13.07.2018

JAXA: Ryugu was likely born from asteroid pieces

NHK has learned that scientists now believe the asteroid Ryugu was likely formed from a collection of asteroid fragments.
Japan's Hayabusa2 spacecraft began observing Ryugu after it reached 20 kilometers from the asteroid on June 27th.
Ryugu is located about 300 million kilometers from Earth and is around 900 meters in diameter. Scientists hope that water and organic materials are present in the asteroid. But how it came into being was not known.
A team of researchers at the Japan Aerospace Exploration Agency is examining images beamed back from the probe.
The group says Ryugu has small and large rocks on its surface, with some estimated to be 100 to 200 meters long.
The team says the terrain is similar to that of the asteroid Itokawa, where the probe's predecessor landed in 2005.
University of Tokyo Professor Seiji Sugita is part of the team. He says one major theory is that Ryugu was formed by gravity drawing together fragments that split off in a collision between a relatively big asteroid and another body.
Sugita says understanding how Ryugu formed will help scientists predict its interior structure. He adds it will also help them decide on which part of the asteroid they should land the probe in a mission to collect rock samples.

Quelle: NHK

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Animation of the stereoscopic global image of asteroid Ryugu. When viewed through red / blue glasses (blue filter over the right eye), the asteroid should look three-dimensional. The images were captured with the Optical Navigation Camera - Telescopic (ONC-T), photographed on June 23, 2018.
Image credit ※: JAXA, University of Aizu, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University and AIST.

These animations show the result of sequential images of asteroid Ryugu taken with the ONC-T (Optical Navigation Camera - Telescopic) during the final approach to Ryugu on June 23, 2018. Images were captured at approximately 10 degrees increments as the asteroid rotates. The distance from the spacecraft to Ryugu at this time was about 40 km.

If you assemble red-blue glasses (placing the blue filter over your right eye) and look at these figures, Ryugu should appear three dimensional. The overall shape of Ryugu and the undulations of the craters and boulders become very clear.

From here on, we will be investigating Ryugu in more detail.

※ If you wish to use the images here, please include the displayed credit. In the case where an abbreviated form is necessary, please use "JAXA, University of Aizu & collaborators".

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The view of Ryugu from the home position

From the "home position" at 20 km away from asteroid Ryugu, Hayabusa2 has been confirming instrument operations in preparation for future observations. The images below show the results of part of this rehearsal observation.

Figure 1: Asteroid Ryugu photographed with the ONC-T from a distance of about 20 km. The image was taken at around 23:13 JST on June 30, 2018.
Image credit ※: JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University, University of Aizu and AIST.

Figure 2: Ryugu photographed with the ONC-T from a distance of about 20 km. This image was taken at around 19:21 JST on June 30, 2018. As the asteroid has rotated, this image is almost the reverse side of Figure 1.
Image credit ※: JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University, University of Aizu and AIST.

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Initial version of the shape model for Ryugu

We previously introduced a global image of asteroid Ryugu, but the Hayabusa2 Project shape model team have also created three-dimensional models of the asteroid. The asteroid was measured using images captured with the ONC-T (Optical Navigation Camera - Telescopic) to form a "shape model" of Ryugu. The shape of Ryugu is fundamental information when considering the formation history of the asteroid and it is also key to future operations by Hayabusa2.

The shape model team have initially used images taken during Hayabusa2's arrival at the asteroid to create the first three-dimensional shape models of Ryugu. This shape models were used in Figures 1 and 2 to show animations of the rotating Ryugu generated using computer graphics.

Figure 1: Shape model of Ryugu by the University of Aizu.
Image credit ※1: University of Aizu, Kobe University (shape model creation), Auburn University (video creation), JAXA.

Figure 2: Shape model of Ryugu by Kobe University.
Image credit ※2: Kobe University, University of Aizu (shape model creation), Auburn University (video creation), JAXA

The shape model team created shape models from the same image data in two different ways. The first method shown in Figure 1 is a type of stereoscopic technique called "Structure-from-Motion" (SfM). This is the same method that is used to create terrain and building shapes from aerial images that are commonly seen when taken by a drone. Figure 2 shows the shape model created with a second method known as "stereophotoclinometry" (SPC). This technique was also used to model the shape of asteroid Itokawa, the destination of the first Hayabusa spacecraft. By comparing the two shape models, we can assess how accurately the shape of Ryugu has been replicated. Although the two models show minor differences, both depict a global shape similar to the bead on an abacus, with recesses that look like craters and boulders of rock on the surface.

If higher resolution images of Ryugu are obtained in future observations, the three-dimensional shape of the asteroid can be clarified in greater detail.

Quelle: JAXA

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17,072018

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Stereo image of asteroid Ryugu
by Dr Brian May

Brian May, the lead guitarist from the British rock band, Queen, has created a stereoscopic image of Ryugu from photographs captured with the ONC-T camera onboard Hayabusa2, so that the asteroid can be viewed in three dimensions. Brian May is an astronomer, with a doctoral degree in astrophysics from Imperial College London. He has a strong interest in planetary defense or space guard, which considers the potential threat to the Earth from meteorites. As part of this, May is a core member of "Asteroid Day", that began about three years ago to increase awareness of asteroids and action that can be taken to protect the Earth.

Held on June 30th each year, Asteroid Day draws attention to the risk of collisions from celestial bodies on the Earth. The day marks the anniversary of the Tunguska explosion in Russia that occurred on June 30, 1908 due to an incoming meteroid. Within Japan, the Japan Spaceguard Association and member of JAXA are also involved in Asteroid Day. In particular, the two asteroids explored by the Hayabusa and Hayabusa2 missions, Itokawa and Ryugu, both have orbits that approach the Earth, and data from these missions is also being used to better understand planetary defense.

Brian May has previously created images to sterescopically view celestial bodies, and approached the Hayabusa2 Project to propose a stereoscopic image of Ryugu. May corresponded with Dr Patrick Michel from the Côte d'Azur Observatory, France and member of the Hayabusa2 Project (the two scientists are seen in Figure 1). According to Michel, Brain May was very pleased when he received the images of asteroid Ryugu from the Hayabusa2 team as the stereo image could then be created very quickly.

• Figure 1: Brian May (left) and Patrick Michel.
  Image credit: Brian May and Patrick Michel

With these images, Brian May created the stereoscopic image pair of Ryugu, revealing the asteroid in three dimensions for the first time (Figure 2). If you can manage the stereoscopic vision, you can see not only the whole form of Ryugu but also the irregularities of the surface.

• Figure 2: Stereoscopic images of asteroid Ryugu created by Brian May from images taken with the ONC-T, posted on Brian May's twitter account.
  https://twitter.com/DrBrianMay/status/1011807159921856523
  Image credit: Brian May
  (Credit for the original image of Ryugu: JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University, Aizu University.)

If it is hard to see in stereoscopic vision from Figure 2, how about Figure 3 below? This figure was created by Yoshiro Yamada, who superimposed the two images made by Brian May in red and blue. Using red-blue stereo glasses (right eye should be blue, the left should be red) the image should then appear in three-dimensions.

• Figure 3: Image to be used with red/blue stereo glasses.
  Image credit: Yoshiro Yamada
  (Credit for the original stereoscopic image is Brian May and credit for the images of Ryugu is JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University, Aizu University.)
  

We also have a video from Brian May (Figure 4), demonstrating how to view asteriod Ryugu in three dimensions.

• Figure 4: Video from Brian May
  Image and video credit: Brian May and Patrick Michel

We think that being able to see Ryugu in three dimensions makes the asteroid appear even more interesting. At the Hayabusa2 Project, we are about to conduct a variety of different analyses of Ryugu, including creating a three-dimensional model of the asteroid in the near future.

Acknowledgement: Dr Brian May agreed with the publication of pictures, images, and videos shown in this post. In addition, Dr Patrick Michel contacted and exchanged data with Brian May. The Hayabusa2 Project thanks both of you.

Quelle: JAXA

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Update: 20.07.2018

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Hayabusa 2 finds large rocks scattered on asteroid Ryugu

The green spots are where rocks are scattered on the surface of asteroid Ryugu in an image captured by the Hayabusa 2 space probe. (Provided by the Japan Aerospace Exploration Agency and other entities)

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The Hayabusa 2 space probe discovered many boulders scattered on the asteroid Ryugu, suggesting it was formed from fragments of other celestial bodies, the Japan Aerospace Exploration Agency (JAXA) said July 19.

More than 100 rocks larger than 8 meters in length were confirmed on the surface of the “spinning top” asteroid from images captured by Hayabusa 2, according to JAXA.

The largest boulder was about 130 meters in length near the south pole.

The rocks are likely too big to be meteor fragments from collisions with Ryugu, which has a diameter of about 900 meters.

“(The finding) is compelling evidence to prove that the Ryugu asteroid was formed by fragments of larger celestial bodies,” said Seiichiro Watanabe, head of the study team and professor of Nagoya University.

The asteroid’s slightly tilted axis of rotation gives Ryugu two seasons: summer and winter. Hayabusa 2 found the temperature ranged from about 20 to 100 degrees on Ryugu’s surface.

The probe is scheduled to approach an area about 1,400 meters from Ryugu to study its gravity and other features on Aug. 6 and 7.

Quelle:The Asahi Shimbun

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Update: 24.07.2018

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Space Explorer Hayabusa2 Prepares to Land on a Diamond-Shaped Asteroid 900 Meters Wide

After traveling 3.2 billion kilometers, the Japanese space probe will attempt to park, pick up samples of the asteroid, then return to earth by 2020

The Japan Space Exploration Agency (JAXA) launched its second asteroid probe, the Hayabusa2, in December 2014. The aim: learning more about how the solar system and possibly life on Earth originated. After meeting up with Ryugu, its target asteroid, on 27 June, Hayabusa2 is now decreasing its altitude (to roughly 5 kilometers above the surface) in order to carry out medium altitude observation. By late August, JAXA will decide where on the space rock’s surface Hayabusa2 will land. The agency intends to have it touch down in a September-October time frame.

JAXA’s plans call for Hayabusa2 to land and take off up to three times during an 18-month period, so it can study conditions at different locations on Ryugu. Upon completion of the probe’s mission and its subsequent return voyage, a capsule carrying its precious asteroid samples will detach itself from the spacecraft and a parachute will deploy at about 10 km above the Earth to provide a soft touchdown. 

This new space mission was launched four years after its predecessor, Hayabusa, returned to Earth after two landings on the Itokawa asteroid—this despite experiencing a series of equipment glitches. Those setbacks included problems with all four of its ion engines, the failure of two of its three reaction wheels, and a disappointing malfunction of the sampling mechanism. 

Despite such technical troubles, JAXA deemed Hayabusa (peregrine falcon in Japanese) an outstanding achievement, because it was still able to return with 1,500 particles from Itokawa—the first time asteroid samples had been captured and brought back to Earth for analysis.

According to Hitoshi Kuninaka, vice president and director general of JAXA’s Institute of Space and Astronautical Science, the agency learned much from the first operation. Kuninaka spoke to the foreign press in Tokyo on Thursday, following Hayabusa2’s rendezvous with Ryugu after a 1,302-day journey through space. He was joined by Makoto Yoshikawa, the mission manager of the Hayabusa2 project.

Apparently, JAXA made some upgrades in response to the original Hayabusa’s difficulties. New equipment and modifications to existing systems, intended to make the mission more fruitful and less fraught with peril, caused Hayabusa2 to weigh in at 609 kilograms, about 100 kg heavier than its predecessor. But its dimensions and architecture are not much different than those of the first probe.

Kuninaka explained that the craft uses an electric propulsion ion engine system consisting of four units that use microwaves to generate charged ions from xenon gas. The ions are then accelerated using an electric field and expelled at high speed, which provides the thrust to propel the craft forward. He noted that JAXA has made the engine more durable and improved the propellant so it delivers more thrust.  

“So, Hayabusa2 can now achieve a velocity of over 30 km a second compared to 5 km a second for conventional chemical propulsion,” says Kuninaka. “And Hayabusa2 is able to reach the asteroid Ryugu and return to earth on just 60 kg of propellant, one-tenth the weight of the craft.”  

Concerning communications, mission manager Yoshikawa noted that the first space probe used a large parabolic X-band antenna. Its successor uses two smaller, but equally powerful planar high-gain antennas: an 8-gigahertz Ka-band antenna for ground communications, and a 32 GHz Ka-band antenna to relay scientific observations to Earth after arriving at the asteroid. The latter can transmit roughly four times as much data as the X-band, but transmission can be attenuated during bad weather. In addition, Japan’s tracking stations are not currently set up to receive radio waves in that portion of the spectrum, so JAXA is using NASA and European space agency tracking stations to enable 24-hour communications with Hayabusa2.

Other important equipment on board the craft include a suite of cameras, a near-infrared spectrometer, a thermal infrared camera, a LIDAR laser altimeter to measure the distance between probe and asteroid, asteroid sampling devices, and three small rover robots (the single rover on the first probe was never deployed). Two new additions are an impactor that will be used to make an artificial crater in order to obtain samples of the asteroid’s internal structure, and a small lander containing several scientific instruments.

The craft’s electric power is generated by a two-winged, solar array paddle system consisting of three panels per wing. This produces 1,460 watts, enough to charge 11 inline-mounted 13.2-ampere-hour lithium-ion batteries that supply power to onboard equipment as needed.

Three traveling robots—Rover-1A, Rover-1B, and Rover-2—will explore Ryugu’s surface. They will be deployed via a Minerva-ll minilander. The first two concentric robots weigh approximately 1.1 kilogram, with dimensions of 18 by 7 centimeters. They each contain a wide-angle and a stereo camera, a temperature sensor and photodiode, and an accelerometer and gyro. Power is supplied by solar cells, and movement by means of internal flywheels.

The optional Rover-2 is some 45 percent taller than its counterparts and contains similar equipment but also incorporates four types of mobility systems, two kinds of bucking mechanisms, an eccentric motor microhop mechanism, and a permanent-magnet-type impact generation mechanism.

In addition, Hayabusa2 will deploy a small lander created jointly by the German Aerospace Center and the French National Center for Space Studies. Dubbed the Mobile Asteroid Surface Scout (MASCOT), it will move location once by jumping.  It carries a wide-angle camera, spectroscopic microscope, thermal radiometer, and a magnetometer to study composition of the asteroid’s surface.

Yoshikawa noted that JAXA has chosen to study asteroids because they are some of the oldest objects in our solar system. The Itokawa asteroid is an S-type asteroid, meaning it is composed of stony materials. Ryugu is a C-type and is assumed to be composed of carbon and other organic materials containing water—key elements for life on Earth.

NASA is conducting a similar mission with its OSIRIS-Rex spacecraft, which it aims to land on the near-Earth asteroid Bennu and bring back with samples. That mission was launched in September 2016, with a return date of 2023. JAXA and NASA plan to exchange samples to further scientific investigation.

From an engineering perspective, JAXA views these missions as manageable within its budget constraints. What’s more, the agency reaps the benefits of creating new technologies that will further deep space exploration. The budget for the Hayabusa mission was US $250 million, while that of the Hayabusa2 is $300 million. “These amounts include the rockets that launched them,” notes Kuninaka.

Quelle: IEEE 

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Update: 27.07.2018

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Ryugu: Ein Asteroid mit Ecken, Kanten - und großen Felsbrocken

Je näher die japanische Hayabusa2-Sonde dem Asteroiden Ryugu kommt, desto mehr Details werden für die Planetenforscher sichtbar: Aus nur noch sechs Kilometern Entfernung nahm die Teleobjektivkamera an Bord der Raumsonde am 20. Juli 2018 die Asteroidenoberfläche mit dem größten Krater des Himmelskörpers auf. "Wir sehen, dass die gesamte Oberfläche von Ryugu mit großen Felsbrocken übersät ist - dies haben wir bisher so noch nicht auf einem Asteroiden gesehen", sagt Prof. Ralf Jaumann, Planetenforscher am Deutschen Zentrum für Luft- und Raumfahrt (DLR) und wissenschaftlicher Leiter der Landesonde MASCOT (Mobile Asteroid Surface Scout) an Bord der japanischen Raumsonde. Voraussichtlich am 3. Oktober 2018 soll MASCOT auf Ryugu landen und dort mit vier Instrumenten die Asteroidenoberfläche untersuchen.

Absinken in Richtung Asteroid

Bisher hatte die japanische Raumfahrtagentur JAXA ihre Sonde in einer Höhe von 20 Kilometern über der Oberfläche des Himmelskörpers betrieben, nachdem Hayabusa2 am 27. Juni 2018 den Asteroiden erreichte. Am 16. Juli hingegen ließen die JAXA-Ingenieure Hayabusa2 von dieser Beobachtungsposition langsam absinken und blickten schließlich aus sechs Kilometern Höhe auf Ryugu. Die Auflösung ist dabei etwa drei bis vier Mal höher als in den Bildern aus 20 Kilometern Höhe, ein Pixel entspricht nun etwa 60 Zentimetern. Fast in der Mitte der Aufnahme ist ein besonders großer Krater zu sehen.

Für Planetenforscher Ralf Jaumann sind die Bilder, die aus etwa 300 Millionen Kilometer Entfernung aus dem All kommen, die Möglichkeit, einen ersten Eindruck von Ryugu zu erhalten: "Es ist wahrscheinlich, dass Ryugu das Bruchstück einer früheren Kollision ist. Allerdings: Wir sind gerade erst einmal seit kurzer Zeit am Asteroiden - und sehen lediglich die Oberfläche." Wie alt der Asteroid ist, wie er im Inneren aussieht, wie hoch seine Dichte ist, ob er aus vielen "zusammengebackenen" Schutt-Teilen oder aus einem größeren Stück besteht, das alles sind die Fragen, die die Planetenforscher unter anderem diskutieren und beantworten wollen.

Vorbereitungen für die Landung

Seit dem 25. Juli 2018 befindet sich die Sonde Hayabusa2 wieder in ihrer Ausgangsposition in 20 Kilometern Abstand von Ryugu. Im August 2018 wird die Sonde dann erneut auf nur noch etwa einen Kilometer Abstand zum Asteroiden sinken, um so seine Gravitation zu messen. Diese beträgt nach Schätzung gerade einmal ein 60.000stel der Erdanziehungskraft. Wichtig sind die detaillierten Aufnahmen von Ryugu, der einen Durchmesser von 900 Metern hat, und die Einschätzung seiner Gravitation auch für die Auswahl der Landestelle von MASCOT. Ende August wird diese mit allen beteiligten internationalen Wissenschaftlern und Ingenieuren festgelegt. Auch Hayabusa2 wird während der Mission zur Oberfläche des Asteroiden sinken und dort mehrfach Bodenproben einsammeln. Ende 2019 macht sich die Sonde dann wieder auf den Weg in Richtung Erde, um dort 2020 mit Proben des Asteroiden anzukommen.

Über die Mission Hayabusa2 und MASCOT

Hayabusa2 ist eine Weltraummission der japanischen Raumfahrtagentur JAXA (Japan Aerospace Exploration Agency) zum erdnahen Asteroiden Ryugu. Der deutsch-französische Lander MASCOT an Bord von Hayabusa2 wurde vom Deutschen Zentrum für Luft- und Raumfahrt (DLR) entwickelt und gebaut in enger Kooperation mit der französischen Raumfahrtagentur CNES (Centre National d'Études Spatiales). Die wissenschaftlichen Experimente an Bord von MASCOT sind Beiträge des DLR, des Institut d'Astrophysique Spatiale und der Technischen Universität Braunschweig. Betrieb und Steuerung des MASCOT-Landers und seiner Experimente erfolgen durch das DLR mit Unterstützung der CNES und in kontinuierlichem Austausch mit der JAXA.

Das DLR-Institut für Raumfahrtsysteme in Bremen entwickelte federführend zusammen mit CNES den Lander und testete ihn. Das DLR-Institut für Faserverbundleichtbau und Adaptronik in Braunschweig war für die stabile Struktur des Landers zuständig. Das DLR Robotik und Mechatronik Zentrum in Oberpfaffenhofen entwickelte den Schwungarm, der Mascot auf dem Asteroiden hüpfen lässt. Das DLR-Institut für Planetenforschung in Berlin steuerte die Kamera MASCAM und das Radiometer MARA bei. Überwacht und betrieben wird der Asteroidenlander aus dem MASCOT-Kontrollzentrum im Nutzerzentrum für Weltraumexperimente (MUSC) am DLR-Standort Köln.

Quelle: DLR