Made to last just five years, the two Voyager spacecraft are still pushing through the vacuum of space, representing humanity beyond the influence of the Sun. Both Voyager 1 and Voyager 2 were launched in 1977, just 15 days apart, with an aim to explore the gas giants in our solar system - Jupiter and Saturn. Much to NASA's surprise, the space probes went on to reveal new secrets of even Uranus and Neptune and became the first man-made objects to reach interstellar space.
The interstellar space is the cold region beyond the heliosphere, the hot plasma bubble at our solar system's edge. While Voyager 1 made its historic entry into interstellar space in August 2012, its twin Voyager 2 crossed the heliosphere in November 2018.
Having been exposed to such harsh conditions for over four decades, the effects are now being felt, which is prompting NASA to consider shutting down the spacecraft. Recently, NASA physicist Ralph McNutt told Scientific American that scientists will continue powering down the two probes.
(Illustration of Voyager 1 and Voyager 2's position; Image: NASA)
Both the Voyagers are equipped with a power source called radioisotope thermoelectric generators (RTGs). This propulsion system uses plutonium to convert the heat produced from their natural radioactive decay into electricity to power the 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 cosmic-ray and charged-particle sensors. However, after 44 years, Voyager 1 has just four functional instruments whereas Voyager 2 has only five.
It has been a few decades since NASA switched off the camera on the probes to save energy for other necessary operations. Moving on, the engineers will switch off the rest of the instruments one by one until the Voyagers lose communication and drift off into the nothingness of space.
Currently 23.3 billion kilometres from Earth, it takes 20 light hours and 33 minutes to establish contact with Voyager 1 whereas it takes a little under 18 light hours to contact Voyager 2 which is approximately 19.5 billion kilometres away.
A report by Scientific American suggested that scientists have estimated that the plutonium powering the probes could run out as soon as 2025 or maybe in the 2030s at the most. Most recently, NASA revealed that Voyager 1's attitude articulation and control system (AACS), which helps the spacecraft maintain its orientation suffered a mystery glitch.