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83-463: The first suggestions of bands and weather on Uranus came in the 19th century, such as an observation in March and April 1884 of a white band circling partially around Uranus's equator, only two years after Uranus's "spring" equinox. In 1986 Voyager 2 discovered that the visible southern hemisphere of Uranus can be subdivided into two regions: a bright polar cap and dark equatorial bands (see figure on

166-502: A 10-hour "volcano watch", it confirmed Voyager 1 ' s observations of active volcanism on the moon Io , and revealed how the moon's surface had changed in the four months since the previous visit. Together, the Voyagers observed the eruption of nine volcanoes on Io, and there is evidence that other eruptions occurred between the two Voyager fly-bys. Jupiter's moon Europa displayed a large number of intersecting linear features in

249-485: A Uranian year (beginning in the 1950s) has shown regular variation in the brightness in two spectral bands , with maxima occurring at the solstices and minima occurring at the equinoxes . A similar periodic variation, with maxima at the solstices, has been noted in microwave measurements of the deep troposphere begun in the 1960s. Stratospheric temperature measurements beginning in the 1970s also showed maximum values near 1986 solstice. The majority of this variability

332-426: A backup for Voyager 1 . Upon successful completion of Voyager 1 's objectives, Voyager 2 would get a mission extension to send the probe on towards Uranus and Neptune. Titan was selected due to the interest developed after the images taken by Pioneer 11 in 1979, which had indicated the atmosphere of the moon was substantial and complex. Hence the trajectory was designed for optimum Titan flyby. Constructed by

415-472: A dark spot on the hemisphere of Uranus that was in darkness for many years indicates that near equinox Uranus entered a period of elevated weather activity. The tracking of numerous cloud features allowed determination of zonal winds blowing in the upper troposphere of Uranus. At the equator winds are retrograde, which means that they blow in the reverse direction to the planetary rotation. Their speeds are from −100 to −50 m/s. Wind speeds increase with

498-530: A degree that allowed the scan platform to resume its function. Voyager 2 , which would have been diverted to perform the Titan flyby if Voyager 1 had been unable to, did not pass near Titan due to the malfunction, and subsequently, proceeded with its mission to explore the Uranian system. The closest approach to Uranus occurred on January 24, 1986, when Voyager 2 came within 81,500 km (50,600 mi) of

581-433: A distance of 1.7 light-years. If undisturbed for 296,000 years , Voyager 2 should pass by the star Sirius (8.6 light-years from Earth) at a distance of 4.3 light-years. Both Voyager space probes carry a gold-plated audio-visual disc , a compilation meant to showcase the diversity of life and culture on Earth in the event that either spacecraft is ever found by any extraterrestrial discoverer . The record, made under

664-461: A faint northern polar collar arose, whereas the southern collar became nearly invisible, although the zonal wind profile remained asymmetric, with northern winds being slightly slower than southern. The mechanism of physical changes is still not clear. Near the summer and winter solstices , Uranus's hemispheres lie alternately either in full glare of the Sun's rays or facing deep space. The brightening of

747-541: A frequency of 0.9-40 MHz. The UEDs were detected from 600,000 km of Uranus over 24 hours, most of which were not visible. However, microphysical modeling suggests that Uranian lightning occurs in convective storms occurring in deep troposphere water clouds. If this is the case, lightning will not be visible due to the thick cloud layers above the troposphere. Uranian lightning has a power of around 10 W, emits 1×10^7 J – 2×10^7 J of energy, and lasts an average of 120 ms. Detailed images from Voyager 2 ' s flyby of

830-654: A frequency range of 50 Hz – 12 kHz at magnetic latitudes 7˚-33˚. These plasma wave detections were possibly triggered by lightning over 20 minutes in the ammonia clouds of the magnetosphere. During Voyager 2 ' s closest approach to Neptune, the PWS instrument provided Neptune’s first plasma wave detections at a sample rate of 28,800 samples per second. The measured plasma densities range from 10 – 10 cm . Voyager 2 discovered previously unknown Neptunian rings , and confirmed six new moons: Despina , Galatea , Larissa , Proteus , Naiad and Thalassa . While in

913-632: A level about one-tenth that of Io. Europa is thought to have a thin crust (less than 30 km (19 mi) thick) of water ice, possibly floating on a 50 km (31 mi)-deep ocean. 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. The closest approach to Saturn occurred at 03:24:05 UT on August 26, 1981. When Voyager 2 passed behind Saturn, viewed from Earth, it utilized its radio link to investigate Saturn's upper atmosphere, gathering data on both temperature and pressure. In

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996-493: A longer, more circular trajectory. Voyager 1 ' s initial orbit had an aphelion of 8.9 AU (830 million mi; 1.33 billion km), just a little short of Saturn's orbit of 9.5 AU (880 million mi; 1.42 billion km). Whereas, Voyager 2 ' s initial orbit had an aphelion of 6.2 AU (580 million mi; 930 million km), well short of Saturn's orbit. In April 1978, no commands were transmitted to Voyager 2 for

1079-636: A major ground station antenna upgrade that took a year to complete. In October 2020, astronomers reported a significant unexpected increase in density in the space beyond the Solar System as detected by the Voyager 1 and Voyager 2 ; this implies that "the density gradient is a large-scale feature of the VLISM (very local interstellar medium ) in the general direction of the heliospheric nose ". On July 18, 2023, Voyager 2 overtook Pioneer 10 as

1162-507: A massive project involving two groups of two probes each, with one group visiting Jupiter, Saturn, and Pluto and the other Jupiter, Uranus, and Neptune. The spacecraft would be designed with redundant systems to ensure survival throughout the entire tour. By 1972 the mission was scaled back and replaced with two Mariner program -derived spacecraft, the Mariner Jupiter-Saturn probes. To keep apparent lifetime program costs low,

1245-530: A period of time, causing the spacecraft to switch from its primary radio receiver to its backup receiver. Sometime afterwards, the primary receiver failed altogether. The backup receiver was functional, but a failed capacitor in the receiver meant that it could only receive transmissions that were sent at a precise frequency, and this frequency would be affected by the Earth's rotation (due to the Doppler effect ) and

1328-523: A single 70-centimeter (28 in) diameter spherical titanium tank. It contained 100 kilograms (220 lb) of hydrazine at launch, providing enough fuel until 2034. The Voyager 2 probe was launched on August 20, 1977, by NASA from Space Launch Complex 41 at Cape Canaveral, Florida , aboard a Titan IIIE / Centaur launch vehicle . Two weeks later, the twin Voyager 1 probe was launched on September 5, 1977. However, Voyager 1 reached both Jupiter and Saturn sooner, as Voyager 2 had been launched into

1411-431: Is a space probe launched by NASA on August 20, 1977, as a part of the Voyager program . It was launched on a trajectory towards the gas giants Jupiter and Saturn and enabled further encounters with the ice giants Uranus and Neptune . It remains the only spacecraft to have visited either of the ice giant planets, and was the third of five spacecraft to achieve Solar escape velocity , which allowed it to leave

1494-468: Is believed to occur due to changes in the viewing geometry . Uranus is an oblate spheroid , which causes its visible area to become larger when viewed from the poles . This explains in part its brighter appearance at solstices. Uranus is also known to exhibit strong zonal variations in albedo (see above). For instance, the south polar region of Uranus is much brighter than the equatorial bands. In addition, both poles demonstrate elevated brightness in

1577-407: Is currently no agreement about whether any changes in wind speed have occurred since 1986, and nothing is known about much slower meridional winds. Determining the nature of this seasonal variation is difficult because good data on Uranus's atmosphere has existed for less than one full Uranian year (84 Earth years). A number of discoveries have however been made. Photometry over the course of half

1660-409: Is known to have a bright south polar region, the north pole is fairly dim, which is incompatible with the model of the seasonal change outlined above. During its previous northern solstice in 1944, Uranus displayed elevated levels of brightness, which suggests that the north pole was not always so dim. This information implies that the visible pole brightens some time before the solstice and darkens after

1743-441: Is not fully known, but it appears that Uranus's extreme axial tilt results in extreme seasonal variations in its weather. Several solutions have been proposed to explain the calm weather on Uranus. One proposed explanation for this dearth of cloud features is that Uranus's internal heat appears markedly lower than that of the other giant planets; in astronomical terms, it has a low internal thermal flux . Why Uranus's heat flux

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1826-499: Is now in its extended mission of studying the interstellar medium . It is at a distance of 138.05  AU (20.7  billion   km ; 12.8 billion  mi ) from Earth as of October 2024 . The probe entered the interstellar medium on November 5, 2018, at a distance of 119.7 AU (11.1 billion mi; 17.9 billion km) from the Sun and moving at a velocity of 15.341 km/s (34,320 mph) relative to

1909-502: Is observed include: Downslope winds occur on the leeward side of mountain barriers when a stable air mass is carried over the mountain by strong winds that increase in strength with height. Moisture is removed and latent heat released as the air mass is orographically lifted. As the air mass descends, it is compression heated. The warm foehn wind , locally known as the Chinook wind , Bergwind or Diablo wind or Nor'wester depending on

1992-525: Is only 0.042 ± 0.047  W/m, which is lower than the internal heat flux of Earth of about 0.075 W/m. The lowest temperature recorded in Uranus's tropopause is 49 K (−224 °C), making Uranus the coldest planet in the Solar System, colder than Neptune . Another hypothesis states that when Uranus was "knocked over" by the supermassive impactor which caused its extreme axial tilt,

2075-434: Is so low is still not understood. Neptune , which is Uranus's near twin in size and composition, radiates 2.61 times as much energy into space as it receives from the Sun. Uranus, by contrast, radiates hardly any excess heat at all. The total power radiated by Uranus in the far infrared (i.e. heat ) part of the spectrum is 1.06 ± 0.08 times the solar energy absorbed in its atmosphere . In fact, Uranus's heat flux

2158-414: Is using to find out what the Solar System is like beyond the heliosphere . As of September 2023 Voyager 2 is transmitting scientific data at about 160 bits per second . Information about continuing telemetry exchanges with Voyager 2 is available from Voyager Weekly Reports. In 1992, Voyager 2 observed the nova V1974 Cygni in the far-ultraviolet, first of its kind. The further increase in

2241-691: The Jet Propulsion Laboratory (JPL), Voyager 2 included 16 hydrazine thrusters, three-axis stabilization , gyroscopes and celestial referencing instruments (Sun sensor/ Canopus Star Tracker) to maintain pointing of the high-gain antenna toward Earth. Collectively these instruments are part of the Attitude and Articulation Control Subsystem (AACS) along with redundant units of most instruments and 8 backup thrusters. The spacecraft also included 11 scientific instruments to study celestial objects as it traveled through space. Built with

2324-650: The Solar System . Launched 16 days before its twin Voyager 1 , the primary mission of the spacecraft was to study the outer planets and its extended mission is to study interstellar space beyond the Sun's heliosphere . Voyager 2 successfully fulfilled its primary mission of visiting the Jovian system in 1979, the Saturnian system in 1981, Uranian system in 1986, and the Neptunian system in 1989. The spacecraft

2407-444: The equinox . Detailed analysis of the visible and microwave data revealed that the periodical changes of brightness are not completely symmetrical around the solstices, which also indicates a change in the albedo patterns. In addition, the microwave data showed increases in pole–equator contrast after the 1986 solstice. Finally in the 1990s, as Uranus moved away from its solstice , Hubble and ground-based telescopes revealed that

2490-535: The inverse-square law . When the spacecraft is unable to communicate with Earth , the Digital Tape Recorder (DTR) can record about 64 megabytes of data for transmission at another time. Voyager 2 is equipped with three multihundred-watt radioisotope thermoelectric generators (MHW RTGs). Each RTG includes 24 pressed plutonium oxide spheres. At launch, each RTG provided enough heat to generate approximately 157 W of electrical power. Collectively,

2573-407: The relative humidity to 100% and create clouds and, under the right conditions, precipitation . Orographic lifting can have a number of effects, including precipitation, rain shadowing, leeward winds, and associated clouds. Precipitation induced by orographic lift occurs in many places throughout the world . Examples include: The highest precipitation amounts are found slightly upwind from

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2656-531: The RTGs supplied the spacecraft with 470 watts at launch (halving every 87.7 years). They were predicted to allow operations to continue until at least 2020, and continued to provide power to five scientific instruments through the early part of 2023. In April 2023 JPL began using a reservoir of backup power intended for an onboard safety mechanism. As a result, all five instruments had been expected to continue operation through 2026. In October 2024 NASA announced that

2739-404: The Solar System's heliosphere is being pushed in. On April 22, 2010, Voyager 2 encountered scientific data format problems. On May 17, 2010, JPL engineers revealed that a flipped bit in an on-board computer had caused the problem, and scheduled a bit reset for May 19. On May 23, 2010, Voyager 2 resumed sending science data from deep space after engineers fixed the flipped bit. In 2013, it

2822-525: The Sun. Voyager 2 has left the Sun's heliosphere and is traveling through the interstellar medium , though still inside the Solar System , joining Voyager 1 , which had reached the interstellar medium in 2012. Voyager 2 has begun to provide the first direct measurements of the density and temperature of the interstellar plasma . Voyager 2 remains in contact with Earth through the NASA Deep Space Network . Communications are

2905-478: The Uranian moon Miranda showed huge canyons made from geological faults . One hypothesis suggests that Miranda might consist of a reaggregation of material following an earlier event when Miranda was shattered into pieces by a violent impact. Voyager 2 discovered two previously unknown Uranian rings. Measurements showed that the Uranian rings are different from those at Jupiter and Saturn. The Uranian ring system might be relatively young, and it did not form at

2988-461: The Voyager flyby. Recent observation also discovered that cloud-features on Uranus have a lot in common with those on Neptune, although the weather on Uranus is much calmer. The dark spots common on Neptune had never been observed on Uranus before 2006, when the first such feature was imaged. In that year observations from both Hubble Space Telescope and Keck Telescope revealed a small dark spot in

3071-420: The brightness at those wavelengths helped in the more detailed study of the nova. In July 1994, an attempt was made to observe the impacts from fragments of the comet Comet Shoemaker–Levy 9 with Jupiter. The craft's position meant it had a direct line of sight to the impacts and observations were made in the ultraviolet and radio spectrum. Voyager 2 failed to detect anything, with calculations showing that

3154-426: The computer software in order to modify the functioning of the remaining thrusters to slow down the clogging of the small diameter hydrazine injector jets. Before uploading the software update on the Voyager 1 computer, NASA will first try the procedure with Voyager 2 , which is closer to Earth. The probe is expected to keep transmitting weak radio messages until at least the mid-2020s, more than 48 years after it

3237-425: The correct attitude of the spacecraft and to point its high-gain antenna in the direction of Earth are out of use due to clogging problems in their hydrazine injector. The spacecraft no longer has backups available for its thruster system and "everything onboard is running on single-string" as acknowledged by Suzanne Dodd, Voyager project manager at JPL , in an interview with Ars Technica . NASA has decided to patch

3320-441: The deep tropospheric circulation , because thick polar clouds and haze may inhibit convection. For a short period in the second half of 2004, a number of large clouds appeared in the Uranian atmosphere, giving it a Neptune -like appearance. Observations included record-breaking wind speeds of 824 km/h and a persistent thunderstorm referred to as "Fourth of July fireworks". Why this sudden upsurge in activity should be occurring

3403-910: The direction of a team including Carl Sagan and Timothy Ferris , includes photos of the Earth and its lifeforms, a range of scientific information, spoken greetings from people such as the Secretary-General of the United Nations and the President of the United States and a medley, "Sounds of Earth", that includes the sounds of whales, a baby crying, waves breaking on a shore, and a collection of music spanning different cultures and eras including works by Wolfgang Amadeus Mozart , Blind Willie Johnson , Chuck Berry and Valya Balkanska . Other Eastern and Western classics are included, as well as performances of indigenous music from around

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3486-462: The distance from the equator, reaching zero values near ±20° latitude, where the troposphere's temperature minimum is located. Closer to the poles, the winds shift to a prograde direction, flowing with its rotation. Wind speeds continue to increase reaching maxima at ±60° latitude before falling to zero at the poles. Wind speeds at −40° latitude range from 150 to 200 m/s. Because the collar obscures all clouds below that parallel, speeds between it and

3569-426: The event also caused it to expel most of its primordial heat, leaving it with a depleted core temperature. Another hypothesis is that some form of barrier exists in Uranus's upper layers which prevents the core's heat from reaching the surface. For example, convection may take place in a set of compositionally different layers, which may inhibit the upward heat transport . Sources Voyager 2 Voyager 2

3652-448: The fireballs were just below the craft's limit of detection. On November 29, 2006, a telemetered command to Voyager 2 was incorrectly decoded by its on-board computer—in a random error—as a command to turn on the electrical heaters of the spacecraft's magnetometer. These heaters remained turned on until December 4, 2006, and during that time, there was a resulting high temperature above 130 °C (266 °F), significantly higher than

3735-538: The flyby. Following a course correction in 1987, Voyager 2 ' s closest approach to Neptune occurred on August 25, 1989. Through repeated computerized test simulations of trajectories through the Neptunian system conducted in advance, flight controllers determined the best way to route Voyager 2 through the Neptune–Triton system. Since the plane of the orbit of Triton is tilted significantly with respect to

3818-431: The height of Uranus's southern summer and could not observe the northern hemisphere . However, at the end of 1990s and the beginning of the twenty-first century, when the northern polar region came into view, Hubble Space Telescope (HST) and Keck telescope initially observed neither a collar nor a polar cap in the northern hemisphere. Thus, Uranus appeared to be asymmetric: bright near the south pole and uniformly dark in

3901-405: The highest regions of the atmosphere, where the pressure was measured at 70 mbar (1.0 psi), Voyager 2 recorded a temperature of 82  K (−191.2  °C ; −312.1  °F ). Deeper within the atmosphere, where the pressure was recorded to be 1,200 mbar (17 psi), the temperature rose to 143 K (−130 °C; −202 °F). The spacecraft also observed that the north pole

3984-589: The intent for eventual interstellar travel, Voyager 2 included a large, 3.7 m (12 ft) parabolic, high-gain antenna ( see diagram ) to transceive data via the Deep Space Network on Earth. Communications are conducted over the S-band (about 13 cm wavelength) and X-band (about 3.6 cm wavelength) providing data rates as high as 115.2 kilobits per second at the distance of Jupiter, and then ever-decreasing as distance increases, because of

4067-399: The low-resolution photos from Voyager 1 . At first, scientists believed the features might be deep cracks, caused by crustal rifting or tectonic processes. Closer high-resolution photos from Voyager 2 , however, were puzzling: the features lacked topographic relief, and one scientist said they "might have been painted on with a felt marker". Europa is internally active due to tidal heating at

4150-589: The magnetic field. Finally, in December 2018, Stone announced that Voyager 2 reached interstellar space on November 5, 2018. Maintenance to the Deep Space Network cut outbound contact with the probe for eight months in 2020. Contact was reestablished on November 2, when a series of instructions was transmitted, subsequently executed, and relayed back with a successful communication message. On February 12, 2021, full communications were restored after

4233-401: The magnetometers were designed to endure, and a sensor rotated away from the correct orientation. On August 30, 2007, Voyager 2 passed the termination shock and then entered into the heliosheath , approximately 1 billion mi (1.6 billion km) closer to the Sun than Voyager 1 did. This is due to the interstellar magnetic field of deep space. The southern hemisphere of

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4316-563: The microwave part of the spectrum, whereas the polar stratosphere is known to be cooler than the equatorial one. So seasonal change seems to happen as follows: poles, which are bright both in visible and microwave spectral bands, come into the view at solstices resulting in brighter planet, whereas the dark equator is visible mainly near equinoxes resulting in darker planet. In addition, occultations at solstices probe hotter equatorial stratosphere. However, there are some reasons to believe that seasonal changes are happening in Uranus. Although Uranus

4399-495: The mission would include only flybys of Jupiter and Saturn, but keep the Grand Tour option open. As the program progressed, the name was changed to Voyager. The primary mission of Voyager 1 was to explore Jupiter, Saturn, and Saturn's largest moon, Titan . Voyager 2 was also to explore Jupiter and Saturn, but on a trajectory that would have the option of continuing on to Uranus and Neptune, or being redirected to Titan as

4482-494: The neighborhood of Neptune, Voyager 2 discovered the " Great Dark Spot ", which has since disappeared, according to observations by the Hubble Space Telescope . The Great Dark Spot was later hypothesized to be a region of clear gas, forming a window in the planet's high-altitude methane cloud deck. Once its planetary mission was over, Voyager 2 was described as working on an interstellar mission, which NASA

4565-410: The north from the collar. In all other respects Uranus looked like a dynamically dead planet in 1986. However, in the 1990s the number of observed bright cloud features grew considerably. The majority of them were found in the northern hemisphere as they started to become visible. The common though incorrect explanation of this fact was that bright clouds are easier to identify in its dark part, whereas in

4648-429: The northern (winter) hemisphere of Uranus. It was located at the latitude of about 28 ± 1° and measured approximately 2° (1300 km) in latitude and 5° (2700 km) in longitude. The feature called Uranus Dark Spot (UDS) moved in the prograde direction relative Uranus's rotation with an average speed of 43.1 ± 0.1 m/s , which is almost 20 m/s faster than the speed of clouds at the same latitude. The latitude of UDS

4731-524: The onboard receiver's temperature, among other things. Voyager 2 ' s closest approach to Jupiter occurred at 22:29 UT on July 9, 1979. It came within 570,000 km (350,000 mi) of the planet's cloud tops. Jupiter's Great Red Spot was revealed as a complex storm moving in a counterclockwise direction. Other smaller storms and eddies were found throughout the banded clouds. Voyager 2 returned images of Jupiter, as well as its moons Amalthea , Io , Callisto , Ganymede , and Europa . During

4814-408: The other hand, UDS demonstrated the highest contrast at 1.6 μm, where GDS were not detected. This implies that dark spots on the two ice giants are located at somewhat different pressure levels—the Uranian feature probably lies near 4 bar. The dark color of UDS (as well as GDS) may be caused by thinning of the underlying hydrogen sulfide or ammonium hydrosulfide clouds. The emergence of

4897-600: The plane of the ecliptic; through course corrections, Voyager 2 was directed into a path about 4,950 km (3,080 mi) above the north pole of Neptune. Five hours after Voyager 2 made its closest approach to Neptune, it performed a close fly-by of Triton , Neptune's largest moon, passing within about 40,000 km (25,000 mi). In 1989, the Voyager 2 Planetary Radio Astronomy (PRA) experiment observed around 60 lightning flashes, or Neptunian electrostatic discharges emitting energies over 7×10 J. A plasma wave system (PWS) detected 16 electromagnetic wave events with

4980-484: The planet's cloudtops. Voyager 2 also discovered 11 previously unknown moons: Cordelia , Ophelia , Bianca , Cressida , Desdemona , Juliet , Portia , Rosalind , Belinda , Puck and Perdita . The mission also studied the planet's unique atmosphere, caused by its axial tilt of 97.8°; and examined the Uranian ring system . The length of a day on Uranus as measured by Voyager 2 is 17 hours, 14 minutes. Uranus

5063-474: The plasma science instrument had been turned off, preserving power for the remaining four instruments. Because of the energy required to achieve a Jupiter trajectory boost with an 825-kilogram (1,819 lb) payload, the spacecraft included a propulsion module made of a 1,123-kilogram (2,476 lb) solid-rocket motor and eight hydrazine monopropellant rocket engines, four providing pitch and yaw attitude control, and four for roll control. The propulsion module

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5146-433: The prevailing winds at the crests of mountain ranges, where they relieve and therefore the upward lifting is greatest. As the air descends the lee side of the mountain, it warms and dries, creating a rain shadow. On the lee side of the mountains, sometimes as little as 15 miles (25 km) away from high precipitation zones, annual precipitation can be as low as 8 inches (200 mm) per year. Areas where this effect

5229-472: The region north of the southern collar. In 2007, however, when Uranus passed its equinox, the southern collar almost disappeared, whereas a faint northern collar emerged near 45 degrees of latitude . The visible latitudinal structure of Uranus is different from that of Jupiter and Saturn , which demonstrate multiple narrow and colorful bands. In addition to large-scale banded structure, Voyager 2 observed ten small bright clouds, most lying several degrees to

5312-728: The region, provide examples of this type of wind, and are driven in part by latent heat released by orographic-lifting-induced precipitation. A similar class of winds, the Sirocco , the Bora and Santa Ana winds , are examples where orographic lifting has limited effect since there is limited moisture to remove in the Saharan or other air masses; the Sirocco, Bora and Santa Ana are driven primarily by ( adiabatic ) compression heating. As air flows over mountain barriers, orographic lift can create

5395-416: The responsibility of Australia's DSS 43 communication antenna , located near Canberra . In the early space age, it was realized that a periodic alignment of the outer planets would occur in the late 1970s and enable a single probe to visit Jupiter , Saturn , Uranus , and Neptune by taking advantage of the then-new technique of gravity assists . NASA began work on a Grand Tour , which evolved into

5478-409: The right). Their boundary is located at about −45 degrees of latitude . A narrow band straddling the latitudinal range from −45 to −50 degrees is the brightest large feature on Uranus's visible surface. It is called a southern "collar". The cap and collar are thought to be a dense region of methane clouds located within the pressure range of 1.3 to 2  bar . Unfortunately Voyager 2 arrived during

5561-432: The same origin. GDS were hypothesized to be anticyclonic vortices in the atmosphere of Neptune, whereas their bright companions were thought to be methane clouds formed in places, where the air is rising ( orographic clouds ). UDS is supposed to have a similar nature, although it looked differently from GDS at some wavelengths. Although GDS had the highest contrast at 0.47 μm, UDS was not visible at this wavelength. On

5644-407: The same time that Uranus did. The particles that make up the rings might be the remnants of a moon that was broken up by either a high-velocity impact or torn up by tidal effects . In March 2020, NASA astronomers reported the detection of a large atmospheric magnetic bubble, also known as a plasmoid , released into outer space from the planet Uranus , after reevaluating old data recorded during

5727-460: The second farthest spacecraft from the Sun. On July 21, 2023, a programming error misaligned Voyager 2 's high gain antenna 2 degrees away from Earth, breaking communications with the spacecraft. By August 1, the spacecraft's carrier signal was detected using multiple antennas of the Deep Space Network . A high-power "shout" on August 4 sent from the Canberra station successfully commanded

5810-464: The south polar cap darkened noticeably (except the southern collar, which remained bright), whereas the northern hemisphere demonstrated increasing activity, such as cloud formations and stronger winds, having bolstered expectations that it would brighten soon. In particular, an analog of the bright polar collar present in its southern hemisphere at −45° was expected to appear in its northern part. This indeed happened in 2007 when Uranus passed an equinox:

5893-417: The south pole are impossible to measure. In contrast, in the northern hemisphere maximum speeds as high as 240 m/s are observed near +50 degrees of latitude. These speeds sometimes lead to incorrect assertions that winds are faster in the northern hemisphere. In fact, latitude per latitude, winds are slightly slower in the northern part of Uranus, especially at the midlatitudes from ±20 to ±40 degrees. There

5976-643: The southern hemisphere the bright collar masks them. Nevertheless, there are differences between the clouds of each hemisphere. The northern clouds are smaller, sharper and brighter. They appear to lie at a higher altitude , which is connected to fact that until 2004 (see below) no southern polar cloud had been observed at the wavelength 2.2  micrometres , which is sensitive to the methane absorption , whereas northern clouds have been regularly observed in this wavelength band . The lifetime of clouds spans several orders of magnitude. Some small clouds live for hours, whereas at least one southern cloud has persisted since

6059-570: The spacecraft to reorient towards Earth, resuming communications. As a failsafe measure, the probe is also programmed to autonomously reset its orientation to point towards Earth, which would have occurred by October 15. As the power from the RTG slowly reduces, various items of equipment have been turned off on the spacecraft. The first science equipment turned off on Voyager 2 was the PPS in 1991, which saved 1.2 watts. Some thrusters needed to control

6142-403: The sunlit hemisphere is thought to result from the local thickening of the methane clouds and haze layers located in the troposphere . The bright collar at −45° latitude is also connected with methane clouds. Other changes in the southern polar region can be explained by changes in the lower cloud layers. The variation of the microwave emission from Uranus is probably caused by changes in

6225-476: The world. The record also contains greetings in 55 different languages. The project aimed to portray the richness of life on Earth and stand as a testament to human creativity and the desire to connect with the cosmos. Orographic cloud Orographic lift occurs when an air mass is forced from a low elevation to a higher elevation as it moves over rising terrain . As the air mass gains altitude it quickly cools down adiabatically , which can raise

6308-436: Was also found to radiate large amounts of ultraviolet light, a phenomenon that is called "dayglow". The average atmospheric temperature is about 60 K (−351.7 °F; −213.2 °C). The illuminated and dark poles, and most of the planet, exhibit nearly the same temperatures at the cloud tops. The Voyager 2 Planetary Radio Astronomy (PRA) experiment observed 140 lightning flashes, or Uranian electrostatic discharges with

6391-426: Was approximately 10 °C (18 °F) cooler at 100 mbar (1.5 psi) than mid-latitudes, a variance potentially attributable to seasonal shifts ( see also Saturn Oppositions ). After its Saturn fly-by, Voyager 2 ' s scan platform experienced an anomaly causing its azimuth actuator to seize. This malfunction led to some data loss and posed challenges for the spacecraft's continued mission. The anomaly

6474-443: Was approximately constant. The feature was variable in size and appearance and was often accompanied by a bright white cloud called Bright Companion (BC), which moved with nearly the same speed as UDS itself. The behavior and appearance of UDS and its bright companion were similar to Neptunian Great Dark Spots (GDS) and their bright companions, respectively, though UDS was significantly smaller. This similarity suggests that they have

6557-407: Was jettisoned shortly after the successful Jupiter burn. Sixteen hydrazine Aerojet MR-103 thrusters on the mission module provide attitude control. Four are used to execute trajectory correction maneuvers; the others in two redundant six-thruster branches, to stabilize the spacecraft on its three axes. Only one branch of attitude control thrusters is needed at any time. Thrusters are supplied by

6640-507: Was launched. NASA says that "The Voyagers are destined—perhaps eternally—to wander the Milky Way." Voyager 2 is not headed toward any particular star. The nearest star is 4.2 light-years away, and at 15.341 km/s, the spacecraft travels one light-year in about 19,541 years - during which time the nearby stars will also move substantially. In roughly 42,000 years, Voyager 2 will pass the star Ross 248 (10.30 light-years away from Earth) at

6723-405: Was originally thought that Voyager 2 would enter interstellar space in two to three years, with its plasma spectrometer providing the first direct measurements of the density and temperature of the interstellar plasma. But the Voyager project scientist, Edward C. Stone and his colleagues said they lacked evidence of what would be the key signature of interstellar space: a shift in the direction of

6806-453: Was shown to have a magnetic field that was misaligned with its rotational axis, unlike other planets that had been visited to that point, and a helix-shaped magnetic tail stretching 10 million kilometers (6 million miles) away from the Sun. When Voyager 2 visited Uranus, much of its cloud features were hidden by a layer of haze; however, false-color and contrast-enhanced images show bands of concentric clouds around its south pole. This area

6889-402: Was traced back to a combination of issues, including a design flaw in the actuator shaft bearing and gear lubrication system, corrosion, and debris build-up. While overuse and depleted lubricant were factors, other elements, such as dissimilar metal reactions and a lack of relief ports, compounded the problem. Engineers on the ground were able to issue a series of commands, rectifying the issue to

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