Oct 04, 2024 11:55:00

NASA shuts down Voyager 2's plasma science instruments after 47 years and 24 billion km of travel

By

Kevin Gill

Voyager 2 , an unmanned space probe launched by NASA on August 20, 1977, is equipped with 10 scientific instruments. However, after 47 years of operation, some of the scientific instruments have stopped working due to performance degradation and power saving, and NASA reported that the plasma science instrument also stopped working at the end of September 2024.

NASA Turns Off Science Instrument to Save Voyager 2 Power | NASA Jet Propulsion Laboratory (JPL)
https://www.jpl.nasa.gov/news/nasa-turns-off-science-instrument-to-save-voyager-2-power/

An interstellar instrument takes a final bow | MIT News | Massachusetts Institute of Technology
https://news.mit.edu/2024/interstellar-instrument-takes-final-bow-1002

Voyager 2, launched in 1977, has traveled 24 billion km in its 47-year space journey, and is currently flying in interstellar space, more than 12.8 billion miles (20.5 billion km) from Earth at the time of writing. The spacecraft is powered by plutonium and consumes about 4 watts of electricity each year.

Voyager 2 is equipped with 10 scientific instruments, including the Spacecraft Subsystem, Low Energy Charged Particle Detector, Magnetometer, Plasma Wave Subsystem, Plasma Science Instrument, Imaging Science Subsystem, Infrared Interferometer Spectrometer and Radiometer, Optical Polarimeter Subsystem, Planetary Radio Astronomy, and Ultraviolet Spectrometer, but its power supply has been gradually reduced after years of operation.

Therefore, NASA engineers have taken measures to keep the scientific instruments on Voyager 2 operational for as long as possible. Specifically, the wide-angle and narrow-angle cameras of the imaging science subsystem were shut down on October 10 and December 5, 1989 to save power, the optical polarimeter subsystem was shut down on April 3, 1991 due to poor performance, the ultraviolet spectrometer was shut down on November 12, 1998 to save power, the infrared interferometer spectrometer and radiometer were shut down on February 1, 2007 to save power, and the planetary radio astronomy was shut down on February 21, 2008 to save power. And on September 26, 2024, the plasma science instruments were also shut down to save power. As a result, there are four scientific instruments on Voyager 2 in operation at the time of writing.

The shutdown of the plasma science instruments will ensure that Voyager 2 has enough power to keep at least one science instrument operational into the 2030s.

The photo below was taken in March 1977 of Voyager 2 before its launch. The photo was taken at the Jet Propulsion Laboratory, which is involved in research and development of NASA's unmanned spacecraft.

The now-defunct Voyager 2 plasma science instrument measures the amount and flow of plasma, which consists of electrically charged particles. Voyager 1 also had a plasma science instrument that stopped working in 1980 and was turned off in 2007 to conserve energy. Voyager 2's plasma science instrument is actually a different instrument called the 'plasma wave subsystem,' which can estimate the plasma density when reduced plasma emissions from the Sun impact the interstellar medium, generating plasma waves.

The Voyager 2 Plasma Science Instrument played a crucial role in confirming that the spacecraft left the heliosphere in 2018. The Plasma Science Instrument consists of four cups, three of which are facing the Sun and are used to observe the solar wind within the heliosphere, while the remaining cups are positioned at right angles to the other three and observe plasma in the planet's magnetosphere, heliosphere, and interstellar space.

However, when Voyager 2 left the heliosphere in 2018 , the plasma flow to the three cups facing the Sun was dramatically reduced, and the fourth cup was only able to collect data once every three months. These factors led to the decision to shut down the plasma science instruments.