The 30-year-old NASA-Japan Aerospace Exploration Agency (JAXA) mission has come to an end with the closure of operations on the Geotail satellite.
Geotail was launched in July 1992 and was designed to study the Earth’s magnetosphere. This is the region around the Earth where the particles of our planet’s magnetic field are affected. It is important for our well-being because it protects us from dangerous radiation from space. Because this radiation comes mainly in the form of the solar wind from the sun, the magnetosphere is not a round bubble – instead, it has the shape of a long tail on the night side of the planet caused by the outflow of particles from the sun.
Geotail orbited the Earth in a highly elliptical orbit which allowed him to study this tail, learning about its structure and dynamics. He used instruments to monitor magnetic and electric fields, as well as to observe plasma and high-energy particles. Originally designed to operate for four years, the satellite has endured 30 years of remarkable operation, providing data for over a thousand scientific papers.
The mission was also significant because it was a partnership between NASA and the Japanese space agency JAXA. “Geotail was a very productive satellite, and it was the first joint NASA-JAXA mission,” Don Fairfield, NASA’s first project scientist for Geotail, said in a statement. “The mission has greatly improved our understanding of how the solar wind interacts with the Earth’s magnetic field to produce magnetic storms and auroras.”
Geotail did not have an easy time of it during all his missions. In 1993, a year after launch, one of its computers failed, and it appeared that one of the mission’s main instruments, the Low Energy Particle experiment, would be unusable. The team tried to reset the computer with no luck, so they opted for a nail-biting option to adjust the satellite’s orbit by sending it around the dark side of the moon, where it would be temporarily blocked from sunlight and without power. After 10 minutes in the dark, the satellite came back out into the sunlight and managed to reset the computer.
This enabled the mission to continue as planned, but after many years of use, components began to fail. In 2012, one of the two data recorders stopped working. The second recorder worked until June 2022, when there was a problem and he could not revive it. Mission operations ended in November 2022, and NASA recently announced that the mission is now officially over.
Geotails leave a legacy of results under the magnetosphere, as well as traces of material in the moon’s extremely thin atmosphere. More recent missions continue its work, such as the Multiscale Magnetospheric mission launched in 2015.