Voyager 1
NASA space probe launched in 1977 / From Wikipedia, the free encyclopedia
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Voyager 1 is a space probe launched by NASA on September 5, 1977, as part of the Voyager program to study the outer Solar System and the interstellar space beyond the Sun's heliosphere. It was launched 16 days after its twin Voyager 2. It communicates through the NASA Deep Space Network (DSN) to receive routine commands and to transmit data to Earth. Real-time distance and velocity data is provided by NASA and JPL.[5] At a distance of 162.7 AU (24.3 billion km; 15.1 billion mi) from Earth as of March 2024[update],[5] it is the most distant human-made object from Earth.[6]
Mission type | Outer planetary, heliosphere, and interstellar medium exploration |
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Operator | NASA/Jet Propulsion Laboratory |
COSPAR ID | 1977-084A[1] |
SATCAT no. | 10321[2] |
Website | voyager |
Mission duration |
|
Spacecraft properties | |
Spacecraft type | Mariner Jupiter-Saturn |
Manufacturer | Jet Propulsion Laboratory |
Launch mass | 815 kg (1,797 lb)[3] |
Dry mass | 721.9 kg (1,592 lb)[4] |
Power | 470 watts (at launch) |
Start of mission | |
Launch date | September 5, 1977, 12:56:00 (1977-09-05UTC12:56Z) UTC |
Rocket | Titan IIIE |
Launch site | Cape Canaveral Launch Complex 41 |
End of mission | |
Last contact | TBD |
Flyby of Jupiter | |
Closest approach | March 5, 1979 |
Distance | 349,000 km (217,000 mi) |
Flyby of Saturn | |
Closest approach | November 12, 1980 |
Distance | 124,000 km (77,000 mi) |
Flyby of Titan (atmosphere study) | |
Closest approach | November 12, 1980 |
Distance | 6,490 km (4,030 mi) |
The probe made flybys of Jupiter, Saturn, and Saturn's largest moon, Titan. NASA had a choice of either doing a Pluto or Titan flyby; exploration of the moon took priority because it was known to have a substantial atmosphere.[7][8][9] 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 and like its sister craft Voyager 2, 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. Voyager 1 crossed the heliopause and entered interstellar space on August 25, 2012, making it the first spacecraft to do so.[10][11] Two years later, Voyager 1 began experiencing a third wave of coronal mass ejections from the Sun that continued to at least December 15, 2014, further confirming that the probe is in interstellar space.[12]
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.[13] Voyager 1's extended mission is expected to continue until at least 2025, although its radioisotope thermoelectric generators (RTGs) may supply enough electric power to operate its scientific instruments until 2036.[14]
On December 12, 2023, NASA announced that Voyager 1's flight data system is currently unable to use its telemetry modulation unit, rendering the probe unable to transmit usable scientific data. It is unknown whether the probe will be able to continue its mission.[15]
History
During the 1960s, a Grand Tour to study the outer planets was proposed which prompted NASA to begin work on a mission during the early 1970s.[16] Information gathered by the Pioneer 10 spacecraft helped Voyager's engineers design Voyager to cope more effectively with the intense radiation environment around Jupiter.[17] However, shortly before launch, strips of kitchen-grade aluminum foil were applied to certain cabling to further enhance radiation shielding.[18]
Initially, Voyager 1 was planned as "Mariner 11" of the Mariner program. 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 substantially from previous Mariner missions.[19]
Spacecraft components
Voyager 1 was constructed by the Jet Propulsion Laboratory.[20][21][22] It has 16 hydrazine thrusters, three-axis stabilization gyroscopes, 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.[23] The spacecraft also included 11 scientific instruments to study celestial objects such as planets as it travels through space.[24]
Communication system
The radio communication system of Voyager 1 was designed to be used up to and beyond the limits of the Solar System. The communication system includes a 3.7-meter (12 ft) diameter high gain Cassegrain antenna to send and receive radio waves via the three Deep Space Network stations on the Earth.[25] 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.[26]
When Voyager 1 is unable to communicate directly with the Earth, its digital tape recorder (DTR) can record about 67 megabytes of data for transmission at a later time.[27] As of 2023[update], signals from Voyager 1 take over 22 hours to reach Earth.[5]
Power
Voyager 1 has three radioisotope thermoelectric generators (RTGs) mounted on a boom. Each MHW-RTG contains 24 pressed plutonium-238 oxide spheres.[28] The RTGs generated about 470 W of electric power at the time of launch, with the remainder being dissipated as waste heat.[29] 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 craft's RTGs will continue to support some of its operations until 2025.[24][28]
- Diagram of RTG fuel container, showing the plutonium-238 oxide spheres
- Model of an RTG unit
Computers
Unlike the other onboard instruments, the operation of the cameras for visible light is not autonomous, but rather it is controlled by an imaging parameter table contained in one of the on-board digital computers, the Flight Data Subsystem (FDS). Since the 1990s, most space probes have been equipped with completely autonomous cameras.[30]
The computer command subsystem (CCS) controls the cameras. The CCS contains fixed computer programs, such as command decoding, fault-detection and fault-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.[31]
The Attitude and Articulation Control Subsystem (AACS) controls the spacecraft orientation (its attitude). It keeps the high-gain antenna pointing towards the Earth, controls attitude changes, and points the scan platform. The custom-built AACS systems on both Voyagers are the same.[32][33]
Scientific instruments
Instrument name | Abr. | Description | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Imaging Science System (disabled) |
(ISS) | Utilized a two-camera system (narrow-angle/wide-angle) to provide images of Jupiter, Saturn and other objects along the trajectory. More
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Ultraviolet Spectrometer (disabled) |
(UVS) | Designed to measure atmospheric properties, and to measure radiation. More
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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. More
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Plasma Spectrometer (defective) |
(PLS) | Investigates the microscopic properties of the plasma ions and measures electrons in the energy range from 5 eV to 1 keV. More
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Planetary Radio Astronomy Investigation (disabled) |
(PRA) | Utilizes a sweep-frequency radio receiver to study the radio-emission signals from Jupiter and Saturn. More
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Plasma Wave Subsystem (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
|
For more details on the Voyager space probes' identical instrument packages, see the separate article on the overall Voyager Program.
- Voyager 1 in a space simulator chamber
- Gold-Plated Record is attached to Voyager 1
- Location of the scientific instruments indicated in a diagram
Timeline of travel
Voyager 1's trajectory seen from Earth, diverging from the ecliptic in 1981 at Saturn and now heading towards the constellation Ophiuchus |
Date | Event |
---|---|
1977-09-05 | Spacecraft launched at 12:56:00 UTC. |
1977-12-10 | Entered asteroid belt. |
1977-12-19 | Voyager 1 overtakes Voyager 2. (see diagram) |
1978-09-08 | Exited asteroid belt. |
1979-01-06 | Start Jupiter observation phase. |
1979-03-05 | Encounter with the Jovian system. |
0006:54 | Amalthea flyby at 420,200 km. |
0012:05:26 | Jupiter closest approach at 348,890 km from the center of mass. |
0015:14 | Io flyby at 20,570 km. |
0018:19 | Europa flyby at 733,760 km. |
1979-03-06 | |
0002:15 | Ganymede flyby at 114,710 km. |
0017:08 | Callisto flyby at 126,400 km. |
1979-04-13 | Phase end |
1980-08-22 | Start Saturn observation phase. |
1980-11-12 | Encounter with the Saturnian system. |
0005:41:21 | Titan flyby at 6,490 km. |
0022:16:32 | Tethys flyby at 415,670 km. |
0023:46:30 | Saturn closest approach at 184,300 km from the center of mass. |
1980-11-13 | |
0001:43:12 | Mimas flyby at 88,440 km. |
0001:51:16 | Enceladus flyby at 202,040 km. |
0006:21:53 | Rhea flyby at 73,980 km. |
0016:44:41 | Hyperion flyby at 880,440 km. |
1980-11-14 | Phase end |
1980-11-14 | Begin extended mission. |
Extended mission | |
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1990-02-14 | Final images of the Voyager program acquired by Voyager 1 to create the Solar System Family Portrait. |
1998-02-17 | Voyager 1 overtakes 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. |
2007-02-02 | Terminated plasma subsystem operations. |
2007-04-11 | Terminated plasma subsystem heater. |
2008-01-16 | Terminated planetary radio astronomy experiment operations. |
2012-08-25 | Crossed the heliopause at 121 AU and entered interstellar space, becoming the first human-made object to exit the solar system[36] |
2014-07-07 | Further confirmation probe is in interstellar space. |
2016-04-19 | Terminated Ultraviolet Spectrometer operations. |
2017-11-28 | "Trajectory correction maneuver" (TCM) thrusters are tested in their first use since November 1980.[37] |
2022-07-14 | Voyager 1 has reached a distance of 23.381 billion km (14.528 billion mi; 156.29 AU) from Earth and 23.483 billion km (14.592 billion mi; 156.97 AU) from the Sun.[38] |
2023-11-14 | Issues with onboard computer render it unable to send usable data back to Earth (NASA engineers working to fix it) [39][40] |
Launch and trajectory
The Voyager 1 probe was launched on September 5, 1977, from Launch Complex 41 at the Cape Canaveral Air Force Station, aboard a Titan IIIE launch vehicle. The Voyager 2 probe had been launched two weeks earlier, on August 20, 1977. Despite being launched later, Voyager 1 reached both Jupiter[41] and Saturn sooner, following a shorter trajectory.[42]
Voyager 1's launch almost failed because Titan's LR-91 second stage shut down prematurely, leaving 1,200 pounds (540 kg) of propellant unburned. Recognizing the deficiency, the Centaur stage's on-board computers ordered a burn that was far longer than planned in order to compensate. Centaur extended its own burn and was able to give Voyager 1 the additional velocity it needed. At cutoff, the Centaur was only 3.4 seconds from propellant exhaustion. If the same failure had occurred during Voyager 2's launch a few weeks earlier, the Centaur would have run out of propellant before the probe reached the correct trajectory. Jupiter was in a more favorable position vis-à-vis Earth during the launch of Voyager 1 than during the launch of Voyager 2. [43]
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), well short of Saturn's orbit.[44]
Flyby of Jupiter
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 miles) from the planet's center.[41] 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.[45]
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. 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.[41]
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.
- Voyager 1 time-lapse movie of Jupiter approach (full-size video)
- Jupiter's Great Red Spot, an anti-cyclonic storm larger than Earth, as seen from Voyager 1
- Europa's lineated but un-cratered face, evidence of currently active geology, at a distance of 2.8 million km.
- Ganymede's tectonically disrupted surface, marked with bright impact sites, from 253,000 km.
Flyby of Saturn
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 encountered Saturn 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.[46]
Voyager 1 found that about seven percent of the volume of Saturn's upper atmosphere is helium (compared with 11 percent of Jupiter's atmosphere), while almost all the rest is hydrogen. 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 500 m/s (1,100 mph). The wind blows mostly in an easterly direction.[42]
The Voyagers found aurora-like ultraviolet emissions of hydrogen 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 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.[46]
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 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 6,400 km (4,000 mi), 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.[47]
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, ending its planetary science mission.[48] Had Voyager 1 failed or been unable to observe Titan, Voyager 2's trajectory would have been altered to incorporate the Titan flyby,[47]: 94 precluding any visit to Uranus and Neptune.[7] The trajectory Voyager 1 was launched into would not have allowed it to continue on to Uranus and Neptune,[48]: 155 but could have been altered to avoid a Titan flyby and travel from Saturn to Pluto, arriving in 1986.[9]
- Crescent Saturn from 5.3 million km, four days after closest approach
- Fractured 'wispy terrain' on Dione's trailing hemisphere.
- The icy surface of Rhea is nearly saturated with impact craters.
- Titan's thick haze layer is shown in this enhanced Voyager 1 image.