The primary purpose of the mission was to study the structure and dynamics of the tail region of the magnetosphere with a comprehensive set of scientific instruments. For this purpose, the orbit has been designed to cover the magnetotail over a wide range of distances: 8 R🜨 to 210 R🜨 from the Earth. This orbit also allowed it to study the boundary region of the magnetosphere as it skims the magnetopause at perigees. In the first two years the double lunar swing-by technique was used to keep apogees in the distant magnetotail. This involved 14 lunar flybys.[2]
In 1993 the computer that controls the Low Energy Particles experiment locked up.[2] Attempts to reset it failed.[2] This problem was solved by changing the trajectory of the craft during a lunar flyby that took place on 26 September 1993 so that it passed through the shadow of the Moon.[2] Power from the batteries was cut while this took place.[2] When the craft left the shadow of the Moon, power returned and the computer started working again.[2]
The apogee was lowered down to 50 R🜨 in mid November 1994 and then to 30 R🜨 in February 1995 in order to study substorm processes in the near-Earth tail region. The present orbit is 9 R🜨 × 30 R🜨 with an inclination of -7° to the ecliptic plane."
Geotail instruments studied electric fields, magnetic fields, plasmas, energetic particles, and plasma waves.[3]
In June 2022, the second and final of Geotail's two data recorders failed, jeopardizing science observation.[6] It was decided to terminate the operation, and the spacecraft was deactivated on 28 November 2022.[7]
Geotail data has been used to show thatflux transfer events move faster than the ambient medium through theMagnetosphere.[8] Those within theMagnetosheath were shown to move both faster and slower than the ambient medium.[8]
During the lunar flybys Geotail identified oxygen, silicon, sodium and aluminium in thelunar atmosphere.[2]
Launches are separated by dots ( • ), payloads by commas ( , ), multiple names for the same satellite by slashes ( / ). Crewed flights are underlined. Launch failures are marked with the † sign. Payloads deployed from other spacecraft are (enclosed in parentheses).
