GEOTAIL is a joint Japan-US project to observe the Earth's magnetotail. The satellite was launched in July 1992 from Florida in the USA onboard the Delta-II launch vehicle. On a long elliptical orbit around the Earth, GEOTAIL conducted long-term observations for more than 30 years, and achieved ground-breaking results, in particular numerous discoveries in the Earth's magnetotail, such as demonstrating that magnetic reconnection occurs at the daytime boundary and tail of the Earth's magnetosphere, clarifying how ions and electrons behave in this region.

GEOTAIL's operation for more than 30 years far exceeded the originally planned three-and-a-half-year mission period. However, by the end of June 2022, both the satellite's installed data recorders stopped operating. Due to lack of sufficient observation data, it was decided to terminate observation operations on November 28, 2022, and stop the operation of the spacecraft and radiowave transmission. The results of the mission will be summarised by the end of March next year.

We would like to express our deepest gratitude to all the organisations and individuals who have cooperating in the operation of GEOTAIL so far.