Asteroid explorer, Hayabusa2,
reporter briefing

July 25, 2017
JAXA Hayabusa2 ProjectTopics
Regarding Hayabusa2,
 Results from the 2nd touchdown operation

2019/07/25

Hayabusa2 reporter briefing

2

Contents
0. Hayabusa2 and mission flow outline
1. Current status and overall schedule of the project
2. The 2nd touchdown operation
3. Images from the 2nd touchdown operation
4. Name of the 2nd touchdown point
5. Upcoming eventsReference material
2019/07/25

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.

2019/07/09

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

LaunchDec 3, 2014

Mission flow
Ryugu arrival

Earth swing-by
Dec 3, 2015

MINERVA-II-1 separation
Sep 21, 2018

June 27, 2018

MASCOT
separation

March 10, 2018

Ryugu departure
NovDec, 2019

completed →July 11, 2019

Impactor (SCI)

Earth return
End of 2020

Feb 22, 2019

Second touchdown

5 April, 2019

(image credit: illustrations including spacecraft by Akihiro Ikeshita, others by JAXA)

2019/07/25

Hayabusa2 reporter briefing

First touchdown5

1. Current project status & schedule overview
Current
status9– Implemented the second touchdown from July 9 – 11.
– Touchdown was carried out safely and Hayabusa2 returned to the home position at about
20 km from the center of Ryugu on July 12.
– BOX-C operation is currently underway (7/20 ~ 31). The lowest altitude will be about
5km during 7 / 25~27.
2015

Schedule
overview

123

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2019/07/25

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Hayabusa2 reporter briefing

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6

2. The 2nd touchdown operation• 2nd touchdown operation2019/7/911• Touchdown date & time 2019/7/1110:06:18 JST on-board time• Touchdown locationC01-CbTarget marker drop area
• Implemented pinpoint touchdown targeting TM-A dropped during PPTD-TM1A.
• Touchdown was detected through fluctuations in the LRF-S2 ranging value due todeformation of the sampler horn upon touchdown.
• Touchdown position accuracy is 60 cm.

2019/07/25

Hayabusa2 reporter briefing7

2. The 2nd touchdown operation
First release
Images from the small monitor
camera (CAM-H).
Images before and after touchdown(10x animation)
Capture time:
2019/7/11
Start 10:03:54 (altitude 8.5m
Finish 10:11:44altitude 150m
image interval between 0.5s~5s
creditJAXA
2019/07/25

Hayabusa2 reporter briefing8

2. The 2nd touchdown operation
PPTD-TM1 image

PPTD-TM1B image$animation%   $  %"!     
 



  "!
TM ' target marker$The left-hand image is taken prior to dropping
the TM and its position is marked. In the
middle image, the TM itself is captured.)

H is the maximum estimatedheight boulder names are nicknames, notofficial designations.

(credit&JAXA#University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University,
University of Aizu, AIST.)

2019/07/25

Hayabusa2 reporter briefing

DEM $Digital Elevation Map% near the
touchdown candidate point$credit&JAXA#University of Tokyo, Kochi University, Rikkyo University,
Nagoya University, Chiba Institute of Technology, Meiji University,
University of Aizu, AIST., Kobe University, University of Occupational andEnvironmental Health)92. The 2nd touchdown operation
Challenges for the 2nd touchdown (difference from the 1st)








Due to the optical system on the wide-angle Optical Navigation Camera ONC-W1 becoming cloudy, it was necessary to lower thestarting altitude for capturing and tracking the TM (45m to 30m)
à For the TM to be in the narrowed field of view of the ONC-W1, the accuracy of the GCP-NAV guidance had to be high.
à Managed with the accuracy of the GCP-NAV guidance resultsTMtarget marker
GCP-NAVGround Control Point
The TM brightness decreased due to the cloudiness of theNavigation) →method to find theoptical system of the ONC-W1.
position and velocity of the spacecraftà High probability of a bright spot other than the TM being misjudged
through observing features on theas the TM
asteroid surface.
à Managed by changing the TM threshold recognition time
LRFLaser Range Finder
LRF measurable distance decreased due to the cloudiness of the LRF optical system.
à Starting altitude for LRF use was lower (17m) than for the first touchdown (28m).
The descent sequence was therefore shifted to a lower altitude and it was necessary to devise safety measures for the spacecraft.
à Timeout was applied.
Distance measurement error increased due to the cloudiness of the LRF optical system.
à Since the range error was predictable, on-board software could correct the range value.
à As a result, there was no issue with the LRF range accuracy.

2019/07/25

Hayabusa2 reporter briefing10

2. The 2nd touchdown operation
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2019/07/25

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Hayabusa2 reporter briefing+image credit-JAXA,
11

2. The 2nd touchdown operation
Operation sequence (low altitude)

Altitude

GCP-NAV
Start hovering

09:40:20

After TM autonomous capture,descent acceleration ΔV



30m





2019/07/25

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Position / speed judgement at altitude 8.5m

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Position / speed judgement ataltitude 12.5m

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During descent, 6 degrees of freedom control
starts using LRF measurement values at alt. 17m

"#  ""#!# "Times shown are actual
on-board times in JST
on July 11, 2019.

10:24:41

09:48:08
!"

After detection of touchdown,
projectile is fired and spacecraft rises

10:06:18#%



 checkpoints for autonomous judgements as to whether Hayabusa2 continues to the next sequence.

Hayabusa2 reporter briefingTimecredit: JAXA
12

2. The 2nd touchdown operation
"  #   "     ! "% &       "  Gate 1 

Decision made on start of descent (@20km)

Gate 2End of confirmation on whether to continue descent %'5km)

Gate 3 End of final descent judgement %GO/NOGO judgement)

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Antenna switching

Gate 4End of confirmation on switching to LGA

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Touchdown

$

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Antenna switching

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End check of the state of the spacecraft

Gate 6

Judgement on return to home position   

Return to home position

2019/07/25

Hayabusa2 reporter briefing

13

Flight data
LIDAR/LRF
history       End waiting forconvergence

Horizontal
movement end

TD target point align end
Horizontal movement start

TD target point alignment
start(12.5m → 8.5m)

LRF range / 6 degrees of
freedom control start(30m → 12.5m)

Descent
acceleration ΔV

2. The 2nd touchdown operation

LRF representative altitudeAt 30m altitude,
get LRF altitude(Error about 6m)

image creditJAXA2. The 2nd touchdown operation
Position accuracy required for target marker capture
altitude
20 km

Estimated orbit

Asteroidrotation
2019/07/25

Autonomous control
for target marker

Target marker
captureReference orbit

Required position accuracy

Descent and hover

30 m

ZHP

altitude30
Target marker

ONC-W1 field of view
YHP

Alt.

Required position
accuracy

Remarks

30 mtan(30)*30 = 17 m

When the altitude is as planned

20 mtan(30)*20 = 11 m

When altitude is 10m lower

Hayabusa2 reporter briefing15

2. The 2nd touchdown operation

Ref. trajectory
Image measure
Est. trajectory

Reference trajectory
Image measurements
Estimated trajectorymeasurement [m]Resultdescent orbithovering altitude
Start hovering

Target marker capturecomplete. Descent re-starts.

On-board time (JST)Final position error in the horizontal direction (X, Y, direction) is estimated to be 3m or less, and the final
position error in the altitude (Z direction) is 5m or less. Target marker capture was successful.
2019/07/25

Hayabusa2 reporter briefing16

2. The 2nd touchdown operation
Countermeasures for decline in camera light reception performance & target marker tracking
The 1st touchdown in February reduced the light reception performance for the Optical
Navigation Camera (ONC-W1).
àTo capture and track the target marker safely and reliably at low altitudes, the image
processing parameters (threshold value for digitizing the image into two graduations ofblack and white) were adjusted.

Target marker image during tracking
at an altitude of 8.5m
Brightness adjusted on the groundThis step makes it possible to recognize even darker target markers, but also makes it
easier to mistake floats (such as dust) around the spacecraft, or bright rocks on the ground,
for target markers.
àUsing images acquired during past operations, the perceived motion of a target marker
versus floating and similar objects is determined, as well as other identifying parameters(such as the threshold for the time needed to capture the target marker, given the
movement between previous and subsequent frames), the size of the target area etc.
àDuring the actual mission, the target marker could be tracked stably even in thepresence of floats.
2019/07/25

Hayabusa2 reporter briefingimage creditJAXA
17

2. The 2nd touchdown operation
DBT/NBT image and target marker tracking
Final descenttarget position

Correctly controlled
to the target position

Attitude error 2.7 deg
Position error 20 cm
Equivalent box width

TM moves from the west

DBT (Differential Bright object Tracking)image actually used by the spacecraft formeasurement

NBT (Normal Bright object Tracking)similar image not used for actual measurement(reference)Video20x

2019/07/25

Hayabusa2 reporter briefingcreditJAXA
18

2. The 2nd touchdown operation

Final descent below 8.5m & touchdown of the spacecraft•

The final descent ΔV for touchdown was performed at an altitude of 8.5m.
Touchdown detection was enabled 50 seconds after the final descent ΔV. Then
touchdown occurred on the asteroid surface. Touchdown was judged by detecting thechange in distance with the LRF-S2, which measures the distance to the tip of thesampler horn that compresses slightly during touchdown.
After touchdown detection, the sequence for firing a 3rd projectile, followed by the
sampling sequences, were performed. An ascending ΔV then caused the spacecraft torise and leave the asteroid surface.
As vibration in the sampler horn is generated by the final descent ΔV, the sequence
was devised so as not to generate unnecessary sampler horn vibration.
At the time of touchdown, the ‘tail-up’ posture is adopted around the Y-axis toprevent collision of the spacecraft with the boulders and other protrusions, based on
the prediction of the spacecraft behaviour.

••

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LRF-S2 measurements before and after touchdown detection
2019/07/25

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10:05:31

Operation sequence from final descent

Hayabusa2 reporter briefing

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19

2. The 2nd touchdown operation• The LRF-S2 emits a laser towards a reflector attached to the tip of the sampler horn.
• This measures distance and intensity value.

LRF-S2

Laser direction
CAM-H

Laser light from the LRF-S2 imaged by CAM-H
At the 2nd touchdownImage creditJAXA
2019/07/25

Hayabusa2 reporter briefing20

2. The 2nd touchdown operation• During the 2nd touchdown, the tail-up posture wasadopted to prevent contact between boulders and otherobstructions with the spacecraft.
• During tail-up, in addition to the spacecraft posturealigning to the terrain surface, the posture is rotated by
10 degrees about the Y-axis of the spacecraft to givethe target attitude for touchdown.

TD target point local vertical direction [m]Final descent below 8.5m & touchdown of the spacecraft

TD target point local horizontal direction [m]Image creditJAXA
2019/07/25

Nominal touchdown attitude during operation plans

Hayabusa2 reporter briefing21

2. The 2nd touchdown operation
2nd touchdown accuracy and sampler horn ground point
2nd touchdown accuracy

Sampler horn ground point     

TM

C01-Cb(radius 3.5 m)

TM
Sampler horn ground point(radius 20 cm)(Credit: JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University, University of Aizu, AIST)

2019/07/25

   

22

2. The 2nd touchdown operation
2nd touchdown sampler horn ground point
Sampler horn ground point

CAM-H images

TM

Consistent with CAM-H image
Image creditJAXA
2019/07/25(Credit: JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University,
Chiba Institute of Technology, Meiji University, University of Aizu, AIST)    23

2. The 2nd touchdown operation
Projector temperature changeImage creditJAXA
2019/07/25

Hayabusa2 reporter briefing24

2. The 2nd touchdown operation
Closing the catcher chamber• Chamber A closed immediately after the 1st
touchdown (February 22).
• Chamber B was open after this, but closed in an
operation on June 24. (A total of 7 descentoperations were conducted while chamber B was
open).
• Chamber C was then open but closed after the 2nd
touchdown on July 11 at 14:10 JST (onboard time).
(The ascent speed was reduced by 2 cm/s at 13:40
JST so that any sample at the tip of the sampler horn
would be collected).

      Image creditJAXA
2019/07/25

Hayabusa2 reporter briefing25

3Images from the 2nd touchdown
Images from the ONC-W1
Capture time:
2019/7/11
10:06:32 JST (on-board time)
Altitude: about 8m(Credit: JAXA, University of Tokyo,
Kochi University, Rikkyo University,
Nagoya University, Chiba Institute ofTechnology, Meiji University,
University of Aizu, AIST)

2019/07/25

Hayabusa2 reporter briefing26

3. Images from the 2nd touchdown
Images from the ONC-W1
Capture time:
2019/7/11
10:08:53 JST (on-board time)
Altitude: about 90m(Credit: JAXA, University of Tokyo,
Kochi University, Rikkyo University,
Nagoya University, Chiba Institute ofTechnology, Meiji University,
University of Aizu, AIST)

2019/07/25

Hayabusa2 reporter briefing27

3. Images from the 2nd touchdown
Firstrelease2nd touchdown ONC-W1/W2
composite panoramic image at analtitude of 8m during the final
descent.
ONC-W2 2019/07/11 10:04:58
JST (onboard time)(Credit: JAXA, Chiba Institute ofTechnology, University of Tokyo,
Kochi University, Rikkyo University,
Nagoya University, Meiji University,
University of Aizu, AIST)

2019/07/25

ONC-W1 2019/07/11 10:04:57
JST (onboard time)

Hayabusa2 reporter briefing28

3. Images from the 2nd touchdown
Explanation

2nd touchdown final descent ONC-W1/W2 composition panoramic image at 8m altitude

TM(Credit: JAXA, Chiba
Institute of Technology,
University of Tokyo, Kochi
University, Rikkyo
University, Nagoya
University, Meiji University,
University of Aizu, AIST)

2019/07/25

Sample horn ground point

SCI crater

1m (In the W1 image)
ONC-W1 2019/07/11 10:04:57 JST onboard time)
Hayabusa2 reporter briefing

ONC-W2 2019/07/11 10:04:58 JST onboard)29Reference: Geometrical relationship between W1/W2 imaging• ONC concentrates on TM image acquisition until the final descent at an altitude of
8.5m.
• After the final descent from an altitude of 8.5m, imaging was performed with theW1 and W2 at altitude 8m, 4.7m and 4.2m (planned values).

W2 field of view
e
d
u
it 4m
t
l
a 
8m

W1 fieldof view
2019/07/25~

SCI craterm02

As the viewing angles for W1 and W2 are slightly

larger than 60 degrees, there is a slight overlap.

Credit: Chiba Institute of Technology

Hayabusa2 reporter briefing

30Reference: positional relationship about the C01 area

W2 view direction
is to the south
 crater side   2019/05/16
Images from an altitude ~0.5km and ~0.6km
2019/07/25

  (Credit: JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University,
Chiba Institute of Technology, Meiji University, University of Aizu, AIST)

Hayabusa2 reporter briefing31

4. Name of the 2nd touchdown point
The name of the 2nd touchdown
point is:Uchide-no-kozuchi

2nd touchdown point

MeaningIn Japanese folklore, theuchide-no-kozuchi is a magic
hammer that can produce greatriches. The samples gathered fromthis site are expected to produce
great scientific results.
(Image credit: JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya
University, Chiba Institute of Technology, Meiji University, University of Aizu, AIST)

2019/07/25

Hayabusa2 reporter briefing32

5. Upcoming events
Operation plans• BOX-C operation from July 20 – 31. The lowest altitude will be
about 5km from July 25 – 27.
Press and media briefings• 8/22 Thursday 15:0016:00 regular press briefings @ Tokyo
office

2019/07/25

Hayabusa2 reporter briefing

33Reference material

2019/07/25

Hayabusa2 reporter briefing

34

Locations for the 1st (TD1) and 2nd (TD2) touchdown




Tamatebako

Uchide-no-kozuchi

2019/5/20
Taken from thehome position(Image credit: JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University, University of Aizu, AIST)

2019/07/25

Hayabusa2 reporter briefing

35

Touchdown locations for the 1st (TD1) and 2nd (TD2) touchdown

TD1

TD2
Uchide-no-kozuchi

Note: Tritonis (landing site for MINERVA-II1), Alice’s Wonderland (MASCOT landing site), Tamatebako (first touchdown point) are nicknames
and not recognised by the International Astronomical Union (IAU). Other places names are official names recognised by the IAU.

2019/07/25

Hayabusa2 reporter briefingimage creditJAXA
36

Optical navigation camera (ONCONCOptical Navigation Camera
Objective: Images fixed stars and the target asteroid forspacecraft guidance and scientific measurements• Global observations of surface topography
Craters, structural topography, rubble, regolith distribution• Global observations of spectroscopic properties of surface
materials
Hydrous mineral distribution, distribution of organic matter,degree of space weathering

W
Fo 2
V

Scientific measurements
• Form and motion of the asteroid:
Diameter, volume, direction of inertial principal axis, nutation

W1
FoV
T
FoV

• High-resolution imaging near the sampling point
Size, form, degree of bonding, and heterogeneity of surface
particles; observation of sampler projectiles and surface
markings

ONC-T
Detector
Viewing direction• Elucidation of features of target asteroid• Distribution of hydrous minerals and organic matter, space
weathering, boulders• Sampling site selection• Basic information on where to collect asteroid samples• Ascertaining sample state• High-resolution imaging of sampling sites

2019/07/25(© JAXA)

ONC-W1
2D Si-CCD (1024  1024 px)

Downward (telephoto)

Viewing angle

6.35  6.35

Focal length

100 m–∞

Spatial resolution

1 m/px @ 10-km alt.
1 cm/px @100-m alt.

Observation wavelength

390, 480, 550, 700, 860, 950, 589.5 nm, and wide

Hayabusa2 reporter briefing

ONC-W2

Downward(wideangle)

Sideward (wide-angle)

65.24  65.24
1 m–∞
10 m/px @10-km alt.
1 mm/px @1-m alt.
485–655 nm

ONC-W2 mounting position

W2
Heat sink

W2
Aperture•

Mounted on the side. Diagonal-downwards
imaging possible.
• Earth imaging during swing-by• MASCOT separation imaging• SCI crater search operation on Ryuguimage creditJAXA

2019/07/25

Hayabusa2 reporter briefing

38