Voyager 2

Voyager 2
Model of a small-bodied spacecraft with a large, central dish and many arms and antennas extending from it
Model of the Voyager spacecraft design
Mission typePlanetary exploration
OperatorNASA / JPL[1]
COSPAR ID1977-076A[2]
Mission duration41 years, 3 months and 27 days elapsed
Planetary mission: 12 years, 1 month, 12 days
Interstellar mission: 29 years, 2 months and 15 days elapsed (continuing)
Spacecraft properties
ManufacturerJet Propulsion Laboratory
Launch mass825.5 kilograms (1,820 lb)
Power470 watts (at launch)
Start of mission
Launch dateAugust 20, 1977, 14:29:00 (1977-08-20UTC14:29Z) UTC
RocketTitan IIIE
Launch siteCape Canaveral LC-41
Flyby of Jupiter
Closest approachJuly 9, 1979, 22:29:00 UTC
Distance570,000 kilometers (350,000 mi)
Flyby of Saturn
Closest approachAugust 25, 1981, 03:24:05 UTC
Distance101,000 km (63,000 mi)
Flyby of Uranus
Closest approachJanuary 24, 1986, 17:59:47 UTC
Distance81,500 km (50,600 mi)
Flyby of Neptune
Closest approachAugust 25, 1989, 03:56:36 UTC
Distance4,951 km (3,076 mi)

Voyager 2 is a space probe launched by NASA on August 20, 1977, to study the outer planets. Part of the Voyager program, it was launched 16 days before its twin, Voyager 1, on a trajectory that took longer to reach Jupiter and Saturn but enabled further encounters with Uranus and Neptune.[4] It is the only spacecraft to have visited either of the ice giant planets.

Its primary mission ended with the exploration of the Neptunian system on October 2, 1989, after having visited the Uranian system in 1986, the Saturnian system in 1981, and the Jovian system in 1979. Voyager 2 is now in its extended mission to study the outer reaches of the Solar System and has been operating for 41 years, 3 months and 27 days as of 17 December 2018. It remains in contact through the NASA Deep Space Network.[5]

At a distance of 119 AU (1.78×1010 km) (about 16.5 light-hours)[6] from the Sun as of late 2018,[7] moving at a velocity of 15.341 km/s (55,230 km/h)[8] relative to the Sun, Voyager 2 is the fourth of five spacecraft to achieve the escape velocity that will allow them to leave the Solar System. The probe left the heliosphere for interstellar space on November 5, 2018,[9][10] becoming the second artificial object to do so, and has begun to provide the first direct measurements of the density and temperature of the interstellar plasma.[11]



In the early space age, it was realized that a periodic alignment of the outer planets would occur in the late 1970s and enable a single probe to visit Jupiter, Saturn, Uranus, and Neptune by taking advantage of the then-new technique of gravity assists. NASA began work on a Grand Tour, which evolved into a massive project involving two groups of two probes each, with one group visiting Jupiter, Saturn, and Pluto and the other Jupiter, Uranus, and Neptune. The spacecraft would be designed with redundant systems to ensure survival through the entire tour. By 1972 the mission was scaled back and replaced with two Mariner-derived spacecraft, the Mariner Jupiter-Saturn probes. To keep apparent lifetime program costs low, the mission would include only flybys of Jupiter and Saturn, but keep the Grand Tour option open.[4]:263 As the program progressed, the name was changed to Voyager.[12]

The primary mission of Voyager 1 was to explore Jupiter, Saturn, and Saturn's moon, Titan. Voyager 2 was also to explore Jupiter and Saturn, but on a trajectory that would have the option of continuing on to Uranus and Neptune, or being redirected to Titan as a backup for Voyager 1. Upon successful completion of Voyager 1's objectives, Voyager 2 would get a mission extension to send the probe on towards Uranus and Neptune.[4]

Spacecraft design

Constructed by the Jet Propulsion Laboratory (JPL), Voyager 2 included 16 hydrazine thrusters, three-axis stabilization, gyroscopes and celestial referencing instruments (Sun sensor/Canopus Star Tracker) to maintain pointing of the high-gain antenna 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.[13]


Built with the intent for eventual interstellar travel, Voyager 2 included a large, 3.7 m (12 ft) parabolic, high-gain antenna (see diagram) to transceive data via the Deep Space Network on the Earth. Communications are conducted over the S-band (about 13 cm wavelength) and X-band (about 3.6 cm wavelength) providing data rates as high as 115.2 kilobits per second at the distance of Jupiter, and then ever-decreasing as the distance increased, because of the inverse-square law. When the spacecraft is unable to communicate with Earth, the Digital Tape Recorder (DTR) can record about 64 kilobytes of data for transmission at another time.[14]


Voyager 2 was equipped with 3 Multihundred-Watt radioisotope thermoelectric generators (MHW RTG). Each RTG includes 24 pressed plutonium oxide spheres, and provided enough heat to generate approximately 157 W of electrical power at launch. Collectively, the RTGs supplied the spacecraft with 470 watts at launch (halving every 87.7 years), and will allow operations to continue until at least 2020.[13][15][16]

Attitude control and propulsion

Because of the energy required to achieve a Jupiter trajectory boost with an 1,819-pound (825 kg) payload, the spacecraft included a propulsion module made of a 2,476-pound (1,125 kg) solid-rocket motor and eight hydrazine monopropellant rocket engines, four providing pitch and yaw attitude control, and four for roll control. The propulsion module was jettisoned shortly after the successful Jupiter burn.

Sixteen hydrazine MR-103 thrusters on the mission module provide attitude control.[17] Four are used to execute trajectory correction maneuvers; the others in two redundant six-thruster branches, to stabilize the spacecraft on its three axes. Only one branch of attitude control thrusters is needed at any time.[18]

Thrusters are supplied by a single 28-inch (70 cm) diameter spherical titanium tank. It contained 230 pounds (100 kg) of hydrazine at launch, providing enough fuel until 2034.[19]

Scientific instruments

Instrument name Abr. Description
Imaging Science System
(ISS) Utilizes a two-camera system (narrow-angle/wide-angle) to provide imagery of Jupiter, Saturn and other objects along the trajectory. More
Narrow Angle Camera Filters[20]
Name Wavelength Spectrum Sensitivity
Clear 280 nm – 640 nm
Voyager - Filters - Clear.png
UV 280 nm – 370 nm
Voyager - Filters - UV.png
Violet 350 nm – 450 nm
Voyager - Filters - Violet.png
Blue 430 nm – 530 nm
Voyager - Filters - Blue.png
' '
Green 530 nm – 640 nm
Voyager - Filters - Green.png
' '
Orange 590 nm – 640 nm
Voyager - Filters - Orange.png
' '
Wide Angle Camera Filters[21]
Name Wavelength Spectrum Sensitivity
Clear 280 nm – 640 nm
Voyager - Filters - Clear.png
' '
Violet 350 nm – 450 nm
Voyager - Filters - Violet.png
Blue 430 nm – 530 nm
Voyager - Filters - Blue.png
CH4-U 536 nm – 546 nm
Voyager - Filters - CH4U.png
Green 530 nm – 640 nm
Voyager - Filters - Green.png
Na-D 588 nm – 590 nm
Voyager - Filters - NaD.png
Orange 590 nm – 640 nm
Voyager - Filters - Orange.png
CH4-JST 614 nm – 624 nm
Voyager - Filters - CH4JST.png
Radio Science System
(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
(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 More
Ultraviolet Spectrometer
(UVS) Designed to measure atmospheric properties, and to measure radiation. More
Triaxial Fluxgate Magnetometer
(MAG) Designed to investigate the magnetic fields of Jupiter and Saturn, the solar-wind interaction with the magnetospheres of these planets, and the interplanetary magnetic field out to the solar wind boundary with the interstellar magnetic field and beyond, if crossed. More
Plasma Spectrometer
(PLS) Investigates the macroscopic properties of the plasma ions and measures electrons in the energy range from 5 eV to 1 keV. More
Low Energy Charged Particle Instrument
(LECP) Measures the differential in energy fluxes and angular distributions of ions, electrons and the differential in energy ion composition. More
Cosmic Ray System
(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
(PRA) Utilizes a sweep-frequency radio receiver to study the radio-emission signals from Jupiter and Saturn. More
Photopolarimeter System
(PPS) Utilized a telescope with a More
Plasma Wave System
(partially disabled)
(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.

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