Voyager 1 is an unmanned space probe developed and launched by NASA on September 5, 1977, as part of the Voyager program to study the outer Solar System and interstellar space beyond the Sun's heliosphere. It was launched 16 days after its twin, Voyager 2. It communicates via NASA's Deep Space Network to receive commands and transmit data back to Earth. As of June 19, 2023, it is the most distant man-made object from Earth, being approximately 159.404 AU (23.846 billion km; 14.817 billion miles) away.
Voyager 1's original targets were Jupiter, Saturn, and their associated moons and rings. The probe made flybys of Jupiter, Saturn, and Titan, Saturn's largest moon. NASA had a choice to do a flyby of either Titan or Pluto; they decided on Titan because it was known to contain 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.
Like its sister craft Voyager 2, Voyager 1's extended mission is to locate and study the regions and boundaries of the outer heliosphere and to begin explroing the interstellar medium. Voyager 1 crossed the heliopause and entered interstellar space on August 25, 2012, and became the first spacecraft to do so. Two years later, Voyager 1 began to experience a third "tsunami wave" of coronal mass ejections from the Sun that continued to last until at least December 15, 2014, further confirming the probe was in interstellar space.
In late 2017, the Voyager team tested the spacecraft's trajectory correction maneuver (TCM) thrusters, the first time the thrusters had been fired since 1980. This allowed Voyager 1's mission to extend by two to three years. Voyager 1's extended mission is not expected to continue past 2025, as that is when its radioisotope thermoelectric generators (RTGS) will no longer supply enough electric power to operate its scientific elements. The spacecraft may remain within the range of the Deep Space Network until around 2036.
Background[]
In the 1960s, NASA proposed the Planetary Grand Tour, a pair of probes to fly all over the outer planets, and planned to work on it in the early 1970s. The data collected by the Pioneer 10 spacecraft helped give Voyager's engineers a better understanding of Jupiter's magnetic field, and helped engineers design better probes to deal more effectively with the intense radiation environment around Jupiter.
Voyager 1 was originally named "Mariner 11" of the Mariner program. Due to budget cuts, NASA created a separate program called the Jupiter-Saturn Mariner Program, and scaled it back to a flyby of Jupiter and Saturn. Later, the program was renamed Project Voyager as the probes design differing greatly from the previous Mariner missions.
Spacecraft components[]
The 3.7 m (12 ft) diameter high gain dish antenna used on the Voyager craft
Voyager 1 was built by the Jet Propulsion Laboratory with an Attitude and Articulation Control Subsystem (AACS), containing 16 hydrazine thrusters, a three-axis stabilized gyroscope, and referencing instruments to keep the probe's radio antenna pointed toward Earth. The system aslo includes redundant units for most instruments and eight spare thrusters. The spacecraft also included 11 scientific instruments for studying celestial bodies such as planets as it travels through space.
Power[]
Voyager 1 has three radioisotope thermoelectric generators (RTGs) mounted on a boom. Each MHW-RTG contains 24 pressed plutonium-238 oxide spheres. When first launched, the RTGs were capable of generating about 470 W of power, while the remainder was dissipated as waste heat. The power output of the RTGs declines over time, due to the 87.7-year half-life of the fuel and degradation of the thermocouples, but the ship's RTGs will continue to support some of its operations running until 2025.
As of April 26, 2025, Voyager 1 has around 69.13% of its plutonium-238 fuel left. By 2050, approximately 56.5% of its fuel will remain.
Computers[]
Unlike the other onboard instruments, Voyager 1's camera is not operated autonomously, but is controlled by an imaging parameter table in one of the onboard computers, the Flight Data Subsystem (FDS). Since the 1990s, most space probes have been equipped with completely autonomous cameras.
The Computer Command Subsystem (CCS) is responsible for controlling the cameras. The CCS contains fixed computer programs such as command decoding, fault-detection and fault-correction routes, antenna pointing programs, and spacecraft sequencing routines. The computer is a modified and improved version of the one used on the Viking orbiters in the 1970s.
The Attitude and Articulation Control System (AACS) controls the orientation (attitude) of the spacecraft. The AACS points the high-gain antenna toward Earth, controls attitude changes, and points the scan platform. The custom-built AACS systems on both Voyagers are the same.
Scientific instruments[]
| Instrument name | Abbreviation | Description | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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(disabled) |
Utilized a dual camera lens system (narrow-angle/wide-angle) to provide images of Jupiter, Saturn, and other objects.
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(disabled) |
Utilized the telecommunication systems of the Voyager spacecraft to determine the physical properties of the planets and moons (ionospheres, atmospheres, mass, gravity fields, densities), as well as the amount and size distribution of matter in Saturn's rings and the ring dimensions. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
(disabled) |
Investigates the global and local energy balance and atmospheric composition of stars. It also obtains the vertical temperature distribution, composition, and thermal properties of planets and moons, and particle sizes in Saturn's rings. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
(disabled) |
Designed for measuring the atmospheric properties and measuring radiation. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
(working) |
Investigates the magnetic fields of Jupiter and Saturn, the interaction of the solar wind with the magnetic spheres of those planets, and the boundary between magnetic fields of interplanetary space to the solar wind and the magnetic fields of interstellar space. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
(partially working) |
Investigates the microscopic properties of plasma ions and measures electrons in the energy range from 5eV to 1keV. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
(working) |
Measures differences in energy flux and angular distribution of ions, electrons, and differences in energetic ion composition. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
(working) |
Used to determine the origin and acceleration process, life history, and dynamic history of cosmic rays, the nucleosynthesis of elements in cosmic ray sources, the behavior of cosmic rays in the interplanetary medium, and the environment in trapped planetary energetic particles. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
(disabled) |
Utilized a sweep-frequency radio receiver to study the radio-emission signals from Jupiter and Saturn. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
(partially working) |
Utilized a telescope with a polarizer to gather information on the surface texture, composition, atmospheric scattering properties, and density of Jupiter and Saturn. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
(working) |
Provides continuous, unsheathed measurements of the electron-density profiles of Jupiter and Saturn, as well as basic information on local wave-particle interactions, to help study the magnetosphere. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Mission profile[]
Timeline of travel[]
Trajectory of Voyager 1 after launch from Earth.
| Date | Event | ||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1977-09-05 | 12:56:00 UTC: Spacecraft launched. | ||||||||||||||||||||||
| 1977-12-10 | Entered the main asteroid belt. | ||||||||||||||||||||||
| 1977-12-19 | Voyager 1 overtakes Voyager 2. | ||||||||||||||||||||||
| 1978-09-08 | Voyager 1 leaves the asteroid belt | ||||||||||||||||||||||
| 1979-01-06 | Beginning of the Jupiter observation phase:
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| 1980-08-22 | Beginning of the Saturn observation phase:
| ||||||||||||||||||||||
| 1980-11-14 | Extended mission begins. |
| Extended Mission | |
|---|---|
| Date | Event |
| 1990-02-14 | Final images of the Voyager program captured by Voyager 1 to make the Solar System Family Portrait. |
| 1998-02-17 | Voyager 1 surpasses Pioneer 10 as the most distant spacecraft from the Sun, at 69.419 AU. Voyager 1 is moving away from the Sun at over 1 AU per year faster than Pioneer 10. |
| 2004-12-17 | Passed the termination shock at 94 AU and entered the heliosheath at 94 AU. |
| 2007-02-02 | Discontinued Plasma Subsystem Operations. |
| 2007-04-11 | Discontinued the heater for the plasma subsystem. |
| 2008-01-16 | Discontinued planetary radio astronomy experiment operations. |
| 2012-08-25 | Crossed the heliopause at 121 AU, and entered interstellar space. |
| 2014-07-07 | Further confirmation of probe reaching interstellar space. |
| 2016-04-19 | The operation of the UV spectrometer was discontinued. |
| 2017-11-28 | For the first time since November 1980, the "Trajectory correction maneuver" (TCM) thrusters are tested. |
Launch[]
Voyager 1 was launched on September 5, 1977 from Cape Canaveral, Florida, on a Titan IIIE launch vehicle. The Voyager 2 probe was launched two weeks earlier, on August 20, 1977. Despite being launched later, Voyager 1 was launched in a shorter trajectory, allowing it to reach both Jupiter and Saturn sooner.
Initially, crews on the ground worried that the spacecraft would not be able to reach Jupiter, because of a roughly one-second underburn in the second stage of the Titan IIIE rocket's burn process. Fortunately, it was confirmed there was still enough fuel burning on the upper stage of the Titan IIIE.
Voyager 1's initial orbit had an aphelion of 8.9 AU (830 million mi), just a little short of Saturn's orbit of 9.5 AU (880 million mi). Voyager 2's initial orbit had an aphelion of 6.2 AU (580 million mi), very short of Saturn's orbit.
Flyby of Jupiter[]
Voyager 1 began photographing Jupiter for the first time in January 1979. On March 5, 1979, Voyager 1 made its closest approach to the center of Jupiter, 349,000 kilometers (217,000 miles) away. Thanks to such a close pass and better camera resolution, the spacecraft was able to gain insight and high-resolution photographs of Jupiter's moons, rings, magnetic field, and radiation belts during the 48-hour close flyby. Voyager 1 completed photographing the Jovian system in April 1979.
The two spacecraft made many important discoveries about Jupiter, and its moons, such as the radiation belt and its never-before-seen planetary rings. The most surprising discovery was of ongoing volcanic activity on the moon Io. This was the first time that volcanoes had been seen on any other body in the Solar System. It appears that activity on Io affects the entire Jovian system. 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. Sulfur, oxygen, and sodium, 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.
Flyby of Saturn[]
After successfully using Jupiter's gravity, both Voyager 1 and Voyager 2 went on to visit Saturn. Voyager 1 flew by Saturn in November 1980, and flew within 124,000 kilometers (77,000 miles) of Saturn's highest cloud-tops on November 12. The spacecraft's cameras detected complex structures in the rings of Saturn, and made observations of Saturn's moon Titan.
Voyager 1 found that about seven percent of Saturn's upper atmosphere is helium (compared to 11 percent of Jupiter's atmosphere), while the rest is nearly all hydrogen. Since Saturn's internal helium abundance was expected to be the same as that of Jupiter's and the Sun's, the lower helium abundance in the upper atmosphere could mean that heavier helium may slowly sink through Saturn's hydrogen. This may explain the excess heat that Saturn radiates over energy it receives from the Sun. Wind speeds are very high on Saturn. Near the equator, Voyager measured wind speeds of around 500 m/s (1,100 mph; 1,770 km/h). The wind blows mostly in an easterly direction.
The Voyagers also discovered aurora-like hydrogen ultraviolet radiation in the atmosphere at mid-latitudes, and auroras at polar latitudes (above 65 degrees). High levels of auroral activity can lead to the formation of complex hydrocarbon molecules, which are transported to the equator. The mid-latitude auroras, which occur only in sunlit regions, remain a mystery, because the electron and iron bombardment known to cause auroras on Earth occur mostly at high latitudes. Both Voyagers measured Saturn's rotational period (the length of a Saturnian day) to be 10 hours, 39 minutes, and 24 seconds.
Voyager 1's mission included a flyby of Saturn's largest moon, Titan, which had been long said to have an atmosphere. Photos taken by Pioneer 11 in 1979 showed Titan's dense and complex atmosphere, further adding to the interest. The flyby of Titan occurred when the spacecraft entered the Saturnian system. Voyager's measurement of the atmosphere's effect on sunlight and ground-based measurements of the probe's effect on radio signals 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 dense atmosphere prevented any naked eye observations of the surface, but measurements of its atmospheric composition, temperature, and pressure led to speculation that lakes of liquid hydrocarbons could exist on its surface.
Because observations of Titan were considered to be vital, the trajectory chosen for Voyager 1 was designed specifically around the optimum Titan flyby, which took it below the south pole of Saturn and out of the ecliptic, ending its planetary science mission. If Voyager 1 failed to flyby or observe Titan, Voyager 2's trajectory could've been altered to flyby Titan, preventing any visits 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, arriving in 1986.
Exit from the heliosphere[]
The Family Portrait of the Solar System taken by Voyager 1. February 14, 1990
Voyager 1 took the first "Family Portrait" of the Solar System on February 14, 1990, which includes the image of Earth known as the Pale Blue Dot. Its cameras were deactivated afterwards to conserve energy for other equipment. The camera software has since been removed from the spacecraft, so it would be complicated 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 69 AU (6.4 billion miles; 10.3 billion km) from the Sun, and overtook Pioneer 10 as the most distant spacecraft. The spacecraft travelled at a speed of around 17 km/s (11 mi/s).
As Voyager 1 headed for interstellar space, the instruments on board continued to study the Solar System. Scientists at Jet Propulsion Laboratory scientists were able to use 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. As of 2013, the probe was moving at a relative velocity to the Sun of around 61,197 kilometers per hour (38,026 mph). At this velocity, Voyager 1 travels at around 523 million km (325 million miles) per year, or about one light-year every 18,000 years.
Termination shock[]
Scientists at Johns Hopkins University Applied Physics Laboratory believe that Voyager 1 entered the termination shock region in February of 2003. This marks the point where the solar wind slows to subsonic speeds. However, some scientists expressed doubt and discussed this in the scientific journal Nature on November 6, 2003.
On the morning of May 25, 2005, in a scientific session at the American Geophysical Union (AGU) in New Orleans, Dr. Ed Stone presented evidence that Voyager 1 had crossed the termination shock in December 15, 2004, at a distance of 94 AU (8,700 million mi) from the Sun.
Heliosheath[]
The Pale Blue Dot image, showing Earth from 6 billion km (3.7 billiom mi) away, appearing as a tiny dot.
The German AMSAT (Amateur Radio Satellite Communications Organization) tracked and received data from Voyager 1 on March 31, 2006. They used a 20-meter (66 ft) dish in Bochum with a long integration technique. The data was collected and verified with data from the Deep Space Network station in Madrid, Spain.
Astronomers confirmed that Voyager 1 had passed the reach of the radial outward flow of the solar wind on December 13, 2010. It is suspected that solar wind at this distance turns sideways because of interstellar wind pushing against the heliosphere. Detections of solar wind have remained consistently at zero since June 2010, providing conclusive evidence of this event. Voyager 1 was around 116 AU (17.4 billion km; 10.8 billion mi) away from the Sun on this date.
Voyager 1 was ordered to change its orientation to measure the sideways motion of the solar wind at that location in space in March of 2011 (around 33 years and 6 months after launch). A test roll done in February had confirmed its ability to maneuver and reorient itself. The course of Voyager 1 remained unchanged. It rotated 70 degrees counterclockwise with respect to Earth to detect the Solar wind. This was the first time that Voyager 1 had done any complex maneuvers since the Family Portrait photograph was taken in February of 1990. After the first roll showed Voyager 1 having no problem in reorienting itself with Alpha Centauri, Voyager 1's guide star, it resumed sending transmissions back to Earth.
On March 9, 2011, the position of Voyager 1 was reported to be at 17.163 hours right ascension, 12.44° declination, and at an ecliptic latitude of 34.9° on March 9, 2011, placing it in the constellation of Ophiuchus when observed from Earth.
On December 1, 2011, it was announced that Voyager 1 had detected the first Lyman-alpha radiation originating from the Milky Way 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.
On December 5, 2011, NASA announced that Voyager 11 had entered a new region referred to as the "cosmic purgatory". Within this 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[]
In June 2012, NASA announced that the probe was detecting changes in the environment 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 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 121 AU from the Sun, although this was not confirmed until the next year.
As of September 2012, sunlight took around 17 hours to get to Voyager 1, which was at a distance of 121 AU. The apparent magnitude of the Sun from the spacecraft was -16.3 (about 30 times brighter than the full Moon). The spacecraft was travelling at 17.043 km/s (10.590 mi/s) relative to the Sun. At this speed, it'd need around 17,565 years to travel a full light year. For comparison, the closest star to the Sun, Proxima Centauri, is around 4.2 light years distant. At the spacecraft's current speed, it would take around 73,775 years to reach it.
In late 2010, researchers reported that particle data from the spacecraft suggested the probe passed through heliopause. Measurements from the spacecraft revealed a steady rise since May in collisions with high energy particles (above 70 MeV), which are though to be cosmic rays emanting from supernova explosions, 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 John 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 [these two criteria] have 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 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.