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FACT SHEET: THE VOYAGER MISSION

The twin spacecraft Voyager 1 and Voyager 2 were launched by NASA during the
summer of 1977 from Cape Canaveral, Florida. As originally designed, the
Voyagers were to conduct closeup studies of Jupiter and Saturn, Saturn's rings
and the larger moons of the two planets.

To accomplish their two-planet mission, the spacecraft were built to last 5
years. But as the mission went on and with the successful achievement of all
its objectives, the additional flybys of the two outermost giant planets,
Uranus and Neptune, proved possible -- and irresistible -- to mission
scientists and engineers at the Jet Propulsion Laboratory in Pasadena,
California.

As the spacecraft flew across the solar system, remote-control reprogramming
was used to endow the Voyagers with greater capabilities than they possessed
when they left Earth. Their two-planet mission became four. Their 5-year
lifetimes stretched to 12 and more.

Eventually, between them, Voyagers 1 and 2 would explore all the giant outer
planets of our solar system, 48 of their moons and the unique systems of rings
and magnetic fields those planets possess.

Had the Voyager missions ended after the Jupiter and Saturn flybys, they still
would have provided the material to rewrite astronomy textbooks. But having
doubled their already ambitious itineraries, the Voyagers returned to Earth
information that has revolutionized the science of planetary astronomy, helping
to resolve key questions while raising intriguing new ones about the origin and
evolution of the planets in this solar system.


HISTORY OF THE VOYAGER MISSION

The Voyager mission was designed to take advantage of a rare geometric
arrangement of the outer planets in the late 1970s and the early 1980s. This
layout of Jupiter, Saturn, Uranus and Neptune, which occurs about every 175
years, allows a spacecraft on a particular flight path to swing from one planet
to the next without the need for large onboard propulsion systems. The flyby of
each planet bends the spacecraft's flight path and increases its velocity
enough to deliver the spacecraft to the next destination. Using this "gravity
assist" technique, the flight time to Neptune can be reduced from 30 years to
12.

While the four-planet mission was known to be possible, it was deemed too
expensive to build a spacecraft that could go the distance, carry the
instruments needed and last long enough to accomplish such a lengthy mission.
Thus, the Voyagers were funded to conduct intensive flyby studies of Jupiter
and Saturn only.

More than 10,000 trajectories were studied before choosing the two that would
allow close flybys of Jupiter and its large moon Io and Saturn and its large
moon Titan. The chosen flight path for Voyager 2 also preserved the option to
continue on to Uranus and Neptune.

NASA managed the launch of both Voyagers from the Cape Canaveral Air Force
Station, Florida. Voyager 2 was launched on August 20, 1977; Voyager 1 was
launched on a faster, shorter trajectory September 5, 1977. Both spacecraft
were delivered to space aboard Titan-Centaur expendable rockets.

The prime Voyager mission to Jupiter and Saturn brought Voyager 1 to Jupiter on
March 5, 1979, and to Saturn on November 12, 1980, followed by Voyager 2 to
Jupiter on July 9, 1979, and Saturn on August 25, 1981.

Voyager 1's trajectory, designed to send the spacecraft closely past the large
moon Titan and behind Saturn's rings, bent the spacecraft's path inexorably
northward out of the ecliptic plane -- the plane in which most of the planets
orbit the Sun. Voyager 2 was aimed to fly by Saturn at a point that would
automatically send the spacecraft in the direction of Uranus.

After Voyager 2's successful Saturn encounter, it was shown that Voyager 2
likely would be able to fly on to Uranus with all instruments operating. NASA
provided additional funding to continue operating the two spacecraft and
authorized JPL to conduct a Uranus flyby. Subsequently, NASA also authorized
the Neptune leg of the mission, which was renamed the Voyager Neptune
Interstellar Mission.

Voyager 2 encountered Uranus on January 24, 1986, returning detailed photos and
other data on the planet, its moons, magnetic field and dark rings. Voyager 1,
meanwhile, continued to press outward, conducting studies of interplanetary
space. Eventually, its instruments may be the first of any spacecraft to sense
the heliopause -- the boundary between the end of the Sun's magnetic influence
and the beginning of interstellar space.

Following Voyager 2's closest approach to Neptune on August 25, 1989, the
spacecraft flew southward, below the ecliptic plane and onto a course that will
take it to interstellar space as well. Reflecting the Voyagers' new
transplanetary destinations, the project is now known as the Voyager
Interstellar Mission.

Voyager 1 is now leaving the solar system, rising above the ecliptic plane at
an angle of about 35 degrees at a rate of about 520 million kilometers (about
320 million miles) a year. Voyager 2 also is headed out of the solar system,
diving below the ecliptic plane at an angle of about 48 degrees and a rate of
about 470 million kilometers (about 290 million miles) a year.

Both spacecraft will continue to study ultraviolet sources among the stars, and
the fields and particles instruments aboard the Voyagers will continue to
search for the boundary between the Sun's influence and interstellar space. The
Voyagers are expected to return valuable data for two or three more decades.
Communications will be maintained until the Voyagers' nuclear power sources can
no longer supply enough electrical energy to power critical subsystems.

The cost of the Voyager 1 and 2 missions -- including launch, mission
operations from launch through the Neptune encounter and the spacecraft's
nuclear batteries (provided by the Department of Energy) -- is $865 million.
NASA budgeted an additional $30 million to fund the Voyager Interstellar
Mission for 2 years following the Neptune encounter.


VOYAGER OPERATIONS

Voyagers 1 and 2 are identical spacecraft. Each is equipped with instruments to
conduct 10 different experiments. The instruments include television cameras,
infrared and ultraviolet sensors, magnetometers, plasma detectors and
cosmic-ray and charged-particle sensors. In addition, the spacecraft radio is
used to conduct experiments.

The Voyagers travel too far from the Sun to use solar panels. Instead, they
were equipped with power sources called radioisotope thermoelectric generators
(RTGs). These RTGs, used on other deep space missions, convert the heat,
produced from the natural radioactive decay of plutonium, into electricity to
power the spacecraft instruments, computers, radio and other systems.

The spacecraft are controlled and their data returned through the Deep Space
Network (DSN), a global spacecraft tracking system operated by JPL for NASA.
DSN antenna complexes are located in California's Mojave Desert; near Madrid,
Spain; and in Tidbinbilla, near Canberra, Australia.

The Voyager project manager for the Interstellar Mission is George P. Textor of
JPL. The Voyager project scientist is Dr. Edward C. Stone of the California
Institute of Technology. The assistant project scientist for the Jupiter flyby
was Dr. Arthur L. Lane, followed by Dr. Ellis D. Miner for the Saturn, Uranus
and Neptune encounters. Both are with JPL. The Voyager program manager at NASA
Headquarters is Ann Merwarth.


JUPITER

Voyager 1 made its closest approach to Jupiter on March 5, 1979, and Voyager 2
followed with its closest approach occurring on July 9, 1979. The first
spacecraft flew within 206,700 kilometers (128,400 miles) of the planet's cloud
tops, and Voyager 2 came within 570,000 kilometers (350,000 miles).

Jupiter is the largest planet in the solar system, composed mainly of hydrogen
and helium, with small amounts of methane, ammonia, water vapor, traces of
other compounds and a core of melted rock and ice. Colorful latitudinal bands
and atmospheric clouds and storms illustrate Jupiter's dynamic weather system.
The giant planet is now known to possess 16 moons. The planet completes one
orbit of the Sun each 11.8 years and its day is 9 hours, 55 minutes.

Although astronomers had studied Jupiter through telescopes on Earth for
centuries, scientists were surprised by many of the Voyager findings. The Great
Red Spot was revealed as a complex storm moving in a counterclockwise
direction. An array of other smaller storms and eddies were found throughout
the banded clouds.

Discovery of active volcanism on the satellite Io was easily the greatest
unexpected discovery at Jupiter. It was the first time active volcanoes had
been seen on another body in the solar system. Together, the Voyagers observed
the eruption of nine volcanoes on Io, and there is evidence that other
eruptions occurred between the Voyager encounters.

Plumes from the volcanoes extend to more than 300 kilometers (190 miles) above
the surface. The Voyagers observed material ejected at velocities up to a
kilometer per second.

Io's volcanoes are apparently due to heating of the satellite by tidal pumping.
Io is perturbed in its orbit by Europa and Ganymede, two other large satellites
nearby, then pulled back again into its regular orbit by Jupiter. This
tug-of-war results in tidal bulging as great as 100 meters (330 feet) on Io's
surface, compared with typical tidal bulges on Earth of one meter (3 feet).

It appears that volcanism on Io affects the entire jovian system, in that it is
the primary source of matter that pervades Jupiter's magnetosphere, the region
of space surrounding the planet influenced by the jovian magnetic field.

Sulfur, oxygen and sodium, apparently erupted by Io's many volcanoes and
sputtered off the surface by impact of high-energy particles, were detected as
far away as the outer edge of the magnetosphere millions of miles from the
planet itself.

Europa displayed a large number of intersecting linear features in the
low-resolution photos from Voyager 1. At first, scientists believed the
features might be deep cracks caused by crustal rifting or tectonic processes.
The closer high-resolution photos from Voyager 2, however, left scientists
puzzled. The features were so lacking in topographic relief that as one
scientist described them, they "might have been painted on with a felt
marker."

There is a possibility that Europa may be internally active due to tidal
heating at a level one-tenth or less than that of Io. Europa is thought to have
a thin crust (less than 30 kilometers or 18 miles thick) of water ice, possibly
floating on a 50-kilometer-deep (30-mile) ocean.

Ganymede turned out to be the largest moon in the solar system, with a diameter
measuring 5,276 kilometers (3,280 miles). It showed two distinct types of
terrain, cratered and grooved, suggesting to scientists that Ganymede's entire
icy crust has been under tension from global tectonic processes.

Callisto has a very old, heavily cratered crust showing remnant rings of
enormous impact craters. The largest craters apparently have been erased by the
flow of icy crust over geologic time. Almost no topographic relief is apparent
in the ghost remnants of the immense impact basins, identifiable only by their
light color and the surrounding subdued rings of concentric ridges.

A faint, dusty ring of material was found around Jupiter. Its outer edge is
129,000 kilometers (80,000 miles) from the center of the planet, and it extends
inward about 30,000 kilometers (18,000 miles).

Two new, small satellites, Adrastea and Metis, were found orbiting just outside
the ring. A third new satellite, Thebe, was discovered between the orbits of
Amalthea and Io.

Jupiter's rings and moons exist within an intense radiation belt of electrons
and ions trapped in the planet's magnetic field. These particles and fields
comprise the jovian magnetosphere or magnetic environment, which extends 3 to 7
million kilometers toward the Sun, and stretches in a windsock shape at least
as far as Saturn's orbit -- a distance of 750 million kilometers (460 million
miles).

As the magnetosphere rotates with Jupiter, it sweeps past Io and strips away
about 1,000 kilograms (1 ton) of material per second. The material forms a
torus, a doughnut-shaped cloud of ions that glow in the ultraviolet. The
torus's heavy ions migrate outward, and their pressure inflates the jovian
magnetosphere to more than twice its expected size. Some of the more energetic
sulfur and oxygen ions fall along the magnetic field into the planet's
atmosphere, resulting in auroras.

Io acts as an electrical generator as it moves through Jupiter's magnetic
field, developing 400,000 volts across its diameter and generating an electric
current of 3 million amperes that flows along the magnetic field to the
planet's ionosphere.


SATURN

The Voyager 1 and 2 Saturn flybys occurred 9 months apart, with the closest
approaches falling on November 12 and August 25, 1981. Voyager 1 flew within
64,200 kilometers (40,000 miles) of the cloud tops, while Voyager 2 came within
41,000 kilometers (26,000 miles).

Saturn is the second largest planet in the solar system. It takes 29.5 Earth
years to complete one orbit of the Sun, and its day is clocked at 10 hours, 39
minutes. Saturn is known to have at least 17 moons and a complex ring system.
Like Jupiter, Saturn is mostly hydrogen and helium. Its hazy yellow hue was
found to be marked by broad atmospheric banding similar to but much fainter
than that found on Jupiter. Close scrutiny by Voyager's imaging systems
revealed long-lived ovals and other atmospheric features generally smaller than
those on Jupiter.

Perhaps the greatest surprises and the most puzzling were found by the Voyagers
in Saturn's rings. It is thought that the rings formed from larger moons that
were shattered by impacts of comets and meteoroids. The resulting dust and
boulder-to house-size particles have accumulated in a broad plane around the
planet varying in density.

The irregular shapes of Saturn's eight smallest moons indicates that they too
are fragments of larger bodies. Unexpected structure such as kinks and spokes
were found in addition to thin rings and broad, diffuse rings not observed from
Earth. Much of the elaborate structure of some of the rings is due to the
gravitational effects of nearby satellites. This phenomenon is most obviously
demonstrated by the relationship between the F-ring and two small moons that
"shepherd" the ring material. The variation in the separation of the moons from
the ring may explain the ring's kinked appearance. Shepherding moons also were
found by Voyager 2 at Uranus.

Radial, spokelike features in the broad B-ring also were found by the Voyagers.
The features are believed to be composed of fine, dust-size particles. The
spokes were observed to form and dissipate in time-lapse images taken by the
Voyagers. While electrostatic charging may create spokes by levitating dust
particles above the ring, the exact cause of the formation of the spokes is not
well understood.

Winds blow at extremely high speeds on Saturn -- up to 1,800 kilometers per
hour (1,100 miles per hour). Their primarily easterly direction indicates that
the winds are not confined to the top cloud layer but must extend at least
2,000 kilometers (1,200 miles) downward into the atmosphere. The characteristic
temperature of the atmosphere is 95 degrees kelvins.

Saturn holds a wide assortment of satellites in its orbit ranging from Phoebe,
a small moon that travels in a retrograde orbit and probably is a captured
asteroid, to Titan, the planet-sized moon with a thick nitrogen-methane
atmosphere. Titan's surface temperature and pressure are 94 degrees kelvins
(-292 degrees Fahrenheit) and 1.5 atmospheres.

Photochemistry converts some atmospheric methane to other organic molecules,
such as ethane, that is thought to accumulate in lakes or oceans. Other more
complex hydrocarbons form the haze particles that eventually fall to the
surface, coating it with a thick layer of organic matter. The chemistry in
Titan's atmosphere may strongly resemble that which occurred on Earth before
life evolved.

The most active surface of any moon seen in the Saturn system was that of
Enceladus. The bright surface of this moon, marked by faults and valleys,
showed evidence of tectonically induced change. Voyager 1 found the moon Mimas
scarred with a crater so huge that the impact that caused it nearly broke the
satellite apart.

Saturn's magnetic field is smaller than Jupiter's, extending only 1 or 2
million kilometers. The axis of the field is almost perfectly aligned with the
rotation axis of the planet.


URANUS

In its first solo planetary flyby, Voyager 2 made its closest approach to
Uranus on January 24, 1986, coming within 81,500 kilometers (50,600 miles) of
the planet's cloud tops.

Uranus is the third largest planet in the solar system. It orbits the Sun at a
distance of about 2.8 billion kilometers (1.7 billion miles) and completes one
orbit every 84 years. The length of a day on Uranus as measured by Voyager 2 is
17 hours, 14 minutes.

Uranus is distinguished by the fact that it is tipped on its side. Its unusual
position is thought to be the result of a collision with a planet-sized body
early in the solar system's history. Given its odd orientation with its polar
regions exposed to sunlight or darkness for long periods, scientists were not
sure what to expect at Uranus.

Voyager 2 found that one of the most striking influences of this sideways
position is its effect on the tail of the magnetic field, which is itself
tilted 60 degrees from the the planet's axis of rotation. The magnetotail was
shown to be twisted by the planet's rotation into a long corkscrew shape behind
the planet.

The presence of a magnetic field at Uranus was not known until Voyager's
arrival. The intensity of the field is roughly comparable to that of Earth's,
though it varies much more from point to point because of its large offset from
the center of Uranus. The peculiar orientation of the magnetic field suggests
that the field is generated at an intermediate depth in the interior where the
pressure is high enough for water to become electrically conducting.

The intensity of radiation within Saturn's radiation belts is such that any
methane trapped in the icy surfaces of the inner moons and ring particles would
quickly darken (within 100,000 years). This may have contributed to the
darkened surfaces of the moons and ring particles, which are almost uniformly
gray.

A high layer of haze was detected around the sunlit pole, which also was found
to radiate large amounts of ultraviolet light, a phenomenon dubbed "dayglow."
The average temperature is about 60 degrees kelvin (-350 degrees Fahrenheit).
Surprisingly, the illuminated and dark poles, and most of the planet, show
nearly the same temperature at the cloud tops.

Voyager found 10 new moons, bringing the total number to 15. Most of the new
moons are small, with the largest measuring about 150 kilometers (about 90
miles) in diameter. The moon Miranda, innermost of the five large moons, was
revealed to be one of the strangest bodies yet seen in the solar system.
Detailed images from Voyager's flyby of the moon showed huge fault canyons as
deep as 20 kilometers (12 miles), terraced layers and a mixture of old and
young surfaces. One theory holds that Miranda may be a reaggregration of
material from an earlier time when the moon was fractured by an violent
impact.

The five large moons appear to be ice-rock conglomerates like the satellites of
Saturn. Titania is marked by huge fault systems and canyons indicating some
degree of geologic, probably tectonic, activity in its history.

Ariel has the brightest and possibly youngest surface of all the Uranian moons
and also appears to have undergone geologic activity that led to many fault
valleys and what seem to be extensive flows of icy material. Little geologic
activity has occurred on Umbriel or Oberon, judging by their old and dark
surfaces.

All nine previously known rings were studied showing the Uranian rings to be
distinctly different from those at Jupiter and Saturn. The ring system may be
relatively young and did not form at the same time as Uranus. Particles that
make up the rings may be remnants of a moon that was broken by a high- velocity
impact or torn up by gravitational effects.


NEPTUNE

When Voyager flew within 5,000 kilometers (3,000 miles) of Neptune on August
25, 1989, the planet was the most distant member of the solar system from the
Sun. (Pluto once again will become most distant in 1999.)

Neptune orbits the Sun every 165 years. It is the smallest planet of this solar
system's gas giants. Neptune is now known to have eight moons, six of which
were found by Voyager. The length of a Neptunian day has been determined to be
16 hours, 6.7 minutes.

Even though Neptune receives only three percent as much sunlight as Jupiter
does, it is a dynamic planet and surprisingly showed several large, dark spots
reminiscent of Jupiter's hurricane-like storms. The largest spot, dubbed the
Great Dark Spot, is about the size of Earth and is similar to the Great Red
Spot on Jupiter. A small, irregularly shaped, eastward-moving cloud was
observed "scooting" around Neptune every 16 hours or so; this "scooter," as
Voyager scientists called it, could be a cloud plume rising above a deeper
cloud deck.

Long, bright clouds, similar to cirrus clouds on Earth, were seen high in
Neptune's atmosphere. At low northern latitudes, Voyager captured images of
cloud streaks casting their shadows on cloud decks below.

The strongest winds on any planet were measured on Neptune. Most of the winds
there blow westward, opposite to the rotation of the planet. Near the Great
Dark Spot, winds blow up to 2,000 kilometers (1,200 miles) an hour.

The magnetic field of Neptune, like that of Uranus, turned out to be highly
tilted -- 47 degrees from the rotation axis and offset at least 0.55 radii
(about 13,500 kilometers or 8,500 miles) from the physical center. Comparing
the magnetic fields of the two planets, scientists think the extreme
orientation may be characteristic of flows in the interiors of both Uranus and
Neptune -- and not the result, in Uranus's case, of that planet's sideways
orientation or of any possible field reversals at either planet.

Voyager's studies of radio waves caused by the magnetic field revealed the
length of a Neptunian day. The spacecraft also detected auroras, but much
weaker than those on Earth and other planets.

Triton, the largest of the moons of Neptune, was shown to be not only the most
intriguing satellite of the Neptunian system, but one of the most interesting
in all the solar system. It shows evidence of a remarkable geologic history,
and Voyager 2 images showed active geyser-like eruptions spewing invisible
nitrogen gas and dark dust particles several kilometers into the tenuous
atmosphere. Triton's relatively high density and retrograde orbit offer strong
evidence that Triton is not an original member of Neptune's family but is a
captured object. If that is the case, tidal heating could have melted Triton in
its originally eccentric orbit, and the moon might even have been liquid for as
long as one billion years after its capture by Neptune.

An extremely thin atmosphere extends about 800 kilometer (500 miles) above
Triton's surface. Nitrogen ice particles may form thin clouds a few kilometers
above the surface. The atmospheric pressure at the surface is about 14
microbars, 1/70,000th the surface pressure on Earth. The surface temperature is
about 38 degrees kelvin (-391 degrees Fahrenheit) the coldest temperature of
any body known in the solar system.

The new moons found at Neptune by Voyager are all small and remain close to
Neptune's equatorial plane. Names selected from mythology's water deities will
be given Neptune's newest moons by the International Astronomical Union.

Voyager 2 solved many of the questions scientists had about Neptune's rings.
Searches for "ring arcs," or partial rings, showed that Neptune's rings
actually are complete, but are so diffuse and the material in them so fine that
they could not be fully resolved from Earth. From the outermost in, the rings
have been designated 1989N1R, 1984N4R, 1989N2R and 1989N3R.

-----

Statistics

             Diameter                            Distance from Sun
 Jupiter     142,984 km/88,846 mi    778,000,000 km/483,000,000 mi

 Jupiter's Moons                       Distance From Planet Center
 Metis       40 km/25 mi                      128,000 km/79,500 mi
 Adrastea    24x20x14 km/14x12x9 mi           129,000 km/80,100 mi
 Amalthea    270x166x150 km/165x103x95 mi    181,300 km/112,600 mi
 Thebe       110x90km/65x55 mi               222,000 km/138,000 mi
 Io          3,630 km/2,225 mi               422,000 km/262,000 mi
 Europa      3,138 km/1,949 mi               661,000 km/414,500 mi
 Ganymede    5,262 km/3,269 mi             1,070,000 km/664,900 mi
 Callisto    4,800 km/3,000 mi            1,883,000 km/1,170000 mi
 Leda        16 km/10 mi                11,094,000 km/6,900,000 mi
 Himalia     186 km/115 mi              11,480,000 km/7,133,000 mi
 Lysithia    36 km/20 mi                11,720,000 km/7,282,000 mi
 Elara       76 km/47 mi                11,737,000 km/7,293,000 mi
 Ananke      30/18 mi                  21,200,000 km/13,173,000 mi
 Carme       40 km/25 mi               22,600,000 km/14,043,000 mi
 Pasiphae    50 km/31 mi               23,500,000 km/14,602,000 mi
 Sinope      36 km/22 mi               23,700,000 km/14,727,000 mi

             Diameter                            Distance from Sun
 Saturn      120,536 km/74,900 mi   1.4  billion km/870 million mi

 Saturn's Moons                        Distance from Planet Center
 Atlas       40x20 km/24x12 mi                137,670 km/85,500 mi
 Prometheus  140x100x80 km/85x60x50 mi        139,353 km/86,600 mi
 Pandora     110x90x80 km/70x55x50 mi         141,700 km/88,500 mi
 Epimetheus  140x120x100 km/85x70x60 mi.      151,472 km/94,124 mi
 Janus       220x200x160 km/135x125x100 mi.   151,422 km/94,093 mi
 Mimas       392 km/243 mi                   185,520 km/115,295 mi
 Enceladus   520 km/320 mi                   238,020 km/147,900 mi
 Tethys      1,060 km/660 km                 294,660 km/183,100 mi
 Telesto     34x28x26 km/20x17x16 mi         294,660 km/183,100 mi
 Calypso     34x22x22 km/20x13x13 mi         294,660 km/183,100 mi
 Dione       1,120 km/695 mi                 377,400 km/234,500 mi
 Helene      36x32x30 km/22x20x19 mi         377,400 km/234,900 mi
 Rhea        1,530 km/950 mi                 527,040 km/327,500 mi
 Titan       5,150 km/3,200 mi             1,221,860 km/759,300 mi
 Hyperion    410x260x220 km/250x155x135 mi 1,481,000 km/920,300 mi
 Iapetus     1,460 km/910 mi             3,560,830 km/2,212,900 mi
 Phoebe      220 km/135 mi              12,952,000 km/8,048,000 mi

             Diameter                            Distance from Sun
 Uranus      51,118 km/31,764 mi       3 billion km/1.8 billion mi

 Uranus's Moons:                       Distance from Planet Center
 Cordelia      26 km/16 mi                     49,800 km/30,950 mi
 Ophelia       30 km/18 mi                     53,800 km/33,400 mi
 Bianca        42 km/26 mi                     59,200 km/36,800 mi
 Juliet        62 km/38 mi                     61,800 km/38,400 mi
 Desdemona     54 km/33 mi                     62,700 km/38,960 mi
 Rosalind      84 km/52 mi                     64,400 km/40,000 mi
 Portia       108 km/67 mi                     66,100 km/41,100 mi
 Cressida      54 km/32 mi                     69,900 km/43,400 mi
 Belinda       66 km/40 mi                     75,300 km/46,700 mi
 Puck         154 km/95 mi                     86,000 km/53,000 mi
 Miranda     472 km/293 mi                    129,900 km/80,650 mi
 Ariel     1,158 km/720 mi                   190,900 km/118,835 mi
 Umbriel   1,172 km/728 mi                   265,969 km/165,300 mi
 Titania   1,580 km/981 mi                   436,300 km/271,100 mi
 Oberon    1,524 km/947 mi                   583,400 km/362,500 mi

             Diameter                            Distance from Sun
 Neptune     49,528 km/30,776 mi     4.5 billion km/2.7 billion mi

 Neptune's Moons:                      Distance from Planet Center
 1989N6        54 km/33 mi                     48,000 km/29,827 mi
 1989N5        80 km/50 mi                     50,000 km/31,000 mi
 1989N3      180 km/110 mi                     52,500 km/32,600 mi
 1989N4       150 km/95 mi                     62,000 km/38,525 mi
 1989N2      190 km/120 mi                     73,600 km/45,700 mi
 1989N1      400 km/250 mi                    117,600 km/73,075 mi
 Triton  2,700 km/1,680 mi                    354,760km/220,500 mi
 Nereid      340 km/210 mi               5,509,090 km/3,423,000 mi