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  • In late 2018, as NASA’s OSIRIS-REx spacecraft neared its

  • target, Bennu, the asteroid grew in detail from a few tiny pixels

  • to an incredibly hi-resolution image. OSIRIS-REx confirmed the

  • asteroid’s basic shape, which was originally observed in 1999

  • by ground-based radar at Arecibo Observatory. What scientists

  • didn’t expect was just how rough and boulder-filled the asteroid

  • would turn out to be. While it can be difficult to fully grasp

  • Bennu’s unfamiliar surface, it’s helpful to understand the scale

  • of what youre seeing here. In this image, the brightest

  • boulder is the length of a horse and the large boulder in this

  • image is the width of a soccer field. Another challenge for the

  • mission is the asteroid’s small size and weak gravity. This

  • means that OSIRIS-REx needs to fly daringly close to the

  • surface in order to enter into orbit. With its orbital A phase,

  • OSIRIS-REx successfully entered the closest-ever orbit for a

  • spacecraft, setting a Guinness World Record in the process.

  • Then, 6 months later, it beat its own record during its

  • orbital B phase and approached to within a few hundred meters

  • of the rocky surface. Because OSIRIS-REx flew so closely over

  • the surface during orbital B, the team was able to map the

  • topography and shape of Bennu better than we have our own

  • Moon. In addition to mapping Bennu, OSIRIS-REx plans to

  • collect and return a sample of the asteroid back to Earth. To

  • do that, the spacecraft will carefully tag the surface of

  • Bennu. The OSIRIS-REx team has selected four possible sample

  • sites for the mission: Osprey, Kingfisher, Nightingale, and

  • Sandpiper. The spacecraft has been closely imaging these sites

  • from different angles to select the best touch-down spot for

  • OSIRIS-REx. What was originally envisioned as a smooth and easy

  • touchdown on Bennu’s surface, has become a complex endeavor to

  • tag a small, crowded space on the asteroidan area no larger

  • than a few parking spots, by mid 2020. The OSIRIS-REx team has

  • already pushed the boundaries of scientific exploration, going

  • from ground-based radar images all the way to being a few

  • hundred meters from the asteroid surface, and is now mere months

  • away from a sample collection attempt.

In late 2018, as NASA’s OSIRIS-REx spacecraft neared its

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小惑星ベヌからのサプライズ (Surprises from Asteroid Bennu)

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    林宜悉 に公開 2021 年 01 月 14 日
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