Current status of the asteroid explorer,
Hayabusa2, leading up to arrival atasteroid Ryugu in 2018
June 14th, 2018
JAXA Hayabusa2 ProjectToday’s Topics
For the Hayabusa2 spacecraft:
・Observation of Ryugu
・Optical Navigation (Hybrid navigation using
optical and radiometric observations）
・Search for satellites
・Schedule2

Contents
0．Hayabusa2 mission overview
１．Current status and project schedule
２．Observation of Ryugu
３．Optical navigation
４．Search for satellites
５．Mission schedule
６．Future plans

3Overview of Hayabusa2
Objective
We will explore and sample the C-type asteroid Ryugu, which is a more primitive typethan 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, the oceans, and life, and maintainand 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 ofobtaining samples from a crater 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, and evolution of materials in the solar system.

(Illustration: Akihiro Ikeshita)
Hayabusa 2 primary specifications

International positioning：
・Japan is a leader in the field of primitive body exploration, and visiting a type-C
asteroid marks a new accomplishment.
・This mission builds on the originality and successes of the Hayabusa mission. In
addition to developing planetary science and solar system exploration technologies inJapan, this mission develops new frontiers in exploration of primitive 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.

Mass
LaunchMissionArrivalEarth return
Stay at asteroid
Target body

Approx. 609 kg
3 Dec 2014
Asteroid return
2018
2020
Approx. 18 months
Near-Earth asteroid Ryugu

Primary instruments
Sampling mechanism, re-entry capsule, optical cameras, laser altimeter, scientificobservation equipment (near-infrared, thermal infrared), impactor, small rovers

4Outline of mission flow
LaunchDecember 3rd, 2014

Asteroid arrival
June 27th, 2018 (planned)▲
Earth swing-by
December 3rd, 2015

Examination of asteroid via remote sensing
observations, followed by the release of
the small lander and rovers. Obtainsamples from the asteroid surface.
Return to Earth
End of 2020

Departure from the asteroid
November – December, 2019

Create artificial
craterSample analysis(Illustration: Akihiro Ikeshita)

After confirming site safety,
touchdown to the crater tocollect subsurface material

Releaseimpactor
Create an artificial crater on
the asteroid surface using
an impact device.
51. Current status and project schedule
Current status：– The distance between Ryugu and the spacecraft is about 750km today (June 14)– Today, we will perform a Trajectory Correction Maneuver (TCM03). Approximate
approach speed of Hayabusa2 after TCM03 is 1.7 m/s.
– Optical navigation will be used until arriving at Ryugu– We are currently observing the light curve of Ryugu and searching for satellites.
– Arrival at Ryugu is scheduled for around June 27.

Schedule overview：
2015
12

Event

3

Initialoperation

2016
10 12

EDVEGA

2017

2018

4

2019

2020

6 7approach
Journey to asteroid

swing-by12

12

Re-entry
Earth return

Asteroid proximity operations

launchEarth swing-by

Arrival at Ryugu

Departure from Ryugu

Capsule re-entry(Dec 3)(Dec 3)(Scheduled: June
27)

(Nov～Dec)(Late 2020)

ESA（MLG/WLH）
Southern hemisphere station
test operations
operations (CAN/MLG)(May 21- 22)
Oct
May

Ion engine operations ※Mar JunMar

May

Optical navigation
May Jul

Nov

Apr

Jan

Jun

Interim period（Solar conjunction）
Dec Jan
TBD

TBD TBD

TBD

6

1. Observation of Ryugu■Optical navigation cameras（ONC-T、ONC-W1）• ONC-T（telescopic）and ONC-W1（wide-angle）arebeing used to image Ryugu.
• Goals: Optical navigation
 Satellite search Scientific observations（asteroid light curve）• At the current time, the size of Ryugu is about 10
pixels on the ONC-T.
■Thermal Infrared Imager（TIR）• Test observation and scientific observation（light
curve）
7

2. Observation of Ryugu
Image of Ryugu taken with the ONC-T (Optical Navigation Camera – Telescopic)

The distance between
Ryugu and the spacecraft
is about 920km.
Ryugu’s brightness is about-6.6 magnitude.
Image of Ryugu taken with the ONC-T on June 13, 2018 at approximately 13:50 JST.
Field of view is 6.3 degrees x 6.3 degrees and the exposure time is about 178 seconds.
Ground observation team: JAXA, Kyoto University, Japan Spaceguard Association, Seoul National University.
ONC team：JAXA, University of Tokyo, Koichi University, Rikkyo University, Nagoya University, Chiba Institute ofTechnology, Meiji University, University of Aizu and AIST.

8

2. Observation of Ryugu
Image of Ryugu taken with the ONC-T (Optical Navigation Camera – Telescopic)

The distance between
Ryugu and the spacecraft
is about 920km.
Ryugu’s brightness is about-6.6 magnitude.
Image of Ryugu taken with the ONC-T on June 13, 2018 at approximately 13:50 JST.
Field of view is 6.3 degrees x 6.3 degrees and the exposure time is about 0.09 seconds.
Ground observation team: JAXA, Kyoto University, Japan Spaceguard Association, Seoul National University.
ONC team：JAXA, University of Tokyo, Koichi University, Rikkyo University, Nagoya University, Chiba Institute ofTechnology, Meiji University, University of Aizu and AIST.

9

2. Observation of Ryugu
Image of Ryugu taken with the ONC-W1 (Optical Navigation Camera – Wide-angle)
The distance between
Ryugu and the spacecraft
is about 920km.
As the measurement of theasteroid position is moreaccurate when Ryugu is
photographed by ONC-T,
the ONC-T data is used for
optical navigation. Imaging
by ONC-W1 is a backup incase imaging with ONC-T
failed.

Image of Ryugu taken with the ONC-W1 on June 13, 2018 at approximately 13:00 JST.
Field of view is 65 degrees x 65 degrees and the exposure time is about 0.2 seconds.
Ground observation team: JAXA, Kyoto University, Japan Spaceguard Association, Seoul National University.
ONC team：JAXA, University of Tokyo, Koichi University, Rikkyo University, Nagoya University, Chiba Institute ofTechnology, Meiji University, University of Aizu and AIST.

10

2. Observation of Ryugu
Image of Ryugu taken with the TIR（Thermal Infrared Imager）

The distance between Ryugu
and the spacecraft is 2100 km.
Image of Ryugu taken with the TIR on June 7, 2018 at approximately 18:45 JST. Field of view on the left
image is 6 degrees x 6 degrees and the right image is a magnification. The exposure time is about 0.5
seconds.
TIR team：JAXA, Hokkaido University of Education, Rikkyo University, University of Aizu, Chiba Institute of Technology, Ashikaga
University, AIST, National Institute for Environmental Studies, Hokkaido Kitami Hokuto High School, University of Tokyo, Max Planck
Institute, DLR, Stirling University.

112. Observation of Ryugu←weak

Signal strengthstrong→Light curve of Ryugu from the TIR (Thermal Infrared Imager)※The absolute value of thesignal strength will beanalyzed in the future.

This light curve
confirms the asteroid’s
rotation is about 7.6hours, as expected.

Light curve of Ryugu obtained with the TIR (change in intensity of the signal). Data is from 37 images taken
between June 7, 2018 at about 17:30 JST to June 8 at about 01:30 JST. Exposure time for each image was 0.5
seconds.
TIR team：JAXA, Hokkaido University of Education, Rikkyo University, University of Aizu, Chiba Institute of Technology, Ashikaga University,
AIST, National Institute for Environmental Studies, Hokkaido Kitami Hokuto High School, University of Tokyo, Max Planck Institute, DLR,
Stirling University.

122. Observations of Ryugu■LIDAR（laser altimeter）
・On June 6, power was turned on and confirmed that thesystem starts up normally. It has been two years since thepower was last turned on.
・Distance measurement to the asteroid will be attempted
once Ryugu is sufficiently close (measurement range is
25km – 30m)
■NIRS3（Near Infrared Spectrometer）
・On June 6, the power was turned on and normal start up
confirmed. It has been about half a year since the power
was last turned on.
・ Observations of Ryugu will be attempted during theapproach in the future.
13

3. Optical Navigation
Reasons for Optical Navigation (hybrid navigation using optical and radiometricmeasurements ):• Necessary technique to arrive at a celestial body 900m in size at a distance 300
million km from Earth.
• The errors (uncertainties) for the orbit of spacecraft and asteroid:
Error in the position estimation
Hayabusa2（At a distance of about 300 million km）

Asteroid Ryugu

About 300km（Using the conventional RARR）
Several km（by DDOR）
About 220km（as of May 2018)

Note） ・RARR is the abbreviation of “Range and Range Rate”, a conventional method to estimate the trajectory of aspacecraft by measuring the distance to the probe and velocity along the line of sight using radiowave
communication.
・DDOR is “Delta Differential One-way Range”, a method of accurately estimating the trajectory by receiving
radiowaves from the probe at two ground stations simultaneously.
・ The size of the error is 3σ (probability of 99.7%)• Using Optical Navigation during the approach to the asteroid reduces theseerrors.
Reference：
A 900m target at a distance of 300 million km is equivalent to a 6cm target at 20,000 km. In
other words, arriving at Ryugu is the same as aiming at a 6cm target in Brazil from Japan!

14

3. Optical Navigation
Basic Principal③ Hybrid navigation using
optical and radiometricobservations
By combining ① radio
navigation and ② opticalnavigation, we can accurately
calculate all three sides of thetriangle in the figure．

② Optical Navigation• By imaging the asteroid from thespacecraft, we measure the asteroid’s
direction from the spacecraft．
• Once we can use LIDAR, the distancecan also be measured．

Orbit of the spacecraft relative to the Earth (Solar System)

Earth’s orbit
around theSun① Radio Navigation
The measurements of distance, the change in frequency
from transmitted & received radiowaves between the
Earth and spacecraft (Doppler effect), and DDOR gives
the trajectory of the spacecraft relative to the Earth．
Note： It is common to refer to “hybrid navigation using
optical and radiometric observations” as simply “Optical
Navigation”.

15

3. Optical Navigation
Principals of Optical Navigation• Take an image of the asteroid against
background stars.
• Based on the asteroid’s location on this star
map, the direction to the asteroid from thespacecraft can be measured.
• By collecting a lot of directional information,
the asteroid’s position and velocity withrespect to the spacecraft can be calculated.
• Rather than heading straight for theasteroid, adding lateral motion to thespacecraft trajectory allows a “moving
stereo view” of the asteroid to give not only
the direction, but also the asteroid’s
distance.

16

3. Optical Navigation
Towards EarthApproach corridor

Approach corridor(Direction of approach while keeping
the asteroid in view of the camera)

6/18
TCM05

6/8
TCM01

6/11
TCM02

Enlarged view
6/20
TCM06

6/14
TCM03
6/16
TCM04

TCM：Trajectory Correction
Maneuver

Asteroid sits at the origin※The trajectory may be changed in future operations.

6/22
TCM07
6/24 TCM08
6/26 TCM09
6/27 Arrival maneuverThis zigzag path increases the stereo visioneffect to increase the accuracy of the approach173. Optical Navigation
Work loop
Received from Hayabusa2:• Thruster injection history• Asteroid image

Seoul National
University
Japan Spaceguard
Association

Kyoto
University

Perform this loop once every
24 – 72 hours

Sent to Hayabusa2:• Thruster injectionplan• Asteroid image plan

Navigation team

JAXA
NEC
Fujitsu

Guidance team

JAXA

Operation team

JAXA
NEC

JAXA
Calculate the direction to
the asteroid from
Hayabusa2 using the imageof stars and asteroid.

Calculate the trajectory of
Hayabusa2 towards Ryugu
based on the asteroid
direction and radio wave
measurements.

Calculate the optimal
trajectory to arrive at theasteroid based on thelatest Hayabusa2 orbit.

From the latest trajectoryplan, send new thruster
injection commands andimage plan to thespacecraft.

18

3. Optical Navigation
Optical Navigation performed using images from the STT（Star Tracker)• Ion engine operation was in progress during May, preventing the Optical Navigation
Camera pointing at Ryugu. Instead, an image of Ryugu was attempted with the Star
Tracker, which is usually used to determine the orientation of the spacecraft.
• Ryugu was observed between May
11 – 14 and Optical Navigation wasused from measurements of theasteroid’s position.
• As a result, the error (uncertainty) in
the position of the asteroid shrankfrom 220km to about 130km.
• Based on the trajectory estimate
obtained form this Optical
Navigation, the final ion engine
operation was performed.

Ryugu photographed with the Star Tracker. The images were taken starting from the right at approximately 01:00 on May
12, 02:00 on May 13 and 01:00 on May 14 (JST). These are taken from the spacecraft in the direction of Pisces. ("Psc" isan abbreviation of Pisces). The field of view is 9 degrees × 7 degrees. (Ground observation team: JAXA, Kyoto University,
Japan Spaceguard Association, Seoul National University.)19

3. Optical Navigation
Optical Navigation performed using images from the STT（Star Tracker)
Orange: Expected position of Ryugu seen from thespacecraft calculated from orbital information prior tousing optical navigation.
Green: Expected position of Ryugu calculated withgreater accuracy using optical navigation data.
Yellow: The direction of the observed Ryugu.

Enlarged section
around the 5/13
observation of
Ryugu.
OPNAV=Optical Navigation20

3. Optical Navigation
Optical Navigation performed using imaged from the ONC (Optical Navigation Camera)

Examples of images with the ONC-T

June 10, distance 1500km

June 6, distance 2600km
TCM：Trajectory Correction Maneuver
TCM

Time（JST）

x-direction velocity

y-direction velocity

z-direction velocity

TCM01

June 8, 2018 12:30〜13:40-24 cm/s-5 cm/s

14 cm/s

TCM02

June 11, 2018 09:30〜10:40

13 cm/s-1 cm/s

26 cm/s※ This is in the home position coordinate system (where the z-axis is in the direction of the Earth from the asteroid).

21

3. Optical Navigation

Distance (km)Distance (km)Change in distance between Ryugu and the spacecraft
6 pixels
6ピクセル
15 pixels
15ピクセル
110ピクセル
110
pixels400ピクセル400 pixels

Enlargement of above plot

Date (June 2018)

Predicted values at the present time.

The number of pixels indicates the expected diameter of
Ryugu when photographed with the ONC-T.

22

3. Optical Navigation

Relative speed (cm/s)

Relative speed (cm/s)

Change in the relative speed between Ryugu and the spacecraft and the TCM

Enlargement of above plot

Date (June 2018)

Predicted values at the present time.

TCM：Trajectory Correction
Maneuver23

3. Optical Navigation
Summary figure24

4. Search for satellites
celestial bodies that may orbit Ryugu

Reasons for a satellite search• Even the low gravity Ryugu can also have satellite(Ryugu image by T. Mueller)？
？
We want to approachwithin the Hill radiusSatellites can exist within this range(Hill radius: ~90 km)••

No matter how small, a collision with a satellite is fatal to the mission. However, if
if there are satellites around Ryugu then it would be scientifically a great
discovery.
Ryugu was searched for orbiting objects from a safe distance (on June 7 at
2,100km). From here, satellites smaller than 1m in diameter could be discovered.
Such observations were also performed for Hayabusa [Fuse et al, 2008]25

4. Search for satellites
time

μGem

Ryugu

Signal overflow
from Ryugu

Satellite search observation record (June 7)① 08:03 – 08:09② 11:06 – 11:12③ 14:17 – 14:23④ 16:35 – 16:41*multiple occasions to capture orbital
movement.
A small satellite emits only a small amount oflight. To capture this, a 178 second exposure
it used for observations (30,000 times longer
than the normal setting).
* Dim stars above magnitude 12 can be seen.

No satellites larger than the detection limit(50cm) were seen.

~200 km
It is safe to approach the stable orbit radius for a satellite smaller than 50cm (up to 50km). As weapproach Ryugu, we will continue to search for smaller satellites.
ONC team：JAXA, University of Tokyo, Koichi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji
University, University of Aizu and AIST.
Ground observation team: JAXA, Kyoto University, Japan Spaceguard Association, Seoul National University.

26

4. Search for satellites
timeEmphasized brightness
μGem

Ryugu

Signal overflow
from Ryugu

Satellite search observation record (June 7)① 08:03 – 08:09② 11:06 – 11:12③ 14:17 – 14:23④ 16:35 – 16:41*multiple occasions to capture orbital
movement.
A small satellite emits only a small amount oflight. To capture this, a 178 second exposure
it used for observations (30,000 times longer
than the normal setting).
* Dim stars above magnitude 12 can be seen.

No satellites larger than the detection limit(50cm) were seen.

~200 km
It is safe to approach the stable orbit radius for a satellite smaller than 50cm (up to 50km). As weapproach Ryugu, we will continue to search for smaller satellites.
ONC team：JAXA, University of Tokyo, Koichi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji
University, University of Aizu and AIST.
Ground observation team: JAXA, Kyoto University, Japan Spaceguard Association, Seoul National University.

27

4. Search for satellites
Reference：Stars brighter than 12
magnitudes are marked
with a circle.

ONC team：JAXA, University ofTokyo, Koichi University, Rikkyo
University, Nagoya University, Chiba
Institute of Technology, Meiji
University, University of Aizu andAIST.
Ground observation team: JAXA,
Kyoto University, Japan Spaceguard
Association, Seoul National
University.

28

5. Mission Schedule
Recent Operations• Continue Optical Navigation• Continue satellite search• Continue scientific observation• Arrival at Ryugu is scheduled for around June 27 (exact date mayvary by a few days, depending on the exact operation situation).
Operation in the asteroid vicinity• The specific schedule will be determined based on observations
between June and August• The current schedule is on the next page.
29

5. Mission schedule
Provisional version
Year

Month, day

Event

Status2018

January 10
June 3June 3June 27
End of July
AugustSept - Oct
Sept - Oct
Nov - Dec
January
FebruaryMar - Apr
Apr - MayJuly
Aug - Nov
Nov - Dec

Third stage of ion engine operation begins
Ion engine operation ends
Start of asteroid approach (distance: 3100km）
Arrival at asteroid Ryugu (altitude 20km）
Medium altitude observations #1（alt. 5km）
Decent to measure gravity （alt.1km）
Period for touchdown operation #1
Period for rover deployment #1
Solar conjunction (communication unavailable)
Medium altitude observations #2（alt. 5km）
Period for touchdown operation #2
Crater generation operation
Period for touchdown operation #3
Period for rover deployment #2
Remain near asteroid
Departure from asteroid

Complete
Complete
Complete
Planning
Planning
Planning
Planning
Planning
Planning
Planning
Planning
Planning
Planning
Planning
Planning
Planning

2019

This schedule may be changed for multiple factors after arrival at Ryugu. Please note
therefore, that the situation is not fixed, except where marked ‘Complete’.

30

6. Future plans
Media correspondence & information disclosure:• Arrival at 20km above Ryugu is scheduled for around June 27. At
this time, a press release will be posted and press briefing (@the Sagamihara campus) will be scheduled.
• We plan to hold regular press briefings after July. (In the next
two months, July 19, August 2, August 23 are planned.)31

Reference material

32Primary spacecraft components
Deployable camera(DCAM3)

X-band highgain antenna

X-band low-gain
antenna

Solar array paddle

X-band midgain antenna
Ka-band highgain antenna

Optical navigation
camera, ONC-T

Laser altimeter,
LIDAR

Thermal infrared
camera, TIR

Near-infrared
spectrometer,
NIRS3

Scientific observation equipment
Star trackers

Ion engine

Near-infrared spectrometer(NIRS3)

RCS thrusters
Optical navigation
cameraONC-T, ONC-W1

Re-entry capsule
Sampler horn

Laser altimeter(LIDAR)

Optical navigation
camera ONC-W2

Small lander & rovers
MASCOT

Minerva ２

MASCOT lander
Thermal infrared camera
(TIR)

II-1A

II-1B

Minerva-II rovers

II-2

Small carry-on impactor (SCI)
Target markers × 5

Built by DLR and
CNES

II-1: By the JAXA Minerva-II teamII-2: By Tohoku Univ. & the Minerva-II
Consortium

Size： 1 ×1. 6×1. 25 m (main body)
Solar paddle deployed width 6 m
Mass ： 609 kg (incl. fuel)33

Remote sensing equipment
Optical Navigation Camera (ONC）

ONC-T (telephoto)

Thermal Infrared Camera (TIR）

ONC-W1,W2 (wide-angle)

Imaging for scientific observation and navigation

Near-infrared Spectrometer (NIRS3）

Infrared spectra including the 3-μm band:
investigates mineral distributions on the asteroid
surface

8–12 μm imaging: Measures asteroid surface temperature

Laser Altimeter (LIDAR）

Measures distance between the asteroid and the spacecraft
in a range of 30 m–25 km

34Optical Navigation Camera (ONC）
ONC：Optical Navigation Camera
Objective: Images fixed stars and the target
asteroid for spacecraft guidance and scientificmeasurements
Scientific measurements：• Form and motion of the asteroid:
Diameter, volume, direction of inertial principal axis,
nutation• 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• High-resolution imaging near the sampling point
Size, form, degree of bonding, and heterogeneity ofsurface particles; observation of sampler projectiles andsurface markings

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

W1
FoV
T
FoV

ONC-W1

ONC-W2

2D Si-CCD (1024 × 1024 px)

Viewing
direction

Downward (telephoto)

Viewingangle

6.35° × 6.35°

65.24° × 65.24°

100 m–∞

1 m–∞

Focal length

Downward (wideangle)

Sideward (wideangle)

Spatialresolution

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

10 m/px @10-km alt.
1 mm/px @1-m alt.

Observation
wavelength

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

485–655 nm

35

Thermal infrared camera (TIR）
TIR=Thermal Infrared Imager
The surface temperature of the asteroid changes overthe day, rising in sunlight and decreasing at night.
Diurnal change in surface temperature is large in finesoils like sand and highly porous rock, and small in denserock.
We will examine the physical state of the asteroid’s
surface by 2D imaging (thermography) of thermalradiation from the asteroid.

Large

400

Night

350

Temp
(K)
Temperature[K]: 2D uncooled bolometer: 8–12 μm: –40 to 150 °C: 0.3 °C
: 328 × 248 (effective): 16°×12°: 20 m (20-km alt.）
5 cm (50-m alt.）

Stone

GravelSand

・ Detector
・ Observation wavelength
・ Observed temperatures
・ Relative accuracy
・ Dimensions
・ Viewing angle
・ Resolution

Small

Temperature change

Night

Day

I=10

300

I=50
I=100

250

I=200

200

I=500

150

I=1000
I=2000

100
-180

-135

-90

-45

0

45

Longitude[deg]
Longitude

90

135

180

36

36

Laser altimeter (LIDAR）
LIDAR: Light Detection And Ranging
Short-range telescope
Beam expander for illumination

・Pulse-type laser altimeter・ A pulse YAG laser with a 1.064-μm
wavelength is emitted toward the target
object, and the altitude is measured bymeasuring the return time of the laser beam.
・ The LIDAR aboard Hayabusa 2 could performmeasurements from 30 m–25 km.
・ LIDAR is a navigation sensor used forapproach and landing at a target, and ascientific observation device used to measureshape, gravity, and surface characteristics,
and for dust observations.
・ It also has a transponder function that canperform space laser ranging (SLR)
experiments with ground LIDAR stations.

(© JAXA)

Long-range Cassegrain telescope
Laser altimeter engineering model
Scientific objectives• Terrain and gravity field observations of the target
asteroid• Observations of albedo distribution at various
surface points• Observations of dust floating around the asteroid• Asteroid form, mass, porosity, and deviation• Asteroid surface roughness• Dust floating phenomena

37

Near-infrared spectrometer (NIRS3)
NIRS3: Near-infrared Spectrometer(‘3’ from 3 μm)
Infrared absorption of hydroxyl groups and water molecules isobserved in 3-μm band reflection spectra in the nearinfrared region. NIRS3 investigates distributions of hydrous
minerals on the asteroid surface by measuring reflection
spectra in the 3-μm band.

Observation wavelength range: 1.8–3.2 µm
Wavelength resolution: 20 nm
Full field of view: 0.1 deg
Spatial resolution: 35 m (20-km alt.)
2 m (1-km alt.）• Detector temperature: –85 to –70 °C• S/N ratio: 50+ (wavelength 2.6 µm)

•
•
•
•

Relative reflectanceOH H2O
Absorption form anddepth vary dependingon the type and amountof hydrous mineral

Near-infrared reflection
spectra of carbonaceouschondrites

Wavelength (µm)(© JAXA)

38

Asteroid Ryugu
Orbit of Ryugu
Name: Ryugu

Permanent designation
Provisional designation: 162173: 1999 JU3Discovered: May 1999

Size

: Approx. 900 m

Shape: Nearly spherical

Rotation period: approx. 7 h 38 min

Rotation orientation: Ecliptic longitude λ= 310°–340°
Ecliptic latitude β= –40°±–15°

Reflectivity: 0.05 (blackish)Type: C type (assumed to comprise materials
containing water and organics)

Orbital radius: Approx. 180,000,000 km

Orbital period: Approx. 1.3 yr

Density and mass

: Density is currently unknown, but presumed tobe 0.5–4.0 g/cm3: Mass is approx. 1.7 × 1011 kg –1.4×1012 kg.

Estimated shape(by T. Mueller）

39

(162173) 1999 JU3 (Ryugu) light curve(from Kim, Choi, Moon et al. A&A 550, L11 (2013))
40

Ion engine operation
Summary of forward cruise ion engine operation■Before swing-by

Phase-3 ion engine operations(2018.01.10–06.03)
Trajectory to Ryugu
Hayabusa 2 orbit

PeriodPhase-2 ion engine operations(2016.11.22–2017.04.26）

Earth orbit
Sun

No. ofthrusters

Δv
m/s

Time
h

Initial check

IES operations test

-

−

−

2015.03.03–21

IES Powered Navigation 1

2

44

409

2015.05.12–13

IES max. thrust test

3

4

24

2015.06.02–06

IES Powered Navigation 2

2

11

102

2015.09.01–2

IES Powered Navigation 3

2

1. 3

12

Launch(2014.12.03)

Arrive at Ryugu(Jun–Jul 2018)

Name

IES：ion engine system

Phase-1 ion engine operations(2016.03.22–05.21, incl. added burns)

Earth swing-by(2015.12.03)■After swing-by
PeriodName

No. of thrusters

Δv
m/s

Time

2016/3/22〜2016/5/21

Phase 1: Ion engine operation

3（2 at times）

127

798 h

2016/11/22〜
2017/4/26

Phase 2: ion engine

3（2 at times）

435

2593

2018/1/10〜2018/6/3

Phase 3: ion engine

2→3

393

2475

41