Asteroid explorer, Hayabusa2,
reporter briefing

March 18, 2019
JAXA Hayabusa2 ProjectTopics
Regarding Hayabusa2:
Descent operations
Small Carry-on Impactor(SCI) operation
Deployable camera(DCAM3)
Impactor experiment science
2019/03/18

Hayabusa2 reporter briefing

2

Contents
0. Hayabusa2 and mission flow outline
1. Current status and overall schedule of the project
2. Descent operation
3. Small Carry-on Impactor (SCI) operation
4. Deployable camera
5. Impactor experiment science
6. Other topics
7. Future plansReference material•

2019/03/18

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.

2019/03/18

Hayabusa2 reporter briefing

Hayabusa 2 primary specifications(Illustration: Akihiro Ikeshita)
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.

4

Mission Flow
Launch3 Dec 2014

Earth returnlate 2020

Sampleanalysis
2019/03/18

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
status9– Descent observation operation (DO-S01) was performed between March 6 – 8, andobservations of the S01 area (touchdown candidate site) were made from an altitudeof 22m.
– In preparation for the Small Carry-on Impactor operation, “Crater Search Operation(Pre-SCI)” (CRA1) will be performed from March 20 to 22.
2015

Schedule
overview

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Hayabusa2 reporter briefing

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2. Descent operation
Descent observation operation(DO-S01)• Investigate the S01 area at low altitudes• Operation scheduleMarch 68(performed)• Descent down to 22m
Crater search operation(Pre-SCI)(CRA1)• Get detailed data on the area to generate a crater with the Small
Carry-on Impactor(SCI)prior to that experiment• Operation schedule: March 2022• Lowest altitude approximately 1.7km
2019/03/18

Hayabusa2 reporter briefing7

2. Descent operation
Location of S01 and CRA1

Note: The observation area of CRA1 is the same as the crater generation area using the Small Carry-on Impactor.

(Image creditJAXA)

2019/03/05

Hayabusa2 reporter briefing8

2. Descent operation
Results of the Descent Observation Operation (DO-S01)
ResultsDetailed data of S01 was successfully
obtained and is currently being analyzed.
The ONC-W1 received roughly half thelight intensity and the image was stained.
Although no major abnormalities on theother instruments were seen, they are
currently being checked.
We confirmed all instruments can be usedwithout any issues for operations otherthan touchdown, including the ONC-W1.
(Image creditJAXA)
2019/03/18

11:00

Hayabusa2 reporter briefing92. Descent operation
First release

Images taken of the S01 area
Scale

Images from the DO-S01 operation
CameraONC-T
Image time(JST)
March 8, 2019 12:24
Image altitude35m(Image creditJAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University,
Chiba Institute of Technology, Meiji University, University of Aizu, AIST. )2019/03/18

Hayabusa2 reporter briefing10

2. Descent operation
Plan for the Crater Search Operation (pre-SCI)(CRA1)
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(Image credit*JAXA)
2019/03/18

Hayabusa2 reporter briefing11

3. Small Carry-on Impactor operation
Outline and purpose of operation• The impact device generates an artificial crater on the surface of Ryugu.
• Collect information about the interior of the asteroid by examining the crater
formation and generated crater.
• At a later date, touchdown at or around the generated crater and try to collectsubsurface material. However, if the condition of the surface of Ryugu isdangerous for touchdown, the touchdown will not be attempted.

Operation schedule• SCI operationApril 46• Crater generation date & time April 5 at 11:36onboard time, JST.
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Hayabusa2 reporter briefing12

3. Small Carry-on Impactor operation
SCISmall Carry-on Impactor
u Shape: conical (diameter 300mmweight 14kg, explosive: ~9.5kg)
u Liner (impactor part): Pure copper (2kg), thickness ~5mm

u Explosive: HMX based PBX (Plastic bonded explosive)!
u Explosive
accelerates liner to 2 km/s in about 1/1000 seconds.
!
!
!

          
2019/03/18

(Image creditJAXA)

Hayabusa2 reporter briefing   

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13

3. Small Carry-on Impactor operation
Test of the Small Carry-on Impactor experiment (SCI)October 1727, 2011

 Experiment location (moment of
ignition)
The projectile is launched towards
the lower left from an enclosed
ignition point (center right)
surrounded by a 3m high concrete
wall.
(Image creditJAXA)

2019/03/18

 Projectile shape
Observed flight speed is 2km/s.
The outer diameter is about
135mm and weight 2kg. The
shape is like a helmet.

 Target pierced
The projectile pierced the target. The markof a single passage is pierced in the target(4m x 4m) at 100m from the launch point.

 Moment of impact
The moment when the projectile collided with the earthand sand target at 100m from the launch point.
Hayabusa2 reporter briefing

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3. Small Carry-on Impactor operation
SCI operation sequence• SCI separation height is 500m
• From SCI separation to
explosion: about 40 minutes• Return to home position: about
2 weeks( &  
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2019/03/18

Hayabusa2 reporter briefing,  ! 
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(Image credit-JAXA)
15

3. Small Carry-on Impactor operation
How to avoid debris and ejecta
Explosion(a)(b)(a) High speed debris(b) High speed ejecta(c) Slow speed ejecta

Ryugu

(c)

(Image credit$JAXA)
2019/03/18

Hayabusa2 reporter briefing!            
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3. Small Carry-on Impactor operation
Selection of impact target point and reason for choice

Impact target point(6.00, 303.00)

Constraint

S01(5.13, 303.39)

Target point at a subearth latitude (~6∘N during the SCI impact (predicted collisionarea has a radius of about 200m = latitude / longitude 30 ∘ in 3σ.

Selection criteria for target points

1st priority Area where a generated crater can be foundL12

2nd priority Area which is suitable for landing→Flat areas with sand layer are desirable.
Collision target point latitude and longitude (6.00 ∘, 303.00 ∘)Flat areas are scattered around the vicinity of the flat region L12 (where the next
touchdown candidate, S01 is located).
Possibility to collect a sample from areas other than TD1 (Horai Fossa and the eastern
hemisphere).
This is a geological area very similar to TD1 and the depth distribution of material andstructure can be discussed by comparing with the TD1 sample with excavated sample.

2019/03/18

Hayabusa2 reporter briefing

Captured by the ONC-T, hoveringfor MASCOT deployment(approximately 3km altitude)(Image creditJAXA, University of Tokyo, et. al.)17

3. Small Carry-on Impactor operation
Altitude

Descent
0.4m/sDescent
0.1m/sSCI
separation

DCAM
separation

Horizontal
retreat

HP:20km

SCI
operation

HP return phase

HP

Vertical retreat(HP: home position)

V = -0.4m/s
deceleration

500m

LIDAR

5km

Time Onboard time (JST)Ground time

2019/03/18

4/5
10:56
11:13

4/5
11:14
11:31

4/5
11:36
11:53

Hayabusa2 reporter briefing

About 2 weeks later(Image creditJAXA)

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4. Deployable camera
Outline of the deployable camera (DCAM3)• Deployable camera has a cylindrical Φ80 mm  78 mm
shape, excluding the protruding lens and antenna.
• There are two built-in cameras; one analog camera that cantransmit images in low resolution but in real time, and one
digital camera for digital communication of high resolution
images.
• There is also an analog and a digital transmitting antenna
for sending images.
• The battery enables imaging and wireless datatransmission for up to 3 hours (depending on conditions).
• Images can be transmitted to the mothership wirelessly
even at distances of 10km or more.
• A small monitor camera (MCAM) is mounted on theseparation mechanism to try and capture images of how
DCAM3 separates and leaves.
2019/03/18

DCAM3 = Deployable Camera 3
Successor to DCAM 1 and 2, mounted on
the solar sail IKAROS
Analog imaging
transmission antenna

Analog camera optics system
Digitalimagingtransmission
antenna

Digital camera
optics system

Hayabusa2 reporter briefingSeparation
mechanism(Image creditJAXA)
19

4. Deployable camera
Outline of observations from deployable camera(DCAM3)• Observe the impact from about 1km distance:- Ryugu- Scattered material generated during the collision- High speed debris (digital only- Low speed dust (digital only- SCI main body before explosion (digital only)• Analog system: color, viewing angle 71ºx53º,
720x526 pixels, resolution about 10m.
Digital system: Monochrome, viewing angle
74ºx74º, 2000x2000 pixel, resolution about 1m.
• Analog system can send data to the mother shipin real time. Digital system is delayed before
sending.

Near field(Digital system)

Far field(Digital system)

Sunabout  (Ogawa et al., Space Sci. Rev. 208, 125-142, 2017)

SCI

Camera
viewing
direction

DCAM3

about
 1 km





(Radius~ 500m)mother ship(Image creditKobe Univ.)

2019/03/18

Hayabusa2 reporter briefing20

5. Impactor Experiment Science

To understand the repeated collisional growth and destruction of celestial body evolution• What kind of impact crater can / cannot form on the surface of Ryugu?
–

Observation of the crater formation process and measurements of the formed crater size and shape.
• Construction of a impact physics model (scaling laws) based on the impact experiment in real asteroid material andenvironment.
• Construction of scaling rules for Ryugu’s collisional history on the surface and surface age estimation (crater chronology)
Scaling law: a universal equation connecting impact conditions andthe properties of the formed crater.

• What’s going on below Ryugu’s surface?
–

Exposure and collection of subsurface material via crater formation → Assessment of the impact of space weathering andsurface flow.

–

In-situ observation of ejecta motion → Estimate subsurface conditions (porosity, particle size distribution etc.)• Does Ryugu’s surface move easily?
–

principal role of DCAM3

Measurement of terrain changes caused by the impact → Understand the effect of impact vibrations, the presence of few small
craters.

• In case we hit a boulder…
–
2019/03/18

Crater on boulder measurement or measurement of fragments from boulder destruction → Estimate strength of asteroid
material
Hayabusa2 reporter briefing21

5. Impactor Experiment Science

Expected crater size
Classification

Subdivision

Crater diameterEjectordeposited layer
diameterApplied scaling law-

Strength regimeMonolithic:>1.5m

Granularlayer:
Particle size
1mm-1.5m

Fine-grained
layer:
Particle size
<1mm

2019/03/18

granular layer

Strength layer
Porosity <40%

70 cm – 10 m

Boulder field
Particle size:
15cm-1.5m< 15 cm – 1 m-

Strength regime

Pebble layer
Particle size:
5-15cm2 – 10 m

4 m – > 20m

Gravity regime

Coarse-grainedlayerParticle size:
1mm- 5cm

2 - > 10 m

4 m - > 20 m

Gravity regime

Porosity 40-45%

1 – 10 m

2 m - > 20 m

Gravitystrength
regimePorosity 45-75%

30 cm – 1m

60 cm - 2 m ?

Gravitystrength
regimePorosity >75%

< 40 cm-

Gravity + strength
regimesingle block

1m

1m

15cm-1.5m 5cm-15cm 1mm-5cm
boulder field pebble layer coarse-grained layer

cohesivestrength layer

fine-grained layer

40-45%
porouslayer

Hayabusa2 reporter briefing

1m

45-70%
highly porous
layer

>70%
fluffylayer

Arakawa, M., Wada, K., Saiki, T. et al. Space Sci Rev (2017) 208: 187.
https://doi.org/10.1007/s11214-016-0290-z

 Distinct ejecta layer deposited around crater.

 The scaling law applied changes depending onwhether the target’s strength or gravity dominates duringcrater formation.

22

5. Impactor Experiment Science

Crater searchbasically, search by eye• DCAM3 imaging → estimate impact position•(a) mosaic

C13

C11

Comparison with pre/post low altitude ONC & TIR imaging(CRA1,2) → impact position, crater identification.

C07

•
•

•

ONC-T resolution17cm/pix altitude 1.7km•

TIR resolution1.7m/pix altitude 1.7km

Images of SCI separation with ONC-W1 etc. → SCI
separation confirmation, explosion location estimation.
In addition, dust observations after SCI impact with TIR and
LIDAR → Collision confirmation

2019/03/18

Hayabusa2 reporter briefing

C08

C04

– Low altitude image scan of predicted impact area two weeks
prior and three weeks after impact.

C17

C10

M01
C06

M02

C05

2 (267 m)

C09

C03

3 (400 m)

C12

From crater exploratory training(ONC-T image mosaic(Image creditJAXA)
23

6. Other topics
Overseas presentations
At the 50th Lunar & Planetary Science Conference (LPSC) –a research meeting in
the USA– there will be a special session of Hayabusa2 and a briefing session for
local media.
DatePlaceMarch1822The Woodland, Texas, US.
Special session for Hayabusa2: 13 oral (3/19), 28 posters (3/20)
There are also several presentations related to Hayabusa2 in other sessions.
Local media briefing session is scheduled to be held on March 19, 11:45  12:30(local time). The content will cover an explanation of touchdown and science
results.
2019/03/18

Hayabusa2 reporter briefing24

7. Future plans
Operation plans• March 2022Crater Search Operation (Pre-SCI) CRA1
• April 46Small Carry-on Impactor operationSCI
Press and media briefings• April 2 14:00 Regular press briefing session JAXA Tokyo
office• April 5 8:30 Press center opens JAXA Sagamihara Campus
2019/03/18

Hayabusa2 reporter briefing

25Reference

2019/03/18

Hayabusa2 reporter briefing

26

Crater excavation depth• Depth of the excavation region is about 1/10 of the crater diameter.

Pre- impact

Crater formation

Excavation region
Rt

Excavation model

An example of numerical simulations of crater formation impacts on a
granular layer (sand). Color corresponds to the depth prior to collision.
(Provided by Koji Wada)(Image creditChiba Institute of Technology)
2019/03/18

Hayabusa2 reporter briefing27

Ejector seen during collision experiments
Large blocks

Granular (sand) layer

Basalt: P=0%

strength

Glass beads (100µm): P=40%

Porosity

Mortar: P=20%

Impact speed: 4km/s
Φ7mm, nylon

2019/03/18

Perlite (3mm): P=80%
Impact speed: 90 m/s
Φ3mm, aluminum

Hayabusa2 reporter briefing

Powder layer

Plaster: P=50%

Strength

P: PorosityφProjectile diameter

Porous silica dust:
P=65%
Impact speed: 3.2km/s
Φ2mm, nylon

Courtesy of Kobe University
Arakawa Laboratory28

Ejector (curtain) size and evolution forecast
Impact on sand (gravity regime)

Impact on bedrock (strength regime)

Arakawa, M., Wada, K., Saiki, T. et al. Space Sci Rev (2017) 208: 187.
https://doi.org/10.1007/s11214-016-0290-z

2019/03/18

Hayabusa2 reporter briefing

29Ejector deposit layer thickness distribution(for impact on sand)
R: Crater radius
h: Ejecta deposit thickness
x: Distance from impact point crater centere.g. when R = 5.1mh = 10cm at x = 9m

(Image creditKobe University)
2019/03/18

Hayabusa2 reporter briefing

30

Ryugu subsurface structure (metamorphic
grade) prediction
If the surface is static…
Metamorphic cause

Layer thickness (depth)Space weathering by solar wind

Several microns

Thermal alteration by solar heating

10 cm

Space weathering by galactic cosmic rays

~1m

No metamorphosis (fresh)>1m

If the surface flows (mixing), doesn't the degree of metamorphism
depend on this depth?
2019/03/18

Hayabusa2 reporter briefing31