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Hayabusa2 Team Looks Toward Sample Collection

With two rovers and a lander already deployed on the asteroid 162173 Ryugu, the Japan Aerospace Exploration Agency (JAXA) must be basking in the glow of an unusually successful venture. Now we turn to a key part of the Hayabusa2 mission, the retrieval of a surface sample. Two touchdown rehearsals have gone well, providing detailed views of the asteroid’s surface. The plan is to return samples to Earth in December of 2020, but let’s continue to take one thing at a time. Sample retrieval can be dicey, as we saw with the first Hayabusa.

Once known as MUSES-C, the original Hayabusa reached asteroid Itokawa in September of 2005 (I can’t believe it was that long ago — as the cliché would have it, it seems like yesterday). A series of enroute problems included a solar flare that damaged the craft’s solar cells and the failure of attitude-adjusting reaction wheels, while the launch of a probe called MINERVA also failed. Nonetheless, surface particles from Itokawa were successfully returned to Earth.

Now the Hayabusa2 team works on landing site selection, no easy task. Keeping the spacecraft safe means looking for regions ideally 100 meters in diameter in which there is an average slope of less than 30 degrees, boulder heights less than 50 centimeters, and an absolute temperature less than 370 Kelvin (97 degrees Celsius). These constraints limit the site to 30 degrees either side of the asteroid’s equator, all this on a diminutive object that presents its own problems.

“Unlike other asteroids we have visited, Ryugu has no powder, no fine-grain regolith. That makes selecting a place to sample more challenging,” said the Planetary Science Institute’s Deborah Domingue. “We are helping characterize the surface to optimize landing site selection.”

Image: This image of asteroid Ryugu was taken with Hayabusa2’s ONC-T (Optical Navigation Camera-Telescopic) on October 15, 2018 from an altitude of 42 meters. The resolution is about 4.6 millimeters per pixel, and this is the highest resolution that Hayabusa2 spacecraft has taken. In fact, this is the highest resolution image that a spacecraft has taken of an asteroid. Credit: JAXA, Tokyo University, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji Univeristy, Aizu University, and AIST.

Along with PSI’s Lucille Le Corre, a co-investigator on the mission’s Optical Navigation Camera (ONC) team, Domingue discussed these and other Hayabusa2 operations at a press conference at the 50th annual meeting of the American Astronomical Society’s Division for Planetary Sciences (DPS) in Knoxville. Hayabusa2 team members present included Masaki Fujimoto, the head of ISAS/JAXA, Hikaru Yabuta, lead of the landing site selection committee and the multi-scale regolith characterization team, Ralf Jaumann, lead for the European Space Agency’s (ESA’s) MASCOT lander, and Eri Tatsumi, the ONC team instrument scientist.

“Since the approach phase began last June, my main goal was to support the Hayabusa2 team in the preparation of touch down operations,” said Le Corre. “In order to assess the sampleability of Ryugu’s terrains I have worked on generating products such as ONC image mosaics and local topographic models. Our data show that the Hayabusa2 team has to carefully select a sampling site to avoid the numerous boulders present on the surface.”

Lacking fine-grained regolith, Ryugu is challenging, and the mission demands a thorough analysis of the surface to ensure a successful sample collection. Three sample collections are planned, the first now likely no sooner than January of 2019. The first two sample collections will use a sampler horn that will catch particles of ejecta raised by the firing of a projectile into the surface. The third sample collection, in the late spring, will collect material dislodged by a kinetic impactor that will produce a crater on the surface of Ryugu.

The image below (taken by a camera that, incidentally, was funded by public contributions) comes from the Hayabusa2 website and shows the sampler horn.

Image: Test photograph of the sampler horn taken by the Small Monitor Camera (CAM-H) on April 16, 2018. The shiny part in the red circle is the target plate of the sampler horn which is illuminated by the LRF-S2 laser. If the laser misses this plate, touchdown is in process and bullets will fire to stir up surface material. Credit: JAXA.

The LRF-S2 laser referred to in the caption is a part of planned sample collection activities. In the image, the LRF-S2 laser beam is hitting the tip of the sampler horn, indicating the craft is ready for touchdown operations. During touchdown, the sampler horn will compress as it touches the surface. JAXA describes the operation this way:

When the distance measurement from LRF-S2 changes or the laser from LRF-S2 deviates from its target at the base of the sampler horn, bullets will be fired to stir up the surface material for collection. This makes the LRF-S2 an important device for successful sample collection.

To keep up with Hayabusa2 operations, keep an eye on Twitter @haya2e_jaxa, from which I drew the tweet below.

And here is the image with possible touchdown area LO8-B, considered the most promising candidate.

Image: The surface of Ryugu captured with the ONC-W1 at an altitude of about 47m. The image was taken on October 15, 2018 at 22:45 JST. The red circle indicates the candidate point for touchdown, L08-B. Credit: JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University, University of Aizu, AIST).

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{ 13 comments… add one }
  • Charley October 26, 2018, 15:27

    At the risk of going all Michael Crichton on everyone, has anybody given any thought to whether or not there might be in Andromeda strain problem here? I don’t think there would be, the. But who really knows what kind of microscopic organisms are floating around having adapted to the harsh vacuum of space

    • Alex Tolley October 27, 2018, 0:07

      Wouldn’t the constant rain of dust and larger meteoric objects onto Earth have contaminated us with any form of extraterrestrial life by now? If an “Andromeda Strain” life form hasn’t consumed us after billions of years, is it really likely that there are even any life forms on asteroids, let alone such Crichtonesque threats? The Moon also proved sterile leaving the Apollo astronauts uncontaminated during their quarantine.

      I would be delighted if any form of life, or even prebiotic chemistry was found on an asteroid or comet, but I think the probability is vanishingly small. We haven’t found life on the far more congenial surface of Mars [yet].

      • Andrei October 28, 2018, 10:33

        No risk at all here, as Alex Tolley said, comets and asteroids have provided dust that been sifting down on Earth for millions of years. If there ever had been something there, (I don’t think so) it have not been able to adapt to Earth conditions.
        Planetary protocol protection will be needed the day we bring samples from inside the ocean moons, Europa, Ganymede, Enceladus etc.
        But from all other worlds, including Titan and even the gas giants, we rather would have to protect any lifeform from Earth conditions, oxygen atmosphere & our high temperature, for it to survive.

  • wdk October 28, 2018, 12:40

    Amid all this I wonder which is the doughnut and which is the hole?

    Seeing a spacecraft’s shadow cast on an asteroid (closer and closer) is a staggering image in and of itself. Like the Curiosity parachute descent spotted by the Mars Orbiter.

    It’s not just the science return.

  • kzb October 29, 2018, 13:55

    The hi-res image does give the term “rubble pile” some reality. Is the asteroid like this all the way through, or is this just a layer of rubble over a large solid mass?

  • Harry R Ray October 31, 2018, 12:14

    Holy Smoke! A new 100 pixel image of asteroid Bennu shows its shape to be remarkably similar to that of Ryugu, just not quite as “pointy” at the top, sides, and bottom.

  • ljk November 2, 2018, 15:40

    https://apod.nasa.gov/apod/ap181101.html

    Hayabusa2 Ascends from Asteroid Ryugu
    Image Credit: JAXA, U. Tokyo, Kochi U., Rikkyo U., Nagoya U., Chiba Tech., Meiji U., U. Aizu, AIST

    Explanation: Will spacecraft Hayabusa2 be able to land safely on asteroid Ryugu? Since arriving in June, pictures show that the surface of kilometer-sized Ryugu is covered with boulders, so that finding a flat enough area for the bus-sized spacecraft to touch down is proving a challenge.

    In the featured video, the shadow of Japan’s robotic Hayabusa2 can be seen on the rugged face of Ryugu while ascending last week from a touchdown rehearsal only 20 meters over the surface. Previously, small frisbee-sized landers detached from Hayabusa2, made contact with the diamond-shaped asteroid’s surface, and started hopping around.

    Studying Ryugu could tell humanity not only about the minor planet’s surface and interior, but about what materials were available in the early Solar System for the development of life. The touchdown of the Hayabusa2 mother ship is slated for early next year, hopefully followed by a soil sample collection for return to Earth.

  • ljk November 19, 2018, 12:11

    Jason Davis • November 15, 2018

    Hayabusa 2 prepares for holiday break as Sun passes between Earth and asteroid Ryugu

    Japan’s Hayabusa2 spacecraft is preparing to spend the rest of 2018 a safe distance from asteroid Ryugu, while the Sun temporarily hinders its communications with Earth.

    The spacecraft has been at the kilometer-wide asteroid since late June, snapping pictures, deploying small probes and preparing to collect a sample for return to Earth in 2020. Now, Earth and Ryugu are about to enter conjunction, a month-long period where they are on opposite sides of the Sun from each other. During this timeframe, the Sun’s radiation makes communications spotty, so the team plans to stop major work and back Hayabusa2 a safe distance away from the asteroid.

    http://www.planetary.org/blogs/jason-davis/hayabusa2-conjunction.html

    • ljk November 19, 2018, 12:14

      This bit of concerning news from the above blog post:

      Another rover named MINERVA-II2 built by a consortium of Japanese universities is scheduled to be deployed next year, but JAXA officials now say a pre-launch check of the rover revealed potential problems.

      “Communication between the rover and spacecraft was fine, but the CPU did not respond,” Tasker said. The mission team is now considering various options, including deploying the rover anyway with just a “small possibility” of data being returned.

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