Voyager spacecraft |
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| Operator | NASA / JPL |
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| Mission type | Flyby |
| Flyby of | Jupiter, Saturn |
| Launch date | 1977-09-05 12:56:00 UTC (34 years, 5 months and 11 days ago) |
| Launch vehicle | Titan IIIE / Centaur |
| Launch site | Space Launch Complex 41 Cape Canaveral Air Force Station |
| Mission duration | In progress (Interstellar mission) (33 years, 1 month and 12 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] |
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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 eventually interstellar space. Operating for 34 years, 5 months and 11 days as of today (16 February 2012), the spacecraft receives routine commands and transmits data back to the Deep Space Network. At a distance of 119 astronomical units (1.78×1010 km) as of October 2011,[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.
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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]
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".
Voyager 1 was constructed by the Jet Propulsion Laboratory. It has 16 hydrazine thrusters, three-axis stabilization gyroscopes, and celestial referencing instruments (sun sensor/Canopus Star Tracker) to keep the probe's'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]
Voyager 1's radio communication system was designed for the probe's ultimate journey beyond the solar system. It includes a large (3.7 meter) parabolic high-gain antenna (see diagram) to communicate with the Deep Space Network on Earth. Communications are conducted over the S-band (13 cm wavelength) and X-band (3.6 cm wavelength) providing bandwidth as high as 115.2 kilobits per second. When the spacecraft is unable to communicate with Earth, the Digital Tape Recorder (DTR) can record up to 62,500 kilobytes of data for transmission when communication is reestablished.[5] It takes about 32 hours for NASA Jet Propulsion Laboratory to receive and send messages to the Voyagers.
Voyager 1 has three Multihundred-Watt radioisotope thermoelectric generators (MHW RTG). Each RTG has 24 pressed plutonium oxide spheres; the heat from the spheres generates approximately 157 watts of power (at launch) - 470 watts total from the three RTGs. The power output of the RTGs declines over time, but Voyager 1's RTGs will allow operations to continue until at least 2025.[5][6] (see diagram 1, 2)
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For more details on the Voyager space probes' identical instrument packages, see the separate article on the overall Voyager Program.
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Media related to the Voyager spacecraft at Wikimedia Commons
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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.
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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.
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Media related to the Voyager 1 Jupiter encounter at Wikimedia Commons
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]
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Media related to the Voyager 1 Saturn encounter at Wikimedia Commons
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 is still the fastest probe in the Solar System.
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).[14] The close flyby of Saturn and Titan gave Voyager 1 a massive advantage with its extra gravity assist.
| Year | End of specific capabilities as a result of the available electrical power limitations |
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| 2007 | Termination of plasma subsystem (PLS) |
| 2008 | Power off Planetary Radio Astronomy Experiment (PRA) |
| 2010 | Terminate scan platform and Ultraviolet spectrometer (UVS) observations |
| 2015 | Termination of Data Tape Recorder (DTR) operations (limited by ability to capture 1.4 kbit/s data using a 70 m/34 m antenna array. This is the minimum rate at which the DTS can read-out data.) |
| 2016 approx | Termination of gyroscopic operations |
| 2020 | Start shutdown of science instruments (as of October 18, 2010[update] the order is undecided but the Low-Energy Charged Particles, Cosmic Ray Subsystem, Magnetometer, and Plasma Wave Subsystem instruments are expected to still be operating)[15] |
| 2025–2030 | Can no longer power any single instrument. |
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.[16] Some other scientists have expressed doubt, discussed in the journal Nature of November 6, 2003.[17] 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.
However, in May 2005 a NASA press release said that consensus was that Voyager 1 was now in the heliosheath.[18] Scientists anticipate that the craft will reach the heliopause in 2015.
Voyager 1 is the farthest human-made object from Earth in the Universe, traveling away from both the Earth and the Sun at a relative speed faster than any other probe.[19]
As of January 04, 2012[update], Voyager 1 is about 120.07704 astronomical units (1.7963270×1010 km) from the Earth and about 119.36376 astronomical units (1.7856564×1010 km) from the Sun.[20] 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 16.12 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.
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.
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).[21]
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.[22] 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.[23] The meridional (north-south) speed of the solar wind, which is suspected to have increased, cannot be inferred in Voyager 1's current configuration. On this date, the spacecraft was approximately 17.3 billion kilometers (116 AU or 10.8 billion miles) from the Sun[24]
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.[25][26]
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".[27]
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.[28]
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.[29][30]
Media related to [//commons.wikimedia.org/wiki/Category:Voyager_1 Voyager 1] at Wikimedia Commons
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