Designed to last only five years, the two Voyager spacecraft are still pushing through the vacuum of space, representing humanity beyond the influence of the Sun. Voyager 1 and Voyager 2 were launched in 1977, just 15 days apart, with the aim of exploring the gas giants of our solar system – Jupiter and Saturn. Much to NASA’s surprise, space probes revealed new secrets even about Uranus and Neptune and became the first man-made objects to reach interstellar space.
Interstellar space is the cold region beyond the heliosphere, the bubble of hot plasma at the edge of our solar system. While Voyager 1 made its historic entry into interstellar space in August 2012, its twin Voyager 2 crossed the heliosphere in November 2018.
After being exposed to such harsh conditions for more than four decades, the effects are now being felt, prompting NASA to consider shutting down the spacecraft. Recently, NASA physicist Ralph McNutt told Scientific American that scientists would continue to shut down both probes.
(Illustration of the position of Voyager 1 and Voyager 2; Image: NASA)
What drives Voyagers forward?
Both Voyagers are equipped with a power source called radioisotope thermoelectric generators (RTGs). This propulsion system uses plutonium to convert the heat produced by their natural radioactive decay into electricity to power spacecraft instruments, computers, radio and other systems.
Each of the space probes is equipped with instruments such as television cameras, infrared and ultraviolet sensors, magnetometers, plasma detectors, and sensors for cosmic rays and charged particles. However, after 44 years, Voyager 1 has only four functioning instruments while Voyager 2 has only five.
NASA will change instruments one by one
It’s been a few decades since NASA turned off the camera on the probes to save power for other necessary operations. Then the engineers will turn off the rest of the instruments one by one until the Voyagers lose communication and drift into the void of space.
Currently 23.3 billion kilometers from Earth, it takes 20 light hours and 33 minutes to make contact with Voyager 1 while it takes just under 18 light hours to contact Voyager 2 which is about 19.5 billion kilometres.
A report by Scientific American suggested that scientists have estimated that the plutonium fueling the probes could run out as early as 2025 or possibly the 2030s at most. More recently, NASA revealed that Voyager 1’s Attitude and Articulation Control System (AACS), which helps the spacecraft maintain orientation, suffered a mysterious problem.