12. October 2018

Nu­mer­ous boul­ders, many rocks, no dust: MAS­COT's zigzag course across the as­ter­oid Ryugu

MASCOT's approach to Ryugu and its path across the surface
MAS­COT's ap­proach to Ryugu and its path across the sur­face
Image 1/5, Credit: JAXA/U Tokyo/Kochi U/Rikkyo U/Nagoya U/ Chiba Inst Tech/Meiji U/U Aizu/AIST.

MASCOT's approach to Ryugu and its path across the surface

Af­ter MAS­COT had sep­a­rat­ed from its moth­er­craft, Hayabusa2's ONC (Op­ti­cal Nav­i­ga­tion Cam­era) record­ing sys­tem, with its three cam­eras, be­gan fol­low­ing MAS­COT’s de­scent to the as­ter­oid Ryugu from a height of 51 me­tres. The im­age sec­tion is ori­ent­ed to the north, and the area shown is lo­cat­ed at ap­prox­i­mate­ly 300 de­grees east and 30 de­grees south. Hayabusa2’s shad­ow can be seen on the low­er right. At the time of the sep­a­ra­tion, it was about noon on Ryugu and the Sun was be­hind Hayabusa2 – the shad­ow is about six by 4.5 me­tres.The points in­di­cate the times at which Hayabusa2 ac­quired im­ages of MAS­COT. The times are in UTC (Co­or­di­nat­ed Uni­ver­sal Time, CEST mi­nus two hours), the first im­age was ac­quired at 01:59 and 40 sec­onds UTC (03:59:40 CEST). The yel­low line in­di­cates the lo­ca­tions at which MAS­COT was still de­scend­ing to­wards Ryugu and where it could be iden­ti­fied in the ONC pho­tos. The blue line be­low the yel­low line is the pro­jec­tion of these po­si­tions on­to the as­ter­oid sur­face – so this shows MAS­COT's flight route was rather straight, and the lan­der touched down on a large edgy block at around 02:23 and 24 sec­onds UTC. From there, the as­ter­oid lan­der hopped along the curved hor­i­zon­tal line to­wards the east-north­east and was then re­peat­ed­ly im­aged by the ONC. At around 02:14 and 04 min­utes UTC MAS­COT came to rest at its first lo­ca­tion on the as­ter­oid. Mean­while, Hayabusa2 as­cend­ed to a high­er ob­ser­va­tion po­si­tion over Ryugu, mak­ing it more dif­fi­cult to iden­ti­fy MAS­COT in the im­ages due to the low­er im­age res­o­lu­tion. On the sec­ond as­ter­oid day, MAS­COT's mo­bil­i­ty mech­a­nism was ac­ti­vat­ed. An­oth­er im­age will show the lan­der on 4 Oc­to­ber at 00:55 and nine sec­onds UTC.
MASCOT image of Ryugu's south polar region
MAS­COT im­age of Ryugu's south po­lar re­gion short­ly af­ter sep­a­ra­tion
Image 2/5, Credit: JAXA/U Tokyo/Kochi U/Rikkyo U/Nagoya U/ Chiba Inst Tech/Meiji U/U Aizu/AIST (links); MASCOT/DLR/JAXA (rechts).

MASCOT image of Ryugu's south polar region shortly after separation

The im­age on the right shows the first im­age ac­quired by the DLR-de­vel­oped MAS­CAM cam­era sys­tem dur­ing Hayabusa2's de­scent, short­ly af­ter sep­a­ra­tion from the land­ing mod­ule at a height of 51 me­tres with a view­ing di­rec­tion to­wards the south pole. The area cap­tured by MAS­CAM is marked as an open tri­an­gle in the overview im­age on the left, which was tak­en with the wide-an­gle cam­era of the ONC (Op­ti­cal Nav­i­ga­tion Cam­era) sys­tem of the Hayabusa2 space­craft. Par­tic­u­lar­ly strik­ing is a huge block near the South Pole, which stands out clear­ly above the hori­zon line and which the sci­en­tists named 'South Po­lar Rock'. It may be sev­er­al dozen, and even up to 100 me­tres tall.
MASCOT image pointing east while descending on Ryugu
MAS­COT im­age point­ing east while de­scend­ing on Ryugu
Image 3/5, Credit: JAXA/U Tokyo/Kochi U/Rikkyo U/Nagoya U/ Chiba Inst Tech/Meiji U/U Aizu/AIST (links); MASCOT/DLR/JAXA (rechts).

MASCOT image pointing east while descending on Ryugu

The sec­ond im­age of the DLR-de­vel­oped MAS­CAM cam­era is di­rect­ed oblique­ly down­ward on the as­ter­oid Ryugu and cov­ers ar­eas east of the de­scent route. The area cov­ered by MAS­CAM is marked as an open trape­zoid in the overview im­age of the wide-an­gle cam­era of the ONC (Op­ti­cal Nav­i­ga­tion Cam­era) sys­tem of Hayabusa2. Com­pared with the first im­age, it is clear that MAS­COT moved tur­bu­lent­ly to­wards Ryugu, as ex­pect­ed, thus per­form­ing turns and rollovers.Both im­ages show a huge boul­der, which oc­cu­pies the east­ern (right) edge of the im­age in the MAS­CAM im­age and is sev­er­al tens of me­tres in length. On the bot­tom left is MAS­COT's shad­ow, which the Sun be­hind the land­ing probe is pro­ject­ing on­to the as­ter­oid sur­face: MAS­COT is 30 cen­time­tres long. Ryugu is a body with no at­mo­sphere, so the out­lines of MAS­COT (right) and Hayabusa2 (left) are sharp in the shad­ows pro­ject­ed on­to the as­ter­oid sur­face.
DLR's MASCAM camera photographed the area of the descent route with a backward-looking view.
MAS­COT's fourth im­age dur­ing the de­scent to Ryugu
Image 4/5, Credit: JAXA/U Tokyo/Kochi U/Rikkyo U/Nagoya U/ Chiba Inst Tech/Meiji U/U Aizu/AIST (left); MASCOT/DLR/JAXA (right)

MASCOT's fourth image during the descent to Ryugu

Be­fore the first con­tact with a large rock on Ryugu, DLR's MAS­CAM cam­era pho­tographed the area of the de­scent route with a back­ward-look­ing view. The area cov­ered by MAS­CAM is marked as an open trape­zoid in the overview im­age of the wide-an­gle cam­era of Hayabusa2's ONC (Op­ti­cal Nav­i­ga­tion Cam­era) sys­tem.
The landing site environment
Af­ter first con­tact with the sur­face: the land­ing site en­vi­ron­ment
Image 5/5, Credit: JAXA/U Tokyo/Kochi U/Rikkyo U/Nagoya U/ Chiba Inst Tech/Meiji U/U Aizu/AIST (links); MASCOT/DLR/JAXA (rechts).

After first contact with the surface: the landing site environment

The fifth im­age ac­quired by the DLR-de­vel­oped MAS­CAM cam­era sys­tem (right) was tak­en short­ly af­ter the first con­tact with the ground, just a few me­tres above the sur­face of Ryugu. The line of sight is di­rect­ed to the north­west and is lo­cat­ed be­tween the two white bound­ary lines in the overview im­age (left) ac­quired by the wide-an­gle cam­era of the ONC (Op­ti­cal Nav­i­ga­tion Cam­era) sys­tem on board Hayabusa2.Just as in the im­ages from high­er al­ti­tudes, no fine ma­te­ri­al, known as re­golith, can be seen, even in the im­me­di­ate vicin­i­ty of the sur­face. Re­golith is formed on at­mo­sphere-less bod­ies due to their per­ma­nent ex­po­sure to high-en­er­gy par­ti­cles from space or mi­crom­e­te­orites due to the weath­er­ing of coars­er ma­te­ri­al in­to dust. In­stead, the area is ex­treme­ly rugged and full of sharp blocks. The land­ing site en­vi­ron­ment is rem­i­nis­cent of the Aby­dos land­ing site of the Phi­lae lan­der, which was re­leased on Comet 67P / Churyu­mov-Gerasi­menko by the Roset­ta space­craft on 12 Novem­ber 2014.
  • The scientists were able to follow the path that MASCOT travelled on the surface of Ryugu on the basis of images and data from the mother probe Hayabusa2 and the lander.
  • Never before in the history of space has a body of the Solar System been explored in this way.
  • Focus: Space, exploration

Six minutes of free fall, a gentle impact on the asteroid and then 11 minutes of rebounding until coming to rest. That is how, in the early hours of 3 October 2018, the journey of the MASCOT asteroid lander began on Asteroid Ryugu – a land full of wonder, mystery and challenges. Some 17 hours of scientific exploration followed this first 'stroll' on the almost 900-metre diameter asteroid. The lander was commanded and controlled from the MASCOT Control Centre at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) site in Cologne in the presence of scientific teams from Germany, France and Japan. MASCOT surpassed all expectations and performed its four experiments at several locations on the asteroid. Never before in the history of spaceflight has a Solar System body been explored in this way. It has now been possible to precisely trace MASCOT’s path on Ryugu’s surface on the basis of image data from the Japanese Hayabusa2 space probe and the lander’s images and data.

"This success was possible thanks to state-of-the-art robotic technology, long-term planning and intensive international cooperation between the scientists and engineers of the three space nations Japan, France and Germany," says Hansjörg Dittus, DLR Executive Board Member for Space Research and Technology about this milestone in Solar System exploration. "We are proud of how MASCOT was able to master its way across the asteroid Ryugu over boulders and rocks and send so much data about its composition back to Earth," says DLR Chair Pascale Ehrenfreund.

MASCOT had no propulsion system and landed in free fall. Six minutes after separating from Hayabusa2, and following the end of a ballistic trajectory, the landing module made its first contact with asteroid Ryugu. On the surface, MASCOT moved through the activation of a tungsten swing arm accelerated and decelerated by a motor. This made it possible for MASCOT to be repositioned to the 'correct' side or even perform hops across the asteroid's surface. The gravitational attraction on Ryugu is just one 66,500th of the Earth's, so the little momentum provided was enough: a technological innovation for an unusual form of mobility on an asteroid surface used for the first time in the history of space travel as part of the Hayabusa2 mission.

Through a rock garden full of rough boulders and no flat surfaces

To reconstruct MASCOT's path across the surface of Ryugu, the cameras aboard the Hayabusa2 mother probe were aimed at the asteroid. The Optical Navigation Cameras (ONC) captured the lander's free fall in several images, detected its shadow on the ground during the flight phase, and finally identified MASCOT directly on the surface in several images. The pattern of the countless boulders distributed on the surface could also be seen in the direction of the respective horizon in oblique photographs of the lander's DLR MASCAM camera. The combination of this information unlocked the unique path traced by the lander.

After the first impact, MASCOT smoothly bounced off a large block, touched the ground about eight times, and then found itself in a resting position unfavourable for the measurements. After commanding and executing a specially prepared correction manoeuvre, MASCOT came to a second halt. The exact location of this second position is still being determined. There, the lander completed detailed measurements during one asteroid day and night. This was followed by a small ‘mini-move’ to provide the MicrOmega spectrometer with even better conditions for measuring the composition of the asteroid material.

Finally, MASCOT was set in motion one last time for a bigger jump. At the last location it carried out some more measurements before the third night on the asteroid began, and contact with Hayabusa2 was lost as the spaceship had moved out of line of sight. The last signal from MASCOT reached the mother probe at 21:04 CEST. The mission was over. "We were expecting less than 16 hours of battery life because of the cold night, says MASCOT project manager Tra-Mi Ho from the DLR Institute of Space Systems. "After all, we were able to operate MASCOT for more than one extra hour, even until the radio shadow began, which was a great success." During the mission, the team named MASCOT's landing site (MA-9) 'Alice's Wonderland', after the eponymous book by Lewis Carroll (1832-1898).

A true wonderland

Having reconstructed the events that took place on asteroid Ryugu, the scientists are now busy analysing the first results from the acquired data and images. "What we saw from a distance already gave us an idea of what it might look like on the surface," reports Ralf Jaumann from the DLR Institute of Planetary Research and scientific director of the MASCOT mission. "In fact, it is even crazier on the surface than expected. Everything is covered in rough blocks and strewn with boulders. How compact these blocks are and what they are composed of, we still do not know. But what was most surprising was that large accumulations of fine material are nowhere to be found – and we did not expect that. We have to investigate this in the next few weeks, because the cosmic weathering would actually have had to produce fine material," continues Jaumann.

"MASCOT has delivered exactly what we expected: an 'extension' of the space probe on the surface of Ryugu and direct measurements on site," says Tra-Mi Ho. Now there are measurements across the entire spectrum, from telescope light curves from Earth to remote sensing with Hayabusa2 through to the microscopic findings of MASCOT. "This will be of enormous importance for the characterisation of this class of asteroids," emphasises Jaumann.

Ryugu is a C-type asteroid – a carbon-rich representative of the oldest bodies of the four-and-a-half-billion year-old Solar System. It is a 'primordial' building block of planet formation, and one of 17,000 known Near-Earth asteroids.

On Earth, there are meteorites with a composition that could be similar to Ryugu's, which are found in the Murchison Range, Australia. However, Matthias Grott from the DLR Institute of Planetary Research and responsible for the radiometer experiment MARA is skeptical as to whether these meteorites are actually representative of Ryugu in terms of their physical properties: "Meteorites such as those found in Murchison are rather massive. However, our MARA data suggests the material on Ryugu is slightly more porous. The investigations are just beginning, but it is plausible to assume that small fragments of Ryugu would not survive the entry into the Earth's atmosphere intact."

About the Hayabusa2 mission and MASCOT

Hayabusa2 is a Japanese space agency (Japan Aerospace Exploration Agency; JAXA) mission to the near-Earth asteroid Ryugu. The German-French lander MASCOT on board Hayabusa2 was developed by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) and built in close cooperation with the French space agency CNES (Centre National d'Etudes Spatiales). DLR, the Institut d'Astrophysique Spatiale and the Technical University of Braunschweig have contributed the scientific experiments on board MASCOT. The MASCOT lander and its experiments are operated and controlled by DLR with support from CNES and in constant interaction with the Hayabusa2 team.

The DLR Institute of Space Systems in Bremen was responsible for developing and testing the lander together with CNES. The DLR Institute of Composite Structures and Adaptive Systems in Braunschweig was responsible for the stable structure of the lander. The DLR Robotics and Mechatronics Center in Oberpfaffenhofen developed the swing arm that allows MASCOT to hop on the asteroid. Das DLR Institute of Planetary Research in Berlin contributed the MASCAM camera and the MARA radiometer. The asteroid lander is monitored and operated from the MASCOT Control Center in the Microgravity User Support Center (MUSC) at the DLR site in Cologne.

MASCOT's 17 hours and 7 minutes on Ryugu

Time (CEST)Event
03:57:21At an altitude of 51 metres above asteroid Ryugu, MASCOT is pushed out of the Hayabusa2 supporting frame by means of a spring mechanism behind a push-off plate at about 4 centimetres per second and starts to descend to Ryugu without control of its ground station.
04:03Approximately six minutes later, MASCOT touches down on Ryugu, making contact with a block of rocks about three to four metres high. The Optical Navigation Camera (ONC) from Hayabusa2 records the process in high-resolution images. At the same time, DLR’s MASCAM acquires 20 images of the asteroid during the descent. MASCOT lands on the designated landing site MA-9 (Alice's Wonderland). It is located at about 300 degrees east and 30 degrees south.
Around 04:34
First location
After another approximately. 31 minutes and several contacts with the surface, MASCOT reaches its first resting position. It is asteroid day at the landing site and the surface measurements start.
Around 06:30At the DLR Control Centre in Cologne it is recognised that MASCOT is lying on an unfavourable side and thus cannot carry out its planned experiments. All systems and experiments are operating as intended.
Around 09:20An unscheduled command from the Earth is sent to Hayabusa2 and from there to MASCOT to activate the swing arm to turn the lander into its intended position for the experiments. The command time to Ryugu, which is about 300 million kilometres away, is about 18 minutes one way.
Around 09:52MASCOT has completed its first day-and-night cycle. The second day on Ryugu begins.
Around. 10:30
Second location
The manoeuvre has brought the desired result. MASCOT is in the right position, is now operational and automatically starts to perform its four experiments again.
Around 12:51The second daylight phase on Ryugu is slowly coming to an end, and MASCOT turns with Ryugu into its second asteroid night.
Around 17:28MASCOT’s third day on Ryugu begins.
Around 18:29
Third location
MASCOT successfully executes a mini-move. This manoeuvre was commanded by the operations team in Cologne to optimise the position of the sensors of the experiments. Further scientific investigations are carried out.
Around 20:04 Fourth locationThe last jump is commanded to MASCOT and the lander goes into the End of Life phase. Further scientific investigations are carried out.
21:04It is the end of the third day for MASCOT on Ryugu. In the meantime, more than 16 hours have passed – the lander’s expected maximum battery life. Contrary to the calculations, the battery still provides some power before the contact with MASCOT breaks off by the entry of a radio shadow and the upcoming night. Instead of 16 hours, the experiments were able to work for 17 hours and 7 minutes.

  • Falk Dambowsky
    Head of Me­dia Re­la­tions, Ed­i­tor
    Ger­man Aerospace Cen­ter (DLR)

    Cor­po­rate Com­mu­ni­ca­tions
    Telephone: +49 2203 601-3959
    Linder Höhe
    51147 Cologne
  • Tra-Mi Ho
    Ger­man Aerospace Cen­ter (DLR)
    In­sti­tute of Space Sys­tems
    Telephone: +49 421 24420-1171
    Robert-Hooke-Straße 7
    28359 Bremen
  • Christian Krause
    Ger­man Aerospace Cen­ter (DLR)

    Mi­cro­grav­i­ty Us­er Sup­port Cen­ter (MUSC), Space Op­er­a­tions and As­tro­naut Train­ing
    Telephone: +49 2203 601-3048
    Linder Höhe
    51147 Köln
  • Manuela Braun
    Ed­i­tor HR
    Ger­man Aerospace Cen­ter (DLR)
    Cen­tral HR Mar­ket­ing
    Telephone: +49 2203 601-3882
    Münchener Straße 20
    82234 Weßling
  • Prof.Dr. Ralf Jaumann
    Freie Uni­ver­sität Berlin
    In­sti­tute of Ge­o­log­i­cal Sci­ences
    Plan­e­tary Sci­ences and Re­mote Sens­ing
    Telephone: +49-172-2355864
    Malteserstr. 74-100
    12249 Berlin

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