After 30 years of in-orbit service, mission operations of the Geotail spacecraft, run by JAXA and NASA, respectively the Japanese and US space agencies, have concluded following the failure of the satellite’s data recorder.
Since its launch on July 24, 1992, Geotail has orbited the Earth, collecting an immense data set on the structure and dynamics of the magnetosphere, Earth’s protective magnetic bubble. Geotail was originally scheduled for a four-year mission, but this was extended several times due to the smooth running of the spacecraft and the high quality of the incoming data, which have contributed to more than a thousand published scientific studies.
While one of Geotail’s two data recorders failed in 2012, the second continued to function until it experienced an anomaly on June 28, 2022. After attempts to repair the recorder remotely failed, it was recently decided to terminate all mission operations.
“Geotail has been a very productive satellite and it was the first joint NASA-JAXA mission,” said Don Fairfield, space scientist emeritus at NASA Goddard Space Flight Center in Greenbelt, Maryland and lead scientist for Geotail’s project. NASA, until its retirement in 2008. “The mission made important contributions to our understanding of how the solar wind interacts with Earth’s magnetic field to produce magnetic storms and auroras.”
Using an elongated orbit, Geotail navigated through the invisible limits of the magnetosphere, collecting data on the physical process to help understand how the flow of energy and particles from the Sun reaches Earth. Geotail made many scientific advances, including helping to figure out the rate at which material passes from the Sun into the magnetosphere, determining the physical processes involved, and identifying oxygen, silicon, sodium, and aluminum in the extremely thin lunar atmosphere.
Artist’s recreation of the Geotail. (Illustration: NASA)
The mission also helped pinpoint the location of a process called magnetic reconnection, which is a major carrier of material and energy from the Sun to the magnetosphere and one of the instigators of auroras. This discovery paved the way for the MMS (Magnetospheric Multiscale) spacecraft mission, which launched in 2015.
Over the years, Geotail collaborated with many of NASA’s other space missions, including MMS, Van Allen Probes, THEMIS (Time History of Events and Macroscale Interactions during Substorms), Cluster, and Wind. With an orbit that sometimes took it as close as 200,000 kilometers from Earth, Geotail helped provide complementary data from remote parts of the magnetosphere to give scientists a complete picture of how events observed in one area affect other regions. Geotail was also combined with observations from the surface to confirm the location and mechanisms of how auroras form.
Although Geotail has finished collecting new data, the scientific discoveries are not over. Scientists will continue to study the Geotail data for years to come. (Source: NASA MDSCC)