FACT SHEET: THE VOYAGER
PLANETARY MISSION



The twin spacecraft Voyager 1 and Voyager 2 were launched by NASA in separate
months in 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 five 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 Voyagers' home 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 the
Earth. Their two-planet mission became four. Their five-year lifetimes stretched to 12
and more.

Eventually, between them, Voyager 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 mission ended after the Jupiter and Saturn flybys alone, it still would
have provided the material to rewrite astronomy textbooks. But having doubled their
already ambitious itineraries, the Voyagers returned to Earth information over the years
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
our 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 1980s which allowed for a four-planet tour
for a minimum of propellant and trip time. 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 it to the next destination. Using this "gravity assist" technique,
first demonstrated with NASA's Mariner 10 Venus/Mercury mission in 1973-74, the
flight time to Neptune was reduced from 30 years to 12.

While the four-planet mission was known to be possible, it was deemed to be too
expensive to build a spacecraft that could go the distance, carry the instruments needed
and last long enough to accomplish such a long 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.

From the NASA Kennedy Space Center at Cape Canaveral, Florida, Voyager 2 was
launched first, on August 20, 1977; Voyager 1 was launched on a faster, shorter
trajectory on 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 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 would likely
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,
continues 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, too, to
interstellar space. 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 is also 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 two 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 devices, 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.

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 (three 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 have apparently been erased by the flow of the 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 three to seven 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 (one 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 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 nine 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 was 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 puzzles 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 the ring's kinked appearance. Shepherding
moons were also found by Voyager 2 at Uranus.

Radial, spoke-like features in the broad B-ring 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
kelvins.

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

Radiation belts at Uranus were found to be of an intensity similar to those at Saturn. The
intensity of radiation within the belts is such that irradiation would quickly darken (within
100,000 years) any methane trapped in the icy surfaces of the inner moons and ring
particles. This may have contributed to the darkened surfaces of the moons and ring
particles, which are almost uniformly gray in color.

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 kelvins (-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 by the spacecraft and showed 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 of our 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, or 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 kelvins (-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 for the new moons were selected from mythology's
water deities by the International Astronomical Union, they are: Naiad, Thalassa,
Despina, Galatea, Larissa, Proteus.

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 Adams, Plateau, Le Verrier
and Galle.

INTERSTELLAR MISSION

The spacecraft are continuing to return data about interplanetary space and some of our
stellar neighbors near the edges of the Milky Way.

As the Voyagers cruise gracefully in the solar wind, their fields, particles and waves
instruments are studying the space around them. In May 1993, scientists concluded that
the plasma wave experiment was picking up radio emissions that originate at the
heliopause -- the outer edge of our solar system.

The heliopause is the outermost boundary of the solar wind, where the interstellar
medium restricts the outward flow of the solar wind and confines it within a magnetic
bubble called the heliosphere. The solar wind is made up of electrically charged atomic
particles, composed primarily of ionized hydrogen, that stream outward from the Sun.

Exactly where the heliopause is has been one of the great unanswered questions in space
physics. By studying the radio emissions, scientists now theorize the heliopause exists
some 90 to 120 astronomical units (AU) from the Sun. (One AU is equal to 150 million
kilometers (93 million miles), or the distance from the Earth to the Sun.

The Voyagers have also become space-based ultraviolet observatories and their unique
location in the universe gives astronomers the best vantage point they have ever had for
looking at celestial objects that emit ultraviolet radiation.

The cameras on the spacecraft have been turned off and the ultraviolet instrument is the
only experiment on the scan platform that is still functioning. Voyager scientists expect to
continue to receive data from the ultraviolet spectrometers at least until the year 2000. At
that time, there not be enough electrical power for the heaters to keep the ultraviolet
instrument warm enough to operate.

Yet there are several other fields and particle instruments that can continue to send back
data as long as the spacecraft stay alive. They include: the cosmic ray subsystem, the
low-energy charge particle instrument, the magnetometer, the plasma subsystem, the
plasma wave subsystem and the planetary radio astronomy instrument. Barring any
catastrophic events, JPL should be able to retrieve this information for least the next 20
and perhaps event the next 30 years.



                   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/165,300mi
Titania     1,580 km/981 mi                  436,300 km/271,100mi
Oberon      1,524 km/947 mi                  583,400km/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

Naiad       54 km/33 mi                       48,000 km/29,827 mi
Thalassa    80 km/50 mi                       50,000 km/31,000 mi
Despina     180 km/110 mi                     52,500 km/32,600 mi
Galatea     150 km/95 mi                      62,000 km/38,525 mi
Larissa     190 km/120 mi                     73,600 km/45,700 mi
Proteus     400 km/250 mi                    117,600 km/73,075 mi
Triton      2,700 km/1,680 mi                354,760km/220,500 mi
Nereid      340km/210 mi                5,509 090 km/3,423,000 mi



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Last Updated: 5/24/95
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E-Mail Address: richard.p.rudd@jpl.nasa.gov