Asteroid explorer, Hayabusa2,
reporter briefing

May 9, 2019
JAXA Hayabusa2 ProjectTopics
Regarding Hayabusa2,• Results from the Crater Search Operation(Post-SCI
• Science from the SCI collision experiment• Future operations
2019/05/09

Hayabusa2 reporter briefing

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Contents
0. Hayabusa2 and mission flow outline
1. Current status and overall schedule of the project
2. Crater Search Operation (Post-SCI) results
3. SCI collision experiment science
4. Future operation plans
5. Science related topics
6. Other topics
7. Future plansReference material
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Hayabusa2 reporter briefing

3Overview of Hayabusa2
Objective
We will explore and sample the C-type asteroid Ryugu, which is a more primitive type than the S-type asteroid
Itokawa that Hayabusa explored, and elucidate interactions between minerals, water, and organic matter in theprimitive solar system. By doing so, we will learn about the origin and evolution of Earth, the oceans, and life, andmaintain and develop the technologies for deep-space return exploration (as demonstrated with Hayabusa), a field
in which Japan leads the world.
Expected results and effects
By exploring a C-type asteroid, which is rich in water and organic materials, we will clarify interactions between
the building blocks of Earth and the evolution of its oceans and life, thereby developing solar system science.
 Japan will further its worldwide lead in this field by taking on the new challenge of obtaining samples from acrater produced by an impacting device.
We will establish stable technologies for return exploration of solar-system bodies.
Features:World’s first sample return mission to a C-type asteroid.
World’s first attempt at a rendezvous with an asteroid and performance of observation before and after projectile
impact from an impactor.
Comparison with results from Hayabusa will allow deeper understanding of the distribution, origins, andevolution of materials in the solar system.
International positioningJapan is a leader in the field of primitive body exploration, and visiting a type-C asteroid marks a newaccomplishment.
This mission builds on the originality and successes of the Hayabusa mission. In addition to developing planetaryscience and solar system exploration technologies in Japan, this mission develops new frontiers in exploration ofprimitive heavenly bodies.
NASA too is conducting an asteroid sample return mission, OSIRIS-REx (launch: 2016; asteroid arrival: 2018;
Earth return: 2023). We will exchange samples and otherwise promote scientific exchange, and expect further
scientific findings through comparison and investigation of the results from both missions.

2019/05/09

Hayabusa2 reporter briefing(Illustration: Akihiro Ikeshita)

Hayabusa 2 primary specifications
Mass
Approx. 609 kg
Launch3 Dec 2014
MissionAsteroid return
Arrival27 June 2018
Earth return2020
Stay at asteroid Approx. 18 months
Target body
Near-Earth asteroid Ryugu
Primary instruments
Sampling mechanism, re-entry capsule, optical cameras, laser
range-finder, scientific observation equipment (near-infrared,
thermal infrared), impactor, miniature rovers.

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Mission Flow
Launch3 Dec 2014

Earth returnlate 2020

Sampleanalysis
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Earth swing-by
3 Dec 2015

Arrival at asteroid
June 27, 2018
Examine the asteroid
by remote sensing
observations. Next,
release a small lander
and rover and also
obtain samples fromthe surface.

Depart asteroid
Nov–Dec 2019

Releaseimpactor
Create artificial
craterAfter confirming safety,
touchdown within the craterand obtain subsurface samples
Hayabusa2 reporter briefing

Use an impactor to create an
artificial crater on the asteroid’s
surface(Illustrations: Akihiro Ikeshita)51. Current project status & schedule overview
Current
status7

Schedule
overview
Event– From April 23 ~ 25, the Crater Search Operation (Post-SCI) (CRA2) was performed
to investigate the crater generated during the collision experiment.
– Future operation plans based on the results of the SCI operation.
– From May 14 ~ 16 a descent operation will be conducted to deploy a target marker.
2015
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Hayabusa2 reporter briefing

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2. Crater Search Operation (Post-SCI) results
Crater Search Operation (Post-SCI) (CRA2)• Detailed data was acquired about the area where the Small
Carry-on Impactor (SCI) appears to have collided.
• Operation4/2325• Descent began 4/24 at 16:42 JSTonboard time• Reached a minimum altitude of approximately 1.7km on 4/25
at 11:16am JSTonboard time).
• Succeeded in imaging the crater → details in Chap.3• The SCI generated the crater almost exactly on target.
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Hayabusa2 reporter briefing

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2. Crater Search Operation (Post-SCI) results
CRA2 location

NoteThe observation area for CRA2 is the same as the area observed in advance of the SCI operation by CRA1.

Image 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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2. Crater Search Operation (Post-SCI) results
Crater Search Operation (Post-SCI) (CRA2) results"))* 
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The observation wereconducted while maintaining
an altitude of about 1.7km.
• Detailed data was acquired on
the area thought to be where
the crater was generated by
the SCI↓
Observations were made asplanned.

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.Image credit0JAXA/- )*"%&')%$)#()(#(&"$$
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Hayabusa2 reporter briefing

92. Crater Search Operation (Post-SCI) results
Collision location image taken prior to collision

Impact target point(6.00, 303.00)
S01(5.13, 303.39)

Near collision pointCollision
target point

L12 L12
Craterarea
 generation

S01
20m

NotePositions shown are approximate. The exact
location of the SCI impact is being analysed.
(Image 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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3. SCI collision experiment science: ejecta• Image of collision ejecta with the DCAM3digital camera
About 14 seconds before the SCI operation

About 3 seconds after the SCI operation

High gain, short exposure mode

High gain, short exposure mode
(Image credit: JAXA, Kobe University, Chiba Institute of Technology, Kochi University, University of Occupational and Environmental Health)2019/05/09

Hayabusa2 reporter briefing11

3. SCI collision experiment science: crater• Terrain change before and after the SCI collision
Before the SCI collision 2019/03/22

After the SCI 2019/04/25(Image 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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3. SCI collision experiment science: crater• Terrain change before and after
the SCI collision.
(Blink image before and after
collision for comparison)– Crater formation– Boulder evacuated and moved– Boulders dispersed around theregion(Image 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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3. SCI collision experiment science: sub-craters(Blink image before and after collision for comparison)•

Changes can be seen before and after
the collision in regions other than the
SCI crater.
– Formation of cratered terrain(upper circle on right-hand figure)– Movement of boulders lower
circle•

These changes are distributed along an
arc on the surface of the asteroid.

(Image 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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3. SCI collision experiment science: sub-craters
These craters were probably generated by SCI fragments. SCI fragment cone

SCI
Collision
point

projected onto theasteroid surface

SCI detonation position

SCI fragment cone

Sub-cratercandidate

S01
Ryugu shape model  
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Hayabusa2 reporter briefing

JAXA/University of Aizu/
Kobe University

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Reference

3. SCI collision experiment science: sub-craters
 Test with SCI small modeldiameter 5cmImplemented in 2009
Collision speed 2.1km/s

Test with SCI ½ scale modeldiameter 15cm)
Implemented in 2011Collision with a paper and veneer target.
Distribution of debris examined.

      
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Hayabusa2 reporter briefing  
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3. SCI collision experiment science: summary••

The SCI impact in the vicinity of the S01 area (distance about 25m) succeeded.
Impact ejecta were seen for several hundred seconds (via DCAM3 images).

•

A nearly circular change in topology over 10m in diameter was identified (via ONC-T
images).

– Low gravity increases the duration (by about 300 times longer than that on the ground).
– Strong suggestion of ejecta deposited in the S01 area.

–
–
–
–

•

Evacuated crater shape: 2 – 3m depth. Side wall surface looks smooth.
Boulder movement (evacuation) can be seen as well as associated terrain change.
Changes to surface reflectivity (darkening) can also be observed (verification required).
An estimate of the surface strength and surface age of Ryugu can be estimated from the crater diameter(next page).

Along an oval circumference*, the formation of secondary craters and boulder movement
can be seen.
– Presumed due to the collision of debris scattered forward from the SCI.

*More precisely: with the SCI detonation point as a vertex, this is the line of intersection between the debris
cone and Ryugu’s surface.
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3. SCI collision experiment science:
surface strength
Sugita et al. 2019, Science
The surface age of Ryugu that is estimated from the density of craters(number per unit area) strongly depends on surface strength.
No strengthà about 9 million years old9 Ma
With strength (2 atm) à about 1.6 million years old160 Ma
⇒ Strength can be estimated from the SCI collision test results

No strength

Same
speed

2019/05/09

Same mass

Strength

Same
speed

Same mass

Hayabusa2 reporter briefing18

3. SCI collision experiment science: perspective
If you know the strength of the surface…

– Constrain the shape formation process and origin of
Ryugu.
– Transport of material from the asteroid belt à Earth••

Meteorites / interplanetary dust formation processes
Meteorite disintegration process in the atmosphere•

Crater science•

Expectations for sub-surface sample acquisition– Empirical analysis of microgravity collisions– Establish scaling laws to connect ground experimental
results with astronomical collision processes.

animation

•– Asteroid surface mixing processes– Space weathering processes on C-type asteroid

SfM shape model from Watanabe et al. 2019, Science
Image creditJAXA/ University of Aizu / Kobe University.
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4. Future operation plans Operation plan concept from May ~ July
• Currently, Ryugu is approaching the Sun (perihelion in September). It will only be possible to land on
Ryugu until the start of July, after which the asteroid temperature will rise.
• By the beginning of June, the crater and state of the spacecraft will have been examined and it willthen be decided if a second touchdown operation will be performed between the end of June and startof July.
• If touchdown is performed, the target point will be selected from the area where there is ejectedmaterial from the artificial crater.
• The name of this operation will be “pinpoint touchdown” (PPTD).
• 2 or 3 low altitude descent observations will be performed in May and June before the PPTD
operation. While performing detailed topographical observations of the landing point candidates, atarget marker will be dropped as a guide for landing in this region.
• 1st 5/145/16
Operation namePPTD-TM1described later
• 2nd End of May
Operation nameDecided later• 3rd First half of June
Operation name: Decided later
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4. Future operation plans
Currently identified touchdown candidate points
L14 area
C01 area

S01 area
Near SCI
collisionpoint• CO1 is the area where the artificial crater was
generated.
• S01 is that area that was observed in March thisyear as a backup candidate site for TD2.
• L14 is a TD2 candidate area in a newly evacuatedarea near the SCI collision point.
• The yellow circles denote all the currently
identified touchdown candidate points (all are 6 ~12 m in diameter)

During the PPTD-TM1 operation, lowaltitude observations will be made of the S01
area and a target marker will be dropped.
(image 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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4. Future operation plans
Outlook for future touchdown operations
The decision to perform a touchdown operation will be based on consideration of thefollowing points:
 Scientific & engineering value of the 2nd touchdown• Is the risk during the touchdown operation small enough and the expected value ofthe second touchdown high enough?
• Is It highly likely that artificial crater ejecta can be collected?
 Feasibility of the touchdown operation• Can the terrain information necessary for touchdown be obtained and a sufficiently
safe touchdown sequence be designed?
• Can the target marker be dropped close to the touchdown target point?
 Spacecraft condition• During the 1st touchdown, the optical system became cloudy due to dust. Can we
confirm that a second touchdown can be performed without any problems given thissituation?
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4. Future operation plans
PPTD-TM1 operation

altitudeHome position return

Home position

20km

Deceleration
ΔV

5km

Targetmarkerseparation~35m

Rising ΔV

5/15~12:302019/05/09

5/15~23:00

5/16~11:30
Hayabusa2 reporter briefing

time
5/17

(JST)

image credit: JAXA
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4. Future operation plans

Low altitude sequence during PPTD-TM1 operation  !   !    "       &   &       !       #  !       !  !     

 !      !   " !        !    !   %    &  !  
 !           ! 

35m

 





 !   !    !        ! "    $     !    !   %           !      



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  
   

! !   "      !   " !   !  ! "   !          $  !        !    "      !

10m

     0m
'image credit: JAXA(

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5. Science related topics(1) The image of Ryugu was used for the coverof the April 19, 2019 issue of Science Magazine,
which included research papers on results fromthe Hayabusa2 mission. Right figure(2) A paper on Ryugu was also published in the
Astrophysical Journal Letters see next pageFirst author: Masatoshi Hirabayashi Auburn
University
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Hayabusa2 reporter briefing

Science Magazine
April 19, 2019 issue25

5. Science related topics
Article published in the Astrophysical Journal Letters• Hirabayashi, M., and 28 colleagues, “The western bulge of
162173 Ryugu formed as a result of a rotationally driven
deformation process,” The Astrophysical Journal Letters,
2019, 874, 1, doi:10.3847/2041-8213/ab0e8bhttps://iopscience.iop.org/article/10.3847/2041-8213/ab0e8bDate published2019/3/26• The shape of Ryugu differs from east to west, with theshape of the western bulge (near 90 degrees W inlongitude) being potentially due to structural changes (suchas a landslide or internal structural alterations) in the pastwhen Ryugu was rotating at a higher speed.
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Hayabusa2 reporter briefing

Hirabayashi et al, 2019 
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6. Other topics
Ryugu shape model release• Presenting Ryugu’s precise 3D model• This will be released in a range of formats, incooperation of the Japan Planetarium
Association (JPA).
• While originally designed for JPA members,
the files are accessible to anyone. Please dotake a look.
• Access here: https://planetarium.jp/ryugu/
CG created from published Ryugu
3D data from JPA Web
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7. Future plans Operation plans• May 1416 Descent and target marker separation operation
PPTD-TM1
 Press and media briefings• May 22 15:00  Press briefing session @ Tokyo office

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Hayabusa2 reporter briefing28Reference

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SCI collision area captured from the home position
with the ONC-T
Before SCI collision

After SCI collision

2019-03-21 13:03JST altitude 14 km

2019-04-17 21:04JST, altitude 19 km

After SCI collision

(image 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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SCI collision area captured from the home position
with the ONC-T
Before SCI collision

After SCI collision

After SCI collision

S01

100 m

100 m

2019-03-21 13:03JST altitude 14 km

2019-04-17 21:04JST, altitude 19 km

100 m(image 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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