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Voyager 2

                   
Voyager 2
A space probe with squat cylindrical body topped by a large parabolic radio antenna dish pointing upwards, a three-element radioisotope thermoelectric generator on a boom extending left, and scientific instruments on a boom extending right. A golden disk is fixed to the body.
Voyager spacecraft
Operator NASA / JPL
Mission type Flyby
Flyby of Jupiter, Saturn, Uranus, Neptune
Launch date 1977-08-20 14:29:00 UTC
(34 years and 10 months ago)
Launch vehicle Titan IIIE / Centaur
Launch site Space Launch Complex 41
Cape Canaveral Air Force Station, Florida, United States
Mission duration

In progress (Interstellar mission)
(32 years, 11 months and 11 days elapsed)

Jupiter flyby
(completed 1979-08-05)
Saturn flyby
(completed 1981-09-25)
Uranus flyby
(completed 1986-02-25)
Neptune flyby
(completed 1989-10-02)
COSPAR ID 1977-076A
Homepage NASA Voyager website
Mass 721.9 kg (1,592 lb)
Power 420 W (3 RTGs)
References:
[1]

The Voyager 2 spacecraft is a 722-kilogram (1,592 lb) space probe launched by NASA on August 20, 1977 to study the outer Solar System and eventually interstellar space. Operating for 34 years and 10 months as of today (20 June 2012), the spacecraft receives routine commands and transmits data back to the Deep Space Network.

Part of the Voyager program with its identical sister craft Voyager 1, the spacecraft is currently in extended mission, tasked with locating and studying the boundaries of the Solar System, including the Kuiper belt, the heliosphere and interstellar space. The primary mission ended December 31, 1989 after encountering the Jovian system in 1979, Saturnian system in 1980, Uranian system in 1986, and the Neptunian system in 1989. It was the first probe to provide detailed images of the outer gas giants.

Contents

  Mission background

  History

Conceived in the 1960s, a Grand Tour proposal to study the outer planets, prompted NASA to begin work on a mission in the early 1970s. The development of the interplanetary probes coincided with an alignment of the planets, making possible a mission to the outer Solar System by taking advantage of the then-new technique of gravity assist.

It was determined that utilizing gravity assists would enable a single probe to visit the four gas giants (Jupiter, Saturn, Uranus, and Neptune) while requiring a minimal amount of propellant and a shorter transit duration between planets. Originally, Voyager 2 was planned as Mariner 12 of the Mariner program however, due to congressional budget cuts, the mission was scaled back to be a flyby of Jupiter and Saturn, and renamed the Mariner Jupiter-Saturn probes. As the program progressed, the name was later changed to Voyager as the probe designs began to differ greatly from previous Mariner missions.[2]

Upon a successful flyby of the Saturnian moon Titan, by Voyager 1, Voyager 2 would get a mission extension to send the probe on towards Uranus and Neptune.[3]

  Golden record

Voyager Golden Record

Each Voyager space probe carries a gold-plated audio-visual disc in the event that either spacecraft is ever found by intelligent life-forms from other planetary systems.[4] The discs carry photos of the Earth and its lifeforms, a range of scientific information, spoken greetings from the people (e.g. the Secretary-General of the United Nations and the President of the United States, and the children of the Planet Earth) and a medley, "Sounds of Earth", that includes the sounds of whales, a baby crying, waves breaking on a shore, and a variety of music.

  Spacecraft design

Constructed by the Jet Propulsion Laboratory, 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.[5]

  Communications

Built with the intent for eventual interstellar travel, Voyager 2 included a large, 3.7-meter parabolic, high-gain antenna (see diagram) to transceive data with the Deep Space Network on Earth. Communications are conducted over the S-band (13 cm wavelength) and X-band (3.6 cm wavelength) providing bandwidth as high as 115.2 kilobits per second. When the spacecraft is unable to communicate with Earth, the Digital Tape Recorder (DTR) is able to record up to 62,500-kilobytes of data to later transmit when communication is reestablished.[5]

  Power

Voyager 1 RTG unit

The spacecraft was built with 3 Multihundred-Watt radioisotope thermoelectric generators (MHW RTG). Each RTG includes 24 pressed plutonium oxide spheres and provide enough heat to generate approximately 157 watts of power at launch. Collectively, the RTGs supply the spacecraft with 470 watts at launch and will allow operations to continue until at least 2020.[5][6][7] (see diagram 1, 2)

  Scientific instruments

For more details on the Voyager space probes' identical instrument packages, see the separate article on the overall Voyager Program.

Images of the spacecraft
Voyager spacecraft diagram
Voyager spacecraft diagram.  
Voyager in transport to a solar thermal test chamber
Voyager in transport to a solar thermal test chamber.  
Gold-Plated Record is attached to Voyager
Gold-Plated Record is attached to Voyager.  
Voyager 2 awaiting payload entry into a Titan/Centaur-6 rocket
Voyager 2 awaiting payload entry into a Titan/Centaur-6 rocket.  
Media related to the Voyager spacecraft at Wikimedia Commons

  Mission profile

Timeline of travel
Date Event
1977-08-20 Spacecraft launched at 14:29:00 UTC.
1977-12-10 Entered asteroid belt.
1977-12-19 Voyager 1 overtakes Voyager 2. (see diagram)
1978-06- Primary radio receiver fails. Remainder of mission flown using backup.
1978-10-21 Exited asteroid belt
1979-04-25 Start Jupiter observation phase
1981-06-05 Start Saturn observation phase.
1985-11-04 Start Uranus observation phase.
1989-06-05 Start Neptune observation phase.
1989-10-02 Begin Voyager Interstellar Mission.
Interstellar phase[10][11][12]
1990-02-14 Final images of the Voyager Program acquired by Voyager 1 to create the Solar System "Family Portrait".
1997-08-20 20 years of continuous flight and operation at 14:29:00 UTC.
1998-11-13 Terminate scan platform and UV observations.
2007-08-20 30 years of continuous flight and operation at 14:29:00 UTC.
2007-09-06 Terminate data tape recorder operations.
2008-02-22 Terminate planetary radio astronomy experiment operations.
2011-11-07 Switch to backup thrusters to conserve power[13]


  Launch and trajectory

The Voyager 2 probe was launched on August 20, 1977, by the National Aeronautics and Space Administration from Space Launch Complex 41 at Cape Canaveral, Florida, aboard a Titan IIIE/Centaur launch vehicle. Two weeks later, the twin Voyager 1 probe would be launched on September 5, 1977. However, Voyager 1 would reach both Jupiter and Saturn sooner, as Voyager 2 had been launched into a longer, more circular trajectory.

  Encounter with Jupiter

The closest approach to Jupiter occurred on July 9, 1979. It came within 570,000 km (350,000 mi) of the planet's cloud tops.[15] It discovered a few rings around Jupiter, as well as volcanic activity on the moon Io.

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 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 two Voyager fly-bys.

The moon 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." Europa is internally active due to tidal heating at 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-kilometer-deep (30 mile) 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 Great Red Spot photographed during the Voyager 2 flyby of Jupiter
The Great Red Spot photographed during the Voyager 2 flyby of Jupiter.  
A transit of Io across Jupiter, July 9, 1979
A transit of Io across Jupiter, July 9, 1979.  
Eruption of a volcano on Io, photographed by Voyager 2
Eruption of a volcano on Io, photographed by Voyager 2.  
A color mosaic of Europa
A color mosaic of Europa.  
A color mosaic of Ganymede
A color mosaic of Ganymede.  
Callisto photographed at a distance of 1 million kilometers
Callisto photographed at a distance of 1 million kilometers.  
One ring of Jupiter photographed during the Voyager 2 flyby of Jupiter
One faint ring of Jupiter photographed during the flyby.  
An eruptive event that occurred as Voyager 2 approached Jupiter
Atmospheric eruptive event on Jupiter.  
Media related to the Voyager 2 Jupiter encounter at Wikimedia Commons

  Encounter with Saturn

The closest approach to Saturn occurred on August 26, 1981.[16]

While passing behind Saturn (as viewed from Earth), Voyager 2 probed Saturn's upper atmosphere with its radio link to gather information on atmospheric temperature and density profiles. Voyager 2 found that at the uppermost pressure levels (seven kilopascals of pressure), Saturn's temperature was 70 kelvins (−203 °C), while at the deepest levels measured (120 kilopascals) the temperature increased to 143 K (−130 °C). The north pole was found to be 10 kelvins cooler, although this may be seasonal (see also Saturn Oppositions).

After the fly-by of Saturn, the camera platform of Voyager 2 locked up briefly, putting plans to officially extend the mission to Uranus and Neptune in jeopardy. Fortunately, the mission's engineers were able to fix the problem (caused by an overuse that temporarily depleted its lubricant), and the Voyager 2 probe was given the go-ahead to explore the Uranian system.

Voyager 2 Saturn approach view
Voyager 2 Saturn approach view.  
North, polar region of Saturn imaged in orange and UV filters
North, polar region of Saturn imaged in orange and UV filters.  
Color image of Enceladus showing terrain of widely varying ages
Color image of Enceladus showing terrain of widely varying ages.  
Cratered surface of Tethys at 594,000 km
Cratered surface of Tethys at 594,000 km.  
Atmosphere of Titan imaged from 2.3 million km
Atmosphere of Titan imaged from 2.3 million km.  
Titan occultation of the Sun from 0.9 million km
Titan occultation of the Sun from 0.9 million km.  
Two-toned Iapetus from Voyager 2, August 22, 1981
Two-toned Iapetus, August 22, 1981.  
"Spoke" features observed in the rings of Saturn
"Spoke" features observed in the rings of Saturn.  
Media related to the Voyager 2 Saturn encounter at Wikimedia Commons

  Encounter with Uranus

The closest approach to Uranus occurred on January 24, 1986, when Voyager 2 came within 81,500 kilometers (50,600 mi) of the planet's cloud tops. Voyager 2 also discovered the moons Cordelia, Ophelia, Bianca, Cressida, Desdemona, Juliet, Portia, Rosalind, Belinda, Perdita and Puck; studied the planet's unique atmosphere, caused by its axial tilt of 97.8°; and examined the Uranian ring system.

Uranus is the third largest (Neptune has a larger mass, but a smaller volume) planet in the Solar System. It orbits the Sun at a distance of about 2.8 billion kilometers (1.7 billion miles), and it 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 unique among the planets in that its axial tilt is about 90°, meaning that its axis is roughly parallel with, not perpendicular to, the plane of the ecliptic. This extremely large tilt of its axis is thought to be the result of a collision between the accumulating planet Uranus with another planet-sized body early in the history of the Solar System. Given the unusual orientation of its axis, with the polar regions of Uranus exposed for periods of many years to either continuous sunlight or darkness, planetary scientists were not at all sure what to expect when observing Uranus.

Voyager 2 found that one of the most striking effects of the sideways orientation of Uranus is the effect on the tail of the planetary magnetic field. This is itself tilted about 60° from the Uranian axis of rotation. The planet's magneto tail was shown to be twisted by the rotation of Uranus into a long corkscrew shape following the planet. The presence of a significant magnetic field for Uranus was not at all known until Voyager's 2 arrival.

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

A high layer of haze was detected around the sunlit pole of Uranus. This area was also found to radiate large amounts of ultraviolet light, a phenomenon that is called "dayglow." The average atmospheric temperature is about 60 K (−350°F/−213°C). Surprisingly, the illuminated and dark poles, and most of the planet, exhibit nearly the same temperatures at the cloud tops.

The Uranian moon Miranda, the innermost of the five large moons, was discovered to be one of the strangest bodies yet seen in the Solar System. Detailed images from Voyager 2's flyby of Miranda showed huge canyons made from geological faults as deep as 20 kilometers (12 mi), terraced layers, and a mixture of old and young surfaces. 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.

All nine of the previously known Uranian rings were studied by the instruments of Voyager 2. These measurements showed that the Uranian rings are distinctly different from those at Jupiter and Saturn. The Uranian ring system might be relatively young, and it did not form at 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.

Uranus as viewed by Voyager 2
Uranus as viewed by Voyager 2  
Departing image of crescent Uranus
Departing image of crescent Uranus.  
Fractured surface of Miranda
Fractured surface of Miranda.  
Ariel as imaged from 130,000 km
Ariel as imaged from 130,000 km.  
Color composite of Titania from 500,000 km
Color composite of Titania from 500,000 km.  
Umbriel imaged from 550,000 km
Umbriel (moon) imaged from 550,000 km.  
Color composite of Oberon
Color composite of Oberon.  
Voyager 2 photo of the Rings of Uranus
The Rings of Uranus imaged by Voyager 2.  
Media related to the Voyager 2 Uranus encounter at Wikimedia Commons

  Encounter with Neptune

Voyager 2's closest approach to Neptune occurred on August 25, 1989.[17][18] Since this was the last planet of our Solar System that Voyager 2 could visit, the Chief Project Scientist, his staff members, and the flight controllers decided to also perform a close fly-by of Triton, the larger of Neptune's two originally known moons, so as to gather as much information on Neptune and Triton as possible, regardless of what angle at which Voyager 2 would fly away from Neptune. This was just like the case of Voyager 1's encounters with Saturn and its massive moon Titan.

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 the plane of the ecliptic, through mid-course corrections, Voyager 2 was directed into a path several thousand miles over the north pole of Neptune. At that time, Triton was behind and below (south of) Neptune (at an angle of about 25 degrees below the Ecliptic), close to the apoapsis of its elliptical orbit. The gravitational pull of Neptune bent the trajectory of Voyager 2 down in the direction of Triton. In less than 24 hours, Voyager 2 traversed the distance between Neptune and Triton, and then observed the northern hemisphere of Triton as it passed over the moon's north pole.

The net and final effect on the trajectory of Voyager 2 was to bend its trajectory south below the plane of the Ecliptic by about 30 degrees. Voyager 2 is on this path permanently, and hence, it is exploring space south of the plane of the Ecliptic, measuring magnetic fields, charged particles, etc., there, and sending the measurements back to the Earth via telemetry.

While in the neighborhood of Neptune, Voyager 2 discovered the "Great Dark Spot", which has since disappeared, according to observations by the Hubble Space Telescope. Originally thought to be a large cloud itself, the "Great Dark Spot" was later hypothesized to be a hole in the visible cloud deck of Neptune.

Neptune's atmosphere consists of hydrogen, helium, and methane. The methane in Neptune's upper atmosphere absorbs the red light from the Sun, but it reflects the blue light from the Sun back into space. This is why Neptune looks blue.

With the decision of the International Astronomical Union to reclassify Pluto as a "plutoid" in 2008, the flyby of Neptune by Voyager 2 in 1989 became the point when every known planet in the Solar System had been visited at least once by a space probe.

Voyager 2 image of Neptune
Voyager 2 image of Neptune.  
Neptune and Triton three days after Voyager's flyby
Neptune and Triton three days after Voyager 2 flyby.  
Despina as imaged from Voyager 2
Despina as imaged from Voyager 2.  
Cratered surface of Larissa
Cratered surface of Larissa.  
Dark surface of Proteus
Dark surface of Proteus.  
Color mosaic of Voyager 2 Triton
Color mosaic of Voyager 2 Triton.  
Cirrus clouds imaged above gaseous Neptune
Cirrus clouds imaged above gaseous Neptune.  
Rings of Neptune taken in occulation from 280,000km
Rings of Neptune taken in occultation from 280,000 km.  
Media related to the Voyager 2 Neptune encounter at Wikimedia Commons

  Interstellar mission

Since its planetary mission is over, Voyager 2 is now described as working on an interstellar mission, which NASA is using to find out what the Solar System is like beyond the heliosphere. On August 30, 2007, Voyager 2 passed the termination shock into the heliosheath, approximately 1 billion miles (1.6 billion km) closer to the Sun than Voyager 1 did.[19] This is due to the local interstellar magnetic field of deep space. The southern hemisphere of the Solar System's heliosphere is being pushed in.[20]

As of February 12, 2012, Voyager 2 was at a distance of around 97.708 AU (14.616 billion km, 9.082 billion miles or 0.001545 light years) from the Sun, deep in the scattered disc, and traveling outward at roughly 3.264 AU per year. [21] It is more than twice as far from the Sun as Pluto, and far beyond the perihelion of 90377 Sedna, but not yet beyond the outer limits of the orbit of the dwarf planet Eris.

Voyager 2 is not headed toward any particular star. If left alone, it should pass by star Sirius, which is currently about 2.6 parsecs from the Sun[22][23] and moving diagonally towards the Sun, at a distance of 1.32 parsecs (4.3 ly, 25 trillion mi) in about 296,000 years.[24]

Voyager 2 is expected to keep transmitting weak radio messages until at least 2025, over 48 years since it was launched.[25]

Year End of specific capabilities as a result of the available electrical power limitations
1998 Terminate scan platform and UV observations
2007 Termination of Digital Tape Recorder (DTR) operations (It was no longer needed due to a failure on the High Waveform Receiver on the Plasma Wave Subsystem (PWS) on June 30, 2002.[26])
2008 Power off Planetary Radio Astronomy Experiment (PRA)
2015 approx Termination of gyroscopic operations
2020 approx Initiate instrument power sharing
2025 or slightly afterwards Can no longer power any single instrument

  Current status

  Simulated view of the position of Voyager 2 as of 8 Feb 2012 showing spacecraft trajectory since launch
yellow spot surrounded by three concentric light-blue ellipses labeled from inside to out: Saturn, Uranus and Neptune. A grey ellipse labeled Pluto overlaps Neptune's ellipse. Four colored lines trails outwards from the central spot: a short red line labeled Voyager 2 traces to the right and up; a green and longer line labeled Pioneer 11 traces to the right; a purple line labeled Voyager traces to the bottom right corner; and a dark blue line labeled Pioneer 10 traces left
  Location and trajectories of Pioneer and Voyager spacecraft, as of July 7, 2007. Note Voyager 2 is further than Pioneer 11 and only appears closer here due to its −55 degree declination, and that Voyager 1's position is drawn too far away.

Voyager 2 is currently transmitting scientific data at about 160 bits per second. Information about continuing telemetry exchanges with Voyager 2 is available from Voyager Weekly Reports.[27]

As of February 8, 2012, Voyager 2, traveling at 15.447 km/s relative to the Sun, is about 98.358 astronomical units (1.47141×1010 km) from the Earth and about 97.658 astronomical units (1.46094×1010 km) from the Sun,[28] at −55.29° declination and 19.888 h right ascension, and is also at an ecliptic latitude of −34.0 degrees, placing it in the constellation Telescopium as observed from Earth.[29]

On November 30, 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 the magnetometers were designed to endure, and a sensor rotated away from the correct orientation. It has not been possible to fully diagnose and correct for the damage caused to the Voyager 2's magnetometer, although efforts to do so are proceeding.[30]

On April 22, 2010, Voyager 2 encountered scientific data format problems as reported by the Associated Press on May 6, 2010.[31] On May 17, 2010, JPL engineers revealed that a flipped bit in an on-board computer had caused the issue, and scheduled a bit reset for May 19.[32] On May 23, 2010, Voyager 2 has resumed sending science data from deep space after engineers fixed the flipped bit.[33] Currently research is being made into making the area of memory with the flipped bit off limits or disallowing its use.

The Low-Energy Charged Particle Instrument is currently operational, and data from this instrument concerning charged particles is being transmitted to Earth. This data permits measurements of the heliosheath and termination shock. There has also been a modification to the on-board flight software to delay turning off the AP Branch 2 backup heater for 1 year. It was scheduled to go off February 2, 2011 (DOY 033, 2011–033).

There are regular posts to Twitter of the current distance of Voyager 2 from Earth in light-travel time.[34]

  See also

  References

  1. ^ "VOYAGER:Mission Information". NASA. 1989. http://starbrite.jpl.nasa.gov/pds/viewMissionProfile.jsp?MISSION_NAME=VOYAGER. Retrieved January 2, 2011. 
  2. ^ Planetary Voyage NASA Jet Propulsion Laboratory – California Institute of Technology. March 23, 2004. Retrieved April 8, 2007.
  3. ^ Chapter 11 "Voyager: The Grand Tour of Big Science" (sec. 268.), by Andrew,J. Butrica, found in From Engineering Science To Big Science ISBN 978-0-16-049640-0 edited by Pamela E. Mack, NASA, 1998
  4. ^ Ferris, Timothy (May 2012). "Timothy Ferris on Voyagers' Never-Ending Journey". Smithsonian Magazine. http://www.smithsonianmag.com/science-nature/Timothy-Ferris-on-Voyagers-Never-Ending-Journey.html. Retrieved 15 June 2012. 
  5. ^ a b c "VOYAGER 2:Host Information". NASA. 1989. http://starbrite.jpl.nasa.gov/pds/viewHostProfile.jsp?INSTRUMENT_HOST_ID=VG2. Retrieved January 2, 2011. 
  6. ^ "Voyager 2 Craft Details". NASA-NSSDC-Spacecraft-Details. NASA. http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1977-076A. Retrieved March 9, 2011. 
  7. ^ Furlong, Richard R.; Wahlquist, Earl J. (1999). "U.S. space missions using radioisotope power systems". Nuclear News 42 (4): 26–34. http://www2.ans.org/pubs/magazines/nn/pdfs/1999-4-2.pdf. Retrieved January 2, 2011. 
  8. ^ "Voyager 1 Narrow Angle Camera Description". NASA / PDS. August 26, 2003. http://pds-rings.seti.org/voyager/iss/inst_cat_na2.html#filters. Retrieved January 17, 2011. 
  9. ^ "Voyager 1 Wide Angle Camera Description". NASA / PDS. August 26, 2003. http://pds-rings.seti.org/voyager/iss/inst_cat_wa2.html#filters. Retrieved January 17, 2011. 
  10. ^ "Voyager 2 Full Mission Timeline" Muller, Daniel, 2010
  11. ^ "Voyager Mission Description" NASA, February 19, 1997
  12. ^ "JPL Mission Information" NASA, JPL, PDS.
  13. ^ http://www.jpl.nasa.gov/news/news.cfm?release=2011-341&rn=news.xml&rst=3189
  14. ^ Basics of space flight: Interplanetary Trajectories
  15. ^ "Voyager 2, July 9, 1979"
  16. ^ Nasa
  17. ^ "Voyager – Fact Sheet". http://voyager.jpl.nasa.gov/news/factsheet.html. Retrieved August 28, 2009. "Following Voyager 2's closest approach to Neptune on August 25, 1989" 
  18. ^ Nardo 2002, p. 15
  19. ^ Voyager 2 Proves Solar System Is Squashed NASA.gov #2007-12-10
  20. ^ Voyager 2 finds solar system's shape is 'dented' # 2007-12-10, Week Ending December 14, 2007. Retrieved Dec 12, 2007.
  21. ^ Where are the Voyagers? - Voyager 2. Retrieved February 12, 2012.
  22. ^ Henry, Dr. Todd J. (July 1, 2006). "The One Hundred Nearest Star Systems". Georgia State University. http://www.chara.gsu.edu/RECONS/TOP100.posted.htm. Retrieved November 27, 2008. 
  23. ^ Distance in light years derived from 3.26/measured parallax of 0.38002 arcseconds as of January 1, 2008
  24. ^ "Voyager – Mission – Interstellar Mission". NASA. June 22, 2007. http://voyager.jpl.nasa.gov/mission/interstellar.html. Retrieved November 27, 2008. 
  25. ^ "Voyager – Spacecraft – Spacecraft Lifetime". NASA Jet Propulsion Laboratory. March 15, 2008. http://voyager.jpl.nasa.gov/spacecraft/spacecraftlife.html. Retrieved May 25, 2008. 
  26. ^ "Voyager – Interstellar Science". NASA Jet Propulsion Laboratory. December 1, 2009. http://voyager.jpl.nasa.gov/science/index.html. Retrieved December 2, 2009. 
  27. ^ http://voyager.jpl.nasa.gov/mission/weekly-reports/index.htm
  28. ^ "Where are the Voyagers?". NASA. http://voyager.jpl.nasa.gov/where/index.html. Retrieved November 04, 2011. 
  29. ^ Peat, Chris. "Spacecraft escaping the Solar System". Heavens Above. http://www.heavens-above.com/solar-escape.asp. Retrieved May 23, 2010. 
  30. ^ Notes on Voyager 2 Quick Look Data: Data after November 29, 2006
  31. ^ John Antczak (May 6, 2010). "NASA working on Voyager 2 data problem". Associated Press. http://www.boston.com/news/nation/articles/2010/05/06/nasa_working_on_voyager_2_data_problem/. 
  32. ^ "Engineers Diagnosing Voyager 2 Data System". Jet Propulsion Laboratory. http://www.jpl.nasa.gov/news/news.cfm?release=2010-151. Retrieved May 17, 2010. 
  33. ^ "NASA Fixes Bug On Voyager 2". http://www.space-travel.com/reports/NASA_Fixes_Bug_On_Voyager_2_999.html. Retrieved May 25, 2010. 
  34. ^ NASAVoyager2 Twitter feed

  Further reading

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