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Return-path: <ota+space.mail-errors@andrew.cmu.edu> X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from beak.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl@andrew.cmu.edu (->+dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl) (->ota+space.digests) ID </afs/andrew.cmu.edu/usr1/ota/Mailbox/0aPSza200VcJA0uE5w>; Thu, 7 Jun 1990 02:10:46 -0400 (EDT) Message-ID: <kaPSz9G00VcJ40sU4d@andrew.cmu.edu> Precedence: junk Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Thu, 7 Jun 1990 02:10:18 -0400 (EDT) Subject: SPACE Digest V11 #500 SPACE Digest Volume 11 : Issue 500 Today's Topics: Voyager Mission Summary (forwarded) Administrivia: Submissions to the SPACE Digest/sci.space should be mailed to space+@andrew.cmu.edu. Other mail, esp. [un]subscription notices, should be sent to space-request+@andrew.cmu.edu, or, if urgent, to tm2b+@andrew.cmu.edu ---------------------------------------------------------------------- Date: 6 Jun 90 17:46:41 GMT From: usc!elroy.jpl.nasa.gov!news@ucsd.edu (Steve Groom) Subject: Voyager Mission Summary (forwarded) This fact sheet was posted to an internal NASA newsgroup in support of today's press conference covering the Voyager missions to the outer planets. I thought it was a very good summary and worth reposting here. -steve stevo@elroy.jpl.nasa.gov ------------------------------------------------------------------------ THE VOYAGER MISSION: A SUMMARY The twin spacecraft Voyager 1 and Voyager 2 were launched by NASA during the summer of 1977 from Cape Canaveral, Fla. 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 (JPL) in Pasadena, Calif. 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 - more - - 2 - 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, Fla. Voyager 2 was launched on Aug. 20, 1977; Voyager 1 was launched on a faster, shorter trajectory Sept. 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 Nov. 12, 1980, followed by Voyager 2 to Jupiter on July 9, 1979, and Saturn on Aug. 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 Jan. 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 Aug. 25, 1989, the spacecraft flew southward, below the ecliptic plane - more - - 3 - 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 - more - - 4 - and Neptune encounters. Both are with JPL. The Voyager program manager at NASA Headquarters, Washington, D.C., 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. - more - - 5 - 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. - more - - 6 - 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 Nov. 12 and Aug. 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 - more - - 7 - (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 Jan. 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. - more - - 8 - 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 Aug. 25, 1989, the planet was the most distant member - more - - 9 - 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 - more - - 10 - 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. - end - 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 - more - - 11 - 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 - more - - 12 - 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 - end - Paula Cleggett-Haleim Mary Beth Murrill Headquarters, Washington, D.C. JPL, Pasadena, Calif. (Phone: 202/453-1547) (Phone: 818/354-5011) JUNE 6, 1990 Steve Groom, Jet Propulsion Laboratory, Pasadena, CA stevo@elroy.jpl.nasa.gov {ames,usc}!elroy!stevo ------------------------------ End of SPACE Digest V11 #500 *******************