the probe observed some notable differences from its twin, Voyager 1.

By Kenneth Chang

The Voyager 2 spacecraft burst out of the bubble of gases expanding from the sun and into the wild of the Milky Way a year ago. It was the second spacecraft to cross that boundary and directly observe the interstellar medium. Its faster-moving twin, Voyager 1, made the crossing six years earlier, in August 2012.

Launched 42 years ago, when Jimmy Carter was president, the twin spacecraft have persisted far longer than envisioned, as has their ability to send scientific findings home to Earth.

In a series of papers published on Monday in Nature Astronomy, scientists report what Voyager 2 observed at the boundary of the solar wind’s bubble and beyond.

“We’re certainly surprised,” Edward C. Stone, the mission’s project scientist, said of the probe’s longevity during a news conference on Thursday. “We’re also wonderfully excited by the fact that they do. When the two Voyagers were launched, the space age was only 20 years old. It was hard to know at that time that anything could last over 40 years.”

In many ways, the measurements echoed Voyager 1’s: a jump in the density of particles accompanied by a sharp decrease in their speed, a shift in the magnetic fields.

Voyager 2 also noted some differences, which could give clues about the complicated dynamics in that region of the solar system.

The sun spews in all directions a continuous stream of particles called the solar wind traveling at a speed of a million miles per hour. The particles are mostly hydrogen, but, heated to some 3 million degrees Fahrenheit, the atoms are ripped apart into protons and electrons.

At a distance of more than 11 billion miles from the sun, the solar wind, thinning out, is increasingly buffeted by the flow of particles in the interstellar wind and a galactic magnetic field generated by the long ago explosions of distant stars. The interstellar wind is much cooler — just tens of thousands of degrees — and denser.

Voyager 2 is heading in a different direction than Voyager 1, which could explain some of the differences. The sun was also more active in 2012, near the maximum phase of its cycle of activity. The sun is now near its lull, known as the solar minimum.

With Voyager 1, the outward velocity of the solar wind dropped to zero long before the boundary; it was pushed sideways. With Voyager 2, the outward velocities fluctuated, sometimes dipping to zero but then rising again.

Curiously, the distances from the sun for the two crossings out of the solar system were similar. Scientists had expected that the bubble would be pushed outward during the solar maximum and collapse inward during the solar minimum.

“A lot of the models leave a lot to be desired,” Stamatios Krimigis, a scientists at the Johns Hopkins Applied Physics Laboratory in Laurel, Md., and the principal investigator of one of the Voyager instruments, said in an interview.

Voyager 2 also measured what scientists describe as a magnetic barrier, “like the pile-up of slowly moving cars on a major highway, a few miles ahead of the scene of an accident,” Leonard F. Burlaga, a scientist working with the spacecraft’s magnetometer, wrote in an email.

When solar wind slows, the density of particles increases and the magnetic field strengthens.

“Again, it’s like the cars, which turn away from the lanes of the accident and move slowly along the available lanes,” Dr. Burlaga said. “The cars are more densely spaced, the drivers are heated, but they eventually move along.”

The missions were originally designed to last four years to fly by Jupiter and Saturn. Voyager 2 also visited Uranus and Neptune. Voyager 2 still has five functioning instruments for measuring the void; Voyager 1 has four.

Both Voyagers are expected to last another five years or so until their batteries die out. Both are powered by electricity generated by the heat of radioactive plutonium. As the plutonium diminishes, the spacecraft receive less and less energy.

Once the Voyagers shut down, there will be no more data from beyond our solar system for years. Only one other spacecraft, the New Horizons probe that flew by Pluto in 2015 and visited another object in the distant Kuiper belt in January this year, is headed that way. But it is moving more slowly and its plutonium power will run out before it reaches interstellar space.

“Right now, when the Voyagers go offline, that’s kind of it unless we do something else,” said Ralph McNutt, a physicist at the Johns Hopkins Applied Physics Laboratory.

Dr. McNutt is leading a study to look at what it might take to build an ultrafast spacecraft that could leave the solar system in a hurry. The development of NASA’s long-delayed giant rocket, the Space Launch System, makes that mission more plausible.

The mission could also perform what is known as an Oberth maneuver, named after Hermann Oberth, a German physicist who came up with the idea in 1927. A probe would first head to Jupiter, using the giant planet’s gravity to accelerate toward the sun. As it then swings around the sun, the spacecraft would fire a rocket engine, accelerating to a speed where it could cover close to a couple of billion miles a year. That would be more than five times the speed of the Voyagers.

That would be tricky to pull off, however. For such a powered flyby to be effective, the probe would have to travel within a million miles or so from the sun.

“Well, it’s not as easy as it sounds,” said Dr. Krimigis, who is taking part in the study which should be completed in a couple of years. “At that distance, every metal we know melts.”

Kenneth Chang has been at The Times since 2000, writing about physics, geology, chemistry, and the planets. Before becoming a science writer, he was a graduate student whose research involved the control of chaos. More about Kenneth Chang

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Two Voyager Spacecraft Still Going Strong After 20 Years 

Twenty years after their launch and long after their planetary reconnaissance flybys were completed, both Voyager spacecraft are now gaining on another milestone -- crossing that invisible boundary that separates our solar system from interstellar space, the heliopause.

Since 1989, when Voyager 2 encountered Neptune, both spacecraft have been studying the environment of space in the outer solar system. Science instruments on both spacecraft are sensing signals that scientists believe are coming from the heliopause -- the outer most edge of the Sun's magnetic field that the spacecraft must pass through before they reach interstellar space.

"During their first two decades the Voyager spacecraft have had an unequaled journey of discovery. Today, even though Voyager 1 is now more than twice as far from the Sun as Neptune, their journey is only half over and more unique opportunities for discovery await the spacecraft as they head toward interstellar space," said Dr. Edward Stone, Voyager project scientist and director of NASA's Jet Propulsion Laboratory, Pasadena, CA. "The Voyagers owe their ability to operate at such great distances from the Sun to their nuclear electric power sources, which provide the electrical power they need to function."

The Sun emits a steady flow of electrically charged particles called the solar wind. As the solar wind expands supersonically into space, it creates a magnetized bubble around the Sun, called the heliosphere. Eventually, the solar wind encounters the electrically charged particles and magnetic field in the interstellar gas. The boundary created between the solar wind and interstellar gas is the heliopause. Before the spacecraft reach the heliopause, they will pass through the termination shock -- the zone in which the solar wind abruptly slows down from supersonic to subsonic speed.

Reaching the termination shock and heliopause will be major milestones for the spacecraft because no one has been there before and the Voyagers will gather the first direct evidence of their structure. Encountering the termination shock and heliopause has been a long-sought goal for many space physicists, and exactly where these two boundaries are located and what they are like still remains a mystery.

"Based on current data from the Voyager cosmic ray subsystem, we are predicting the termination shock to be in the range of 62 to 90 astronomical units (AU) from the Sun. Most 'consensus' estimates are currently converging on about 85 AU. Voyager 1 is currently at about 67 AU and moving outwards at 3.5 AU per year, so I would expect crossing the termination shock sometime before the end of 2003," said Dr. Alan Cummings, a co- investigator on the cosmic ray subsystem at the California Institute of Technology.

"Based on a radio emission event detected by the Voyager 1 and 2 plasma wave instruments in 1992, we estimate that the heliopause is located at110 to 160 AU from the Sun," said Dr. Donald A. Gurnett, principal investigator on the plasma wave subsystem at the University of Iowa. (One AU is equal to 150 million kilometers, or 93 million miles, or the distance from the Earth to the Sun.)

"The low-energy charged particle instruments on the two spacecraft continue to detect ions and electrons accelerated at the Sun and at huge shock waves, tens of AU in radius, that are driven outward through the solar wind. During the past five years, we have observed marked variations in this ion population, but have yet to see clear evidence of the termination shock. We should always keep in mind that our theories may be incomplete and the shock may be a lot farther out than we think," said Dr. Stamatios M. Krimigis, principal investigator for the low energy charged particle subsystem at The Johns Hopkins University Applied Physics Laboratory.

Voyager 2 was launched first on Aug. 20, 1977 and Voyager 1 was launched a few weeks later on a faster trajectory on Sept. 5. Initially both spacecraft were only supposed to explore two planets -- Jupiter and Saturn. But the incredible success of those two first encounters and the good health of the spacecraft prompted NASA to extend Voyager 2's mission on to Uranus and Neptune. As the spacecraft flew across the solar system, remote-control reprogramming has given the Voyagers greater capabilities than they possessed when they left the Earth.

There are four other science instruments that are still functioning and collecting data as part of the Voyager Interstellar Mission. The plasma subsystem measures the protons in the solar wind. "Our instrument has recently observed a slow, year-long increase in the speed of the solar wind which peaked in late 1996, and we are now observing a slow decrease in solar wind velocity," said Dr. John Richardson, of the Massachusetts Institute of Technology, principal investigator on the plasma subsystem. "We think the velocity peak coincided with the recent solar minimum. As we approach the solar maximum in 2000 the solar wind pressure should decrease, which will result in the termination shock and heliopause moving inward towards the Voyager spacecraft."

The magnetometer on board the Voyagers measures the magnetic fields that are carried out into interplanetary space by the solar wind. The Voyagers are currently measuring the weakest interplanetary magnetic fields ever detected and those magnetic fields being measured are responsive to charged particles that cannot be detected directly by any other instruments on the spacecraft, according to Dr. Norman Ness, principal investigator on the magnetometer subsystem at the Bartol Research Institute, University of Delaware.

Other science instruments still collecting data include the planetary radio astronomy subsystem and the ultraviolet spectrometer subsystem.

Voyager 1 encountered Jupiter on March 5, 1979, and Saturn on November 12, 1980 and then, because its trajectory was designed to fly close to Saturn's large moon Titan, Voyager 1's path was bent northward by Saturn's gravity, sending the spacecraft out of the ecliptic plane, the plane in which all the planets except Pluto orbit the Sun. Voyager 2 arrived at Jupiter on July 9, 1979, and Saturn on August 25, 1981, and was then sent on to Uranus on January 25, 1986 and Neptune on August 25, 1989. Neptune's gravity bent Voyager 2's path southward, sending it out of the ecliptic plane as well and on toward interstellar space.

Both spacecraft have enough electrical power and attitude control propellant to continue operating until about 2020, when the available electrical power will no longer support science instrument operation. Spacecraft electrical power is supplied by Radioisotope Thermoelectric Generators (RTGs) that provided approximately 470 watts power at launch. Due to the natural radioactive decay of the plutonium fuel source, the electrical energy provided by the RTGs is continually declining. At the beginning of 1997, the power generated by Voyager 1 had dropped to 334 watts and to 336 watts for Voyager 2. Both of these power levels represent better performance than had been predicted before launch.

The Voyagers are now so far from home that it takes nine hours for a radio signal traveling at the speed of light to reach the spacecraft. Science data are returned to Earth in real-time to the 34-meter Deep Space Network (DSN) antennas located in California, Australia and Spain. Voyager 1 will pass the Pioneer 10 spacecraft in January 1998 to become the most distant human- made object in our solar system.

Voyager 1 is currently 10.1 billion kilometers (6.3 billion miles) from Earth, having traveled 11.9 billion kilometers (7.4 billion miles) since its launch. The Voyager 1 spacecraft is departing the solar system at a speed of 17.4 kilometers per second (39,000 miles per hour).

Voyager 2 is currently 7.9 billion kilometers (4.9 billion miles) from Earth, having traveled 11.3 billion kilometers (6.9 billion miles) since its launch. The Voyager 2 spacecraft is departing the solar system at a speed of 15.9 kilometers per second (35,000 miles per hour).

JPL, a division of the California Institute of Technology, manages the Voyager Interstellar Mission for NASA's Office of Space Science, Washington, D. C.

Voyager 2 Trajectory through the Solar System

• Released Thursday, August 31, 2017
• Visualizations by:
• Tom Bridgman

This visualization tracks the trajectory of the Voyager 2 spacecraft through the solar system. Launched on August 20, 1977, it was one of two spacecraft sent to visit the giant planets of the outer solar system. Like Voyager 1, Voyager 2 flew by Jupiter and Saturn, but the Voyager 2 mission was extended to fly by Uranus and Neptune before being directed out of the solar system. To fit the 40 year history of the mission into a short visualization, the pacing of time accelerates through most of the movie, starting at about 5 days per second at the beginning and speeding up to about 11 months per second after the planet flybys are past. The termination shock and heliopause are the 'boundaries' created when the plasma between the stars interacts with the plasma flowing outward from the Sun. They are represented with simple grid models and oriented so their 'nose' is pointed in the direction (Right Ascension = 17h 24m, declination = 17 degrees south) represented by more recent measurements from other missions.

Visualization centered on the Voyager 2 trajectory through the solar system.

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Check out Voyager at NASA/JPL for more information.

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Opening view of Earth orbit looking outward to the rest of the solar system.

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Voyager 2 (and 1) cross the orbit of Mars, slightly above the ecliptic plane to avoid the asteroid belt between Mars & Jupiter.

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The camera moves out ahead of the Voyagers for a view back at the inner solar system.

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Voyager 2 just after the Jupiter flyby on July 9, 1979.

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Voyager 2 just after the Saturn flyby on August 26, 1981.

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Voyager 2 just before the Uranus flyby on January 24, 1986.

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Voyager 2 just after the Neptune flyby on August 25, 1989.

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Using Neptune for a gravity-assist, Voyager 2 is directed below the plane of the solar system and continues outward.

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Voyager 2 crosses the termination shock around May of 2006.

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Voyager 2 crosses the heliopause.

A slightly sped-up version of the Voyager 2 visualization above, reducing the time for the Voyagers to cross the asteroid belt.

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• Planets & Moons
• Planetary Science
• Solar System

Please give credit for this item to: NASA's Scientific Visualization Studio

• Tom Bridgman  (Global Science and Technology, Inc.)
• Genna Duberstein  (USRA)
• Scott Wiessinger  (USRA)
• Kathalina Tran  (KBR Wyle Services, LLC)

Project support

• Laurence Schuler  (ADNET Systems, Inc.)
• Ian Jones  (ADNET Systems, Inc.)

Release date

This page was originally published on Thursday, August 31, 2017. This page was last updated on Wednesday, November 15, 2023 at 12:05 AM EST.

• Voyager @ 40
• Voyager Retrospective

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David Shortt • Sep 27, 2013

Gravity assist

With the recent announcement by NASA that the 36 year-old spacecraft Voyager 1 has officially entered interstellar space at a distance from the Sun about four times further than Neptune's orbit, and with Voyager 2 not far behind, it seems worthwhile to explore how humans managed to fling objects so far into space.

Interplanetary spacecraft often use a maneuver called a gravity assist in order to reach their targets. Voyager 2 famously used gravity assists to visit Jupiter, Saturn, Uranus and Neptune in the late 1970s and 1980s. Cassini used two assists at Venus and one each at Earth and Jupiter in order to reach Saturn. New Horizons will arrive at Pluto in 2015 thanks to an assist at Jupiter. And Messenger used assists at Earth, Venus and three times at Mercury itself not to speed up, but to slow down enough to finally be captured by Mercury.

Mission planners use gravity assists because they allow the objective to be accomplished with much less fuel (and hence with a much smaller, cheaper rocket) than would otherwise be required. Lifting extra fuel into orbit, just so it can be used later, is exponentially expensive. Furthermore, the extra speed gained by gravity assists dramatically reduces the duration of a mission to the outer planets.

Gravity assists seem a bit mysterious, like one is getting something for nothing. This feeling can persist even if you know some physics. Since energy is conserved, you reason, how can a spacecraft obtain a net velocity boost by passing by a planet? Energy conservation suggests the spacecraft should speed up while approaching the planet, but then lose the same speed while departing. Recently I was talking with a colleague, an excellent plasma physicist who knew the phrase "gravity assist" but thought it must be marketing hyperbole because he didn't believe it could actually work. The mystery begs to be explained.

The key to understanding how a gravity assist works is to consider the problem from two different points of view, or reference frames. It's convenient to think about reference frames for both the planet and for the sun (or the solar system). For economy of language I'll call them the "planet frame" and the "sun frame."

In the planet frame, the planet sits still (by definition!). More importantly, since the planet is so much more massive than the spacecraft, the planet sits almost exactly at the center of mass of the two objects and does not react by any measurable amount as a result of the encounter. For example, Jupiter is about 10 to the 24th power times more massive than the Voyager spacecraft, so Jupiter ignores an encounter to an extremely high degree of precision. This means the spacecraft's total energy, made up of kinetic energy (energy of motion) plus potential energy (energy due to proximity to a massive object), is conserved throughout the encounter in this frame.

In the planet frame, then, the spacecraft indeed speeds up on approach and slows down by the same amount while departing, just like my colleague thought. During the approach, as the spacecraft falls into the gravity well of the planet, it gains kinetic energy (i.e. speed) and loses gravitational potential energy, trading one for the other just like a ball rolling downhill. After the encounter it climbs back out of the gravity well and loses whatever kinetic energy it gained during the approach, ending up with the same final speed it started with. The direction of the spacecraft changes during the encounter, however, so typically it leaves the planet heading in a different direction. The amount of deflection can be controlled by adjusting how close the spacecraft comes to the planet. The closer it gets, the greater the deflection. It's possible to have a very small deflection, near zero degrees, by arranging a wide miss. The maximum deflection is 180 degrees, sending the spacecraft back where it came from, obtained by arranging an extremely close approach. Mathematically the spacecraft's path is a hyperbola, so we say the spacecraft follows a hyperbolic trajectory in the planet frame.

Now let's consider what the encounter looks like in the Sun frame, where the Sun is stationary and the planet is moving. The difference between the planet frame and the Sun frame is just the velocity of the planet with respect to the Sun. To convert from the planet frame to the Sun frame, we simply add the velocity of the planet to both the planet and the spacecraft. This velocity is a vector, which means direction is important, and it can be in any arbitrary direction depending on the planet's position in its orbit at the time of the encounter (It also changes with time because the planet is following a curved orbit around the sun, but during the relatively short encounter with the spacecraft it's a reasonable approximation to consider the planet as moving in a straight line). Because the direction of the spacecraft changes when it encounters the planet and because the original direction of the spacecraft is also arbitrary, it's not immediately obvious how the encounter will look in the Sun frame. The arbitrariness of the directions gives rise to a rich set of possible behavior in the Sun frame, all in accordance with Newton's laws of motion, even though in the planet frame the encounters are simple hyperbolic trajectories. Crucially, because the direction changes, the speed of the spacecraft is different before and after the encounter when viewed in the Sun frame. The outgoing speed is not the same as the incoming speed, and the spacecraft can either speed up or slow down. Let's see by example how this works.

Figure 1 shows a made-up example of an encounter. The top panel shows the encounter in the Sun frame, in which the planet (in black) is moving to the right, and the spacecraft (in blue) experiences a gravity assist. The bottom panel shows the view from the planet frame, in which the spacecraft approaches the planet from below and the planet sits still. I chose the approach parameters so that the trajectory is bent through approximately 90 degrees in the planet frame. In the planet frame the spacecraft leaves the planet with the same speed with which it approached, but in the Sun frame it's clear the spacecraft gains quite a bit of speed. You can see how the spacecraft approaches the planet from behind, accelerates as it gets closer, and "slingshots" around the planet. In this example the spacecraft gains about 60% of the planet's own velocity. We'll see later on that this example is fairly close to what happened to Voyager 2 at Jupiter, Saturn and Uranus.

How does this happen? Consider that in the bottom panel the spacecraft initially moves vertically with some velocity, call it v . After the encounter it leaves the planet with the same velocity v , but in the horizontal direction. To convert to the sun frame, we add the planet's velocity (which I chose arbitrarily to be v in the horizontal direction) to both the planet and the spacecraft. Using the Pythagorean Theorem, in the Sun frame the spacecraft initially has a total velocity equal to the square root of the sum of the squares of the vertical and horizontal velocities, that is v times the square root of 2, or about 1.4 v . It leaves the planet with v + v = 2 v in the horizontal direction, having gained about 0.6 v , or about 60% of the planet's velocity. This shows clearly why the velocity of the spacecraft in the Sun frame increases during the encounter - it's because the spacecraft's direction of motion changes to point along the planet's direction.

This is a general rule of thumb for gravity assists: if, after the encounter, the spacecraft is pointing more along the planet's direction than it was before the encounter, its speed will increase. But where does the energy come from to accelerate the spacecraft? In fact it comes from the planet's own energy of motion. In the Sun frame, there is a transfer of momentum and kinetic energy from the planet to the spacecraft. The planet slows down very slightly in its orbit, and the spacecraft speeds up. Newton's third law states, "To every action there is an equal and opposite reaction," and that's true in this case. Because the planet is so much more massive than the spacecraft, the transfer doesn't affect the planet to any measurable extent, but to the spacecraft it's a big deal. For example, we can calculate that during the Voyager encounters with Jupiter in 1979, Jupiter slowed down by roughly 10 to the -24th power kilometers per second -- a change much too small to measure. But each Voyager gained about 10 km/s, a pretty big number and enough to put them on a fast path to Saturn (and in the case of Voyager 2, to Uranus and Neptune as well) and eventual escape from the solar system.

Depending on the relative direction of motion of the planet and the spacecraft, a gravity assist can either speed up, slow down, or merely change the direction of the spacecraft. Figure 2 shows a gallery of possibilities. The center panel (e) shows the view in the planet frame, and the other panels show the sun frame with 8 different directions for the planet's motion. The trajectories in panels (a), (b) and (d) slow down the spacecraft, those in panels (f), (h) and (i) speed it up, and those in panels (c) and (g) change the direction but not the speed. Panel (f) is the same example we considered in Figure 1. It's worth emphasizing that every panel depicts a correct solution of Newton's laws, so any of these could be arranged by a mission designer if needed.

Before looking at a real mission, let's recap what we know so far. In the planet frame, the trajectory is hyperbolic with the same velocity before and after the encounter but with the path deflected through some angle. In the Sun frame this results in trajectories that can speed up or slow down the spacecraft in addition to changing its direction, depending on the geometry of the encounter. Total energy is conserved, and the planet loses (or gains) an insignificant but real amount of velocity, while the spacecraft's velocity and direction may change by a large amount.

Next let's consider a practical example. Voyager 2 is a good choice because it used gravity assists to visit all four of the outer planets: Jupiter, Saturn, Uranus and Neptune. (Voyager 1 followed a similar trajectory up to Saturn, but then had to leave the plane of the solar system and forgo any more planets because mission planners arranged the encounter to include a close approach of Saturn's large and fascinating moon Titan. Voyager 2 did not have a Titan encounter and went on to visit Uranus and Neptune.)

Figure 3 shows a plot of the path of Voyager 2 from its launch from Earth in 1977 through its encounter with Neptune 12 years later. For simplicity the plot omits the orbits of Mercury, Venus and Mars. The axes are labeled in astronomical units, or AU, with the sun at the center (1 AU is the average distance between the Earth and the sun). Notice the particularly sharp "left turns" Voyager 2 makes at Jupiter and Saturn. Viewed as a whole, though, the path of Voyager 2 is a reasonably smooth spiral from Earth to Neptune. This is no accident. The outer planets line up in such a fortuitous way about every 175 years, and it encourages the idea of using gravity assists repeatedly to direct the spacecraft to the next target.

Figures 4-7 show close-up animations of the encounters at the four outer planets in both the Sun frame and the planet frame. For all the figures, the frame rate is 1 frame per day, the trajectories are shown for 20 days before and after the moment of closest approach, and all the figures are shown at the same spatial scale for comparison, with a width of about 0.6 AU. The Jupiter encounter in Figure 4 looks a lot like panel (i) in Figure 2. You can see how unusual the Jupiter encounter looks in the Sun frame, with the spacecraft experiencing a "bump" in its trajectory as it first accelerated toward massive Jupiter, then whipped around behind it. At Saturn, the encounter in Figure 5 looks a lot like panel (f) in Figure 2. Notice the high speed of the encounter - Voyager was moving fast due to the speed it gained at Jupiter, and the approach had to be very close in order to execute the screaming left turn needed to reach Uranus. The modest left turn at Uranus, shown in Figure 6, looks tame by comparison. Finally, at Neptune in Figure 7, Voyager 2 actually turned slightly right, thereby losing some speed. The reason is that mission planners wanted to arrange a close flyby of Neptune's large moon Triton, and this necessitated flying mostly over Neptune's north pole and making a slight right turn in addition to plunging down, out of the plane of the solar system (the plunge down is not visible in Figure 7 since it's a view from overhead).

Another insight from the animations is that Voyager 2's speed increased quite a bit during its journey. Figure 8 confirms this by plotting the spacecraft's speed in the sun frame (in blue) vs. its distance from the sun in AU. Also plotted, in red, is the escape velocity from the sun, i.e. the speed necessary at that distance to ensure escape from the solar system. After leaving Earth but before its encounter with Jupiter, Voyager 2 lacked enough speed to escape the sun's gravity (the blue curve lies below the red curve between 1 AU and 5 AU). During the Jupiter encounter, Voyager 2 gained enough speed to enable it to leave the solar system - the blue curve stays above the red curve beyond Jupiter. It gained about 10 km/s at Jupiter, about 5 km/s at Saturn, about 2 km/s at Uranus, and lost about 2 km/s at Neptune. As of September 2013, Voyager 2 is over 102 AU from the sun and still traveling at about 15 km/s. Due to its slightly different trajectory, Voyager 1 is over 125 AU from the sun and traveling about 17 km/s, and NASA recently announced that Voyager 1 has officially entered interstellar space.

Thanks to gravity assists, the Voyagers are headed to the stars.

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30 years ago: voyager 2 explores neptune, johnson space center.

In the summer of 1989, NASA’s Voyager 2 became the first spacecraft to fly by Neptune, its final planetary encounter. Managed by the Jet Propulsion Laboratory in Pasadena, California, Voyagers 1 and 2 were a pair of spacecraft launched in 1977 to explore the outer planets. Initially targeted only to visit Jupiter and Saturn, Voyager 2 took advantage of a rare planetary alignment that occurs once every 175 years to complete two additional encounters in the outer solar system. In January 1986, Voyager 2 became the first spacecraft to investigate Uranus and used that planet’s gravity to alter its trajectory to explore Neptune, the outermost planet of the solar system. Because of Neptune’s great distance from the Sun, engineers made changes to Voyager’s imaging techniques to accommodate light levels only 3% of what they were during the Jupiter encounter. Short exposures were on the order of 15 seconds while longer ones were measured in minutes. Image motion compensation techniques were programmed into Voyager’s computer to maintain clear photographs at those long exposures coupled with the spacecraft’s velocity. NASA also upgraded the tracking antennas of the Deep Space Network to increase their sensitivity to receive Voyager’s signals from Neptune’s distance. Because of its remoteness, relatively little was known about Neptune prior to the Voyager encounter. It had two known moons, the larger Triton orbiting relatively close to the planet but in a retrograde direction, indicating it might have been captured by Neptune, and tiny Nereid in a far-flung but posigrade orbit. Observations from Earth seemed to indicate that Neptune was encircled by dark rings or ring arcs, but the evidence was inconclusive.

Each Voyager carried a suite of 11 instruments, including: 

• an imaging science system consisting of narrow-angle and wide-angle cameras to photograph the planet and its satellites;
• a radio science system to determine the planet’s physical properties;
• an infrared interferometer spectrometer to investigate local and global energy balance and atmospheric composition;
• an ultraviolet spectrometer to measure atmospheric properties;
• a magnetometer to analyze the planet’s magnetic field and interaction with the solar wind;
• a plasma spectrometer to investigate microscopic properties of plasma ions;
• a low energy charged particle device to measure fluxes and distributions of ions;
• a cosmic ray detection system to determine the origin and behavior of cosmic radiation;
• a planetary radio astronomy investigation to study radio emissions from Jupiter;
• a photopolarimeter to measure the planet’s surface composition; and
• a plasma wave system to study the planet’s magnetosphere.

Voyager 2 began to observe Neptune on June 5, 1989, at a distance of 73 million miles. Even at this range, Voyager’s images were already four times better than those obtained by Earth-based telescopes. It soon made the first of its many discoveries of the encounter: the moon later named Proteus orbiting about 73,000 miles from Neptune, and with a diameter of 260 miles actually larger than the known moon Nereid – it is not clear how it had escaped detection by Earth-based telescopes. By early August, Voyager 2 had discovered three more small moons (Despina, Galatea, and Larissa) orbiting closer to the planet than Proteus. Larissa had been spotted in 1981 but Voyager 2 confirmed its existence. The photographs of Neptune revealed a dynamic atmosphere including an Earth-sized storm system named the Great Dark Spot and wind speeds reaching up to 1,000 miles per hour. Voyager returned the first images of Neptune’s rings which turned out to be a system of five rings composed mostly of dark dust and discovered two more small moons (Thalassa and Naiad). Like at Saturn and Uranus, the rings and four of the moons at Neptune form an intricate interrelated system. The spacecraft also imaged Neptune’s previously discovered moon Nereid at low resolution from about 3 million miles away. Voyager discovered that Neptune’s magnetic field was not only tilted 47o from the planet’s axis but also significantly offset from the planet’s center.

On Aug. 25, passing about 3,408 miles above Neptune’s north pole, Voyager 2 made its closest approach to any planet since leaving Earth in 1977. This close encounter trajectory allowed Voyager 2 to pass about 25,000 miles from Triton about five hours later. Triton was the last solid body the spacecraft explored and the encounter did not disappoint with several amazing discoveries. With relatively few impact craters, Triton’s surface is believed to be young, having been remodeled by melting. Despite Triton’s frigid -392o F surface temperature, Voyager’s images revealed evidence of geysers spewing dark material into the moon’s tenuous atmosphere that deposited back onto the surface. Voyager passed behind both Neptune and Triton, with instruments returning data about their atmospheres. The spacecraft also returned spectacular images of the two bodies backlit by the Sun. On its outbound journey, Voyager 2 continued to study Neptune until Oct. 2, 1989.  In all, it had returned more than 9,000 images of the planet, its rings and its moons as well as a treasure trove of scientific information, tremendously increasing our knowledge of the most distant planet in the solar system.

Following its reconnaissance of Neptune, Voyager 2 began its Interstellar Mission extension that continues to this day. Over the years, several of the spacecraft’s instruments have been turned off to conserve power, beginning with the imaging system in 1989, but it continues to return data about cosmic rays and the solar wind. On Nov. 5, 2018, six years after its twin, Voyager 2 crossed the heliopause, the boundary between the heliosphere, the bubble-like region of space created by the Sun, and the interstellar medium. It is expected that Voyager 2 will continue to return data from interstellar space until about 2025. And just in case it may one day be found by an alien intelligence, Voyager 2 like its twin carries a gold plated record that contains information about its home planet, including recordings of terrestrial sounds, music and greetings in 55 languages. Instructions on how to play the record are also included.

Two Voyager Spacecraft Still Going Strong After 20 Years

Twenty years after their launch and long after their planetary reconnaissance flybys were completed, both Voyager spacecraft are now gaining on another milestone -- crossing that invisible boundary that separates our solar system from interstellar space, the heliopause.

Since 1989, when Voyager 2 encountered Neptune, both spacecraft have been studying the environment of space in the outer solar system. Science instruments on both spacecraft are sensing signals that scientists believe are coming from the heliopause -- the outer most edge of the Sun's magnetic field that the spacecraft must pass through before they reach interstellar space.

"During their first two decades the Voyager spacecraft have had an unequaled journey of discovery. Today, even though Voyager 1 is now more than twice as far from the Sun as Neptune, their journey is only half over and more unique opportunities for discovery await the spacecraft as they head toward interstellar space," said Dr. Edward Stone, Voyager project scientist and director of NASA's Jet Propulsion Laboratory, Pasadena, CA. "The Voyagers owe their ability to operate at such great distances from the Sun to their nuclear electric power sources, which provide the electrical power they need to function."

The Voyagers owe their ability to operate at such great distances from the Sun to their nuclear electric power sources, which provide the electrical power they need to function.

Dr. Edward Stone

Voyager Project Scientist

The Sun emits a steady flow of electrically charged particles called the solar wind. As the solar wind expands supersonically into space, it creates a magnetized bubble around the Sun, called the heliosphere. Eventually, the solar wind encounters the electrically charged particles and magnetic field in the interstellar gas. The boundary created between the solar wind and interstellar gas is the heliopause. Before the spacecraft reach the heliopause, they will pass through the termination shock -- the zone in which the solar wind abruptly slows down from supersonic to subsonic speed.

Reaching the termination shock and heliopause will be major milestones for the spacecraft because no one has been there before and the Voyagers will gather the first direct evidence of their structure. Encountering the termination shock and heliopause has been a long-sought goal for many space physicists, and exactly where these two boundaries are located and what they are like still remains a mystery.

"Based on current data from the Voyager cosmic ray subsystem, we are predicting the termination shock to be in the range of 62 to 90 astronomical units (AU) from the Sun. Most 'consensus' estimates are currently converging on about 85 AU. Voyager 1 is currently at about 67 AU and moving outwards at 3.5 AU per year, so I would expect crossing the termination shock sometime before the end of 2003," said Dr. Alan Cummings, a co- investigator on the cosmic ray subsystem at the California Institute of Technology.

"Based on a radio emission event detected by the Voyager 1 and 2 plasma wave instruments in 1992, we estimate that the heliopause is located at 110 to 160 AU from the Sun," said Dr. Donald A. Gurnett, principal investigator on the plasma wave subsystem at the University of Iowa. (One AU is equal to 150 million kilometers, or 93 million miles, or the distance from the Earth to the Sun.)

"The low-energy charged particle instruments on the two spacecraft continue to detect ions and electrons accelerated at the Sun and at huge shock waves, tens of AU in radius, that are driven outward through the solar wind. During the past five years, we have observed marked variations in this ion population, but have yet to see clear evidence of the termination shock. We should always keep in mind that our theories may be incomplete and the shock may be a lot farther out than we think," said Dr. Stamatios M. Krimigis, principal investigator for the low energy charged particle subsystem at The Johns Hopkins University Applied Physics Laboratory.

Voyager 2 was launched first on Aug. 20, 1977 and Voyager 1 was launched a few weeks later on a faster trajectory on Sept. 5. Initially both spacecraft were only supposed to explore two planets -- Jupiter and Saturn. But the incredible success of those two first encounters and the good health of the spacecraft prompted NASA to extend Voyager 2's mission on to Uranus and Neptune. As the spacecraft flew across the solar system, remote-control reprogramming has given the Voyagers greater capabilities than they possessed when they left the Earth.

There are four other science instruments that are still functioning and collecting data as part of the Voyager Interstellar Mission. The plasma subsystem measures the protons in the solar wind. "Our instrument has recently observed a slow, year-long increase in the speed of the solar wind which peaked in late 1996, and we are now observing a slow decrease in solar wind velocity," said Dr. John Richardson, of the Massachusetts Institute of Technology, principal investigator on the plasma subsystem. "We think the velocity peak coincided with the recent solar minimum. As we approach the solar maximum in 2000 the solar wind pressure should decrease, which will result in the termination shock and heliopause moving inward towards the Voyager spacecraft."

The magnetometer on board the Voyagers measures the magnetic fields that are carried out into interplanetary space by the solar wind. The Voyagers are currently measuring the weakest interplanetary magnetic fields ever detected and those magnetic fields being measured are responsive to charged particles that cannot be detected directly by any other instruments on the spacecraft, according to Dr. Norman Ness, principal investigator on the magnetometer subsystem at the Bartol Research Institute, University of Delaware.

Other science instruments still collecting data include the planetary radio astronomy subsystem and the ultraviolet spectrometer subsystem.

Voyager 1 encountered Jupiter on March 5, 1979, and Saturn on November 12, 1980 and then, because its trajectory was designed to fly close to Saturn's large moon Titan, Voyager 1's path was bent northward by Saturn's gravity, sending the spacecraft out of the ecliptic plane, the plane in which all the planets except Pluto orbit the Sun. Voyager 2 arrived at Jupiter on July 9, 1979, and Saturn on August 25, 1981, and was then sent on to Uranus on January 25, 1986 and Neptune on August 25, 1989. Neptune's gravity bent Voyager 2's path southward, sending it out of the ecliptic plane as well and on toward interstellar space.

Both spacecraft have enough electrical power and attitude control propellant to continue operating until about 2020, when the available electrical power will no longer support science instrument operation. Spacecraft electrical power is supplied by Radioisotope Thermoelectric Generators (RTGs) that provided approximately 470 watts power at launch. Due to the natural radioactive decay of the plutonium fuel source, the electrical energy provided by the RTGs is continually declining. At the beginning of 1997, the power generated by Voyager 1 had dropped to 334 watts and to 336 watts for Voyager 2. Both of these power levels represent better performance than had been predicted before launch.

The Voyagers are now so far from home that it takes nine hours for a radio signal traveling at the speed of light to reach the spacecraft. Science data are returned to Earth in real-time to the 34-meter Deep Space Network (DSN) antennas located in California, Australia and Spain. Voyager 1 will pass the Pioneer 10 spacecraft in January 1998 to become the most distant human- made object in our solar system.

Voyager 1 is currently 10.1 billion kilometers (6.3 billion miles) from Earth, having traveled 11.9 billion kilometers (7.4 billion miles) since its launch. The Voyager 1 spacecraft is departing the solar system at a speed of 17.4 kilometers per second (39,000 miles per hour).

Voyager 2 is currently 7.9 billion kilometers (4.9 billion miles) from Earth, having traveled 11.3 billion kilometers (6.9 billion miles) since its launch. The Voyager 2 spacecraft is departing the solar system at a speed of 15.9 kilometers per second (35,000 miles per hour).

JPL, a division of the California Institute of Technology, manages the Voyager Interstellar Mission for NASA's Office of Space Science, Washington, D. C.

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

Emma Bowman

Artist's concept of NASA's Voyager spacecraft. After the Voyager 1 and its replica Voyager 2 launched in 1977, their power sources are slowly dying. NASA/JPL-Caltech hide caption

Artist's concept of NASA's Voyager spacecraft. After the Voyager 1 and its replica Voyager 2 launched in 1977, their power sources are slowly dying.

NASA's Voyager 2 spacecraft, which has been probing the outer bounds of the solar system for over 45 years, is running out of power. But a new plan aims to keep its interstellar mission alive for at least three more years.

The Voyager 2, first launched in 1977, has been helping scientists investigate faraway planets and understand how the heliosphere — the sun's outermost atmospheric bubble-like layer that traps particles and magnetic fields — protects Earth from its volatile interstellar environment.

With Voyager 2's power supply dwindling, NASA was about to shut down one of its five science instruments onboard the spacecraft. To keep it going, engineers had already sacrificed heaters and other nonessential parts that drained power. But engineers have now found a way to tap reserve power from a safety mechanism that regulates the spacecraft's voltage.

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

"The move will enable the mission to postpone shutting down a science instrument until 2026, rather than this year," NASA's Jet Propulsion Laboratory said this past week.

Voyager 2 and its twin, Voyager 1 (launched the same year), are the only spacecraft to have ventured beyond the heliosphere.

Ed Stone, who was the chief scientist at NASA's Jet Propulsion Lab before he retired last year, has spent over half his life dedicated to the Voyager program. He oversaw the spacecrafts churn out one discovery after another as they explored Jupiter, Saturn, Uranus and Neptune.

"What it revealed was how complex and dynamic the solar system really is. Before Voyager, the only known active volcanoes were here on Earth," Stone told NPR in 2017 . "Then we flew by Jupiter's moon, Io, and it has 10 times the volcanic activity of earth. Before Voyager, the only known oceans in the solar system were here on Earth. Then we flew by another moon of Jupiter, Europa, which it turns out has a liquid water ocean beneath its icy crust."

Voyager 2 is 12.3 billion miles away from Earth and counting . Voyager 1, also facing an expiration date as it also loses power, is 14.7 billion miles away.

"The science data that the Voyagers are returning gets more valuable the farther away from the Sun they go, so we are definitely interested in keeping as many science instruments operating as long as possible," Linda Spilker, the Voyager program's project scientist at the Jet Propulsion Lab, said in a statement.

NASA, meanwhile, has been working to make sure the Voyagers' legacy doesn't end with a slow fizzle, with officials weighing expensive and complex proposals from several groups for a new, long-term probe.

NASA's Voyager 1 spacecraft finally phones home after 5 months of no contact

On Saturday, April 5, Voyager 1 finally "phoned home" and updated its NASA operating team about its health.

NASA's interstellar explorer Voyager 1 is finally communicating with ground control in an understandable way again. On Saturday (April 20), Voyager 1 updated ground control about its health status for the first time in 5 months. While the Voyager 1 spacecraft still isn't sending valid science data back to Earth, it is now returning usable information about the health and operating status of its onboard engineering systems. 

Thirty-five years after its launch in 1977, Voyager 1 became the first human-made object to leave the solar system and enter interstellar space . It was followed out of our cosmic quarters by its space-faring sibling, Voyager 2 , six years later in 2018. Voyager 2, thankfully, is still operational and communicating well with Earth. 

The two spacecraft remain the only human-made objects exploring space beyond the influence of the sun. However, on Nov. 14, 2023, after 11 years of exploring interstellar space and while sitting a staggering 15 billion miles (24 billion kilometers) from Earth, Voyager 1's binary code — computer language composed of 0s and 1s that it uses to communicate with its flight team at NASA — stopped making sense.

Related: We finally know why NASA's Voyager 1 spacecraft stopped communicating — scientists are working on a fix

In March, NASA's Voyager 1 operating team sent a digital "poke" to the spacecraft, prompting its flight data subsystem (FDS) to send a full memory readout back home.

This memory dump revealed to scientists and engineers that the "glitch" is the result of a corrupted code contained on a single chip representing around 3% of the FDS memory. The loss of this code rendered Voyager 1's science and engineering data unusable.

The NASA team can't physically repair or replace this chip, of course, but what they can do is remotely place the affected code elsewhere in the FDS memory. Though no single section of the memory is large enough to hold this code entirely, the team can slice it into sections and store these chunks separately. To do this, they will also have to adjust the relevant storage sections to ensure the addition of this corrupted code won't cause those areas to stop operating individually, or working together as a whole. In addition to this, NASA staff will also have to ensure any references to the corrupted code's location are updated.

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On April 18, 2024, the team began sending the code to its new location in the FDS memory. This was a painstaking process, as a radio signal takes 22.5 hours to traverse the distance between Earth and Voyager 1, and it then takes another 22.5 hours to get a signal back from the craft. 

By Saturday (April 20), however, the team confirmed their modification had worked. For the first time in five months, the scientists were able to communicate with Voyager 1 and check its health. Over the next few weeks, the team will work on adjusting the rest of the FDS software and aim to recover the regions of the system that are responsible for packaging and returning vital science data from beyond the limits of the solar system.

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

Robert Lea is a science journalist in the U.K. whose articles have been published in Physics World, New Scientist, Astronomy Magazine, All About Space, Newsweek and ZME Science. He also writes about science communication for Elsevier and the European Journal of Physics. Rob holds a bachelor of science degree in physics and astronomy from the U.K.’s Open University. Follow him on Twitter @sciencef1rst.

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• Robb62 'V'ger must contact the creator. Reply
• Holy HannaH! Couldn't help but think that "repair" sounded extremely similar to the mechanics of DNA and the evolution of life. Reply
• Torbjorn Larsson *Applause* indeed, thanks to the Voyager teams for the hard work! Reply
• SpaceSpinner I notice that the article says that it has been in space for 35 years. Either I have gone back in time 10 years, or their AI is off by 10 years. V-*ger has been captured! Reply

Admin said: On Saturday, April 5, Voyager 1 finally "phoned home" and updated its NASA operating team about its health. The interstellar explorer is back in touch after five months of sending back nonsense data. NASA's Voyager 1 spacecraft finally phones home after 5 months of no contact : Read more

evw said: I'm incredibly grateful for the persistence and dedication of the Voyagers' teams and for the amazing accomplishments that have kept these two spacecrafts operational so many years beyond their expected lifetimes. V-1 was launched when I was 25 years young; I was nearly delirious with joy. Exploring the physical universe captivated my attention while I was in elementary school and has kept me mesmerized since. I'm very emotional writing this note, thinking about what amounts to a miracle of technology and longevity in my eyes. BRAVO!!! THANK YOU EVERYONE PAST & PRESENT!!!

• EBairead I presume it's Fortran. Well done all. Reply

SpaceSpinner said: I notice that the article says that it has been in space for 35 years. Either I have gone back in time 10 years, or their AI is off by 10 years. V-*ger has been captured!

EBairead said: I presume it's Fortran. Well done all.

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NASA’S Out Of The Box Thinking Brings Voyager Probe Back Online

We know that the people who work at NASA are some of the smartest and most educated people in the world.

And you know, you can’t put a price on being able to think on your feet.

NASA’s 46yo Voyager 1 spacecraft went offline for more than five months, but after some “ inventive sleuthing ,” the team at the Jet Propulsion Lab has it sending back usable data.

This probe, along with its twin Voyager 2, are the only two spacecraft to reach interstellar space. In November of 2023, it began sending back incomprehensible code.

They managed to trace the issue back to the flight data subsystem (FDS), which packages scientific and engineering data before it gets sent back to Earth.

Given the spacecraft’s age and long-term prospects, the fact that this clever hack worked at all is something of a miracle.

They discovered a piece of the subsystem’s memory was out of order, which made the data all but useless. They couldn’t move the affected code around, because it was too large to be stored elsewhere.

Their solution? Slicing up the affected code into sections so they could store it in different places in the FDS.

This was not a quick process, given that Voyager 1 is over 15 billion miles away, and a signal takes 45 hours to get there and back.

“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.”

They’re thrilled at being able to check on the spacecraft’s health and status once again, no matter how long it lasts.

It’s pretty amazing technology if you think about it.

If you thought that was interesting, you might like to read about a second giant hole has opened up on the sun’s surface. Here’s what it means.

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The post NASA’S Out Of The Box Thinking Brings Voyager Probe Back Online first on TwistedSifter .

• The Contents
• The Making of
• Where Are They Now
• Frequently Asked Questions
• Q & A with Ed Stone

golden record

Where are they now.

• frequently asked questions
• Q&A with Ed Stone

mission  /  science

Hyperbolic orbital elements.

VOYAGER 1 AND 2 HYPERBOLIC ORBITAL ELEMENTS November 1989

The following are hyperbolic elements for NASA's Voyager 1 and 2 during various legs of their travels to the outer planets of the solar system.

Voyager 1 was launched in September 1977 and flew by Jupiter and Saturn. Voyager 2 was launched in August 1977 and flew by Jupiter, Saturn, Uranus and Neptune. Both spacecraft are now headed out of the solar system into interstellar space.

These data were provided by Steve Matousek, trajectory engineer for the Voyager Project at the Jet Propulsion Laboratory.

Abbreviations used:

ET = Ephemeris Time a = semi-major axis (kilometers) e = eccentricity i = inclination (degrees)

OM = longitude of ascending node (degrees) (big omega) o = argument of perifocus (degrees) (small omega) M = mean anomaly (degrees)

i, OM and o are Sun-centered, Earth ecliptic of 1950.0, except at planetary encounters where the elements are planet-centered.

EARTH INJECTION TO JUPITER

Epoch = 9/8/77 09:08:17 ET a = 745,761,000 e = .797783 i = 1.032182 OM = -17.565509 o = -.767558 M = .304932

JUPITER-CENTERED

Epoch = 3/5/79 12:05:26 ET a = -1,092,356 e = 1.318976 i = 3.979134 OM = 119.454908 o = -62.062795 M = 0.

JUPITER TO SATURN

Epoch = 4/24/79 07:33:03 ET a = -593,237,000 e = 2.302740 i = 2.481580 OM = 112.975465 o = -1.527299 M = 19.156329

SATURN-CENTERED

Epoch = 11/12/80 23:46:30 ET a = -166,152 e = 2.107561 i = 65.893904 OM = -167.106611 o = -58.836017 M = 0.

POST-SATURN

Epoch = 1/1/91 00:00:00 ET a = -480,926,000 e = 3.724716 i = 35.762854 OM = 178.197845 o = -21.671355 M = 688.967795

Epoch = 8/23/77 11:29:11 ET a = 544,470,000 e = .724429 i = 4.825717 OM = -32.940520 o = 11.702680 M = -.888403

Epoch = 7/9/79 22:29:51 ET a = -2,184,140 e = 1.330279 i = 6.913454 OM = 147.253921 o = -95.715216 M = 0.

Epoch = 9/15/79 11:07:25 ET a = -2,220,315,000 e = 1.338264 i = 2.582320 OM = 119.196938 o = -9.170896 M = 4.798319

Epoch = 8/26/81 03:24:57 ET a = -332,965 e = 1.482601 i = 3.900931 OM = 60.314852 o = 88.222252 M = 0.

SATURN TO URANUS

Epoch = 10/17/81 18:43:56 ET a = -579,048,000 e = 3.480231 i = 2.665128 OM = 76.860491 o = 112.289600 M = 10.350850

URANUS-CENTERED

Epoch = 1/24/86 17:59:47 ET a = -26,694 e = 5.014153 i = 11.263200 OM = -80.927265 o = -86.390059 M = 0.

URANUS TO NEPTUNE

Epoch = 6/9/87 00:00:00 ET a = -448,160,000 e = 5.806828 i = 2.496223 OM = -100.376161 o = -46.104011 M = 315.018680

NEPTUNE-CENTERED

Epoch = 8/25/89 03:56:36 ET a = -24,480 e = 2.194523 i = 115.956093 OM = 114.507068 o = 113.992391 M = 0.

POST-NEPTUNE

Epoch = 1/1/91 00:00:00 ET a = -601,124,000 e = 6.284578 i = 78.810177 OM = 100.934989 o = 130.043962 M = 342.970736