Once Voyager’s planetary journey ended, it was possible to begin a new mission phase. After the final planetary stop, both probes were able to reach escape velocity into the solar system and break free from the Sun’s gravity. They have been interstellar since 2012 for Voyager 1 and 2018 for Voyager 2. We know this because the spacecraft’s sensors showed that after these dates, the number and energy of charged particles from the Sun became lower than those detected from the galactic environment. . This was a great opportunity to study the boundaries of the solar system and the environment beyond it.
The secret to a long life
Reaching such distances is not possible without a suitable energy source. Many spacecraft use solar panels, but they become useless when they get too far from the sun (the furthest spacecraft to use solar panels is the Juno spacecraft orbiting Jupiter). Voyager’s secret lies in its atomic heart. Both ships are equipped with three radioisotope thermoelectric generators (RTGs). This is a small generator that can generate electricity directly on board. Each RTG contains 24 plutonium-238 oxide spheres with a total mass of 4.5 kilograms.
Plutonium-238 is an unstable isotope that undergoes radioactive decay. The plutonium atoms in the RTG emit alpha particles consisting of two protons and two neutrons that collide with the RTG canister and heat it. The heat is then converted into electricity.
However, over time, the onboard plutonium is depleted and the RTG produces less and less energy. So Voyager is slowly dying. Nuclear batteries have a lifespan of up to 60 years.
To conserve the spacecraft’s remaining energy, the mission team is gradually shutting down various instruments on the spacecraft that are still operational. For example, in October, Voyager 2’s plasma science instrument, which measures charged atoms passing through the spacecraft, was turned off. The same equipment on Voyager 1 was powered down in 2007 due to a malfunction. These instruments are used to study charged particles in the Sun’s magnetic field, and it was these very detectors that determined in 2018 that Voyager 2 had left the heliosphere and entered interstellar space.
Four active instruments remain, including magnetometers and other instruments used to study the galactic environment, such as cosmic rays and interstellar magnetic fields. But these are in later years. Within the next 10 years, it’s hard to say exactly when, but both spacecraft’s batteries will be permanently depleted.
This story was originally WIREDItaly Translated from Italian.
(Tag translation) Science
