On the 23rd of last month, in interstellar space outside the solar system, 24.1 billion km away from Earth. In this empty space, the space probe Voyager 1 received a software (SW) update command sent from the National Aeronautics and Space Administration (NASA) Jet Propulsion Laboratory (JPL). It only takes 22 hours for the command that left California, USA, to be transmitted to Voyager 1 at the speed of light. The life of the ‘eternal traveler’ Voyager 1, which is approaching 50 years since launch, has been extended by more than 5 years.
○Resolving thruster tube fuel residue
According to the scientific community on the 3rd, this SW update, which was carried out on both Voyager 1 and 2, solved the problem of accumulation of thruster fuel tube residue. Voyager 1 and Voyager 2 are twin spacecraft launched in August and September 1977, respectively.
Thrusters fire automatically occasionally to control the spacecraft’s attitude. This is to align the spacecraft antenna toward the Earth. Only when this work is done properly can communication take place smoothly. The thruster’s fuel residue had accumulated in the tube over the past 46 years, but NASA calculated that the accumulation had increased significantly recently. NASA believed that reducing the number of thruster operations could reduce the frequency of thruster fuel residue accumulation.
Through this SW update, the thruster rotation radius was increased by 1 degree in the up, down, left, and right directions. The number of thruster operations was reduced. Linda Spilker, a researcher at NASA JPL, said, “Every time we encounter a problem that is not in our operational map (playbook), we use our creativity to solve it.”
Modification (patch) of the computer program inside the spacecraft was also carried out. Last May, NASA engineers noticed that Voyager 1’s Attitude Control System (AACS) computer was sending unusual data. NASA modified the data to be bypassed and sent to another computer inside the spacecraft that was operating normally. Patch work was also performed on Voyager 2, which could experience the same problem.
○The only spacecraft that has left the solar system
Voyager 1 and 2, which weigh 721 kg, are nicknamed ‘the greatest navigators in human history.’ This is by sailing through outer space, which is four times the distance from the Sun to Pluto (about 5.9 billion km). Voyager 1 explored the vicinity of Jupiter and Saturn and transmitted numerous photos to Earth. Jupiter’s giant oval pattern, called the Great Red Spot, and Saturn’s moon Titan are the results of images taken by Voyager 1. Voyager 2 became the only spacecraft to visit all four planets in the solar system, passing by Jupiter and Saturn, followed by Uranus and Neptune.
Since then, they have been setting records as the most distant object created by mankind, including the longest-distance communication, the longest-distance photograph of Earth, and the first observation of the solar system’s plasma shield. At this very moment, it is leaving the solar system at a speed of 60,976 km per hour (Voyager 1).
Preparations for the launch of Voyager 1 and 2 began in the 1960s. At that time, NASA shifted its space exploration area from the moon to the planets. By using the unique planetary alignment that occurs once every 175 years, it is possible to use the ‘swing-by’ navigation method of accelerating Jupiter, Saturn, Uranus, and Neptune using their respective gravity. Voyager 1 and 2 were launched after more than 10 years of preparation. The time to reach Neptune was significantly shortened (11 years and 10 months) compared to when using its own propulsion (estimated to be over 30 years).
Voyager 1 and 2 use power produced by a radioisotope thermoelectric generator (RTG) using plutonium. The explanation is that solar panels cannot be used because they must operate even in places where sunlight is weak. The power produced at the time of launch was 470W (watts), but the output is decreasing by about 4W per year. The current output is only about 249W.
Due to a decrease in power, NASA is taking out the 11 science payloads mounted on Voyager 1 and 2 one by one. The ultraviolet spectrometer (UVS), infrared radio system (IRIS), and imaging science subsystem (ISS) are turned off.
○ LP in preparation for encountering alien life forms
One of the most famous photos in astronomy, ‘Pale Blue Dot’ was taken by Voyager 1. On February 14, 1990, NASA astronomer Carl Sagan proposed a plan to turn Voyager 1, which was flying near Pluto, for the last time before turning off its camera and take a picture of the Earth. He said, “I wanted to teach people that the Earth is just an insignificant entity floating in the vast universe.”
Voyager 1 and 2 are preparing to encounter extraterrestrial life. Both spacecraft were loaded with gold-plated copper vinyl records containing information about Earth. The surface of the LP is engraved with instructions on how to play records and mathematical methods for measuring the positions of the solar system and the Earth. The LP version contains greetings in 55 languages around the world, including the Korean “Hello,” along with the sounds of the Earth’s nature and music.
Voyager 1 and 2 will reach the outer boundary of the solar system, the ‘Oort Cloud’ (an area of hundreds of millions of small celestial bodies surrounding the solar system) 300 years later. It is expected that it will be approximately 20,000 years before it completely leaves the Oort Cloud.
It will take more than 10,000 more years for Voyager 1 and 2 to reach the alien stars Proxima Centauri and Ross 248, respectively.
Reporter Kim Jin-won [email protected]
