After 47 years of exploring the cosmos and unraveling countless mysteries, Voyager 2's plasma science experiment has been shut down for the final time. Although this was inevitable due to Voyager 2's need to conserve power, it is a sad end to one of humanity's most successful space experiments.

The probe is currently 12.8 billion miles (20.5 billion kilometers) from Earth. It needs to save as much power as possible to continue sending us at least some data from its current position.

This has forced the team behind Voyager 2's ongoing maintenance to shut down this venerable scientific device. With the shutdown of the PSE, we close a chapter in our research into solar system plasma dynamics, which is key to understanding space weather and planetary magnetospheres.

Join us as we look at this now-defunct, man's most distant scientific experiment.

What is the Plasma Science Experiment?

Developed at MIT, the PSE, also known as the Plasma Spectrometer (PLS), serves as Voyager 2's eyes and ears, measuring the charged particles that influence our solar system and beyond. The device is designed to measure charged particles in the magnetosphere of planets, the solar wind and the interstellar medium – the matter between stars.

As NASA explains, The PLS uses two Faraday cup detectors. One is aligned along the Earth-spacecraft line, the other is at right angles to that line.

In operation, the Earth-directed detector measures the macroscopic properties of the plasma ions, allowing precise determination of their speed, density and pressure. During these measurements, three consecutive energy scans are carried out with a relative energy fluctuation (ΔE/E) of 20%, 7, 2% and 1.8% performed.

These scans covered a range of flows from subsonic to highly supersonic – a sideways Faraday cup measured electrons in the energy range from 5 eV to 1 keV.

Since its launch with the Voyager 2 spacecraft in 1977, the PLS has discovered new phenomena near the outer planets and in the solar wind throughout the solar system. This experiment confirmed the exact time at which Voyager 2 crossed the heliosphere, leaving the Sun's influence and entering interstellar space.

This is the first of a series of scientific instruments that will be phased out in the coming years. On September 26, Voyager 2 PLS sent its final message from nearly 13 billion miles away before receiving the final shutdown order.

The PLS made some amazing discoveries

Throughout their lifetime, the PLS (and Voyager 2) has made incredible contributions to our understanding of the cosmos. The most important of these was the discovery of lo Torus around Jupiter's moon Io.

This is a doughnut-shaped clump of plasma that surrounds the gas giant's moon. The instrument also determined that the plasma donut is composed primarily of sulfur and oxygen.

Since its discovery, scientists have been convinced that the donut probably arose from the Io volcanic series. Other instruments aboard Voyager These were also discovered by probes.

But that's just one of many discoveries the probe and the PLS have made. As John Richardson, senior research scientist at MIT's Kavli Institute for Astrophysics and Space Exploration, told MIT, important discoveries have also been made around Saturn, Neptune and Uranus.

“At Saturn, PLS found a magnetosphere full of water and oxygen that was torn away from Saturn's icy moons. For Uranus and Neptune, the tilt of the magnetic fields caused PLS to see smaller density features, with Uranus' plasma disappearing near the planet,” he said.

Another breakthrough was the discovery of the end of the heliopause in our solar system, confirmed by a noticeable decrease in the plasma emanating from the Sun.

“This signaled the end of the solar wind and the beginning of the local interstellar medium (LISM). Although PLS is not designed to measure the LISM, it has continually measured interstellar plasma flows beyond the heliosphere,” Richardson said WITH.

Voyager 2's energy is expected to last until 2030

Both Voyagers The probes were equipped with three radioisotope thermogenerators (MHW RTGs) with several hundred watts. Each RTG contains 24 pressed plutonium oxide spheres, meaning that each RTG produced approximately 158 watts of electrical power upon launch.

These power supplies have no moving parts and are generally considered a highly reliable option for spacecraft. Voyager's long legacy Probes are proof of this.

With a half-life of around 87.7 years, the probe should have enough energy at least until 2020. Since then, the probe has borrowed the additional power it requires from its reserve battery, which is intended for use in emergencies.

However, this is not sustainable if the probe continues to conduct some scientific experiments in the future. For this reason, the PLS was chosen to be the first of its instruments to be retired.

According to Richardson, power aboard Voyager 2 is decreasing by about 4 watts per year. The probe itself is nuclear powered with plutonium. With the PLS shut down indefinitely, there should be enough power onboard to keep other lower-powered instruments running well into the 2030s.

After that, the RTGs will likely be weakened to the point where the probe's electronics no longer have enough power to run or send signals back to Earth. Furthermore, the probe could survive for billions of years if most or all of its instruments were turned off!

Voyager 2 will outlive humanity

Voyager 2 is expected to reach the closest stars to Earth in about 30,000 years and then continue into space indefinitely.

At least until the Milky Way collides with the Andromeda Galaxy in around 4.5 billion years. Depending on what happens during this event, the probe could be ejected into the intergalactic medium, where it could survive for trillions of years.

At that point, Earth, our sun, the Milky Way, and many other parts of the galaxy will be a distant memory. It is a sobering thought that at the end of days, a tiny spacecraft launched in the 1970s may be the last existing evidence that our species, indeed sentient life at all, ever existed.

But in some ways, Voyager 1 and 2 and future space probes that we are likely to send to the stars will be humanity's lasting legacy. So please don't be too sad about Voyager 2 and its twin.