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posted by martyb on Sunday January 06 2019, @11:04AM   Printer-friendly
from the will-the-touchdown-be-followed-by-a-field-goal? dept.

Japan's asteroid mission faces 'breathtaking' touchdown

The ultimate objective [of the Hayabusa2 spacecraft near asteroid Ryugu], to bring asteroid samples back to Earth, will allow lab studies that can reveal much more about the asteroid's age and content. ISAS engineers programmed the craft to perform autonomous landings, anticipating safe touchdown zones at least 100 meters in diameter. Instead, the biggest safe area within the first landing zone turned out to be just 12 meters wide.

That will complicate what was already a nail-biting operation. Prior to each landing, Hayabusa2 planned to drop a small sphere sheathed in a highly reflective material to be used as a target, to ensure the craft is moving in sync with the asteroid's rotation. Gravity then pulls the craft down gently until a collection horn extending from its underside makes contact with the asteroid; after a bulletlike projectile is fired into the surface, soil and rock fragments hopefully ricochet into a catcher within the horn. For safety, the craft has to steer clear of rocks larger than 70 centimeters.

During a rehearsal in late October, Hayabusa2 released a target marker above the 12-meter safe circle; unfortunately, it came to rest more than 10 meters outside the zone. But it is just 2.9 meters away from the edge of a second possible landing site that's 6 meters in diameter. Engineers now plan to have the craft first hover above the target marker and then move laterally to be above the center of one of the two sites. Because the navigation camera points straight down, the target marker will be outside the camera's field of view as Hayabusa2 descends, leaving the craft to navigate on its own.

"We are now in the process of selecting which landing site" to aim for, says Fuyuto Terui, who is in charge of mission guidance, navigation, and control. Aiming at the smaller zone means Hayabusa2 can keep the target marker in sight until the craft is close to the surface; the bigger zone gives more leeway for error, but the craft will lose its view of the marker earlier in the descent.

Assuming the craft survives the first landing, plans call for Hayabusa2 to blast a 2-meter-deep crater into Ryugu's surface at another site a few months later, by hitting it with a 2-kilogram, copper projectile. This is expected to expose subsurface material for observations by the craft's cameras and sensors; the spacecraft may collect some material from the crater as well, using the same horn device. There could be a third touchdown, elsewhere on the asteroid. If all goes well, Hayabusa2 will make it back to Earth with its treasures in 2020.


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  • (Score: 0) by Anonymous Coward on Sunday January 06 2019, @04:23PM (1 child)

    by Anonymous Coward on Sunday January 06 2019, @04:23PM (#782773)

    Will we, in the next 10000 years, be able to live in solitude in a place where you would always see the dark sky above you?

  • (Score: 2) by HiThere on Sunday January 06 2019, @05:23PM

    by HiThere (866) Subscriber Badge on Sunday January 06 2019, @05:23PM (#782796) Journal

    It's hard to predict that far ahead, but that's not the way to bet. Expect space habitats to be populous, and well lighted. I suppose if you go down to the basement you'll be able to see dark space under your feet...

    --
    Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.