Mallika Dureja
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The joint NASA-JAXA Geotail spacecraft has been in orbit for 30 years, but its mission operations have ended because its last data recorder broke.
Since its launch on July 24, 1992, Geotail has been in orbit around Earth, gathering a huge amount of information about the structure and behaviour of the magnetosphere, the protective magnetic bubble around Earth. Geotail was supposed to run for four years, but the mission was extended several times because the data it sent back was so good that it was used in more than a thousand scientific papers.
After 30 years, it’s time for the Geotail mission to retire.
Launched in 1992 to study Earth's magnetosphere, Geotail – the 1st joint NASA/JAXA mission – has long outlived its planned 4-year lifetime, contributing to over 1,000 science publications. More: https://t.co/O3u0ezNzmY pic.twitter.com/gCR4f4JFfG
— NASA Sun & Space (@NASASun) January 18, 2023
One of Geotail’s two data recorders broke in 2012, but the other one kept working until June 28, 2022, when something strange happened. After a failed attempt to fix the recorder remotely, the mission stopped running on November 28, 2022.
“Geotail has been a very useful satellite, and it was the first joint NASA-JAXA mission,” said Don Fairfield, emeritus space scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and NASA’s first project scientist for Geotail until he retired in 2008. “The mission helped us learn a lot about how the solar wind and Earth’s magnetic field work together to make magnetic storms and auroras.”
With a long orbit, Geotail sailed through the invisible edges of the magnetosphere. It studied the physical processes at work there to learn more about how energy and particles from the Sun reach Earth. Scientists learned a lot from Geotail. For example, it helped them figure out how quickly material from the Sun gets into the magnetosphere, what physical processes are going on at the edge of the magnetosphere, and where oxygen, silicon, sodium, and aluminium are in the lunar atmosphere.
The mission also helped figure out where a process called “magnetic reconnection” happens. Magnetic reconnection is a major way that material and energy from the Sun get into the magnetosphere, and it is one of the things that causes the aurora. This discovery paved the way for the Magnetospheric Multiscale mission, or MMS, which started in 2015.
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Over the years, Geotail worked with many of NASA’s other space missions, such as MMS, Van Allen Probes, the Time History of Events and Macroscale Interactions during Substorms mission, Cluster, and Wind. With an orbit that took it as far as 120,000 miles from Earth at times, Geotail helped scientists get a full picture of how events in one area affect other areas by giving them data from faraway parts of the magnetosphere. Geotail was also combined with observations made on the ground to confirm where and how auroras form.
Even though Geotail is done gathering new data, scientists are still making new discoveries. In the coming years, scientists will keep looking at Geotail’s data.
