Voyager 2 is a space probe launched by NASA on August 20, 1977, as a part of the Voyager program. It was launched on a trajectory towards the gas giants (Jupiter and Saturn) and enabled further encounters with the ice giants (Uranus and Neptune). The only spacecraft to have visited either of the ice giant planets, it was the third of five spacecraft to achieve Solar escape velocity, which allowed it to leave the Solar System. Launched 16 days before its twin Voyager 1, the primary mission of the spacecraft was to study the outer planets and its extended mission is to study interstellar space beyond the Sun's heliosphere.
Voyager 2 successfully fulfilled its primary mission of visiting the Jovian system in 1979, the Saturnian system in 1981, Uranian system in 1986, and the Neptunian system in 1989. The spacecraft is now in its extended mission of studying the interstellar medium. It is at a distance of from Earth .
The probe entered the interstellar medium on November 5, 2018, at a distance of from the Sun and moving at relative to the Sun. Voyager 2 has left the Sun's heliosphere and is traveling through the interstellar medium, though still inside the Solar System, joining Voyager 1, which reached the interstellar medium in 2012. Voyager 2 has begun to provide the first direct measurements of the density and temperature of the interstellar plasma.
Voyager 2 is in contact with Earth through the NASA Deep Space Network.NASA Voyager – The Interstellar Mission Mission Overview. . Communications are the responsibility of Australia's DSS 43 communication antenna, part of the Canberra communication complex; the craft's southern trajectory puts it out of range of the network's Goldstone and Madrid complexes.
History
Background
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 throughout the entire tour. By 1972 the mission was scaled back and replaced with two Mariner program-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. As the program progressed, the name was changed to Voyager.Planetary Voyage NASA Jet Propulsion Laboratory – California Institute of Technology. March 23, 2004. Retrieved April 8, 2007.
The primary mission of Voyager 1 was to explore Jupiter, Saturn, and Saturn's largest 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 1s objectives, Voyager 2 would get a mission extension to send the probe on towards Uranus and Neptune. Titan was selected due to the interest developed after the images taken by Pioneer 11 in 1979, which had indicated the atmosphere of the moon was substantial and complex. Hence the trajectory was designed for optimum Titan flyby.
Spacecraft design Constructed by the California-based Jet Propulsion Laboratory (JPL), Voyager 2, whose bus is shaped like a decagonal prism, included 16 hydrazine thrusters, three-axis stabilization, gyroscopes and celestial referencing instruments (a Sun sensor, and a 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.
Communications Built with the intent for eventual interstellar travel, Voyager 2 included a large, parabolic, high-gain antenna (see diagram) to transceive data via the Deep Space Network on Earth. Communications are conducted over the S-band (about 13 cm wavelength) and X-band (about 3.6 cm wavelength), providing data rates of up to 115.2 kilobits per second at the distance of Jupiter; this rates decreases according to inverse-square law as it travels farther away from Earth. When the spacecraft is out of line-of-sight and unable to communicate, a digital tape recorder (DTR) can record about 64 megabytes of data for transmission at a later time.
Power
Voyager 2 is equipped with three multihundred-watt radioisotope thermoelectric generators (MHW RTGs). Each RTG includes 24 pressed plutonium oxide spheres. At launch, each RTG provided enough heat to generate approximately 157 W of electrical power. Collectively, the RTGs supplied the spacecraft with 470 watts at launch (halving every 87.7 years). They were predicted to allow operations to continue until at least 2020, and continued to provide power to five scientific instruments through the early part of 2023. In April 2023 JPL began using a reservoir of backup power intended for an onboard safety mechanism. As a result, all five instruments had been expected to continue operation through 2026.
However, in October 2024, NASA announced that the plasma science instrument had been turned off on September 26, 2024, preserving power for the remaining four instruments. In March 2025, NASA announced its plans to shut off Voyager 2’s low-energy charged particle (LECP) instrument also on March 24, 2025 to manage the gradually diminishing power supply while continuing to keep three science instruments operational.
On August 4, 2026, engineers at NASA's Jet Propulsion Laboratory announced the successful completion of a delicate "simultaneous" swap of multiple power-consuming devices for lower-power alternatives available aboard Voyager 2 that freed up power to keep all three of the spacecraft's remaining science instruments usable for at least one additional year. This procedure which was internally nicknamed "Big Bang" required switching off a set of powered devices aboard Voyager 2 and substituting them with lower-power alternatives, all the while ensuring the spacecraft remains warm enough to continue operating in the near absolute zero temperatures of interstellar space. Without this activity, the mission would have had to turn off another instrument on Voyager 2 before the end of 2026.
Attitude control and propulsion Because of the energy required to achieve a Jupiter trajectory boost with an payload, the spacecraft included a propulsion module made of a 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 Aerojet MR-103 thrusters on the mission module provide attitude control. 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.
Thrusters are supplied by a single diameter spherical titanium tank. It contained of hydrazine at launch, providing enough fuel to last until 2034.
Scientific instruments
Instrument name Abr. Description (ISS) A two-camera system (narrow-angle/wide-angle) provides imagery of the outer planets and other objects along the trajectory. Filters Narrow Angle Camera Filters Name Wavelength Spectrum Sensitivity Clear 280–640 nm;460 nm center UV 280–370 nm;325 nm center Violet 350–450 nm;400 nm center Blue 430–530 nm;480 nm center ' ' ' Green 530–640 nm;585 nm center ' ' ' Orange 590–640 nm;615 nm center ' ' ' Wide Angle Camera Filters Name Wavelength Spectrum Sensitivity Clear 280–640 nm;460 nm center ' ' ' Violet 350–450 nm;400 nm center Blue 430–530 nm;480 nm center CH4-U 536–546 nm;514 nm center Green 530–640 nm;585 nm center Na-D 588–590 nm;589 nm center Orange 590–640 nm;615 nm center CH4-JST 614–624 nm;619 nm center (RSS) Used 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. (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. (UVS) Designed to measure atmospheric properties, and to measure radiation. (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. (PLS) Investigates the macroscopic properties of the plasma ions and measures electrons in the energy range from 5 eV to 1 keV. (LECP) Measures the differential in energy fluxes and angular distributions of ions, electrons and the differential in energy ion composition. (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. (PRA) Uses a sweep-frequency radio receiver to study the radio-emission signals from Jupiter and Saturn. (PPS) Used 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. (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.
Mission profile
Timeline of travel Date Event 1977-08-20 Spacecraft launched at 14:29:00 UTC. 1977-12-10 Entered asteroid belt. 1977-12-19 Voyager 1 overtakes Voyager 2 (see diagram). 1978-06 Primary radio receiver fails. The remainder of the mission flown using backup. 1978-10-21 Exited asteroid belt. 1979-04-25 Start Jupiter observation phase. Time Event 1979-07-08 Encounter with Jovian system. 12:21 Callisto flyby at 214,930 km. 1979-07-09 07:14 Ganymede flyby at 62,130 km. 17:53 Europa flyby at 205,720 km. 20:01 Amalthea flyby at 558,370 km. 22:29 Jupiter closest approach at 721,670 km from the center of mass. 23:17 Io flyby at 1,129,900 km. 1979-08-05 Phase Stop 1981-06-05 Start Saturn observation phase. Time Event 1981-08-22 Encounter with Saturnian system. 01:26:57 Iapetus flyby at 908,680 km. 1981-08-25 01:25:26 Hyperion flyby at 431,370 km. 09:37:46 Titan flyby at 666,190 km. 22:57:33 Helene flyby at 314,090 km. 1981-08-26 01:04:32 Dione flyby at 502,310 km. 02:22:17 Calypso flyby at 151,590 km. 02:24:26 Mimas flyby at 309,930 km. 03:19:18 Pandora flyby at 107,000 km. 03:24:05 Saturn closest approach at 161,000 km from the center of mass. 03:33:02 Atlas 287,000 km. 03:45:16 Enceladus flyby at 87,010 km. 03:50:04 Janus at 223,000 km. 04:05:56 Epimetheus at 147,000 km. 06:02:47 Telesto at 270,000 km. 06:12:30 Tethys flyby at 93,010 km. 06:28:48 Rhea flyby at 645,260 km. 1981-09-04 01:22:34 Phoebe flyby at 2,075,640 km. 1981-09-25 Phase Stop 1985-11-04 Start Uranus observation phase.