Voyager 1 vs Voyager 2: Distance & Instruments

Voyager 1 is farther from Earth than Voyager 2, but both carry nearly identical scientific instruments, with a few key differences in power and camera systems. As of early 2025, Voyager 1 is about 24.9 billion kilometers (15.5 billion miles) from Earth, while Voyager 2 is about 20.9 billion kilometers (13.0 billion miles) away. Both spacecraft were launched in 1977 to study the outer planets and have since become the only human-made objects to enter interstellar space.

Launch and Mission Paths

NASA launched Voyager 2 on August 20, 1977, and Voyager 1 on September 5, 1977. Although Voyager 2 lifted off first, Voyager 1 took a faster, more direct trajectory that allowed it to reach Jupiter and Saturn sooner. Voyager 2 took advantage of a rare planetary alignment to visit Jupiter, Saturn, Uranus, and Neptune, making it the only spacecraft to fly by all four gas giants. Voyager 1’s primary mission was to study Jupiter and Saturn, but it also captured the famous “Pale Blue Dot” photograph of Earth from a distance of about 6 billion kilometers.

The two spacecraft used gravity assists to gain speed: Voyager 1 swung past Jupiter in March 1979 and Saturn in November 1980. Voyager 2 flew past Jupiter in July 1979, Saturn in August 1981, Uranus in January 1986, and Neptune in August 1989. After completing their planetary encounters, both continued on trajectories that carried them out of the solar system.

Distance from Earth and the Sun

Distance is the most direct comparison between the two spacecraft, but it changes constantly as they travel. The table below shows approximate distances as of early 2025:

• Voyager 1: about 24.9 billion km (15.5 billion miles) from Earth, and about 24.3 billion km (15.1 billion miles) from the Sun.
• Voyager 2: about 20.9 billion km (13.0 billion miles) from Earth, and about 20.5 billion km (12.7 billion miles) from the Sun.

Voyager 1 is farther because it followed a shorter, faster path to Jupiter and Saturn, and it also received a stronger gravity assist from Saturn. Voyager 2’s slower trajectory, while allowing extra planetary flybys, put it on a different course that is now slightly behind Voyager 1 in distance.

Both spacecraft are moving at roughly 15–17 kilometers per second relative to the Sun. Voyager 1 is currently moving away at about 17 km/s, while Voyager 2 is moving at about 15 km/s. These speeds mean the distance gap between them will continue to grow over time.

Scientific Instruments on Board

The two Voyager spacecraft carry nearly identical suites of scientific instruments, designed to measure magnetic fields, plasma, cosmic rays, and other particles. Here is a breakdown of the main instruments:

• Magnetometer (MAG): Measures magnetic fields and helps map the heliosphere.
• Plasma Science (PLS): Measures solar wind plasma (electrons and ions) in the outer heliosphere.
• Low-Energy Charged Particles (LECP): Detects ions and electrons in the range of tens of keV to hundreds of MeV.
• Cosmic Ray System (CRS): Measures cosmic rays and energetic particles from the Sun and beyond.
• Plasma Wave System (PWS): Measures plasma waves and electron density.
• Ultraviolet Spectrometer (UVS): Measures ultraviolet light from stars and planetary atmospheres.
• Imaging Science System (ISS): Two cameras (narrow-angle and wide-angle) for visible-light images.
• Photopolarimeter System (PPS): Measures polarization of light (used for planetary atmospheres).
• Infrared Interferometer Spectrometer (IRIS): Measures infrared radiation to study temperature and composition.

There are a few notable differences between the two spacecraft. Voyager 1’s photopolarimeter failed in 1980 after the Saturn encounter, so it no longer returns polarization data. Voyager 2’s ultraviolet spectrometer failed in 1998, and its plasma instrument has been degraded since 2007 but still returns limited data. Both spacecraft have had some instruments turned off over time to conserve power.

Power and Communication Systems

Both Voyagers are powered by radioisotope thermoelectric generators (RTGs) that convert heat from plutonium-238 decay into electricity. Each RTG initially provided about 470 watts at launch, but the power output decreases by about 4 watts per year as the plutonium decays and thermocouples degrade. As of 2025, each spacecraft has roughly 220–230 watts available, down from the original ~470 watts.

To keep the most important instruments running, NASA has had to shut down some heaters and non-essential systems. In 2023, mission engineers turned off some instruments on both spacecraft to extend their lifetimes. The spacecraft communicate with Earth using the Deep Space Network (DSN), but the signals are extremely weak by now—about 20 billion times weaker than the signal from a typical FM radio station.

Each Voyager carries a 3.7-meter (12-foot) dish antenna that transmits at 23 watts (Voyager 1) or 21.3 watts (Voyager 2). The signal takes about 23 hours to reach Earth from Voyager 1 and about 19 hours from Voyager 2. Because the spacecraft are so far away, the data rate is only about 160 bits per second—far slower than a dial-up modem.

Interstellar Space and the Heliopause

Both Voyagers have crossed the heliopause, the boundary where the Sun’s solar wind meets the interstellar medium. Voyager 1 crossed it in August 2012 at a distance of about 121.6 AU (astronomical units) from the Sun. Voyager 2 crossed it in November 2018 at about 119 AU. One AU is the average Earth-Sun distance, about 150 million kilometers (93 million miles).

After crossing the heliopause, both spacecraft entered interstellar space, where they measure the density and temperature of the plasma outside the solar system. Voyager 2’s plasma instrument (PLS) was still working at the time of its crossing, providing the first direct measurements of interstellar plasma density. Voyager 1’s PLS had failed in 1980, so it relied on the plasma wave system to infer plasma density from oscillations.

The two spacecraft are now exploring the interstellar medium from two different directions. Voyager 1 is heading roughly toward the constellation Ophiuchus, while Voyager 2 is heading toward the constellation Pavo. Their different paths give scientists a three-dimensional view of the heliosphere’s interaction with the galaxy.

Golden Records and Other Cargo

Both Voyagers carry a Golden Record—a 12-inch gold-plated copper disk containing sounds and images selected to represent life on Earth. The records include greetings in 55 languages, music from different cultures, natural sounds like wind and surf, and 115 images. They also contain instructions on how to play the record, using a stylus and a diagram of the spacecraft’s position relative to pulsars.

Each spacecraft also carries a small, gold-plated aluminum plaque with a diagram of the solar system and the spacecraft’s trajectory. The Golden Records are designed to last for billions of years in space, serving as a time capsule of humanity’s existence.

Current Status and Future Outlook

As of 2025, both Voyagers are still operational, but they are aging. NASA has had to manage power carefully, turning off some instruments and heaters to keep the spacecraft alive. In 2024, Voyager 1 experienced a communications glitch that was resolved by switching to a different radio transmitter. Voyager 2 has had similar issues, including a brief loss of contact in 2023 when a command accidentally pointed its antenna away from Earth.

Mission engineers estimate that the Voyagers have enough power to keep at least one instrument running until about 2030, and possibly longer if they continue to shut down systems. After that, the spacecraft will fall silent but will continue to drift through the galaxy for billions of years.

The Voyager missions have provided the most detailed data we have on the outer planets and the edge of the solar system. Their longevity is a testament to the robust design of 1970s-era spacecraft and the careful management of a mission that has far outlived its original five-year plan.

Frequently Asked Questions

Which Voyager is farther from Earth?

Voyager 1 is farther from Earth than Voyager 2. As of early 2025, Voyager 1 is about 24.9 billion km away, while Voyager 2 is about 20.9 billion km away. The gap exists because Voyager 1 took a faster trajectory and received a stronger gravity assist from Saturn.

Did Voyager 1 or Voyager 2 visit more planets?

Voyager 2 visited more planets: Jupiter, Saturn, Uranus, and Neptune. Voyager 1 only visited Jupiter and Saturn. Voyager 2 remains the only spacecraft to have flown by Uranus and Neptune.

Are the instruments on both Voyagers identical?

Yes, the instrument suites are nearly identical, but some individual instruments have failed or degraded differently. For example, Voyager 1’s photopolarimeter failed early, while Voyager 2’s ultraviolet spectrometer failed later. Both spacecraft still have working magnetometers, cosmic ray detectors, and plasma wave systems.

How long does it take for a signal to reach Earth from each Voyager?

It takes about 23 hours for a signal from Voyager 1 to reach Earth, and about 19 hours for Voyager 2. This time increases as the spacecraft move farther away.

When will the Voyagers stop working?

NASA estimates that the Voyagers will have enough power to operate at least one instrument until about 2030. After that, they will become inert and continue to drift through the galaxy. The exact end date depends on how long the remaining power can be stretched.

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