Voyager 1

Voyager spacecraft
Operator	NASA / JPL
Mission type	Flyby
Flyby of	Jupiter, Saturn
Launch date	1977-09-05 12:56:00 UTC (34 years, 9 months and 21 days 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) (33 years, 5 months and 22 days elapsed) Jupiter encounter (completed 1979-04-13) Saturn encounter (completed 1980-12-14)
COSPAR ID	1977-084A
Homepage	NASA Voyager website
Mass	721.9 kg (1,592 lb)
Power	420 W (3 RTGs)
References: [1]

The Voyager 1 spacecraft is a 722 kilogram (1,592 lb) space probe launched by NASA in 1977, to study the outer Solar System and interstellar medium. Operating for 34 years, 9 months and 18 days as of today (current operation time), the spacecraft receives routine commands and transmits data back to the Deep Space Network. At a distance of 120 astronomical units (1.8x10¹⁰ km) as of February 2012,^[2] it is the farthest man-made object from Earth. Voyager 1 is now in the heliosheath, which is the outermost layer of the heliosphere. It will most likely be the first probe to leave the Solar System.

Being a part of the Voyager program with its sister craft Voyager 2, the spacecraft is 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 November 20, 1980, after encountering the Jovian system in 1979 and the Saturnian system in 1980.^[3] It was the first probe to provide detailed images of the two largest planets and their moons.

Mission background[link]

History[link]

In the 1960s, a Grand Tour to study the outer planets was proposed. This prompted NASA to begin work on a mission in the early 1970s. The development of the interplanetary probes coincided with a favorable alignment of the planets, which would allow a probe to reach the outer Solar System by means of the then-new gravity assist technique.

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 1 was planned as Mariner 11 of the Mariner program. However, 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 as the probe designs began to differ greatly from previous Mariner missions.^[4]

Golden record[link]

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. The discs carry photos of the Earth and its lifeforms, a range of scientific information, spoken greetings from 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 collection of Earth music, including works by Mozart and Chuck Berry's "Johnny B. Goode".

Spacecraft design[link]

Voyager 1 was constructed by the Jet Propulsion Laboratory. It has 16 hydrazine thrusters, three-axis stabilization gyroscopes, and referencing instruments (sun sensor/Canopus Star Tracker) 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 as it traveled through space.^[5]

Communication system[link]

The radio communication system of Voyager 1 was designed to be used up to and beyond the limits of the solar system during the extremely-long flight of this space probe. The communication system includes a 3.7 meter diameter parabolic dish high-gain antenna (see diagram) to send and receive radio waves via the three Deep Space Network stations on the Earth. These modulated waves are placed in the S-band (about 13 cm in wavelength) and X-band (about 3.6 cm in wavelength) which provided a bit rate as high as 115.2 kilobits per second when Voyager 1 was at the distance of Jupiter from the Earth, and many fewer kilobits per second at larger distances.

When Voyager 1 is unable to communicate directly with the Earth, its digital tape recorder (DTR) can record up to 62,500 kilobytes of data for transmission at another time. ^[5] The length of time needed to send messages to Voyager 1 or to receive messages on the Earth depends on the straight-line distance between the two according to the simple equation t = D/c, where D is the distance and c is the speed of light (about 300,000 km/sec).

Power[link]

Voyager 1 has three large radioisotope thermoelectric generators (RTGs). Each RTG contains 24 pressed plutonium-238 oxide spheres. The heat from the spheres generated about 157 watts of electric power at the launch, with the remainder being dissipated as waste heat. Hence there was a total of about 470 watts of electric power provided by the three RTGs.

The power output of the RTGs does decline over time, but the RTGs of Voyager 1 will support some of its operations to continue through about 2025.^[5][6] (see diagram 1, 2)

Scientific instruments[link]

Expand

Instrument Name Abr. Description Imaging Science System (disabled) (ISS) Utilized a two-camera system (narrow-angle/wide-angle) to provide imagery of Jupiter, Saturn and other objects along the trajectory. More Filters Narrow Angle Camera Filters[7] Name Wavelength Spectrum Sensitivity Clear 280–640 nm UV 280–370 nm Violet 350–450 nm Blue 430–530 nm ' ' ' Green 530–640 nm ' ' ' Orange 590–640 nm ' ' ' Wide Angle Camera Filters[8] Name Wavelength Spectrum Sensitivity Clear 280–640 nm ' ' ' Violet 350–450 nm Blue 430–530 nm CH4-U 536–546 nm Green 530–640 nm Na-D 588–590 nm Orange 590–640 nm CH4-JST 614–624 nm Principal investigator: Bradford Smith / University of Arizona (PDS/PRN website) Data: PDS/PDI data catalog, PDS/PRN data catalog Radio Science System (disabled) (RSS) Utilized the telecommunications system of the Voyager spacecraft to determine the physical properties of planets and satellites (ionospheres, atmospheres, masses, gravity fields, densities) and the amount and size distribution of material in Saturn's rings and the ring dimensions. More Principal investigator: G. Tyler / Stanford University PDS/PRN overview Data: PDS/PPI data catalog, PDS/PRN data catalog (VG_2803), NSSDC data archive Infrared Interferometer Spectrometer (disabled) (IRIS) Investigates both global and local energy balance and atmospheric composition. Vertical temperature profiles are also obtained from the planets and satellites as well as the composition, thermal properties, and size of particles in Saturn's rings. More Principal investigator: Rudolf Hanel / NASA Goddard Space Flight Center (PDS/PRN website) Data: PDS/PRN data catalog, PDS/PRN expanded data catalog (VGIRIS_0001, VGIRIS_002), NSSDC Jupiter data archive Ultraviolet Spectrometer (active) (UVS) Designed to measure atmospheric properties, and to measure radiation. More Principal investigator: A. Broadfoot / University of Southern California (PDS/PRN website) Data: PDS/PRN data catalog Triaxial Fluxgate Magnetometer (active) (MAG) Designed to investigate the magnetic fields of Jupiter and Saturn, the interaction of the solar wind with the magnetospheres of these planets, and the magnetic field of interplanetary space out to the boundary between the solar wind and the magnetic field of interstellar space, if crossed. More Principal investigator: Norman Ness / NASA Goddard Space Flight Center (website) Data: PDS/PPI data catalog, NSSDC data archive Plasma Spectrometer (defective) (PLS) Investigates the macroscopic properties of the plasma ions and measures electrons in the energy range from 5 eV to 1 keV. More Principal investigator: John Richardson / MIT (website) Data: PDS/PPI data catalog, NSSDC data archive Low Energy Charged Particle Instrument (active) (LECP) Measures the differential in energy fluxes and angular distributions of ions, electrons and the differential in energy ion composition. More Principal investigator: Stamatios Krimigis / JHU/APL / University of Maryland (JHU/APL website / UMD website / KU website) Data: UMD data plotting, PDS/PPI data catalog, NSSDC data archive Cosmic Ray System (active) (CRS) Determines the origin and acceleration process, life history, and dynamic contribution of interstellar cosmic rays, the nucleosynthesis of elements in cosmic-ray sources, the behavior of cosmic rays in the interplanetary medium, and the trapped planetary energetic-particle environment. More Principal investigator: Edward Stone / CalTech / NASA Goddard Space Flight Center (website) Data: PDS/PPI data catalog, NSSDC data archive Planetary Radio Astronomy Investigation (disabled) (PRA) Utilizes a sweep-frequency radio receiver to study the radio-emission signals from Jupiter and Saturn. More Principal investigator: James Warwick / University of Colorado Data: PDS/PPI data catalog, NSSDC data archive Photopolarimeter System (defective) (PPS) Utilized a telescope with a polarizer to gather information on surface texture and composition of Jupiter and Saturn and information on atmospheric scattering properties and density for both planets. More Principal investigator: Arthur Lane / JPL (PDS/PRN website) Data: PDS/PRN data catalog Plasma Wave System (active) (PWS) Provides continuous, sheath-independent measurements of the electron-density profiles at Jupiter and Saturn as well as basic information on local wave-particle interaction, useful in studying the magnetospheres. More Principal investigator: Donald Gurnett / University of Iowa (website) Data: PDS/PPI data catalog

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 1 in a space simulator chamber.   Gold-Plated Record is attached to Voyager 1.   Voyager 1 awaiting payload entry into a Titan/Centaur-6 rocket.

Media related to the Voyager spacecraft at Wikimedia Commons

Mission profile[link]

Launch and trajectory[link]

The Voyager 1 probe was launched on September 5, 1977, from Space Launch Complex 41 at Cape Canaveral, Florida, aboard a Titan IIIE/Centaur launch vehicle. The twin Voyager 2 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 lifted off with a Titan IIIE/Centaur   Trajectory of Voyager 1 primary mission.

Encounter with Jupiter[link]

Voyager 1 began photographing Jupiter in January 1979. Its closest approach to Jupiter was on March 5, 1979, at a distance of about 349,000 kilometers (217,000 mi) from the planet's center. Due to 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 two Voyager space probes made a number of important discoveries about Jupiter, its satellites, its radiation belts, and its never-before-seen planetary rings. The most surprising discovery in the Jovian system was the existence of volcanic activity on the moon Io, which had not been observed either from the ground, or by Pioneer 10 or Pioneer 11.

The Great Red Spot as seen from Voyager 1.   False color detail of Jupiter's atmosphere.   View of lava flows radiating from the volcano Ra Patera on Io.   Volcanic eruption on Io photographed from Voyager 1.

Europa as seen from Voyager 1 at a distance of 2.8 million km.   Icy surface of Ganymede as photographed from 253,000 km.   Valhalla crater on Callisto as imaged by Voyager 1 in 1979.   Voyager 1 time lapse movie of Jupiter approach. Full size video here

Media related to the Voyager 1 Jupiter encounter at Wikimedia Commons

Encounter with Saturn[link]

The gravitational assist trajectories at Jupiter were successfully carried out by both Voyagers, and the two spacecraft went on to visit Saturn and its system of moons and rings. Voyager 1's Saturnian flyby occurred in November 1980, with the closest approach on November 12, 1980, when the space probe came within 124,000 kilometers (77,000 mi) of Saturn's cloud-tops. The space probe's cameras detected complex structures in the rings of Saturn, and its remote sensing instruments studied the atmospheres of Saturn and its giant moon Titan.

Because Pioneer 11 had one year earlier detected a thick, gaseous atmosphere over Titan, the Voyager space probes' controllers at the Jet Propulsion Laboratory elected for Voyager 1 to make a close approach of Titan, and of necessity end its Grand Tour there. (For the continuation of the Grand Tour, see the Uranus and Neptune sections of the article on Voyager 2.)

Its trajectory with a close fly-by of Titan caused an extra gravitational deflection that sent Voyager 1 out of the plane of the ecliptic, thus ending its planetary science mission. Voyager 1 could have been commanded onto a different trajectory, whereby the gravitational slingshot effect of Saturn's mass would have steered and boosted Voyager 1 out to a fly-by of Pluto. However, this plutonian option was not exercised, because the other trajectory that led to the close fly-by of Titan was decided to have more scientific value and less risk.^[11]

Saturn from 5.3 million km, four days after its closest approach.   Mimas at a range of 425,000 km from Voyager 1.   Tethys photographed by Voyager 1 from 1.2 million km.   Fractured terrain on Dione.

Impact craters on the surface of Rhea appear similar to Mercury.   Titan's thick haze layer is shown in this enhanced Voyager 1 image.   Layers of haze covering Saturn's satellite Titan.   Voyager 1 image of Saturn's F Ring.

Media related to the Voyager 1 Saturn encounter at Wikimedia Commons

Interstellar mission[link]

The "family portrait" of the Solar System taken by Voyager 1

On February 14, 1990, Voyager 1 took the first ever "family portrait" of our Solar System as seen from outside,^[12] which includes the famous image known as "Pale Blue Dot". It is estimated that both Voyager craft have sufficient electrical power to operate their radio transmitters until at least 2025, which will be over 48 years after launch.

On November 17, 1998, Voyager 1 overtook Pioneer 10 as the most distant man-made object from Earth, at a distance of 69.419 AU (1.03849×10¹⁰ km). It is currently the most distant functioning space probe to receive commands and transmit information to Earth. The spacecraft's mission now is its eternal mission, to study and wander the interstellar medium. Scientists expect it to cross the heliopause sometime between 2012–2015. At 17.26 km/s (10.72 mi/s)^[13] it has the fastest heliocentric recession speed of any man-made satellite.^[14]

Provided Voyager 1 does not collide with any stellar objects, the New Horizons space probe will never pass it, despite being launched from Earth at a faster speed than either Voyager spacecraft. New Horizons is traveling at about 15 km/s, 2 km/s slower than Voyager 1, and is still slowing down. When New Horizons reaches the same distance from the sun as Voyager 1 is now, its speed will be about 13 km/s (8 mi/s).^[15] The close flyby of Saturn and Titan gave Voyager 1 a massive advantage with its extra gravity assist.

Heliopause[link]

Voyager 1 is currently within the heliosheath and approaching interstellar space.

As Voyager 1 heads for interstellar space, its instruments continue to study the Solar System; Jet Propulsion Laboratory scientists are using the plasma wave experiments aboard Voyager 1 and 2 to look for the heliopause, the boundary at which the solar wind transitions into the interstellar medium.

Scientists at the Johns Hopkins University Applied Physics Laboratory believe that Voyager 1 entered the termination shock in February 2003.^[17] Some other scientists have expressed doubt, discussed in the journal Nature of November 6, 2003.^[18] In a scientific session at the American Geophysical Union meeting in New Orleans on the morning of May 25, 2005, Dr. Ed Stone presented evidence that Voyager 1 crossed the termination shock in December 2004.

The issue will not be resolved until other data becomes available, since Voyager 1's solar-wind detector ceased functioning in 1990. This failure has meant that termination shock detection must be inferred from the data from the other instruments on board.^[19][20][21]

However, in May 2005 a NASA press release said that consensus was that Voyager 1 was now in the heliosheath.^[22] Scientists anticipate that the craft will reach the heliopause in 2015.

Current status[link]

Simulated view of the position of Voyager 1 as of 8 February 2012 showing spacecraft trajectory since launch.

Simulated view from Voyager 1. Planet orbits are shown but no planets are visible from this distance.

As of May 21, 2011^[update], the spacecraft is at 12.44° declination and 17.163 hours right ascension, and is at an ecliptic latitude of 34.9° (the ecliptic latitude changes very slowly), placing it in the constellation Ophiuchus as observed from the Earth. NASA continues its daily tracking of Voyager 1 with its Deep Space Network. This network measures both the elevation and azimuth angles of the incoming radio waves from Voyager 1, and it also measures the distance from the Earth to Voyager 1.

As of February 08, 2012^[update], Voyager 1 is about 120.06973 astronomical units (1.7962176×10¹⁰ km) from the Earth and about 119.70479 astronomical units (1.7907582×10¹⁰ km) from the Sun.^[23] The magnitude of the Sun from Voyager 1 is −16.4, or the dimmest as seen from any of the five space probes leaving the Solar System. Radio signals traveling at the speed of light between Voyager 1 and Earth take 16.5 hours to cross the distance between the two. (To compare, Proxima Centauri, the closest star to our Sun, is about 4.2 light-years distant or 2.65×10⁵ AU.) Voyager 1's current relative velocity to the sun is 17,060 m/s (61,400 km/h; 38,200 mph). This calculates as 3.599 AU per year, about 10% faster than Voyager 2. At this velocity, 73,600 years would pass before reaching the nearest star, Proxima Centauri, were the spacecraft traveling in the direction of that star. Voyager 1 will need about 14,000 years at its current velocity to travel one light year, therefore 40,000 years will pass before coming anywhere near other stars or planets. Voyager 1 is predicted to enter the interstellar medium between 2012–15, though some scientists say it will be in 2014. Voyager 1 is still the farthest man made object in the universe from Earth.

Voyager 1 is not heading towards any particular star, but in about 40,000 years it will pass within 1.6 light years of the star AC+79 3888, which is at present in the constellation Camelopardalis. That star is generally moving towards our Solar System at about 119 km/s (430,000 km/h; 270,000 mph).^[24]

Events[link]

On February 17, 1998, Voyager 1 became the farthest man-made object from Earth, passing Pioneer 10 at 69 AU from the sun. From this day onwards to the present, Voyager 1 has been the farthest man made object from Earth, and no probe has passed its distance and there are no probes predicted to be launched in the next 20 years that will pass the probe.

On December 18, 2004, Voyager 1 passed the termination shock. This marks the point where the solar wind slows to subsonic speeds. This is the unofficial date of departure from the Solar System. While the spacecraft still remains under the sun's influence, at the termination shock particles from the interstellar medium interact with solar particles, signaling that the hypothetical heliopause is not far from this point. Six years later in 2010 Voyager 1 entered an area of the heliosheath where the solar wind outward speed is 0, or flowing sideways relative to the sun. This signals that Voyager 1 is getting very close to entering the interstellar medium.

On March 31, 2006, the amateur radio operators from AMSAT in Germany tracked and received radio waves from Voyager 1 using the 20-meter (66 ft) dish at Bochum with a long integration technique. Retrieved data was checked and verified against data from the Deep Space Network station at Madrid, Spain.^[25] This is believed to be the first such tracking of Voyager 1.

On December 13, 2010, it was confirmed that Voyager 1 passed the reach of the solar wind emanating from the Sun. It is suspected that solar wind at this distance turns sideways due to interstellar wind pushing against the heliosphere. Since June 2010, detection of solar wind has been consistently at zero, providing conclusive evidence of the event.^[26] The meridional (north-south) speed of the solar wind, which is suspected to have increased, cannot be inferred in Voyager 1's current configuration.^{[citation needed]} On this date, the spacecraft was approximately 17.3 billion kilometers (116 AU or 10.8 billion miles) from the Sun^[27]

On March 8, 2011, Voyager 1 was commanded to change its position to detect the current direction of the solar wind. A test roll done in February 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. The spacecraft will be maneuvered again in the coming months to further analyze the solar wind. The spacecraft after the first roll had no problem in reorienting itself with Alpha Centauri, Voyager 1's guide star, to begin sending transmissions back to Earth. This is a major milestone in the Voyager interstellar program. Voyager 2 is still detecting outward flow of solar wind but it is estimated that in the coming months or years it will experience the same conditions as Voyager 1.^[28][29]

On June 15, 2011, the distance to the interstellar medium was recalculated, which is now believed to be much less than previously thought. NASA believes that Voyager 1 may cross into the space between the stars sometime in the next year or so. The Low Energy Charged Particle device on Voyager 1 has detected the outward flow of the solar wind to be at zero. This means it is flowing parallel up and down to the sun, signaling that the interstellar medium is very close. Voyager 2 still has more travel time before it reaches the interstellar medium, while scientists believed Voyager 1 will enter interstellar space "at any time".^[30]

On December 1, 2011, it was announced that Voyager 1 detected the first Lyman-alpha radiation originating from the Milky Way galaxy. Lyman-alpha radiation had previously been detected from other galaxies, but due to interference from the Sun, the radiation from the Milky Way was not detectable.^[31]

On December 5, 2011, it was announced that Voyager 1 had entered a new region referred to as a "cosmic purgatory" by NASA. Within this stagnation region, charged particles streaming from the sun slow and turn inward, and the solar system's magnetic field has doubled in strength as interstellar space appears to be applying pressure. Energetic particles originating in the solar system have declined by nearly half, while the detection of high-energy electrons from outside has increased by 100 fold. The inner edge of the stagnation region is located approximately 113 astronomical units from the sun, while the outer edge is unknown.^[32][33]

See also[link]

Spaceflight portal

References[link]

External links[link]

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• Explanation of VIM

v t e Spacecraft missions to Jupiter Orbiters Galileo Juno (en route) Descent probes Galileo probe Flybys Pioneer 10 11 Voyager 1 2 Ulysses Cassini New Horizons Future missions Jupiter Icy Moon Explorer Proposed missions Io Volcano Observer Jupiter Magnetospheric Orbiter Jupiter flybys in other missions: New Horizons 2 (flyby only) Innovative Interstellar Explorer (flyby only) Uranus Orbiter (flyby only) Neptune Orbiter (flyby only) Jupiter and Trojan asteroid exploration (flyby only) Undeveloped missions Pioneer H Tsiolkovsky mission Europa Orbiter Jovian Europa Orbiter Jupiter Icy Moons Orbiter Europa Lander Europa Jupiter System Mission-Laplace Jupiter Ganymede Orbiter Jupiter Europa Orbiter Related topics Deep Space Network Portal:Robotics Exploration of Io Moons of Jupiter Bold italics indicates active missions, even if they passed Jupiter already

v t e Spacecraft missions to Saturn Flybys Pioneer 11 Voyager 1 Voyager 2 Orbiters Cassini Probes Huygens (Titan only) Proposed missions Kronos Titan Mare Explorer AVIATR (Titan only) Saturn Ring Observer Saturn entry probe Enceladus missions Canceled missions Saturn mission Titan and Enceladus Mission Titan Explorer Titan Saturn System Mission Bold italics indicates active missions