''Voyager 1'' is a
space probe
A space probe is an artificial satellite that travels through space to collect scientific data. A space probe may orbit Earth; approach the Moon; travel through interplanetary space; flyby, orbit, or land or fly on other planetary bodies; or ent ...
launched by
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research.
NASA was established in 1958, succeeding t ...
on September 5, 1977, as part of the
Voyager program
The Voyager program is an American scientific program that employs two robotic interstellar probes, ''Voyager 1'' and ''Voyager 2''. They were launched in 1977 to take advantage of a favorable alignment of Jupiter and Saturn, to Flyby (spacef ...
to study the outer
Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...
and
interstellar space
Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a near-perfect vacuum containing a low density of particles, predo ...
beyond the Sun's
heliosphere
The heliosphere is the magnetosphere, astrosphere and outermost atmospheric layer of the Sun. It takes the shape of a vast, bubble-like region of space. In plasma physics terms, it is the cavity formed by the Sun in the surrounding interstell ...
. Launched 16 days after its twin ''
Voyager 2
''Voyager 2'' is a space probe launched by NASA on August 20, 1977, to study the outer planets and interstellar space beyond the Sun's heliosphere. As a part of the Voyager program, it was launched 16 days before its twin, ''Voyager 1'', on a ...
'', ''Voyager 1'' has been operating for as of . It communicates through NASA's
Deep Space Network
The NASA Deep Space Network (DSN) is a worldwide Telecommunications network, network of American spacecraft communication ground segment facilities, located in the United States (California), Spain (Madrid), and Australia (Canberra), that suppo ...
to receive routine commands and to transmit data to Earth. Real-time distance and velocity data is provided by
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research.
NASA was established in 1958, succeeding t ...
and
JPL
The Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center in the City of La Cañada Flintridge, California, United States.
Founded in the 1930s by Caltech researchers, JPL is owned by NASA an ...
.
At a distance of from Earth ,
it is the most distant human-made object from Earth.
The probe made
flybys of
Jupiter
Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but ...
,
Saturn
Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...
, and Saturn's largest
moon
The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
,
Titan
Titan most often refers to:
* Titan (moon), the largest moon of Saturn
* Titans, a race of deities in Greek mythology
Titan or Titans may also refer to:
Arts and entertainment
Fictional entities
Fictional locations
* Titan in fiction, fictiona ...
. NASA had a choice of either doing a
Pluto
Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of trans-Neptunian object, bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the S ...
or Titan flyby; exploration of the moon took priority because it was known to have a substantial atmosphere.
''Voyager 1'' studied the weather, magnetic fields, and rings of the two gas giants and was the first probe to provide detailed images of their moons.
As part of the
Voyager program
The Voyager program is an American scientific program that employs two robotic interstellar probes, ''Voyager 1'' and ''Voyager 2''. They were launched in 1977 to take advantage of a favorable alignment of Jupiter and Saturn, to Flyby (spacef ...
and like its sister craft ''
Voyager 2
''Voyager 2'' is a space probe launched by NASA on August 20, 1977, to study the outer planets and interstellar space beyond the Sun's heliosphere. As a part of the Voyager program, it was launched 16 days before its twin, ''Voyager 1'', on a ...
'', the spacecraft's extended mission is to locate and study the regions and boundaries of the outer heliosphere and to begin exploring the
interstellar medium
In astronomy, the interstellar medium is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstella ...
. ''Voyager 1'' crossed the
heliopause and entered
interstellar space
Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a near-perfect vacuum containing a low density of particles, predo ...
on August 25, 2012, making it the first spacecraft to do so.
Two years later, ''Voyager 1'' began experiencing a third "tsunami wave" of
coronal mass ejections
A coronal mass ejection (CME) is a significant release of plasma (physics), plasma and accompanying magnetic field from the Sun's Solar corona, corona into the heliosphere. CMEs are often associated with solar flares and other forms of solar ac ...
from the
Sun
The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
that continued to at least December 15, 2014, further confirming that the probe is indeed in interstellar space.
In a further testament to the robustness of ''Voyager 1'', the Voyager team tested the spacecraft's ''trajectory correction maneuver'' (TCM) thrusters in late 2017 (the first time these thrusters had been fired since 1980), a project enabling the mission to be extended by two to three years.
''Voyager 1''s extended mission is expected to continue until about 2025, when its
radioisotope thermoelectric generator
A radioisotope thermoelectric generator (RTG, RITEG), sometimes referred to as a radioisotope power system (RPS), is a type of nuclear battery that uses an array of thermocouples to convert the heat released by the decay of a suitable radioacti ...
s (RTGs) will no longer supply enough electric power to operate its scientific instruments.
Mission background
History
In the 1960s, a
Grand Tour
The Grand Tour was the principally 17th- to early 19th-century custom of a traditional trip through Europe, with Italy as a key destination, undertaken by upper-class young European men of sufficient means and rank (typically accompanied by a tuto ...
to study the outer planets was proposed which prompted NASA to begin work on a mission in the early 1970s.
Information gathered by the ''
Pioneer 10
''Pioneer 10'' (originally designated Pioneer F) is an American space probe, launched in 1972 and weighing , that completed the first mission to the planet Jupiter. Thereafter, ''Pioneer 10'' became the first of five artificial objects to ach ...
'' spacecraft helped Voyager's engineers design Voyager to cope more effectively with the intense radiation environment around Jupiter.
However, shortly before launch, strips of kitchen-grade
aluminum foil
Aluminium foil (or aluminum foil in North American English; often informally called tin foil) is aluminium prepared in thin metal leaves with a thickness less than ; thinner gauges down to are also commonly used. Standard household foil is typ ...
were applied to certain cabling to further enhance radiation shielding.
Initially, ''Voyager 1'' was planned as "''Mariner 11''" of the
Mariner program
The Mariner program was conducted by the American space agency NASA to explore other planets. Between 1962 and late 1973, NASA's Jet Propulsion Laboratory (JPL) designed and built 10 robotic interplanetary probes named Mariner to explore the in ...
. Due to 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, since the probe designs began to differ greatly from previous Mariner missions.
Spacecraft components
![Voyager Program - High-gain antenna diagram](https://upload.wikimedia.org/wikipedia/commons/e/ee/Voyager_Program_-_High-gain_antenna_diagram.png)
''Voyager 1'' was constructed by the
Jet Propulsion Laboratory
The Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center in the City of La Cañada Flintridge, California, United States.
Founded in the 1930s by Caltech researchers, JPL is owned by NASA an ...
.
It has 16
hydrazine
Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly toxic unless handled in solution as, for example, hydrazine ...
thrusters,
three-axis stabilization
Spacecraft attitude control is the process of controlling the orientation of a spacecraft (vehicle/satellite) with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, et ...
gyroscopes
A gyroscope (from Ancient Greek γῦρος ''gŷros'', "round" and σκοπέω ''skopéō'', "to look") is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axis of rotat ...
, and
referencing instruments to keep the probe's radio antenna pointed 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 such as
planets
A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a young ...
as it travels through space.
Communication system
The radio
communication system
A communications system or communication system is a collection of individual telecommunications networks, transmission systems, relay stations, tributary stations, and terminal equipment usually capable of interconnection and interoperati ...
of ''Voyager 1'' was designed to be used up to and beyond the limits of the
Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...
. The communication system includes a
diameter
In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid for ...
high gain
Cassegrain antenna
In telecommunications and radar, a Cassegrain antenna is a parabolic antenna in which the feed antenna is mounted at or behind the surface of the concave main parabolic reflector dish and is aimed at a smaller convex secondary reflector suspende ...
to send and receive
radio waves
Radio waves are a type of electromagnetic radiation with the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz (GHz) and below. At 300 GHz, the corresponding wavelength is 1 mm (short ...
via the three
Deep Space Network
The NASA Deep Space Network (DSN) is a worldwide Telecommunications network, network of American spacecraft communication ground segment facilities, located in the United States (California), Spain (Madrid), and Australia (Canberra), that suppo ...
stations on the Earth.
The craft normally transmits data to Earth over Deep Space Network Channel 18, using a frequency of either 2.3 GHz or 8.4 GHz, while signals from Earth to Voyager are transmitted at 2.1 GHz.
When ''Voyager 1'' is unable to communicate directly with the Earth, its digital
tape
Tape or Tapes may refer to:
Material
A long, narrow, thin strip of material (see also Ribbon (disambiguation):
Adhesive tapes
* Adhesive tape, any of many varieties of backing materials coated with an adhesive
*Athletic tape, pressure-sensitiv ...
recorder (DTR) can record about 67 megabytes of data for transmission at another time.
signals from ''Voyager 1'' take over 21 hours to reach Earth.
Power
''Voyager 1'' has three
radioisotope thermoelectric generator
A radioisotope thermoelectric generator (RTG, RITEG), sometimes referred to as a radioisotope power system (RPS), is a type of nuclear battery that uses an array of thermocouples to convert the heat released by the decay of a suitable radioacti ...
s (RTGs) mounted on a boom. Each
MHW-RTG
The Multihundred-Watt radioisotope thermoelectric generator (MHW RTG) is a type of US radioisotope thermoelectric generator (RTG) developed for the Voyager spacecraft, ''Voyager 1'' and ''Voyager 2''.
Each RTG has a total weight of 37.7 kg ...
contains 24 pressed
plutonium-238
Plutonium-238 (238Pu or Pu-238) is a fissile, radioactive isotope of plutonium that has a half-life of 87.7 years.
Plutonium-238 is a very powerful alpha emitter; as alpha particles are easily blocked, this makes the plutonium-238 isotope suitab ...
oxide spheres.
The RTGs generated about 470 W of
electric power
Electric power is the rate at which electrical energy is transferred by an electric circuit. The SI unit of power is the watt, one joule per second. Standard prefixes apply to watts as with other SI units: thousands, millions and billions o ...
at the time of launch, with the remainder being dissipated as waste heat.
The power output of the RTGs declines over time due to the 87.7-year
half-life
Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ato ...
of the fuel and degradation of the thermocouples, but the craft's RTGs will continue to support some of its operations until 2025.
File:Voyager Program - RTG diagram 1.png, Diagram of RTG fuel container, showing the plutonium-238
Plutonium-238 (238Pu or Pu-238) is a fissile, radioactive isotope of plutonium that has a half-life of 87.7 years.
Plutonium-238 is a very powerful alpha emitter; as alpha particles are easily blocked, this makes the plutonium-238 isotope suitab ...
oxide spheres
File:Voyager Program - RTG diagram 2.png, Diagram of RTG shell, showing the power-producing silicon
Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic tab ...
-germanium
Germanium is a chemical element with the symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid in the carbon group that is chemically similar to its group neighbors s ...
thermocouple
A thermocouple, also known as a "thermoelectrical thermometer", is an electrical device consisting of two dissimilar electrical conductors forming an electrical junction. A thermocouple produces a temperature-dependent voltage as a result of the ...
s
File:Voyager Program - RTG upclose.png, Model of an RTG unit
Computers
Unlike the other onboard instruments, the operation of the cameras for
visible light
Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...
is not autonomous, but rather it is controlled by an imaging parameter table contained in one of the on-board
digital computer
A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations ( computation) automatically. Modern digital electronic computers can perform generic sets of operations known as programs. These pro ...
s, the Flight Data Subsystem (FDS). Since the 1990s, most space probes have been equipped with completely
autonomous
In developmental psychology and moral, political, and bioethical philosophy, autonomy, from , ''autonomos'', from αὐτο- ''auto-'' "self" and νόμος ''nomos'', "law", hence when combined understood to mean "one who gives oneself one's ow ...
cameras.
The computer command subsystem (CCS) controls the cameras. The CCS contains fixed computer programs, such as command decoding, fault-detection and -correction routines, antenna pointing routines, and spacecraft sequencing routines. This computer is an improved version of the one that was used in the 1970s
Viking orbiters.
The Attitude and Articulation Control Subsystem (AACS) controls the spacecraft orientation (its
attitude
Attitude may refer to:
Philosophy and psychology
* Attitude (psychology), an individual's predisposed state of mind regarding a value
* Metaphysics of presence
* Propositional attitude, a relational mental state connecting a person to a pro ...
). It keeps the
high-gain antenna
A directional antenna or beam antenna is an antenna which radiates or receives greater power in specific directions allowing increased performance and reduced interference from unwanted sources. Directional antennas provide increased performance ...
pointing towards
the Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surface ...
, controls attitude changes, and points the scan platform. The custom-built AACS systems on both Voyagers are the same.
Scientific instruments
''For more details on the Voyager space probes' identical instrument packages, see the separate article on the overall
Voyager Program
The Voyager program is an American scientific program that employs two robotic interstellar probes, ''Voyager 1'' and ''Voyager 2''. They were launched in 1977 to take advantage of a favorable alignment of Jupiter and Saturn, to Flyby (spacef ...
.''
Mission profile
Timeline of travel
Launch and trajectory
![Animation of Voyager 1 trajectory](https://upload.wikimedia.org/wikipedia/commons/1/1e/Animation_of_Voyager_1_trajectory.gif)
The ''Voyager 1'' probe was launched on September 5, 1977, from
Launch Complex 41
Space Launch Complex 41 (SLC-41), previously Launch Complex 41 (LC-41), is an active launch site at Cape Canaveral Space Force Station. As of 2020, the site is used by United Launch Alliance (ULA) for Atlas V launches. Previously, it had been use ...
at the
Cape Canaveral Air Force Station
Cape Canaveral Space Force Station (CCSFS) is an installation of the United States Space Force's Space Launch Delta 45, located on Cape Canaveral in Brevard County, Florida.
Headquartered at the nearby Patrick Space Force Base, the statio ...
, aboard a
Titan IIIE
The Titan IIIE or Titan 3E, also known as the Titan III-Centaur, was an American expendable launch system. Launched seven times between 1974 and 1977, it enabled several high-profile NASA missions, including the Voyager program, Voyager and Viki ...
launch vehicle
A launch vehicle or carrier rocket is a rocket designed to carry a payload (spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pad, launch pads, supported by a missile launch contro ...
. The ''
Voyager 2
''Voyager 2'' is a space probe launched by NASA on August 20, 1977, to study the outer planets and interstellar space beyond the Sun's heliosphere. As a part of the Voyager program, it was launched 16 days before its twin, ''Voyager 1'', on a ...
'' probe had been launched two weeks earlier, on August 20, 1977. Despite being launched later, ''Voyager 1'' reached both Jupiter
and Saturn sooner, following a shorter trajectory.
''Voyager 1'' initial orbit had an aphelion of , just a little short of Saturn's orbit of . ''Voyager 2''s initial orbit had an aphelion of , well short of Saturn's orbit.
Flyby of Jupiter
![Voyager-1 Jupiter-flyby March-5-1979](https://upload.wikimedia.org/wikipedia/commons/a/ac/Voyager-1_Jupiter-flyby_March-5-1979.png)
''Voyager 1'' began photographing
Jupiter
Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but ...
in January 1979. Its closest approach to Jupiter was on March 5, 1979, at a distance of about from the planet's center.
Because of the greater photographic resolution allowed by a closer approach, most observations of the moons, rings, magnetic fields, and the
radiation belt environment of the Jovian system were made during the 48-hour period that bracketed the closest approach. Voyager 1 finished photographing the Jovian system in April 1979.
The discovery of ongoing volcanic activity on the moon
Io was probably the greatest surprise. It was the first time active volcanoes had been seen on another body in the
Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...
. It appears that activity on Io affects the entire
Jovian system
There are 82 known moons of Jupiter, not counting a number of moonlets likely shed from the inner moons. All together, they form a satellite system which is called the Jovian system. The most massive of the moons are the four Galilean moons: ...
. Io appears to be the primary source of matter that pervades the Jovian magnetosphere – the region of space that surrounds the planet influenced by the planet's strong
magnetic field
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...
.
Sulfur
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
,
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
, and
sodium
Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable iso ...
, apparently erupted by Io's volcanoes and sputtered off the surface by the impact of high-energy particles, were detected at the outer edge of the
magnetosphere of Jupiter
The magnetosphere of Jupiter is the cavity created in the solar wind by the planet's magnetic field. Extending up to seven million kilometers in the Sun's direction and almost to the orbit of Saturn in the opposite direction, Jupiter's magnetosp ...
.
The two Voyager space probes made a number of important discoveries about Jupiter, its satellites, its radiation belts, and its never-before-seen
planetary rings
A ring system is a disc or ring, orbiting an astronomical object, that is composed of solid material such as dust and moonlets, and is a common component of satellite systems around giant planets. A ring system around a planet is also known as ...
.
File:Jupiter from Voyager 1 PIA02855 thumbnail 300px max quality.ogv, alt=Voyager 1 time lapse movie of Jupiter approach, ''Voyager 1'' time-lapse movie of Jupiter approach ( full-size video)
File:Great Red Spot From Voyager 1.jpg, Jupiter's Great Red Spot
The Great Red Spot is a persistent high-pressure region in the atmosphere of Jupiter, producing an anticyclonic storm that is the largest in the Solar System. Located 22 degrees south of Jupiter's equator, it produces wind-speeds up to 432 ...
, an anti-cyclonic storm larger than Earth, as seen from ''Voyager 1'', alt=The Great Red Spot
The Great Red Spot is a persistent high-pressure region in the atmosphere of Jupiter, producing an anticyclonic storm that is the largest in the Solar System. Located 22 degrees south of Jupiter's equator, it produces wind-speeds up to 432 ...
as seen from ''Voyager 1''
File:Volcanic crater with radiating lava flows on Io.jpg, alt=View of lava flows radiating from the volcano Ra Patera on Io, View of sulfur-rich lava flows radiating from the volcano Ra Patera
Ra Patera is an extraterrestrial volcano located on Io, one of the four Galilean moons of Jupiter. An active volcano, it was first studied in 1979 via Voyager stereo imagery to determine its geology, topography, and the source of its eruptions. ...
on Io
File:Vulcanic Explosion on Io.jpg, The eruption plume of the volcano Loki
Loki is a god in Norse mythology. According to some sources, Loki is the son of Fárbauti (a jötunn) and Laufey (mentioned as a goddess), and the brother of Helblindi and Býleistr. Loki is married to Sigyn and they have two sons, Narfi or Na ...
rises over the limb of Io, alt=A volcanic eruption plume rises over the limb of Io
File:PIA01970.jpg, alt=Europa as seen from Voyager 1 at a distance of 2.8 million km, Europa
Europa may refer to:
Places
* Europe
* Europa (Roman province), a province within the Diocese of Thrace
* Europa (Seville Metro), Seville, Spain; a station on the Seville Metro
* Europa City, Paris, France; a planned development
* Europa Cliff ...
's lineated but un-cratered face, evidence of currently active geology, at a distance of 2.8 million km.
File:Ganymede - PIA02278.jpg, alt=Icy surface of Ganymede as photographed from 253,000 km, Ganymede's tectonically disrupted surface, marked with bright impact sites, from 253,000 km.
Flyby of Saturn
![Animation of Voyager 1 around Saturn](https://upload.wikimedia.org/wikipedia/commons/1/18/Animation_of_Voyager_1_around_Saturn.gif)
The gravitational assist trajectories at Jupiter were successfully carried out by both Voyagers, and the two spacecraft went on to visit
Saturn
Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...
and its system of moons and rings. ''Voyager 1'' encountered Saturn in November 1980, with the closest approach on November 12, 1980, when the space probe came within of Saturn's cloud-tops. The space probe's cameras detected complex structures in the
rings of Saturn
The rings of Saturn are the most extensive ring system of any planet in the Solar System. They consist of countless small particles, ranging in size from micrometers to meters, that orbit around Saturn. The ring particles are made almost entirel ...
, and its
remote sensing
Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object, in contrast to in situ or on-site observation. The term is applied especially to acquiring information about Earth ...
instruments studied the atmospheres of Saturn and its giant moon
Titan
Titan most often refers to:
* Titan (moon), the largest moon of Saturn
* Titans, a race of deities in Greek mythology
Titan or Titans may also refer to:
Arts and entertainment
Fictional entities
Fictional locations
* Titan in fiction, fictiona ...
.
''Voyager 1'' found that about seven percent of the volume of Saturn's upper atmosphere is
helium
Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...
(compared with 11 percent of Jupiter's atmosphere), while almost all the rest is
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
. Since Saturn's internal helium abundance was expected to be the same as Jupiter's and the Sun's, the lower abundance of helium in the upper atmosphere may imply that the heavier helium may be slowly sinking through Saturn's hydrogen; that might explain the excess heat that Saturn radiates over energy it receives from the Sun. Winds blow at high speeds on Saturn. Near the equator, the Voyagers measured winds about . The wind blows mostly in an easterly direction.
The Voyagers found
aurora
An aurora (plural: auroras or aurorae), also commonly known as the polar lights, is a natural light display in Earth's sky, predominantly seen in high-latitude regions (around the Arctic and Antarctic). Auroras display dynamic patterns of bri ...
-like
ultraviolet
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...
emissions of
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
at mid-latitudes in the atmosphere, and auroras at polar latitudes (above 65 degrees). The high-level auroral activity may lead to the formation of complex
hydrocarbon molecules that are carried toward the
equator
The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can als ...
. The mid-latitude auroras, which occur only in sunlit regions, remain a puzzle, since bombardment by electrons and ions, known to cause auroras on Earth, occurs primarily at high latitudes. Both Voyagers measured the
rotation of Saturn (the length of a day) at 10 hours, 39 minutes, 24 seconds.
''Voyager 1''s mission included a flyby of Titan, Saturn's largest moon, which had long been known to have an atmosphere. Images taken by ''
Pioneer 11
''Pioneer 11'' (also known as ''Pioneer G'') is a robotic space probe launched by NASA on April 5, 1973, to study the asteroid belt, the environment around Jupiter and Saturn, solar winds, and cosmic rays. It was the first probe to encounter ...
'' in 1979 had indicated the atmosphere was substantial and complex, further increasing interest. The Titan flyby occurred as the spacecraft entered the system to avoid any possibility of damage closer to Saturn compromising observations, and approached to within , passing behind Titan as seen from Earth and the Sun. Voyager's measurement of the atmosphere's effect on sunlight and Earth-based measurement of its effect on the probe's radio signal were used to determine the atmosphere's composition, density, and pressure. Titan's mass was also measured by observing its effect on the probe's trajectory. The thick haze prevented any visual observation of the surface, but the measurement of the atmosphere's composition, temperature, and pressure led to speculation that lakes of liquid hydrocarbons could exist on the surface.
Because observations of Titan were considered vital, the trajectory chosen for ''Voyager 1'' was designed around the optimum Titan flyby, which took it below the south pole of Saturn and out of the plane of the
ecliptic
The ecliptic or ecliptic plane is the orbital plane of the Earth around the Sun. From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic again ...
, ending its planetary science mission.
Had ''Voyager 1'' failed or been unable to observe Titan, ''Voyager 2''
's trajectory would have been altered to incorporate the Titan flyby,
precluding any visit to Uranus and Neptune.
The trajectory ''Voyager 1'' was launched into would not have allowed it to continue on to Uranus and Neptune,
but could have been altered to avoid a Titan flyby and travel from Saturn to
Pluto
Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of trans-Neptunian object, bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the S ...
, arriving in 1986.
File:Crescent Saturn as seen from Voyager 1.jpg, alt=View of Saturn lit from the right. Saturn
Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...
's globe casts its shadow over the rings to the left. Part of the lower hemisphere can be seen through the rings. Some of the spoke-like ring features are visible as bright patches., Crescent Saturn
Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...
from 5.3 million km, four days after closest approach
File:Voyager1-saturn-f-ring.jpg, alt=Voyager 1 image of Saturn's F Ring, ''Voyager 1'' image of Saturn's narrow, twisted and braided F Ring
The rings of Saturn are the most extensive ring system of any planet in the Solar System. They consist of countless small particles, ranging in size from micrometers to meters, that orbit around Saturn. The ring particles are made almost entirel ...
.
File:Voyager 1 - view of Saturn's moon Mimas.jpg, alt=Mimas at a range of 425,000 km from Voyager 1, Mimas
Mimas may refer to:
*Mimas (Giant), son of Gaia in Greek mythology, one of the Gigantes
* Mimas (''Aeneid''), a son of Amycus and Theono, born the same night as Paris, who escorted Aeneas to Italy
*Karaburun, a town and district in Turkey, formerl ...
at a range of 425,000 km; the crater Herschel is at upper right
File:Tethys - PIA01974.jpg, alt=Tethys photographed by Voyager 1 from 1.2 million km, Tethys, with its giant rift valley
A rift valley is a linear shaped lowland between several highlands or mountain ranges created by the action of a geologic rift. Rifts are formed as a result of the pulling apart of the lithosphere due to extensional tectonics. The linear dep ...
Ithaca Chasma
Ithaca Chasma is a valley (graben) of Saturn's moon Tethys, named after the island of Ithaca, in Greece. It is up to wide, deep and long, running approximately three-quarters of the way around Tethys' circumference, making it one of the long ...
, from 1.2 million km.
File:Dione from Voyager 1.jpg, alt=Fractured terrain on Dione imaged from a distance of 240,000 km from Voyager 1, Fractured 'wispy terrain' on Dione Dione may refer to:
Astronomy
*106 Dione, a large main belt asteroid
*Dione (moon), a moon of Saturn
*Helene (moon), a moon of Saturn sometimes referred to as "Dione B"
Mythology
*Dione (Titaness), a Titaness in Greek mythology
*Dione (mythology) ...
's trailing hemisphere.
File:Rhea - PIA02270.jpg, alt=Impact craters on the surface of Rhea appear similar to Earth's Moon, The icy surface of Rhea is nearly saturated with impact crater
An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters ...
s.
File:Titan's thick haze layer-picture from voyager1.jpg, alt=Cream-colored section of a disk is separated from the black space above by a fuzzy blue curve, Titan's thick haze layer is shown in this enhanced ''Voyager 1'' image.
File:Titan Haze.jpg, alt=orange coloured area at bottom right is separated from black space at upper left by diagonal series of blue bands, Layers of haze
Haze is traditionally an atmospheric phenomenon in which dust, smoke, and other dry particulates suspended in air obscure visibility and the clarity of the sky. The World Meteorological Organization manual of codes includes a classification ...
, composed of complex organic compounds, covering Saturn's satellite Titan
Titan most often refers to:
* Titan (moon), the largest moon of Saturn
* Titans, a race of deities in Greek mythology
Titan or Titans may also refer to:
Arts and entertainment
Fictional entities
Fictional locations
* Titan in fiction, fictiona ...
.
Exit from the heliosphere
![PIA23645-Earth-PaleBlueDot-6Bkm-Voyager1-orig19900214-upd20200212](https://upload.wikimedia.org/wikipedia/commons/d/d2/PIA23645-Earth-PaleBlueDot-6Bkm-Voyager1-orig19900214-upd20200212.jpg)
On February 14, 1990, ''Voyager 1'' took the first "
family portrait Family Portrait may refer to:
Portraiture painting
* Family Portrait (Hals, four persons), ''Family Portrait'' (Hals, four persons), a 1635 painting by Frans Hals
* Family Portrait (Hals, five persons), ''Family Portrait'' (Hals, five persons), ...
" of the Solar System as seen from outside,
which includes the image of planet Earth known as ''
Pale Blue Dot
''Pale Blue Dot'' is a photograph of planet Earth taken on February 14, 1990, by the ''Voyager 1'' space probe from a record distance of about kilometers ( miles, 40.5 AU), as part of that day's ''Family Portrait'' series of images of the ...
''. Soon afterward, its cameras were deactivated to conserve energy and computer resources for other equipment. The camera software has been removed from the spacecraft, so it would now be complex to get them working again. Earth-side software and computers for reading the images are also no longer available.
On February 17, 1998, ''Voyager 1'' reached a distance of from the Sun and overtook ''
Pioneer 10
''Pioneer 10'' (originally designated Pioneer F) is an American space probe, launched in 1972 and weighing , that completed the first mission to the planet Jupiter. Thereafter, ''Pioneer 10'' became the first of five artificial objects to ach ...
'' as the most distant spacecraft from Earth.
Travelling at about ,
it has the fastest heliocentric
recession speed of any spacecraft.
As ''Voyager 1'' headed for interstellar space, its instruments continued to study the Solar System. Jet Propulsion Laboratory scientists used the
plasma wave In plasma physics, waves in plasmas are an interconnected set of particles and fields which propagate in a periodically repeating fashion. A plasma is a quasineutral, electrically conductive fluid. In the simplest case, it is composed of electron ...
experiments aboard ''Voyager 1'' and ''2'' to look for the
heliopause, the boundary at which the
solar wind
The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between . The composition of the sola ...
transitions into the
interstellar medium
In astronomy, the interstellar medium is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstella ...
.
, the probe was moving with a relative velocity to the Sun of about .
With the velocity the probe is currently maintaining, ''Voyager 1'' is traveling about per year, or about one
light-year
A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...
per 18,000 years.
Termination shock
![Voyager Path](https://upload.wikimedia.org/wikipedia/commons/5/53/Voyager_Path.svg)
Scientists at the
Johns Hopkins University
Johns Hopkins University (Johns Hopkins, Hopkins, or JHU) is a private university, private research university in Baltimore, Maryland. Founded in 1876, Johns Hopkins is the oldest research university in the United States and in the western hem ...
Applied Physics Laboratory
The Johns Hopkins University Applied Physics Laboratory (Applied Physics Laboratory, or APL) is a not-for-profit University Affiliated Research Center, university-affiliated research center (UARC) in Howard County, Maryland. It is affiliated w ...
believe that ''Voyager 1'' entered the
termination shock
The heliosphere is the magnetosphere, astrosphere and outermost atmospheric layer of the Sun. It takes the shape of a vast, bubble-like region of space. In plasma physics terms, it is the cavity formed by the Sun in the surrounding interstell ...
in February 2003.
This marks the point where the solar wind slows to subsonic speeds. Some other scientists expressed doubt, discussed in the journal ''
Nature
Nature, in the broadest sense, is the physics, physical world or universe. "Nature" can refer to the phenomenon, phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. ...
'' of November 6, 2003.
The issue would not be resolved until other data became available, since ''Voyager 1'' solar-wind detector ceased functioning in 1990. This failure meant that termination shock detection would have to be inferred from the data from the other instruments on board.
In May 2005, a NASA press release said that the consensus was that ''Voyager 1'' was then in the
heliosheath
The heliosphere is the magnetosphere, astrosphere and outermost atmospheric layer of the Sun. It takes the shape of a vast, bubble-like region of space. In plasma physics terms, it is the cavity formed by the Sun in the surrounding interst ...
.
In a scientific session at the
American Geophysical Union
The American Geophysical Union (AGU) is a 501(c)(3) nonprofit organization of Earth, atmospheric, ocean, hydrologic, space, and planetary scientists and enthusiasts that according to their website includes 130,000 people (not members). AGU's act ...
meeting in
on May 25, 2005, Dr.
Ed Stone
Edward Carroll Stone (born January 23, 1936) is an American space scientist, professor of physics at the California Institute of Technology, and former director of the NASA Jet Propulsion Laboratory (JPL).
Biography
Stone was born in Knoxvil ...
presented evidence that the craft crossed the termination shock in late 2004.
This event is estimated to have occurred on December 15, 2004, at a distance of from the Sun.
Heliosheath
On March 31, 2006,
amateur radio operator
An amateur radio operator is someone who uses equipment at an amateur radio station to engage in two-way personal communications with other amateur operators on radio frequencies assigned to the amateur radio service. Amateur radio operators hav ...
s from
AMSAT
AMSAT is a name for amateur radio satellite organizations worldwide, but in particular the Radio Amateur Satellite Corporation (AMSAT) with headquarters at Washington, D.C. AMSAT organizations design, build, arrange launches for, and then opera ...
in Germany tracked and received radio waves from ''Voyager 1'' using the dish at
Bochum
Bochum ( , also , ; wep, Baukem) is a city in North Rhine-Westphalia. With a population of 364,920 (2016), is the sixth largest city (after Cologne, Düsseldorf, Dortmund, Essen and Duisburg) of the most populous Germany, German federal state o ...
with a long integration technique. Retrieved data was checked and verified against data from the
Deep Space Network
The NASA Deep Space Network (DSN) is a worldwide Telecommunications network, network of American spacecraft communication ground segment facilities, located in the United States (California), Spain (Madrid), and Australia (Canberra), that suppo ...
station at Madrid, Spain.
[ ] This seems to be the first such amateur tracking of ''Voyager 1''.
It was confirmed on December 13, 2010, that ''Voyager 1'' had passed the reach of the radial outward flow of the
solar wind
The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between . The composition of the sola ...
, as measured by the Low Energy Charged Particle device. It is suspected that solar wind at this distance turns sideways because of interstellar wind pushing against the heliosphere. Since June 2010, detection of solar wind had been consistently at zero, providing conclusive evidence of the event.
On this date, the spacecraft was approximately from the Sun.
''Voyager 1'' was commanded to change its orientation to measure the sideways motion of the solar wind at that location in space in March 2011 (~33yr 6mo from launch). A test roll done in February had confirmed the spacecraft's ability to maneuver and reorient itself. The course of the spacecraft was not changed. It rotated 70 degrees counterclockwise with respect to Earth to detect the solar wind. This was the first time the spacecraft had done any major maneuvering since the
''Family Portrait'' photograph of the planets was taken in 1990. After the first roll the spacecraft had no problem in reorienting itself with
Alpha Centauri
Alpha Centauri ( Latinized from α Centauri and often abbreviated Alpha Cen or α Cen) is a triple star system in the constellation of Centaurus. It consists of 3 stars: Alpha Centauri A (officially Rigil Kentaurus), Alpha Centaur ...
, ''Voyager 1''
's guide star, and it resumed sending transmissions back to Earth. ''Voyager 1'' was expected to enter interstellar space "at any time". ''Voyager 2'' was still detecting outward flow of solar wind at that point but it was estimated that in the following months or years it would experience the same conditions as ''Voyager 1''.
The spacecraft was reported at 12.44° declination and 17.163 hours right ascension, and at an ecliptic latitude of 34.9° (the ecliptic latitude changes very slowly), placing it in the constellation
Ophiuchus
Ophiuchus () is a large constellation straddling the celestial equator. Its name comes from the Ancient Greek (), meaning "serpent-bearer", and it is commonly represented as a man grasping a snake. The serpent is represented by the constella ...
as observed from the Earth on May 21, 2011.
On December 1, 2011, it was announced that ''Voyager 1'' had detected the first
Lyman-alpha radiation originating from the
Milky Way
The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye ...
galaxy. Lyman-alpha radiation had previously been detected from other galaxies, but because of interference from the Sun, the radiation from the Milky Way was not detectable.
NASA announced on December 5, 2011, that ''Voyager 1'' had entered a new region referred to as a "cosmic purgatory". Within this stagnation region, charged particles streaming from the Sun slow and turn inward, and the Solar System's magnetic field is doubled in strength as interstellar space appears to be applying pressure. Energetic particles originating in the Solar System decline by nearly half, while the detection of high-energy electrons from outside increases 100-fold. The inner edge of the stagnation region is located approximately 113 AU from the Sun.
Heliopause
NASA announced in June 2012 that the probe was detecting changes in the environment that were suspected to correlate with arrival at the
heliopause.
''Voyager 1'' had reported a marked increase in its detection of charged particles from interstellar space, which are normally deflected by the solar winds within the
heliosphere
The heliosphere is the magnetosphere, astrosphere and outermost atmospheric layer of the Sun. It takes the shape of a vast, bubble-like region of space. In plasma physics terms, it is the cavity formed by the Sun in the surrounding interstell ...
from the Sun. The craft thus began to enter the interstellar medium at the edge of the Solar System.
''Voyager 1'' became the first spacecraft to cross the heliopause in August 2012, then at a distance of from the Sun, although this was not confirmed for another year.
As of September 2012, sunlight took 16.89 hours to get to ''Voyager 1'' which was at a distance of 121 AU. The
apparent magnitude
Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...
of the Sun from the spacecraft was -16.3 (about 30 times brighter than the full Moon).
The spacecraft was traveling at relative to the Sun. It would need about 17,565 years at this speed to travel a
light-year
A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...
.
To compare,
Proxima Centauri
Proxima Centauri is a small, low-mass star located away from the Sun in the southern constellation of Centaurus. Its Latin name means the 'nearest tarof Centaurus'. It was discovered in 1915 by Robert Innes and is the nearest-kno ...
, the closest star to the Sun, is about 4.2
light-year
A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...
s () distant. Were the spacecraft traveling in the direction of that star, 73,775 years would pass before ''Voyager 1'' would reach it. (''Voyager 1'' is heading in the direction of the constellation
Ophiuchus
Ophiuchus () is a large constellation straddling the celestial equator. Its name comes from the Ancient Greek (), meaning "serpent-bearer", and it is commonly represented as a man grasping a snake. The serpent is represented by the constella ...
.
)
In late 2012, researchers reported that particle data from the spacecraft suggested that the probe had passed through the heliopause. Measurements from the spacecraft revealed a steady rise since May in collisions with high energy particles (above 70 MeV), which are thought to be
cosmic ray
Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...
s emanating from
supernova
A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when ...
explosions far beyond the
Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...
, with a sharp increase in these collisions in late August. At the same time, in late August, there was a dramatic drop in collisions with low-energy particles, which are thought to originate from the Sun.
Ed Roelof, space scientist at Johns Hopkins University and principal investigator for the Low-Energy Charged Particle instrument on the spacecraft, declared that "most scientists involved with ''Voyager 1'' would agree that
hese two criteriahave been sufficiently satisfied".
However, the last criterion for officially declaring that ''Voyager 1'' had crossed the boundary, the expected change in magnetic field direction (from that of the Sun to that of the interstellar field beyond), had not been observed (the field had changed direction by only 2 degrees
), which suggested to some that the nature of the edge of the heliosphere had been misjudged.
On December 3, 2012, Voyager project scientist Ed Stone of the
California Institute of Technology
The California Institute of Technology (branded as Caltech or CIT)The university itself only spells its short form as "Caltech"; the institution considers other spellings such a"Cal Tech" and "CalTech" incorrect. The institute is also occasional ...
said, "Voyager has discovered a new region of the heliosphere that we had not realized was there. We're still inside, apparently. But the magnetic field now is connected to the outside. So it's like a highway letting particles in and out."
The magnetic field in this region was 10 times more intense than ''Voyager 1'' encountered before the termination shock. It was expected to be the last barrier before the spacecraft exited the Solar System completely and entered interstellar space.
Interstellar medium
In March 2013, it was announced that ''Voyager 1'' might have become the first spacecraft to enter interstellar space, having detected a marked change in the plasma environment on August 25, 2012. However, until September 12, 2013, it was still an open question as to whether the new region was interstellar space or an unknown region of the Solar System. At that time, the former alternative was officially confirmed.
In 2013 ''Voyager 1'' was exiting the Solar System at a speed of about per year, while ''Voyager 2'' is going slower, leaving the Solar System at per year. Each year, ''Voyager 1'' increases its lead over ''Voyager 2''.
''Voyager 1'' reached a distance of from the Sun on May 18, 2016.
On September 5, 2017, that had increased to about from the Sun, or just over 19 light-hours; at that time, ''Voyager 2'' was from the Sun.
Its progress can be monitored at NASA's website (see
§ External links).
File:Cosmic Rays at Voyager 1.png, Plot showing a dramatic increase in the rate of cosmic ray
Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...
particle detection by the ''Voyager 1'' spacecraft (October 2011 through October 2012)
File:Solar wind at Voyager 1.png, Plot showing a dramatic decrease in the rate of solar wind
The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between . The composition of the sola ...
particle detection by ''Voyager 1'' (October 2011 through October 2012)
![Interstellar probes (cropped)](https://upload.wikimedia.org/wikipedia/commons/7/7c/Interstellar_probes_%28cropped%29.jpg)
On September 12, 2013, NASA officially confirmed that ''Voyager 1'' had reached the
interstellar medium
In astronomy, the interstellar medium is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstella ...
in August 2012 as previously observed. The generally accepted date of arrival is August 25, 2012 (approximately 10 days before the 35th anniversary of its launch), the date durable changes in the density of energetic particles were first detected.
By this point, most space scientists had abandoned the hypothesis that a change in magnetic field direction must accompany a crossing of the heliopause;
a new model of the heliopause predicted that no such change would be found.
A key finding that persuaded many scientists that the heliopause had been crossed was an indirect measurement of an 80-fold increase in electron density, based on the frequency of
plasma oscillations observed beginning on April 9, 2013,
triggered by a
solar outburst that had occurred in March 2012
(electron density is expected to be two orders of magnitude higher outside the heliopause than within).
Weaker sets of oscillations measured in October and November 2012
provided additional data. An indirect measurement was required because ''Voyager 1''
's plasma spectrometer had stopped working in 1980.
In September 2013, NASA released recordings of audio
transductions of these plasma waves, the first to be measured in interstellar space.
While ''Voyager 1'' is commonly spoken of as having left the Solar System simultaneously with having left the heliosphere, the two are not the same. The Solar System is usually defined as the vastly larger region of space populated by bodies that orbit the Sun. The craft is presently less than one-seventh the distance to the
aphelion
An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion.
General description
There are two apsides in any ellip ...
of
Sedna, and it has not yet entered the
Oort cloud
The Oort cloud (), sometimes called the Öpik–Oort cloud, first described in 1950 by the Dutch astronomer Jan Oort, is a theoretical concept of a cloud of predominantly icy planetesimals proposed to surround the Sun at distances ranging from 2 ...
, the source region of
long-period comet
A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena are ...
s, regarded by astronomers as the outermost zone of the Solar System.
In October 2020, astronomers reported a significant unexpected increase in density in the
space
Space is the boundless three-dimensional extent in which objects and events have relative position and direction. In classical physics, physical space is often conceived in three linear dimensions, although modern physicists usually consider ...
beyond the
Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...
as detected by the ''Voyager 1'' and ''
Voyager 2
''Voyager 2'' is a space probe launched by NASA on August 20, 1977, to study the outer planets and interstellar space beyond the Sun's heliosphere. As a part of the Voyager program, it was launched 16 days before its twin, ''Voyager 1'', on a ...
''
space probe
A space probe is an artificial satellite that travels through space to collect scientific data. A space probe may orbit Earth; approach the Moon; travel through interplanetary space; flyby, orbit, or land or fly on other planetary bodies; or ent ...
s. According to the researchers, this implies that "the density gradient is a large-scale feature of the
VLISM (very local
interstellar medium
In astronomy, the interstellar medium is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstella ...
) in the general direction of the
heliospheric nose".
In May 2021, NASA reported on the continuous measurement, for the first time, of the density of material in interstellar space and, as well, the detection of interstellar sounds for the first time.
In May 2022, NASA reported that ''Voyager 1'' had begun transmitting "mysterious" and "peculiar"
telemetric data to the
Deep Space Network
The NASA Deep Space Network (DSN) is a worldwide Telecommunications network, network of American spacecraft communication ground segment facilities, located in the United States (California), Spain (Madrid), and Australia (Canberra), that suppo ...
(DSN). It confirmed that the operational status of the craft remained unchanged, but that the issue stemmed from the Attitude Articulation and Control System (AACS). NASA's
Jet Propulsion Laboratory
The Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center in the City of La Cañada Flintridge, California, United States.
Founded in the 1930s by Caltech researchers, JPL is owned by NASA an ...
(JPL) published a statement on May 18, 2022, that the AACS was functional but sending invalid data. The problem was eventually traced to the AACS sending its telemetry through a computer that had been non-operational for years, resulting in data corruption. In August 2022, NASA transmitted a command to the AACS to utilize another computer, which resolved the problem. An investigation into what caused the initial switch is underway, though engineers have hypothesized that the AACS had executed a bad command from another onboard computer.
Future of the probe
Remaining lifespan
![Voyager 1 Radio Signal 21 Feb 2013](https://upload.wikimedia.org/wikipedia/commons/1/12/Voyager_1_Radio_Signal_21_Feb_2013.jpg)
In December 2017, NASA successfully fired up all four of ''Voyager 1''s trajectory correction maneuver (TCM) thrusters for the first time since 1980. The TCM thrusters will be used in the place of a degraded set of jets which were used to help keep the probe's antenna pointed towards the Earth. Use of the TCM thrusters will allow ''Voyager 1'' to continue to transmit data to NASA for two to three more years.
Due to the diminishing electrical power available, the Voyager team has had to prioritize which instruments to keep on and which to turn off. Heaters and other spacecraft systems have been turned off one by one as part of power management. The fields and particles instruments that are the most likely to send back key data about the heliosphere and interstellar space have been prioritized to keep operating. Engineers expect the spacecraft to continue operating at least one science instrument until around 2025.
Far future
File: VoyagerOne Aug 2 2018.png, Simulated view of ''Voyager 1'' relative to the Solar System on August 2, 2018.
File: Voyagerprobes Aug 2 2018.png, Simulated view of the Voyager probes relative to the Solar System and heliopause on August 2, 2018.
File:NearSunStarsSimple.jpg, In about 50,000 years ''Voyager 1'' will be as distant as several nearby stars
Provided ''Voyager 1'' does not collide with anything and is not retrieved, the ''
New Horizons
''New Horizons'' is an Interplanetary spaceflight, interplanetary space probe that was launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research ...
'' space probe will never pass it, despite being launched from Earth at a higher speed than either Voyager spacecraft. The Voyager spacecraft benefited from multiple planetary flybys to increase its heliocentric velocities, whereas ''New Horizons'' received only a single such boost, from its Jupiter flyby. , ''New Horizons'' is traveling at about , slower than ''Voyager 1'' and is still slowing down.
''Voyager 1'' is expected to reach the theorized
Oort cloud
The Oort cloud (), sometimes called the Öpik–Oort cloud, first described in 1950 by the Dutch astronomer Jan Oort, is a theoretical concept of a cloud of predominantly icy planetesimals proposed to surround the Sun at distances ranging from 2 ...
in about 300 years
and take about 30,000 years to pass through it.
Though it is not heading towards any particular star, in about
40,000 years, it will pass within of the star
Gliese 445
Gliese 445 (Gl 445 or AC +79 3888) is an M-type main sequence star in the northern part of the constellation Camelopardalis.
Location
It is currently 17.1 light-years from Earth and has an apparent magnitude of 10.8. It is visible f ...
, which is at present in the
constellation
A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.
The origins of the e ...
Camelopardalis
Camelopardalis is a large but faint constellation of the northern sky representing a giraffe. The constellation was introduced in 1612 or 1613 by Petrus Plancius. Some older astronomy books give Camelopardalus or Camelopardus as alternative for ...
and 17.1 light-years from Earth.
That star is generally moving towards the
Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...
at about .
NASA says that "The Voyagers are destined—perhaps eternally—to wander the Milky Way."
In 300,000 years, it will pass within less than 1 light year of the M3V star TYC 3135-52-1.
Golden record
![The Sounds of Earth - GPN-2000-001976](https://upload.wikimedia.org/wikipedia/commons/7/7b/The_Sounds_of_Earth_-_GPN-2000-001976.jpg)
Each Voyager space probe carries a gold-plated
audio-visual disc, should the spacecraft ever be found by intelligent life forms from other planetary systems.
The disc carries photos of the
Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
and its lifeforms, a range of scientific information, spoken greetings from people such as the
Secretary-General of the United Nations
The secretary-general of the United Nations (UNSG or SG) is the chief administrative officer of the United Nations and head of the United Nations Secretariat, one of the six principal organs of the United Nations.
The role of the secretary-g ...
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 including works by
Wolfgang Amadeus Mozart
Wolfgang Amadeus Mozart (27 January 17565 December 1791), baptised as Joannes Chrysostomus Wolfgangus Theophilus Mozart, was a prolific and influential composer of the Classical period. Despite his short life, his rapid pace of composition r ...
,
Blind Willie Johnson
Blind Willie Johnson (January 25, 1897 – September 18, 1945) was an American gospel blues singer, guitarist and evangelist. His landmark recordings completed between 1927 and 1930—thirty songs in total—display a combination of powerful "ch ...
,
Chuck Berry
Charles Edward Anderson Berry (October 18, 1926 – March 18, 2017) was an American singer, songwriter and guitarist who pioneered rock and roll. Nicknamed the " Father of Rock and Roll", he refined and developed rhythm and blues into th ...
and
Valya Balkanska
Valya Mladenova Balkanska ( bg, Валя Младенова Балканска; born 8 January 1942) is a Bulgarian folk music singer from the Rhodope Mountains known locally for her wide repertoire of Balkan folk songs, but in the West mainly fo ...
. Other Eastern and Western classics are included, as well as various performances of indigenous music from around the world. The record also contains greetings in 55 different languages.
See also
References
External links
NASA Voyager website''Voyager 1'' Mission Profileb
NASA's Solar System ExplorationPosition of ''Voyager 1'' (Live-Counter)''Voyager 1'' (NSSDC Master Catalog)Heavens-above.com: Spacecraft Escaping the Solar System– current positions and diagrams
JPL Voyager Telecom Manual''Voyager 1'' Has Outdistanced the Solar Wind*
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*
NASA space probes
Missions to Saturn
Missions to Jupiter
Radio frequency propagation
Spacecraft escaping the Solar System
1977 in spaceflight
1977 in the United States
September 1977 events in the United States
1977 robots
Nuclear-powered robots
Spacecraft launched by Titan rockets
Spacecraft launched in 1977
Articles containing video clips
Individual space vehicles