Asteroid explorer, Hayabusa2,
reporter briefing

October 28, 2019
JAXA Hayabusa2 ProjectTopicsRegarding Hayabusa2,
Results from the target marker separation
operationResult from the MINERVA-II2Rover2
separation operation Rover2 (MINERVA-II2) will also be described by Tohoku
University, representing the university consortium
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Hayabusa2 reporter briefing

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Contents
0. Hayabusa2 and mission flow outline
1. Current status and overall schedule of the project
2. Target marker separation operation results
3. MINERVA-II2 (Rover2) separation operation results
4. Naming the target marker
5. Future plansReference
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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 fieldin 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.

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Hayabusa2 reporter briefing

Hayabusa 2 primary specifications(Illustration: Akihiro Ikeshita)
MassApprox. 609 kgLaunch
3 Dec 2014Mission
Asteroid returnArrival
27 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Launch
Dec 3, 2014

Mission flow
Ryugu arrival

Earth swing-by
Dec 3, 2015

MINERVA-II-1 separation

June 27, 2018

Sep 21, 2018

MASCOT
separation
Oct 3, 2018

Ryugu departure
NovDec, 2019

completed →July 11, 2019

Impactor (SCI)

Earth return
End of 2020

Second touchdown

5 April, 2019

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

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Hayabusa2 reporter briefing

First touchdown
Feb 22, 20195

1. Current project status & schedule overview
Currentstatus8–––

Scheduleoverview
Event

The separation operation for MINERVA-II2 (Rover 2) was conducted from September 28 to October 3.
The separation was able to occur as scheduled on October 3 at 00:57 JST (on-board time).
The spacecraft then remained at an altitude of about 8km and observed Rover2, before returning to thehome position on October 15.
BOX-C operation will be conducted between October 19 to October 30. The minimum altitude will beabout 4km between October 24  26. Data will be acquired using onboard science instruments.
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Hayabusa2 reporter briefing

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2. Target marker separation operation results
Target marker separation operation sequence results
altitudeObservation with sun behind

HP:20 [km]HP Box-A return

Slow descent

Descent speed
020cm/s

Separation altitude
1km

ONC-T,W1 ONC-T,W1

2 TM separation
Separation interval is about 5 minutes(equatorial and polar directions)

Image creditJAXA
2019/10/28

    
Hayabusa2 reporter briefing    Time (JST)72. Target marker separation operation resultsllsun light

Point 1: Target marker (TM) separation operationTM orbit injection
Polar orbita stable orbit with good observability
Equatorial orbitan orbit with a higher
contribution to the gravity estimate.
Injection to completely different orbits
TM imaging method and observation location /attitudelImage from a distance (20km) where thetrajectory of the TM can fit entirely within view.

lTo utalize the TM retroreflectivity, the bright TM
was imaged when the Sun was behind thespacecraft.
Image capture interval set to 30 minutes.

l

ONC-T field of view(± about 3°)
Orange: TM-E (Equator) orbit
Blue: TM-C (Poles) orbit

TM orbit seen from the spacecraftexample of designed trajectoryRelationship between TM orbit
and spacecraft for TM observation(design time)Image creditJAXA

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Hayabusa2 reporter briefing8

2. Target marker separation operation results
Point 2: Target marker (TM) separation operationDescent start position

Execution of slow descent / ascent /hovering with "natural motion in highaccuracy"l 1 year of exploration has allowed
skilled control of the spacecraft aroundthe asteroid.
l Spacecraft was lowered along a naturalorbit trajectory.

TM observation position

TM separation positionu Control intervalThis time, once a day ⇔ normally need once every 10 minutes

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Hayabusa2 reporter briefing

TM separation time
• Position uncertainty: 19.5m• Velocity uncertainty: 3.6mm/s

image creditJAXA
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2. Target marker separation operation results
TM-E (equatorial orbit) and TM-C (polar orbit) (ONC-T) orbiting the asteroidFirstrelease 

(animation

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

10(Image credit: JAXA Chiba Institute of Technology AIST Rikkyo University University of Tokyo Kochi University Nagoya University Meiji University University of Aizu)

2. Target marker separation operation results
TM-E (equatorial orbit) and TM-C (polar orbit) (ONC-T) orbiting the asteroidFirst
release TM-Eequatorial(Image credit: JAXA, Chiba Institute ofTechnology, AIST, Rikkyo University,
University of Tokyo, Kochi University,
Nagoya University, Meiji University,
University of Aizu)

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 TM-Cpolar

112. Target marker separation operation resultsFirst
release

TM-EEquatorial orbit

TM-CPolar orbit

Identification ofwhere TM-E
(equatorial orbit) andTM-C (polar orbit)
landed on asteroid
Ryugu after orbit.

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

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Hayabusa2 reporter briefing

123MINERVA-II2 (Rover2) separation operation results
HP return
HP:20 [km]Slow descent

Observation
altitude810km
ONC-T,W1

separation
1km

ONC-T,W1

Rover2
separation

Towards equator

9/28
10:30
2019/10/28

10/3
0:57
Hayabusa2 reporter briefing

10/10
11:35

10/15
11:45

Time(JST)13

3MINERVA-II2 (Rover2) separation operation results Design of orbit injection condition for Rover2l Unstable trajectory that can reliably land Rover2 on the asteroid.
lllRover2 imaging method and observation position / attitude
As the rover is darker than the TM, images were taken from a low
altitude with a long exposure time (about 3 minutes).
To capture the image of the rover passing through the field of view,imaging was performed at frequent 10 minutes internals.
The rover was found in a large number of images.

 Execution of slow descent / ascent / hovering with "natural
motion in high accuracy"l The team used the experience gained from the TM orbits.

ONC-T field of view
(about 3 degrees)

7 .9 k m

Point of separation operation for Rover2

Relationship between the rover orbit and spacecraftfor observation (design time)

Rover2 trajectory

Image creditJAXA
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Hayabusa2 reporter briefing

143MINERVA-II2 (Rover2) separation operation results
First release(animation) 
 

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

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Hayabusa2 reporter briefing

153MINERVA-II2 (Rover2) separation operation results
First release

Rover2 captured with both the ONC-T and ONC-W1(two images taken at almost the same time)
ONC-T field of view

ONC-T field of view

RyuguRyugu(Image credit: JAXA, Chiba Institute of Technology, AIST, Rikkyo University, University of Tokyo, Kochi University, Nagoya University, Meiji University, University of Aizu)

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3MINERVA-II2 (Rover2) separation operation resultsnEstimated trajectory•From orbit estimation after the operation, the rover reached theasteroid surface about 1 day after separation (about 1.25 orbits)

nONC imaging•••

Successful observation during orbiting in addition to imaging
during separation.
Confirmation of rover in 15 images using ONC-W1
Confirmation of rover in 14 images with ONC-Tn

Communication••

Secure communication link with Rover2 even after separation.
Communication was possible even after the periods of shadow
passing.
Communication remains possible after landing.
Detecting the ranging signal with Rover2.

••

Rover2 estimated trajectory and ONC-T imaging /communication link (during orbit) period
Period ofsuccessfulimaging withONC-T (red)Rover2 separation
positionRover2 trajectory

For details, see the report from the university consortium.
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Hayabusa2 reporter briefing

Period of successfulcommunication
during orbit (green)
Rover2 landing
positionimage creditJAXA

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Results obtained from the separation operations•

The need for a rehearsal operation was introduced during the study for the Rover2operation. This led to the idea of using the TM separation and that results could bemaximised by combining the two operations.

•This was the world’s first successful experiment of multiple artificial satellites into theorbit around a small celestial body.

•The operations also achieved the world’s smallest artificial satellite (TM) around an
extraterrestrial body.

•Successfully acquired data for gravity field estimating by multiple artificial orbits using
different observation data types (optical observation, radiowaves).

•

A new gravity estimation method was put into practice and the operation was completed.

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Background and appreciation of executions of the orbit operation
for the target marker and the MINERVA-II2 rover.

Hayabusa2 Project Manager Yuichi Tsuda• The idea of orbiting an object around an asteroid was born at the beginning of the development for Hayabusa2 (around2012), during a discussing with the Hayabusa2 Project Astrodynamics Science Team. Since the time schedule of development
was tight, we could not inculude this idea into the plans for Hayabusa2, but the idea continued to be developed as a topic ofresearch (Astrodyanmics).
• By combining the orbit of the MINERVA-II2 rover with that for the target marker that had already been studied in advance, anew role for the MINERVA-II2 rover was fashioned that could improve the results for the gravity science. Professor Daniel
Scheeres and his group at the University of Colorado, Boulder and Professor Junichiro Kawaguchi at ISAS were deeply
involved in this work. The university consortium were also actively involved in the decision to make this major change to how
this rover would be used.
• We were very fortunate to receive radiowaves from MINERVA-II2 after separation, which included a ranging signal. By
combining the radio signal and the observations from Hayabusa2 of the two target markers and MINERVA-II2 in orbit, weestablished a new gravitational field measurement method that has never previously been used. This is also a world first for‘the smallest-object constellation around a small celestial body’!
• We were able to create the new effective plan to use the MINERVA-II2 Rover which had some problems with great teamwork.
As a result, the MINERVA-II2 Rover worked well in its new role. I am very proud of these things, because they symbolize themission of Hayabusa2. For all those who helped realize such flexible and innovative science with Hayabusa2, including theHayabusa2 Mission team, Astrodynamics team, university consortium team including Tohoku University and the University ofColorado Boulder, I thank you deeply.
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4. Name for the orbiting target markers
We decided to give the target markers used for the orbital operation the following names:• TM-CSputnik (Спутник• TM-EExplorer
Reason• These two target markers are the first artificial satellites to orbit around asteroid Ryugu. The
first satellite series on Earth were named Sputnik and Explorer.
• In Russian, ‘Sputnick’ begins with a ‘C’, so this name was chosen for TM-C, while‘Explorer’ with an ‘E’ went to TM-E.
• Sputnik 1 has a larger orbit inclination angle (inclination with respect to the equatorialplane) and is closer to the TM-C orbit.
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4. Name for the orbiting target markers
         (Image credit: JAXA, Chiba Institute of Technology, AIST, Rikkyo University, University of Tokyo, Kochi University, Nagoya University, Meiji University, University of Aizu)

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5. Future plans
Operation schedule
October 19-30
November  December

BOX-C operation
Departure from Ryugu

Press briefings
November 12 afternoon

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Press conference Sagamihara campus

Hayabusa2 reporter briefing

22Reference

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Optical navigation camera (ONCONCOptical Navigation Camera
Objective: Images fixed stars and the target asteroidfor spacecraft guidance and scientific measurements• Global observations of surface topography
Craters, structural topography, rubble, regolith distribution

W
Fo 2V

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

W1
FoV• 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 of surface
particles; observation of sampler projectiles and surface
markings• Elucidation of features of target asteroid• Distribution of hydrated 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(© JAXA)
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TFoV
ONC-T
Detector
Viewing direction

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(wide-angle)

Sideward (wideangle)

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

W2Heat sink

W2Aperture•

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

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Target marker• Body (ball) size: about 10cm diameter• Retroreflective film on the surface• 4 bar rolling prevention• Many polyimide small balls inside• Separation orderB→A→E→C→D• 2018/10/25: B dropped• 2019/05/30: A dropped• 2019/09/17 E and C dropped
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ABC

DE

Image creditJAXA
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Target marker separation
Target marker C separation
separation time2019/9/17 01:24 JST

animation

Target marker E separation
separation time2019/9/17 01:17 JST

Animation of the target markers taken from the spacecraft. Images captured at 4s intervals. In the first image, the distanceto the target marker is about 1m, and in the final image is is about 9m (the target marker is not dropping, but thespacecraft moves away from the target marker.)creditJAXAChiba Institute of TechnologyUniversity of TokyoKochi UniversityRikkyo University, Nagoya University, Meiji University, University of Aizu, AIST. 

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