How do the spacecraft work, how do we know where they are, and what comes next? These answers use NASA/JPL sources and explain the tracker’s readings.
Sources checked .
Where the Voyagers started, where they are now and why their journeys differ.
Both spacecraft are beyond the heliopause, in interstellar space. Voyager 1 crossed this boundary in 2012 and Voyager 2 in 2018. That does not mean they have also passed the distant Oort Cloud or escaped the Sun’s gravitational influence.
The homepage tracker shows their current distances from Earth and the Sun. We do not repeat a fixed distance here because it changes with time and with Earth’s motion.
Voyager 2 launched on 20 August 1977, followed by Voyager 1 on 5 September. Both were originally intended to study Jupiter, Saturn, their rings and their large moons in detail.
Voyager 2’s trajectory preserved the possibility of continuing to Uranus and Neptune. Extensions to the mission subsequently made use of that opportunity.
Voyager 1 flew past Jupiter and Saturn. Voyager 2 visited Jupiter, Saturn, Uranus and Neptune. These were close flybys: the spacecraft did not remain in orbit around those planets.
Both missions also observed moons, rings and the environments around the planets. Their different routes therefore offered different scientific opportunities.
Launch order does not determine distance order. Voyager 1 had a faster, shorter trajectory to Jupiter and Saturn and reached both before Voyager 2.
Its encounter with Saturn and Titan sent it out of the plane of the planets. Voyager 2 continued towards Uranus and Neptune. Their present separation follows from these trajectories and gravity assists.
It studies the environment at the edge of the heliosphere and beyond: magnetic fields, particles and plasma waves. Measurements in two different directions help explain how the region shaped by the solar wind meets the surrounding interstellar medium.
Not all original instruments remain in operation. Today’s working instruments must be distinguished from the original experiments, and any status list should state when it was checked.
Sources: NASA/JPL — Voyager 2 enters interstellar space ↗ · NASA/JPL — Spacecraft design and instruments ↗.
No. After Saturn, Voyager 1 headed above the plane of the planets; after Neptune, Voyager 2 continued below it. Above and below refer to the ecliptic, not an absolute up and down in space.
Distance in kilometres alone does not describe direction. Our map uses JPL position vectors to show it, while planetary orbits and the boundaries of regions remain schematic.
How we track the spacecraft, communicate with them and interpret their readings.
Through radio tracking with the Deep Space Network. Signal travel time provides distance information; changes in frequency, known as Doppler shift, reveal information about the spacecraft’s motion.
Observations are combined with a trajectory model. This is neither a photograph of the spacecraft from Earth nor a position supplied by an ordinary GPS receiver. Our website uses the resulting JPL Horizons ephemerides.
Sources: NASA/JPL — Locating distant spacecraft ↗ · NASA/JPL — Deep Space Network ↗.
No. The browser loads stored NASA/JPL Horizons trajectory data and interpolates between their time points to calculate the position for the current time. The readings can change continuously without a new radio connection to the spacecraft.
The date of the data and the time of the calculation are different. A smoothly changing counter also does not mean the website automatically knows the spacecraft’s immediate technical condition.
The spacecraft transmits information by radio through its main antenna. Large antennas in the Deep Space Network receive it on Earth; that network also supports other interplanetary missions.
Commands travel the other way, from Earth to the spacecraft. Its main antenna must point appropriately, so maintaining its orientation is an important part of operations.
Sources: NASA/JPL — Deep Space Network ↗ · NASA/JPL — Spacecraft design and instruments ↗.
Radio signals travel at the speed of light in a vacuum. Even at that speed, crossing interplanetary distances is not instantaneous. A command must first reach the spacecraft, and the response then makes the return journey.
The tracker shows one-way and round-trip travel times. The latter excludes command-processing delays and waiting for scheduled communications. The calculation also accounts for Earth’s and the spacecraft’s motion during transmission.
Sources: NASA/JPL — Speed of light and astronomical units ↗.
Each spacecraft has three radioisotope thermoelectric generators. They turn heat from the radioactive decay of plutonium-238 into electricity. Their power therefore does not come from solar panels.
Available electrical power gradually declines. The team must allocate it among science instruments, communications, heaters and other systems. The remaining plutonium percentage in our tracker is not the remaining electrical power percentage.
Sources: NASA/JPL — Spacecraft design and instruments ↗ · NASA/JPL — Power conservation, April 2026 ↗.
The cameras were switched off to free power and memory for other scientific instruments. Their control software was also removed. Voyager 1’s last images date from 1990.
Our gallery contains archival images or later processing of those data. An illustration of the spacecraft is not a live camera view. Continuing the science mission does not mean continuing photography.
Earth orbits the Sun. During part of the year it moves towards a spacecraft in a way that reduces their separation, even while the spacecraft continues outwards from the Sun.
A negative distance change is therefore not, by itself, an error or a sign that the spacecraft has turned around. We distinguish speed relative to the Sun from the change in distance relative to Earth.
Some problems can be worked around by changing software or operating procedures, but this is not physically replacing a damaged component. In April 2024, the team restored readable engineering data from Voyager 1 by moving affected software code to other memory locations.
Interventions require careful diagnosis and must allow for the signal’s long travel time. That particular success does not mean every fault can be repaired from Earth.
Sources: NASA/JPL — Engineering data restored, April 2024 ↗.
What we can say about the future, and where uncertainty remains.
They have crossed the heliopause, the heliosphere’s boundary, and entered the interstellar medium. But if the Solar System is defined by objects gravitationally bound to the Sun, it also includes the distant Oort Cloud, which still lies ahead of the spacecraft.
Leaving the heliosphere must therefore not be confused with passing beyond the entire Solar System or reaching a place where the Sun’s gravity stops acting.
No. Insufficient electricity limits instruments and communications, but does not itself stop the spacecraft’s motion. NASA describes their continuing flight even after contact is lost.
The end of science measurements, the end of radio communications and the continued journey of the physical spacecraft are different things, not a single event.
Not as a guaranteed deadline. Operations depend on available power, temperatures, the condition of components and which power-saving changes succeed. NASA therefore publishes evolving estimates and specific operational decisions.
We do not turn plutonium decay into a fixed date for the last signal. An old forecast in an archived article is not automatically a valid current plan.
Each carries a Golden Record: a physical recording of images, sounds, music and greetings from Earth. Its cover includes playback instructions and information about the message’s origin.
The possibility of someone finding the record is not a prediction that this will happen. It is a message carried for that eventuality, not planned communication with a particular civilisation.
Sources: NASA/JPL — The Golden Record ↗.