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  • richardmitnick 1:42 pm on January 2, 2019 Permalink | Reply
    Tags: Asteroid Ryugu, , , , Breathtaking touchdown, , ,   

    From Science Magazine: “Japan’s asteroid mission faces ‘breathtaking’ touchdown” 

    AAAS
    From Science Magazine

    Jan. 2, 2019
    Dennis Normile

    1
    Hayabusa2 imaged its shadow during a rehearsal descent. JAXA

    JAXA/Hayabusa 2 Credit: JAXA/Akihiro Ikeshita

    Japan’s Hayabusa mission made history in 2010 for bringing back to Earth the first samples ever collected on an asteroid. But the 7-year, 4-billion-kilometer odyssey was marked by degraded solar panels, innumerable mechanical failures, and a fuel explosion that knocked the spacecraft into a tumble and cut communications with ground control for 2 months. When planning its encore, Hayabusa2, Japan’s scientists and engineers were determined to avoid such drama. They made components more robust, enhanced communications capabilities, and thoroughly tested new technologies.

    But the target asteroid, Ryugu, had fresh surprises in store. “By looking at the details of every asteroid ever studied, we had expected to find at least some wide flat area suitable for a landing,” says Yuichi Tsuda, Hayabusa2’s project manager at the Japan Aerospace Exploration Agency’s Institute of Space and Astronautical Science (ISAS), which is headquartered in Sagamihara. Instead, when the spacecraft reached Ryugu in June 2018—at 290 million kilometers from Earth—it found a cragged, cratered, boulder-strewn surface that makes landing a daunting challenge. The first sampling touchdown, scheduled for October, was postponed until at least the end of this month, and at a symposium here on 21 and 22 December, ISAS engineers presented an audacious new plan to make a pinpoint landing between closely spaced boulders. “It’s breathtaking,” says Bruce Damer, an origins of life researcher at the University of California, Santa Cruz.

    Yet most everything else has gone according to plan since Hayabusa2 was launched in December 2014. Its cameras and detectors have already provided clues to the asteroid’s mass, density, and mineral and elemental composition, and three rovers dropped on the asteroid have examined the surface. At the symposium, ISAS researchers presented early results, including evidence of an abundance of organic material and hints that the asteroid’s parent body once held water. Those findings “add to the evidence that asteroids rather than comets brought water and organic materials to Earth,” says project scientist Seiichiro Watanabe of Nagoya University in Japan.

    Ryugu is 1 kilometer across and 900 meters top to bottom, with a notable bulge around the equator, like a diamond. Visible light observations and computer modeling suggest it’s a porous pile of rubble that likely agglomerated dust, rocks, and boulders after another asteroid or planetesimal slammed into its parent body during the early days of the solar system. Ryugu spins around its own axis once every 7.6 hours, but simulations suggest that during the early phase of its formation, it had a rotation period of only 3.5 hours. That probably produced the bulge, by causing surface landslides or pushing material outward from the core, Watanabe says. Analyzing surface material from the equator in an Earth-based laboratory could offer support for one of those scenarios, he adds. If the sample has been exposed to space weathering for a long time, it was likely moved there by landslides; if it is relatively fresh, it probably migrated from the asteroid’s interior.

    So far, Hayabusa2 has not detected water on or near Ryugu’s surface. But its infrared spectrometer has found signs of hydroxide-bearing minerals that suggest water once existed either on the parent body or on the asteroid, says Mutsumi Komatsu, a planetary materials scientist at the Graduate University for Advanced Studies in Hayama, Japan. The asteroid’s high porosity also suggests it once harbored significant amounts of water or ice and other volatile compounds that later escaped, Watanabe says. Asteroids such as Ryugu are rich in carbon as well, and they may have been responsible for bringing both water and carbon, life’s key building block, to a rocky Earth early in its history. (Comets, by contrast, are just 3% to 5% carbon.)

    Support for that theory, known as the late heavy bombardment, comes from another asteroid sample return mission now in progress. Early last month, NASA’s OSIRISREx reached asteroid Bennu, which is shaped like a spinning top as well and, the U.S. space agency has reported, has water trapped in the soil. “We’re lucky to be able to conduct comparative studies of these two asteroid brothers,” Watanabe says.

    Geologist Stephen Mojzsis of the University of Colorado in Boulder is not convinced such asteroids will prove to be the source of Earth’s water; there are other theories, he says, including the possibility that a giant Jupiter-like gaseous planet migrated from the outer to the inner solar system, bringing water and other molecules with it around the time Earth was formed. Still, findings on Ryugu’s shape and composition “scientifically, could be very important,” he says.

    Some new details come from up-close looks at the asteroid’s surface. On 21 September, Hayabusa2 dropped a pair of rovers the size of a birthday cake, named Minerva-II1A and -II1B, on Ryugu’s northern hemisphere. Taking advantage of its low gravity to hop autonomously, they take pictures that have revealed “microscopic features of the surface,” Tsuda says. And on 5 October, Hayabusa2 released a rover developed by the German and French space agencies that analyzed soil samples in situ and returned additional pictures.

    The ultimate objective, 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.

    See the full article here .


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  • richardmitnick 1:11 pm on June 17, 2018 Permalink | Reply
    Tags: Asteroid Ryugu, , , , , ,   

    From NASA Spaceflight: “Sample return mission Hayabusa2 approaching Asteroid Ryugu” 

    NASA Spaceflight

    From NASA Spaceflight

    June 15, 2018
    Justin Davenport

    1
    The Japanese asteroid sampling mission Hayabusa2, launched on December 3, 2014 aboard an H-IIA rocket from Tanegashima, Japan, has nearly completed its long flight to asteroid Ryugu (formerly 1999 JU3) after a five year mission and an Earth flyby.

    The mission was approved as a follow-on to the Hayabusa mission which became the first probe to sample an asteroid when it landed on the young “rubble pile” asteroid Itokawa, though the mission had its share of problems.

    The Hayabusa mission to Itokawa had problems with one of its four ion engines from the start of the mission after a solar flare damaged the craft and two reaction wheels failed before its approach to Itokawa.

    The hopper that was supposed to land on the surface missed the asteroid and flew off into deep space, the sampling mechanism did not function properly, and although Hayabusa was able to land on Itokawa, it suffered thruster leaks and another ion engine failed during the trip home, and contact was lost for several weeks after the second landing on Itokawa, delaying Hayabusa’s departure to Earth.

    Despite this, 1,500 microscopic samples from Itokawa were successfully returned and examined after the capsule landed in the Woomera test range in Australia in 2010.

    The Hayabusa2 follow-on has one more reaction wheel (to make four) and improved, higher thrust ion engines, along with a backup asteroid sampling system, and the spacecraft is in good health so far.

    Hayabusa2 is a 600 kilogram (1300 pound) spacecraft that is based on the Hayabusa craft, with some improvements.

    It is powered by two solar panels and uses an ion engine with xenon propellant as its main propulsion source. The ion engine technology was first used in the Deep Space One experimental spacecraft in the late 1990’s and also has been successfully used in the Dawn asteroid probe as well.

    2
    Hayabusa2 IKON engines. JAXA

    Although the thrust is very low it is continuous and can be used to propel a spacecraft to very high velocities over time, very efficiently.

    The craft also features thrusters and four reaction wheels to maintain its position in space as well as four auxiliary lander/hopper craft, a sub-satellite, and an impactor, along with sampling mechanisms, a full suite of science instruments and a reentry capsule to return samples to Earth.

    The Hayabusa2 mission is intended to image and sample the asteroid 1999 JU3, discovered in May 1999, now known as Ryugu, and to return samples of the asteroid, including samples excavated from an impactor to collect materials from under the surface, to Earth for analysis in laboratories.


    Besides the primary and backup sample collectors, the mission includes three MINERVA “hoppers” similar to the one used on the original Hayabusa mission that will land at several locations on the surface to study these locations with cameras and thermometers.

    An impactor (SCI) with a 2 kg pure copper lump (Liner) will be used to excavate a crater on the surface, and there will be a sub-satellite that will be released to observe the impact.

    The main imaging instrument is the ONC (Optical Navigation Camera) which has telephoto and wide-angle modes, and which is being used right now to provide optical images of Ryugu, which are being used to navigate Hayabusa2 safely to the asteroid. Once at Ryugu, this instrument will image the surface.

    Other instruments that will be used are the TIR (Thermal Infrared Camera) which will measure the asteroid’s surface temperature, the NIRS3 (Near Infrared Spectrometer) which will check the distribution of minerals on the surface using the 3 micron band, and the laser altimeter (LIDAR) which measures the distance between the spacecraft and the asteroid.

    International contributions include a small robotic lander (10 kilograms or 20 pounds) called MASCOT that is a joint venture of DLR (Germany) and CNES (France), while NASA is providing communications through the Deep Space Network.

    NASA Deep Space Network

    3
    MASCOT. DLR

    MASCOT’s purpose is to provide extremely detailed mineralogical and geological surveys of the asteroid’s surface, providing up to 16 hours of data with a battery set to last 2 asteroidal days, and will use four instruments (MicrOmega – a hyperspectral microscope, MAG – a magnetometer, CAM – a camera, and MARA – a radiometer) to do this.

    MASCOT will “jump” to various sites on the surface using a robotic arm to study these sites in detail, after being released from Hayabusa2 100 meters (328 feet) above the surface of the asteroid. MASCOT systems are based on designs from Rosetta/Philae, Phobos-Grunt, and ExoMars.

    The Hayabusa2 craft has finished its first correction burn and is now less than 600 kilometers (372 miles) away from asteroid Ryugu. Over the coming days the asteroid, which is now seen as a small round object, will become much more visible and surface features will be seen.

    The craft is also searching for any satellites that may be orbiting the asteroid, and have not detected any so far (detection limit: larger than 50 cm). Other asteroids such as Ida have been found to have satellites, and satellites can be hazards to navigation for spacecraft like Hayabusa2.

    Ryugu itself is approximately 880 meters wide (nearly a kilometer), rotates around its axis every 7 hours 38 minutes, and is thought to be very dark (0.05 albedo). Ryugu orbits from a distance just within Earth’s orbit to as far as just outside Mars’ orbit around the Sun, and its orbital radius around the Sun is 180 million kilometers (111 million miles), orbiting the Sun in 1.3 Earth years.

    It is believed that Ryugu is an older C-type asteroid that may have material from the beginning of the solar system (including water and organics), or at least more ancient material, as opposed to Itokawa, an S-type asteroid. Ryugu appears to be mostly spherical, unlike Itokawa’s potato shape, and we are seeing the asteroid in more detail as the spacecraft draws closer.

    3
    Its arrival at Ryugu is set for June 27th, and Hayabusa2 will be 20 km (12 miles) above the surface on that date, as things currently stand. The arrival will be followed by a press conference in Sagamihara, Japan.

    After arrival, Hayabusa2 will start imaging the asteroid, with medium altitude observations at 5 km (3 miles) starting at the end of July. In August, Hayabusa2 is set to measure the asteroid’s gravity by going to an altitude of 1 km (0.6 miles) above the surface, and in the fall (September – October timeframe) the first touchdown and MINERVA deployment are set to occur.

    After solar conjunction in late fall (November – December) where communication will not be possible with the probe, Hayabusa2 will resume contact afterward and conduct more medium altitude observations at 5 km to start 2019, with the second touchdown in February and the artificial crater experiment using the impactor in the spring (March – April timeframe).

    The third touchdown on the asteroid will follow in April or May, and another MINERVA deployment will follow in July. The Hayabusa2 craft will remain near Ryugu until the end of 2019 (November or December) when it will depart for Earth after 18 months at Ryugu. The sample delivery reentry capsule is set to be returned to Earth in late 2020.

    4
    Rover deployment. JAXA

    Asteroids are remnants of the building blocks of the solar system and can tell us important details about how the solar system, and by extension Earth and ourselves, came to be, and asteroids can and have endangered life on this planet throughout geologic history. Most notably, a 10 kilometer (6 mile) wide asteroid hit the area of the Yucatán in Mexico 65 million years ago and ended the reign of the dinosaurs.

    A future asteroid could pose a similar threat to humanity and Ryugu is classified as one of these “potentially hazardous asteroids” (PHAs) in the Apollo group.

    What we learn about these asteroids will inform how we intercept one if the time ever came. Finally, asteroids are being looked at as potential sites for mining metals for future industries, and the composition of asteroids like Ryugu will inform mining plans as well.

    For all these reasons, missions like Hayabusa2, Osiris-Rex (to approach Bennu in 2 months), and others are very important efforts to understand the solar system.

    See the full article here .


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  • richardmitnick 5:44 am on December 6, 2016 Permalink | Reply
    Tags: Asteroid Ryugu, , , ,   

    From Seeker: “Quest to Reveal Asteroid’s Mysteries Before Japanese Spacecraft’s Visit” 

    Seeker bloc

    SEEKER

    Dec 5, 2016
    ELIZABETH HOWELL

    hayabasu2-spacecraft
    Artist’s concept of Hayabusa-2 approaching asteroid 162173 Ryugu (1999 JU3). Image Credit: JAXA

    A Japanese spacecraft is on its way to some daring work at an asteroid. Hayabusa 2 is expected to reach Asteroid Ryugu in June or July 2018 and will drop several tiny landers on to its surface. The spacecraft itself will scoop up a sample of asteroid material for return back to Earth, just as its predecessor Hayabusa did at asteroid Itokawa a decade ago.

    It’s clear that a lot of engineering and precision is needed to achieve these maneuvers, far from home and in a zone that doesn’t easily give second chances. So as Hayabusa 2 moves towards its target, astronomers on Earth are looking at Ryugu as much as they can to learn about its properties.

    “Before you can send an interplanetary mission to a small body, it is important to know its orbit with the best possible accuracy, but you also have to know the object’s properties,” said Thomas Mueller, co-investigator for Hayabusa’s thermal infrared imager instrument, in an email to Seeker. He is also leading the efforts to do a characterization of Ryugu before Hayabusa 2’s arrival.

    The latest research is based on analyzing results from the European Herschel Space Observatory (in April 2012) and the NASA Spitzer Space Telescope (between January and May 2013). The astronomers attempted to map the rotation of the object using its light curve (the change in light as seen from Earth), which in turn led to estimating its spin and surface composition. A paper based on the research was recently published on the prepublishing site arXiv, and has been accepted in the journal Astronomy & Astrophysics.

    ESA/Herschel
    ESA/Herschel spacecraft

    NASA/Spitzer Telescope
    NASA/Spitzer Telescope

    2
    The shadow of Hayabusa, along with a target marker (circled, at left), is shown on asteroid Itokawa in November 2005. Credit: JAXA

    Mueller, who works with the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, has been interested in learning about small bodies in the solar system since his Ph.D. thesis, which he completed in 1997 — where he tried to apply infrared measurements of well-known targets to objects that were less well known, but still scientifically interesting. He’s been working to characterize Ryugu (in collaboration with the Japan Aerospace and Exploration Agency, or JAXA) since 2008.

    “Mission targets like Itokawa (Hayabusa mission in 2005) or Ryugu (Hayabusa-2 mission) always attracted my attention for many reasons,” Mueller added, providing a list: “(1) The possibility to compare my model predictions with ‘ground-truth’ at some point; (2) the relation to space projects (I worked in the European Space Agency for several years); (3) the connection between near-Earth objects and Earth (NEAs as a risk for Earth, but also as the origin of life, water and heavy element supply); (4) to find out more about the building blocks of the planets.”

    Specifically for Ryugu, Mueller says the latest research will help engineers adjust their instrument settings, do risk assessments and develop plans for what the spacecraft will do when it gets there. Some of the things they have covered include Ryugu’s estimated size, brightness (known as albedo), rotation period and spin axis, thermal properties and where grains of different sizes are distributed.

    But there are challenges with observing a small object from so far away. The new paper notes that because Ryugu is nearly spherical, it made it hard to get a light curve. So the astronomers combined radiometric and lightcurve inversion techniques to come up with an estimation of Ryugu’s physical and thermal properties.

    3
    A view of asteroid Itokawa based on data from the Hayabusa spacecraft. Credit: JAXA

    “In all our observations, we see Ryugu as a perfect point source (we cannot resolve the target from Earth distance),” Mueller added. “However, we are able to derive not only the size, shape, spin properties, but also things like the (most-likely) surface material (carbonaceous, complex organics?) or predominant grain sizes on the surface (1-10 mm).”

    He added that both Itokawa and Ryugu are “fantastic opportunities” to see how well models hold up against ground truth. The astronomers are lucky to have this opportunity, as only a fraction of small bodies are visited by spacecraft, he said.

    “Other experts in the field of small-body characterization/modelling will very likely pick up our published observations to make their own predictions,” he added. “It is very exciting for us to see who gets closest to the truth.”

    See the full article here .

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