The two “twin” spacecraft Voyager 1 and Voyager 2 continue to explore the universe 45 years after their launch from Earth, now located 22 light-hours away from our planet.
Voyager 2 was launched from the Kennedy Space Center in Florida on August 20, 1977, followed by its twin, Voyager 1, about two weeks later. While Voyager 1 focused on Jupiter and Saturn, Voyager 2 visited both of these planets as well as Uranus and Neptune. Voyager 2 is also the only human-made instrument to explore these two planets in the 20th century.
In November 2018, NASA announced that Voyager 2 had crossed the outer edge of the Solar System, while Voyager 1 crossed this boundary back in 2012.
Both Voyager 1 and 2 are currently exploring the “interstellar space”, the vast expanse between different star systems. Using the NASA Eyes on the Solar System application, viewers can track the spacecraft’s trajectories, updated every five minutes. Distance and speed are updated in real-time.
Operational Instruments After 45 Years
Voyager 1 and Voyager 2 are now approximately 23 billion kilometers from Earth. Since Voyager 2 was originally a backup for Voyager 1, both spacecraft share identical designs and contain 10 scientific instruments. Currently, each spacecraft has four of its instruments still operational.
This test model was displayed in the space simulation chamber at NASA’s laboratory in 1976. This is a replica of the two Voyager spacecraft launched in 1977. (Image: NASA/JPL-Caltech).
The first is the Cosmic Ray Subsystem (CRS), an instrument designed to detect high-energy particles, typically found in high radiation fields surrounding planets like Jupiter. These particles pass through the CRS, leaving a trace that indicates their presence.
This instrument provides information on energy levels, origins, acceleration processes, and the dynamics of cosmic rays in our galaxy, while also contributing to our understanding of the nuclear synthesis of elements in cosmic ray sources. CRS has enabled the Voyagers to measure particle charge in the magnetospheres of Jupiter, Saturn, Uranus, and Neptune.
The Low-Energy Charged Particle (LECP) instrument can be envisioned as a piece of wood, with the particles it records resembling bullets. The faster the bullet travels, the deeper it penetrates the wood, and LECP reveals the speed of these particles. The number of “bullet holes” over time indicates how many particles come from the solar wind and from the planets, while the direction of the bullets engraved in the wood shows the particles’ movement direction.
Simulation of Voyager 2 through NASA’s real-time tracking application. (Image: NASA).
The Magnetometer (MAG) has the primary task of measuring changes in the Sun’s magnetic field over distance and time, to determine whether each planet has a magnetic field and how their moons interact with these fields.
Lastly, the communication instruments with Earth, the Plasma Wave System (PWS) and the Radio Science System (PRA), feature a V-shaped antenna. PWS covers a frequency range from 10 Hz to 56 kHz, while the PRA receiver has two frequency bands, from 20.4 kHz to 1300 kHz and from 2.3 MHz to 40.5 MHz.
What Have the Two Voyagers Achieved?
NASA initially expected the two Voyager missions to last five years; now they have been operational for 45 years and continue to collect valuable scientific data from the farthest reaches of space humans have ever reached.
The two spacecraft have shown how interstellar space interacts with the solar wind, a stream of charged particles released by the Sun. Voyager has also provided data on the heliosphere, a protective bubble surrounding the Solar System.
The heliosphere is created by the solar wind and shaped by conditions in interstellar space. The boundary of the Solar System—where the solar wind ends and interstellar space begins—is referred to as the heliopause.
Each NASA Voyager spacecraft is equipped with three radioisotope thermoelectric generators (RTGs) as shown in the image. RTGs provide power to the spacecraft by converting heat released from the decay of plutonium-238 into electrical energy. (Image: NASA/JPL-Caltech).
NASA states that the Voyager spacecraft have provided researchers with new information about interstellar space. For example, they found that cosmic rays outside the heliosphere are about three times stronger than those deep inside the heliosphere.
Scientists have combined observations from Voyager with data from newer missions “to gain a more complete picture of the Sun and how the heliosphere interacts with interstellar space,” NASA reported.
Nicola Fox, the director of heliophysics at NASA headquarters in Washington D.C., stated that Voyager has provided information about the Sun’s influence throughout our solar system.
Each Voyager spacecraft is powered by a thermoelectric system containing plutonium. As plutonium decays, the heat released diminishes, and the spacecraft lose power. To compensate for this phenomenon, NASA reported that it has turned off all non-essential systems, including heaters that protect instruments from the extreme cold of space.
However, the space agency reports that even though the heaters have been turned off since 2019, some instruments remain operational. NASA scientists are still unclear why Voyager continues to function at temperatures significantly lower than its original design tolerances.
“After 45 years of continuous exploration of space, Voyager 1 and 2 continue to provide humanity with observations of uncharted territories,” said Linda Spilker, a scientist at NASA’s Jet Propulsion Laboratory.
