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Japan's Hayabusa2 probe ends ion engine burn on return to Earth for Dec. sample drop-off

Happy members of the Hayabusa2 team are seen celebrating the space probe's successful completion of its last ion engine burn on its return to Earth, in this image from the team's Twitter account.
The Hayabusa2 project Twitter account is seen formally confirming that the ion engines have stopped as expected (above), and then saying, "We did it!!!!" in the tweet below.

TOKYO -- Japan's Hayabusa2 space probe has completed its last ion engine-powered maneuvers on its return to Earth for a scheduled drop off of materials collected from the asteroid Ryugu, according to a Sept. 17 announcement by the Japan Aerospace Exploration Agency (JAXA).

    Hayabusa2 will reportedly now enter the final phase of its fly-past of Earth, and on Dec. 6 a capsule containing rocks and other samples from Ryugu is expected to land in the Australian desert.

    Hayabusa2, which departed Ryugu in November 2019, has used its four ion engines in two periods, as planned: between November 2019 and February 2020, and again between May and August. The most recent burn, which began at just past 10 p.m. on Sept. 15 and ran until 3:15 a.m. on Sept. 17, was to make minor adjustments to the probe's entry into Earth orbit. Hayabusa2 has used its ion engines for over 9,000 hours during the round-trip to Ryugu.

    Ion engines use electricity to accelerate matter, giving them propulsive energy. Although their power is minimal, the craft's acceleration can be increased by continuously firing them. Hayabusa2's predecessor Hayabusa was Japan's first space probe to fully employ the technology.

    JAXA associate professor and head developer Kazutaka Nishiyama said of the probe's final ion engine firing, "On the previous Hayabusa project, they (the ion engines) wore out at the end of the trip, stumbling toward the goal and only just made it. By contrast, Hayabusa2 is in a state where it can still demonstrate its full propulsive power. The ion engine is fulfilling its role, so let's pass the baton on to the next generation (for the trip to the next asteroid). Thank you very much!"

    Hayabusa2 will fire its chemical thrusters once to adjust its speed once at the end of October, twice in November and then once in December, which should put it in orbit over Australia. After the capsule has been released on Dec. 5, the chemical thrusters will fire again to propel Hayabusa2 away from Earth, at which point it will travel on to its next destination: the asteroid 1998KY26.

    (Japanese original by Etsuko Nagayama, Opinion Group)

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