Candidates for landing sites
for the Hayabusa2 mission;;August 23, 2018
JAXA Hayabusa2 ProjectTopics
Regarding Hayabusa2:
HCandidates for landing sites for touchdown, MASCOT,
and MINERVA-IIContents
0. Hayabusa2 & mission flow outline
1. Project status & overall schedule
2. Landing site candidates and expected dates
3. Selection of touchdown site candidates
4. Science discussions for touchdown site candidates
5. Selection of landing site candidates for MASCOT
6. Selection of landing site candidates for MINERVA-II
7. Strategy toward the successful touchdown
8. Future plans

Overview of Hayabusa2
ObjectiveWe 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 the primitive solar
system. By doing so, we will learn about the origin and evolution of Earth, theoceans, and life, and maintain and develop the technologies for deep-space return
exploration (as demonstrated with Hayabusa), a field in which Japan leads theworld.

Expected results and effects
HBy exploring a C-type asteroid, which is rich in water and organic materials, wewill clarify interactions between the building blocks of Earth and the evolution of
its oceans and life, thereby developing solar system science.
H Japan will further its worldwide lead in this field by taking on the new challenge ofobtaining samples from a crater produced by an impacting device.
HWe will establish stable technologies for return exploration of solar-system bodies.

Features:
HWorld’s first sample return mission to a C-type asteroid.
HWorld’s first attempt at a rendezvous with an asteroid and performance ofobservation before and after projectile impact from an impactor.
HComparison with results from Hayabusa will allow deeper understanding of the
distribution, origins, and evolution of materials in the solar system.

International positioningL
HJapan is a leader in the field of primitive body exploration, and visiting a type-C
asteroid marks a new accomplishment.
HThis mission builds on the originality and successes of the Hayabusa mission. In
addition to developing planetary science and solar system exploration
technologies in Japan, this mission develops new frontiers in exploration ofprimitive heavenly bodies.
HNASA too is conducting an asteroid sample return mission, OSIRIS-REx (launch:
2016; asteroid arrival: 2018; Earth return: 2023). We will exchange samples andotherwise promote scientific exchange, and expect further scientific findings
through comparison and investigation of the results from both missions.

(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.

Mission flow
Launch3 Dec 2014

Arrival at asteroid
une 27, 2018
B▲
Earth swing-by
3 Dec 2015

Examine the asteroid by remote sensing
observations. Next, release a small lander androver and also obtain samples from the surface.

Earth returnlate 2020

Depart asteroid
Nov–Dec 2019

Create artificial
craterSample analysis(Illustrations: Akihiro Ikeshita)

After confirming safety, touchdown
within the crater and obtain
subsurface samples

Releaseimpactor

Use an impactor to create
an artificial crater on theasteroid’s surface1. Current project status& schedule overview

Current statusL– On August 5, we began operations for gravity measurement, approaching
Ryugu to an altitude minimum of 851m at around 08:10 JST on August 7.
The spacecraft then returned to the home position on August 10.
– Based on the data obtained to date, we investigated possible landing points.
– BOX-B operations began on August 18 (scheduled to return to BOX-A on
September 7).

Schedule overview:
2015
3

12

Event	

0-5-&.
12*3&5-10

2016
10 12

$

launch	*(2017

4

48-0+ ':&3 60

1630*:51&45*31-)

2020
12

Arrival at Ryugu	60* !* *0512
3:
&35,3*5630

45*31-)2319-/-5:12*3&5-104

Earth swing-by	*(

&3 &:2019

6 7

&2231&(,"I %J
5*4512*3&5-104 Southern hemisphere station
operations (CAN/MLG)	
&:  
(5
&:

Ion engine operations ※	

2018

Departure from Ryugu	17N*(Capsule re-entry	&5*


Optical navigation	
 Solar conjunction	
&: 6. 17*(
17

23

&0

60

#

##

#Points to note in this documentPay attention to the orientation of the asteroid!

Public images so far have shown
the northern direction of the Solar
System (direction of the Earth’s
North Pole) pointing upwards.

In this document, like a typical map, north isdrawn pointing upwards. As Ryugu rotates
backwards, Ryugu’s “north” is at the bottom of
the left-hand figure, but the top in this map (topand bottom are reversed).
From now on, public images also show thenorthern direction of Ryugu pointing upwards.
north pole

Earth
North Pole

north pole
I©JAXACU. of Aizu et al.J

Ryugu has a reverse rotation (retrograde)I©JAXAJExample of a Ryugu “map”

2. Landing site candidates andexpected dates
Landing Site SelectionILSS) conference:
BHHeld on August 17, 2018
BH109 attendees (including remote participants)
BH39 participants from overseas (14 from DLR, 2 from CNES and 2 from NASA)
BHDiscussion took place from 10 am to 7 pm.BBBBBB↓
Determined candidate landing points for spacecraft touchdown, MASCOT & MINERVA-II

I©JAXAJ

August 17, 2018: Group photo of LSS meeting2. Landing site candidates andexpected dates
Determined landing site candidates
BBBTouchdown
L L08IbackupLL07CM04JBBBMASCOT
L MA-9BBBMINERVA-II-1 L N6

I©JAXA, University of Tokyo & collaboratorsJ

2. Landing site candidates andexpected dates
Determined landing site candidates
BBBTouchdown
LL08IbackupLL07CM04JBBBMASCOT
L MA-9BBBMINERVA-II-1 L N6
Touchdown

I©JAXA, University of Tokyo & collaboratorsJ

MASCOT

MINERVA-II-K2. Landing site candidates andexpected dates

Operation Schedule

BBBTouchdown 1 rehearsal 1:
September 11 ~ 12
BBBBBBBBBIArrival at lowest altitude : September 12J
BBBMINERVA-II-1 operation:
September 20 ~ 21
BBBBBBBBBIMINERVA-II-1 separationLSeptember 21J
BBBMASCOT operation:
October 2 ~ 4
BBBBBBBBBIMASCOT separationLOctober 3J
Touchdown 1 rehearsal 2:
BBBTouchdown 1:

mid-Octoberlate-OctoberNote: date of operations may be changed. 3. Selection of touchdown site candidates
Prerequisites for touchdown candidate points, part 1
Range on the celestial body where the spacecraft can land
The spacecraft can move along the line connecting the Earth and Ryugu.
BB↓
The region where the spacecraft can land is the area within about 200 m to the north andsouth of Ryugu’s equator (range of about ±30° latitude)

Within	  200m	  north	  and	
  south	
  of	
  
the	
  equator	
  (about	
  ±30° latitude)

Spacecraft

rotation axis

I©JAXACU. of Aizu et al.)

Sun
Earth

Spacecraft
movement3. Selection of touchdown site candidatesPrerequisites for touchdown candidate points, part 2
Surface conditions suitable for landing(1) Average slope within 30° < ← Limit due to orientation of solar panels (2) Flat region with 100m diameter ← Navigation guidance accuracy
(3) Boulder height less than 50cmB← Length of sampler horn
(4) Absolute temperature less than 370KI97=JB← Within operating temperature range of equipment < Mhis angle

Sun
Spacecraft

Earth

asteroidSpacecraft movement

3. Selection of touchdown site candidates
Procedure of the selection of landing site candidates
Step 1:Safety score analyses

Box-A, Box-C, Mid-alt
B

Box-A: alt. 20km
Box-CLalt. 6km
Medium altitudeL
alt. 5km

p Rotation modelp Shape model

Step 2:Visual evaluationp Optical images

Step 3:Feasibility analysesp Temperature mapp Longitude accessibilityp Boulder density

Choose safe landing site based on
attitude of probe, surface
inclination, terrain conditions etc.

From the images from the Optical
Navigation Cameras, investigate
the boulder coverage, presence ofobstacles, surface flatness etc
needed to chose the right place.
Confirm temperature andoperation conditions for the timeof landing. Precisely examine the
distribution of boulders.
3. Selection of touchdown site candidates
Narrow down touchdown candidates: Step 1, from shape modelI© U of Aizu, Kobe U., JAXAJI©JAXAJ

Shape model (right) based on data acquired
during the Medium Altitude Operation, and thedifference in surface elevation on Ryugu (left)

Safety score for each point is calculated by using the shape model.
BItems consideredL
BBHSun angleIangle between +z axis of S/C and the sun)
BBHSlope angle
BBHRoughness

The safety scorevalue can aid
selecting a safe
location. 3. Selection of touchdown site candidates
Narrow down touchdown candidates: Step 1, from shape model
100m×100m area.
I14> x 14> in lat., long.J

I©JAXAJ

Select candidates for landing sites from locations
with a high degree of safety (low safety value
score).

Safety score distribution.
A smaller value indicatedhigher safety. Gray indicatesregions above a score of 30.

11 low latitude (“L”) and 4
middle latitudes (“M”) wereselected.

3. Selection of touchdown site candidates
Narrow down touchdown candidates: Step 2, from images
Choose candidate sites from images
captured with the Optical
Navigation Cameras:
BFeatures to noteL
BBHBoulder coverage
BBHObstacles on the east side<
BBHflatness

Narrow down to four low
latitude (“L”) and three midlatitude (“M”) sites.
<Since the spacecraft will approach from the east
when landing, obstacles on the east side are
dangerous.

I©JAXACU. Tokyo et al.J3. Selection of touchdown site candidates
Narrow down touchdown candidates: Step 2, from images
Candidate sites: four low latitude (“L”) and three mid-latitude (“M”)

I©JAXACU. Tokyo et al.J3. Selection of touchdown site candidates
Narrow down touchdown candidates: Step 3, feasibility
Further narrowing down from 7 candidates (4 low latitude, 3 mid-latitude)
Surface temperature:absolute temperatureof 370 K or less.

7 candidate points all OK

Longitude dependence of surface
approach: communication withground tracking stations uninterrupted

7 candidate points all OK
Boulder number density:less boulders are preferred
Compare the 7 possible sites

Surface temperature distribution mapI©JAXACAshikaga U et al. J3. Selection of touchdown site candidates
Narrow down touchdown candidates: Step 3, feasibility
Further narrowing down from 7 candidates (4 low latitude, 3 mid-latitude)
Create boulder map and check boulder coverage

I©JAXACU. Tokyo et alJ

Example boulder map

3. Selection of touchdown site candidates
Narrow down touchdown candidates: Step 3, feasibility
Further narrowing down from 7 candidates (4 low latitude, 3 mid-latitude)
Creating boulder maps
L05

L07

L08

M01

M03

M04

L12

Distribution of boulders.
The size of boulders with adiameter greater than 3m
is indicated by marker sizeand color. Brown is forboulders larger than 10m.
I©JAXAJ3. Selection of touchdown site candidates
Narrow down touchdown candidates: Step 3, feasibility
Further narrowing down from 7 candidates (4 low latitude, 3 mid-latitude)
Determining boulder coverage

Low latitudeMid- latitudeAt low latitudes, L08, L07 inorder. At mid-latitudes, M04Lower latitudes are
preferable for ease of
landingTouchdown candidate point is
L08 (backup: L07, M04)

I©JAXAJ

<Touch down point will be fixedby considering the results of thefirst rehearsal operation that will bedone before the touchdown.



4. Science discussions for touchdown
site candidates
Features of Ryugu
J Top shape with a very circular equatorial bulge
J Radius: mean 450 mBBBBBBIequatorial 500 mCpolar 440 mJ
J Mass: 450 million tonIGM30 m3s-2 )<J Rotation axis: (λ, β) = (180, -87)J Obliquity: 8°
J Rotation periodLP = 7.63 hours
J Reflectance factor Iv-bandJL0.02

I©JAXACUniversity of

J Crater number density: as much as those on Itokawa and Eros Tokyo & collaboratorsJ
J Many boulders: the largest near the south pole is ~130 m across
J Optical spectra: flat spectra, bluer in equatorial bulge and poles
J NIR spectra: uniform flat (slightly redder) spectra with weak water absorption
J brightness temperatureLstrong roughness effect (flat diurnal Temperature
variation), higher thermal inertia in the equatorial bulge
I<The gravity at the equator is eighty-thousandth of the Earth and a few times of
Itokawa)



4. Science discussions for touchdown
site candidates
Scientific evaluation points of landing site candidates■ Point 1: surface properties
HExamine surface temperature and thermophysical properties using the Thermal Infrared
Imager data.
HExamine composition differences using spectral data from the Near Infrared Spectrometer.
HExamine terrain, geology and space weathering from different wavelength images from the
Optical Navigation Camera.
BB↓< Evaluate potential scientific merit.
■ Point 2: safety
HExamine size and spatial distribution of boulders (from images and laser altimeter data). BB↓< Evaluate safety by estimating the number of small boulders from the boulder size
distribution.
■ Point 3: sample yield
HEstimate surface grain sizes from observational data from the Thermal Infrared Imager.
BB↓< From the particle size of surface regolith, evaluate where the maximum amount of sample
can be gathered. 4. Science discussions for touchdown
site candidates
The points for scientific evaluation of the landing site candidates:
one example from observation data.

ONC-T spectral slope map (Box-C)
I©JAXA, University of Tokyo & collaboratorsJ

4. Science discussions for touchdown
site candidates
Summary of the scientific evaluation of landing point candidates
site

Point 1surface properties

Point 2
safety

L5
L7
L8
L12

22
22
22
22

29
31
31
31

12
12
12
11

63
65
65
64

M1
M3
M4

21
21
21

33
30
33

13
13
13

67
64
67

Candidate

Surface temperature, visible / nearinfrared spectrum etc. There is no
big differences across the surface,which is almost uniform. However,there are minor differences.
Spectral characteristics indicatethat lower latitudes may containmore diverse particles.

Point 3
Total
Sample yield
Although no big
difference inevaluation, L08 & L07
are good for low
latitude (L). M1 & M4
are good if mid-latitude(M) is preferred.

Mid-latitudes (M) seem to have many smaller
sized particles, which is expected to increase thesample yield.
Safety is evaluated from information such as
number density of boulders, estimated number ofsmaller boulders and surface roughness.


4. Science discussions for touchdown
site candidates
Summary of the scientific evaluation of landing point candidates
Scientifically important points:
I1J Difference in mixing ratio of Ryugu surface material has a low
dependence on location.
I2J A diversity of different materials are present mixed together on
Ryugu’s surface.
I3J Regardless of where the sample is collected, there is a highpossibility of gathering diversified materials that represent thewhole of Ryugu.

5. Selection of landing site candidates
for MASCOTMASCOT (Mobile Asteroid Surface Scout )J Created by DLR (German Aerospace Center)and CNES (French National Centre for SpaceStudies)
J Small lander with mass approx. 10 kg
J Carries four scientific instruments
J Can move only once, by jumping

I©JAXAJ

Scientific instruments aboard MASCOT
DeviceFunction

Wide-angle camera(MASCAM)

Imaging at multiple wavelengths

Spectroscopic microscope(MicrOmega)

Investigation of mineralcomposition and characteristics

Thermal radiometer (MARA)

Surface temperature measurements

Magnetometer (MASMAG)

Magnetic field measurements

Flight model (©	
  DLR)	
  

MASCOT5. Selection of landing site candidates
for MASCOT
Criteria for the selection of landing site candidates for MASCOTJ Probability to land outside the candidates for touchdown > 95 %J Probability to have RF link during at least 40% of the asteroid period > 90 %J Probability to have a good daylight ratio (between 40% and 70%) > 90 %J Selection among remaining candidates to have one candidate per reachable
and suitable zone, in northern as well as in southern hemisphere
J No overlap with the landing site candidates for MINERVA-II

computed 10,000  100,000 Monte-Carlo trials
Further conditions

10 candidates

6 candidates & prioritization

HTemperature (illumination, orientation, heating,prior separation, asteroid surface temperature,night temperature underneath MASCOT)
HOperation
HBoulders
HObservation conditions for four instruments5. Selection of landing site candidates
for MASCOT
Scientific Criteria for Landing SiteInstrument

Criteria for Landing Site

MicrOmega

Composition of C-rich and/or OH-rich content.
Low Temperature of landing site for high SNR (signal-to-noise ratio).

MASCAM

Boulders in the field of view
Fine grained particles
Compositional heterogeneity (color!)
Fresh material (non-weathered)

MARA

Thin to no regolith layer.
Landing or hopping close to boulders preferable.
Preferentially less thermally altered region.

MASMAG

Low thermal inertia for fine grained fraction of the regolith
Homogeneous thermal inertia (link the MARA + TIR data)
Low rock abundance -> no inhomogeneities in the FoV (field of view)
Remote sensing instruments onboard HY2 give preliminary information on
Ryugu : no big variation over the surface à homogenous 

5. Selection of landing site candidates
for MASCOT
Landing site candidates for MASCOTLL selected 10
candidates (MA-1
MA-10)	
  I©DLR,CNESJ

Light blue shows the first contact points and blue shows the first settlement
points. The candidates of touchdown sites are shown by red squares (lowlatitude) and pink squares (mid- latitude). 

5. Selection of landing site candidates
for MASCOTMASCOT Ranking meeting (Toulouse Aug 14)

I© CNES/Rémi Benoît, 2018)

Fruitful meeting, useful rehearsal and training (thanks to JAXA)=> complex process but all milestones/deliveries were reachedaccording to the schedule 

5. Selection of landing site candidates
for MASCOT
Landing site candidates for MASCOTLLSelection from
10 candidates and the order of priority

I©DLR,CNESJ

Priority of landing siteLMA-9 > MA-1 > MA-10 > MA-7 > MA-5 > MA-2



5. Selection of landing site candidates
for MASCOTMASCOT landing site©JAXA, University Tokyo, Kochi University, Rikkyo University, Nagoya University,
Chiba Institute of Technology, Meiji University, University of Aizu, AIST, CNES, DLR

6. Selection of landing site candidates
for MINERVA-II
Release of MINERVA-II-1 A & BIMINERVA-II-2 will be released next yearJ	
  MINERVA-II-1A, 1B

Produced
at JAXAMINERVA-II-1ACMINERVA-II-1B
Specification

MINERVA-II-2
Created by the MINERVA-II
consortium (Tohoku
University, Tokyo Denki
University, Osaka
University, Yamagata
University, Tokyo
University of Science)

I©JAXAJ

HsizeLdiameter 17cmCheight 7cm
HweightLabout Kkg each
HActuatorL2 DC motors
HMounted sensorLcamera, photodiode,accelerometerCthermometer, gyro.
HCommunication speedL32kbpsImaxJ

6. Selection of landing site candidates
for MINERVA-II
Conditions for MINERVA-II landing site selectionL
H Landing site does not overlap with spacecraft touchdown candidates.
H Landing site does not overlap with MASCOT landing site candidates.
H The altitude of the spacecraft after separation must not be lower than 30m.
H Ensure communication with ground station.
H Not high temperature region, and fewer parts in shadow
HDue to the equatorial ridge, separation near the equator results in widely spaced
landing points to the north and south.
HSeparating in the southern hemisphere may result
Landingin a spacecraft altitude below 30m.
north
locationsouth

HSeparate in northern hemisphere,
more than 100m north of the equator.

Separation
position

I©JAXAJ When separating near the equator, thelanding position spread north and south.

6. Selection of landing site candidates
for MINERVA-II
Landing site candidates for MINERVA-II: northern hemisphere

Possible overlap
with mid-latitude
touchdown

No communication
with ground station
Longitude 0°
I©JAXAJ

HTouchdownHconfirm no overlap with
MASCOT's landing site.
HAlso consider observability etc. using the
ONC-T camera.

Candidate locationsL
N6 > N1 > N7 

7. Strategy toward the successful touchdown
Landing	  site	  candidates	
  selected	
  at	
  this	  stage.

A Initial planDCandidate site search?E

DReﬁne	  ?E	
  DLanding	
  opera�on	
  ?E	
  

Iden�fy	  mul�ple	
  technically	
  landable	
  areas

Select	  2	
  -­‐	  3	  sites	
  by	
  ranking	  areas	  of	
  scien�ﬁcally	
  high	  valuePerform	  rehearsal	
  descent	
  &	
  landing	
  for	
  high	  priority	
  candidate	
  sites	  

DCandidate site search@EDReﬁne	  @E

DLanding	
  opera�on	
  @E

HHH

Further	  examina�on	
  of	
  landing	  feasibility	
  necessary	  at	
  this	  stage.

ANew planDCandidate site searchE

Iden�fy	  mul�ple	
  rela�vely	
  safe	  areas

Depending	
  on	
  situa�on,	
  reimplement	
  from	  landing	
  site	
  selec�on	
  based	  on	
  opera�onal	
  knowledge

Repeat for each landingDReﬁneE	  Select	
  1	
  –	
  3	
  sites	
  with	  high	
  scien�ﬁc	
  merit	
  Landing Site Selection(LSS). Conducted atconference.

Operational
proficiency


DGather informationEb

By landing rehearsals & landing
gear operations, collect low altitude
and descent guidance information.

High resolution
surface images
Landing gear
operational dataDLanding (trial) operationE

Landing attempt. Depending on
circumstances, stop half-way anduse data to analyze landing area. 

Repeat	  while	  reﬁning	
  landing	
  technique	
  and	
  improving	
  this	
  sequence.



7. Strategy toward the successful touchdown
Important point
Detail of surface from low altitudeHow far can thenavigation
guidance accuracy
be increased?

I©JAXACGFJ

Ryugu surface taken from an altitude of about 1km.

8. Future Plans■Schedule for press briefings
J Sept. 5 IWedJ11:00N12:00
J Sept. 27 IThursJ14:30N15:30■Outreach and events (in Japanese)Ø Events for Children
J Why Hayabusa2? Any questions classroom
J Sept. 2 (Sunday) 2 – 4pm
J Sagamihara City Museum
J Online broadcast planned(Time : JST)
