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Japan-U.S. Geotail Mission Officially Comes to an End After 30 Glorious Years

The aging satellite, which has been observing Earth's magnetosphere since 1992, suffered a recent data recorder malfunction that led to its demise.

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An illustration of the Geotail spacecraft.
An illustration of the Geotail spacecraft.
Illustration: JAXA

An irreparable software glitch has put an end to Geotail, a JAXA-NASA joint mission. The satellite observed Earth’s magnetosphere for more than 30 years within an extremely elliptical orbit, but the mission has officially been terminated, according to JAXA’s Institute of Space and Astronautical Science (ISAS).

Geotail launched on July 24, 1992, from Cape Canaveral Air Force Station in Florida as a joint mission of NASA and the Japan Aerospace Exploration Agency (JAXA). The satellite had been sailing through the magnetic envelope that surrounds Earth—the protective layer known as the magnetosphere.

But on June 28, Geotail’s last remaining data recorder malfunctioned, leaving the probe with no means to collect its science data. Geotail was originally equipped with two data recorders, but one data recorder stopped working in 2012 after collecting 20 years worth of data. The remaining recorder outlasted its deceased companion by 10 years before malfunctioning itself.

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JAXA’s mission engineers discovered the data recorder anomaly and the two space agencies had been trying to decide the fate of Geotail ever since. On November 28, it was decided that the mission could not continue; the probe’s operations are now officially over, including its radio wave transmissions. The full results of the mission will be summarized by the end of March 2023, according to ISAS.

Geotail had far outlived its original mission timeline of four years, observing the elongated tail of Earth’s magnetosphere and sending back valuable data on auroras and the type of material being emitted by the Sun, among other scientific observations pertaining to Earth’s atmosphere.

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Earth’s magnetosphere is a giant magnetic field that surrounds our planet, protecting us from solar wind, radiation from the Sun, and cosmic rays from deep space. The magnetosphere is shaped by Earth’s north and south poles, as well as a steady stream of particles emitted by the Sun.

The satellite was placed into an extremely elliptical orbit around Earth, observing the far region of the magnetotail at first. Over time, however, the spacecraft’s lower orbit allowed it to get closer and study the substorms that took place near Earth, in addition to passing just inside the magnetosphere’s boundary plane on the dayside, according to NASA.

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The time has come for us to bid farewell to Geotail, but the small satellite certainly fed scientists with enough information to warrant its legacy for years to come.

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