Operation status for the asteroid explorer,Hayabusa2, in the vicinity of Ryugu

September 5, 2018
JAXA Hayabusa2 ProjectTopics
Regarding Hayabusa2 :l Current statusl Astrodynamicsl MINERVA-9



Contents
0. Hayabusa2 & mission flow outline
1. Project status & overall schedule
2. Box-B operation
3. Small Monitoring Camera (CAM-H)
4. Astrodynamics
5. MINERVA-9
6. Operation schedule
7. 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 solarsystem. 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
BBy 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 ofits oceans and life, thereby developing solar system science.
B 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.
BWe will establish stable technologies for return exploration of solar-system bodies.

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

International positioningG
BJapan is a leader in the field of primitive body exploration, and visiting a type-C
asteroid marks a new accomplishment.
BThis 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.
BNASA 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
MassApprox. 609 kgLaunch
3 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>▲
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Points to note
Pay attention to the orientation of the asteroid 	!
Ryugu images show the northern
direction of Ryugu pointing
upwards.
north pole
NorthPoleC©JAXAD

C©JAXA?U. of Aizu et al.D

north pole

Example of a Ryugu “map”

1. Current project status& schedule overview

Current statusG– Box-B operations began on August 18. On August 24, the spacecraft reached 9km
in the +y direction, followed by 9km in the –x direction on August 31. Purpose ofthe operation was to image Ryugu around the south pole and evening side.
– Preparation for the approach operations to be carried out in September and October.
– Rehearsal 1 for the touchdown operation is scheduled from September, 11-12.

Schedule overview:
2015
312

Event	

.+3+#,
/0'1#3+/.

2016
10 12

!

launch	'% 2017

426+.)$8

#1 4.

/41.'83/#23'1/+&2020
12

Arrival at Ryugu	4.' 

''.31218
#13*1'341.

23'1/+&01/7+-+38/0'1#3+/.2

Earth swing-by	
'% #1 #8

2019

6 7

#001/#%*C"D3'23/0'1#3+/.2 Southern hemisphere station
operations (CAN/MLG)	
#8  
%3
#8

Ion engine operations ※	

2018

Departure from Ryugu	/5J'%

Capsule re-entry	
#3'  

Optical navigation	 Solar conjunction	#8 4, /5'%
/5

01

#.

4.

 



2F
FBox-B Operation
Box-B Operation
+y

8/24
(0,9) km+xBig Boulder
SouthPole

20km
8/31

FarSide Rotation

8/18
Home Position
The SUN
9/7
Earth(-9,0) km
C©JAXAD2F
FBox-B Operation
Ryugu imaged during Box-B operations
Image captured with the Optical Navigation Camera – Telescopic (ONC-T) on August 24 at around17:00 JST. Image taken from +y = about 9km. The distance to Ryugu is about 22 km. Image credit: JAXA, U. of Tokyo, Kochi U, Rikkyo U, Nagoya U, Chiba Institute of Technology, Meiji U, U of Aizu, AIST. 

3FFSmall Monitor Camera CCAM−HDD
L Camera built & mounted from donation funds.
L View down sampler horn.

C©JAXAD3F
FSmall Monitor Camera CCAM−HDDCurrent appearance of sampler hornSampler horn imaged by the Small MonitorCamera (CAM-H) on August 14, 2018

C©JAXAD3F
FSmall Monitor Camera CCAM−HDD
ReferenceSampler horn test photograph captured by theSmall Monitor Camera (CAM-H) on April 16,
2018. The shiny surface in the red circle is thetarget plate of the sampler horn irradiated with theLRF-S2 laser. Sampler horn test photograph by
the Small Monitor Camera(CAM-H) on December 5, 2014.
C©JAXAD4F
FAstrodynamics
L What is astrodynamics?
– General flight dynamics handled in space engineering.
– Orbital and attitude motion, navigation, guidance, control etc.
L Hayabusa2 astrodynamics team activities– Orbit estimation of the Hayabusa2 probe and asteroid Ryugu.
– Creation and evaluation of the gravitational field model ofasteroid Ryugu.
– Evaluation of orbital motion in the vicinity of the asteroid.
– Estimation of asteroid parameters used for exploratory
operations and influence the actual operation system.
L What we learned from previous observations:– Gravity of the asteroidCmassD
Topics for today– Dynamical environment near the asteroid– Asteroid’s orbit4F
FAstrodynamics
Analysis method– By simultaneously using radio observation data (range, range-rate etc) of the spacecraft
acquired by the ground stations, relative observational data of the asteroid acquired by
the onboard instruments (laser altimeter & camera images), the precise orbit of the probe
and the gravitational acceleration from asteroid Ryugu were estimated.
– The gravity estimate for asteroid Ryugu was carried out using data acquired during theGravity Measurement Descent Operation (performed 8/6- 7 ). Combined with thevolume information calculated from the shape model, it is possible to estimate the bulk
density of the asteroid.
– The dynamic environment near asteroid Ryugu could then be evaluated, using theestimated gravity information. Image of precise orbit determination

4F
FAstrodynamics
Distance
fromasteroid
centerDescent Phase
BNo trajectory correction
control (free-fall)BImage navigation continues

GCP-NAV descent
CPerform trajectory
correction controlD

Rising Phase
BNo trajectory correction
control (free-rise)
BImage navigation continues

Home Position
Recoveryoperation20km

Vinitial = -0.1m/s

6520m
5500m

End GCP-NAV
HP Return ΔV~1400mIncrease ΔVTimeUTCJST

8/6 ~01:00
8/6 ~10:00

Groundstation

UDSC~11:00~20:00DSN(MAD)

8/7 ~08:50~23:108/7 ~08:10

DSN(GDS)

time~17:50

UDSC

DSN(MAD)4F
FAstrodynamics
l Descent phase began from
~6,500m altitude, continuingwith free-fall motion for about
12 hours.
l Performed trajectory control
ΔV at the lowest point (altitude~850m) and changed to risingphase.
l Relative to the orientation of
the rotation of the asteroid, in
the asteroid fixed coordinatesystem, the orbit approachedand ascended at the equatorial
plane (XY plane) of theasteroid.
l GM (G: gravitational constant,M: mass) obtained during theGravity Measurement Descent
Operation is:

Return to HP

Start descent

RisingLowest point

descent

C©JAXAD

GM=~30 (m3/s2):>MassG~450 million tons

Orbit trajectory in the roid fixed coordinate system
4F
FAstrodynamics
L Evaluation of the acceleration environment on the asteroid surface
from the estimated gravitational information.
L The acceleration information in the vicinity of the asteroid will be usedfor future touchdown operations etc.
ü The surface acceleration variation
is of the order of 0.110.15 [mm/s 2]ü The acceleration near the poles islarge, and small in the vicinity ofthe equator.
ü Gravity at the equator isL Approx. 1/80,000 the Earth.
L Several times Itokawa.
(mm/ s2)

Acceleration on the surface of Ryugu

C©JAXAD5. Asteroid Exploration RoverMINERVA-991
MINERVA-II is the successor of MINERVA installed in Hayabusa spacecraft.	  
MINERVA-II1(Rover-1A, Rover-1B)

Producedat JAXAC©JAXAD

H Cooperation makers, universities, groups, etc.I
Aichi University of Technology, University of Aizu,Addnics corp.EAntenna Giken Co., Ltd., ELNA ,CesiaTechnoEThe University of Tokyo, Tokyo
Denki University? Digital Spice Corp., Nittoh Inc.EMaxon Japan, DLR, ZARMl Weight (including deployment)
MIMERVA-II1 :2.5kgl MINERVA-II1
Twin rovers5. Asteroid Exploration RoverMINERVA-991
MIcro Nano Experimental Robot Vehicle for Asteroid
the Second Generation

L New hopping mobility
L Adaptation with AI
L Small, light-weight,
L Low power consumption
L Autonomous behavior

C©JAXADL Scientific observation（stereo sensing, thermometer)5. Asteroid Exploration RoverMINERVA-991
bodysizeweightactuators
sensorscom.

Cylinder (hexadecagonal pole)
Diameter: (180[mm]
Height: 70[mm]1A:1151[g], 1B:1129[g]DC motor
4 cameras(1A), 3 cameras(1B)
photodiodes, accelermeter
thermometers, gyro
32k[bps](max)5. Operation Sequence(Not to Scale)
Altitude[Event](6) Additional free fall for
preventing plume(2) GCP-NAV altitude control offcontamination(3) FF ΔV to decelerate descent(7) Ascent ΔV(5) MINERVA separationvelocity(9) MINERVA landing(1) GCP-NAV(4) Wait for attitude control
convergence(8) Attitude scan(10) HP Keeping

HP:20 [km]constant descentvelocity e.g. 10 [cm/s]<A�er	  350sec	  of	  ;	  “Lateral	  dV2	  (A�er	  Separa�on)”	  Trigger Altitude:60 [m] (TBD)
free fall
Separation
Altitude 50 ~55m(TBD)
Ascent Altitude
G30 + β [m] (TBD);at	  LIDAR	  Alt.	  60m	  “Lateral	  dV1	  (Before	  Separa�on)	  ”	  “GCP-­‐NAV	  end”	  	  Point B:
1st Contacton SurfaceONC-W2

Point A:MINERVA
Separation

ONC-T

Point C:
Final settlement
PointONC-W1Time
Candidate ofSimulation Epoch(Not to Scale)
HP: Home Position6. Operation Schedule
Operation Schedule>>>Touchdown 1 rehearsal 1:
September 11 ~ 12>>>>>>>>>CArrival at lowest altitude : September 12D>>>MINERVA-II-1 operation:
September 20 ~ 21>>>>>>>>>CMINERVA-II-1 separationGSeptember 21D>>>MASCOT operation:
October 2 ~ 4>>>>>>>>>CMASCOT separationGOctober 3D
Touchdown 1 rehearsal 2:>>>Touchdown 1:

mid-Octoberlate-OctoberNote: date of operations may be changed.
6F
FRehearsal 1 for Touchdown 1
Outline: Touchdown rehearsal for information collectionand abortion strategy development.

Descent toaltitude 30mDescent starts
Gat 16:00 on Sep.11

The final approach
Gat 14 on Sep. 12.HP recoveryonC©JAXAD

Sept. 13

7. Future Plans■Schedule for press briefings
L Sept. 27 CThursdayD15:30J16:30
L Oct. 11 CThursdayD15:30J16:30 (TBD)■Press Center (Sagamihara)
L Sept. 21 (Friday) : MINERVA-II Operation
L Oct. 3 (Wednesday) : MASCOT OperationReferenceHome Position Coordinate System
EarthThe Sun

ZHP

YHP
Ryugu

XHP

BOX definition
Earth Sun

Home position
coordinate system
CXHP, YHP, ZHPD
BOX-A

CReference materialD
BOX-B

BOX YHP-direction size
BOX-C

BOX-A operationGoperations while hovering at
20km altitude. Regular operation standard.
BOX-B operationGTour observation. Hovering
area extended horizontally to enable
observations to either side of the asteroid.
asteroid averageradius

asteroid center of mass

BOX-C operationGHovering area extended
vertically to enable observations at lowaltitude. Selection of landing site candidates forMINERVA-9
9Conditions for MINERVA-II landing site selectionGp Landing site does not overlap with spacecraft touchdown candidates.
p Landing site does not overlap with MASCOT landing site candidates.
p The altitude of the spacecraft after separation must not be lower than 30m.
p Ensure communication with ground station.
n Ensure communication with Hayabusa2 spacecraft.
n Not high temperature region, and fewer parts in shadow
BDue to the equatorial ridge, separation near the equator results in widely spaced landing
points to the north and south.
BSeparating in the southern hemisphere may result
Landingnorthlocation
in a spacecraft altitude below 30m.
south

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

Separation
position

C©JAXAD When separating near the equator, thelanding position spread north and south.Selection of landing site candidates for
MINERVA-9
9Landing site candidates for MINERVA-II: northern hemisphere

Possible overlapwith mid-latitude
touchdown

No communication
with ground station
Longitude 0°
C©JAXAD

BTouchdownBconfirm no overlap with
MASCOT's landing site.
BAlso consider observability etc. using theONC-T camera.

Candidate locationsG
N6 > N1 > N7 Strategy toward the successful touchdown
Landing	  site	  candidates	  selected	  at	  this	  stage.

= Initial plan
@Candidate site search;A@Reﬁne	  ;A	  @Landing	  opera�on	  ;A	  Iden�fy	  mul�ple	  technically	  landable	  areasSelect	  2	  -­‐	  3	  sites	  by	  ranking	  areas	  of	  scien�ﬁcally	  high	  value

Perform	  rehearsal	  descent	  &	  landing	  for	  high	  priority	  candidate	  sites	  @Candidate site search<A@Reﬁne	  <A

@Landing	  opera�on	  <ABBBFurther	  examina�on	  of	  landing	  feasibility	  necessary	  at	  this	  stage.

=New plan
@Candidate site searchA

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 landing@ReﬁneA	  Select	  1	  –	  3	  sites	  with	  high	  scien�ﬁc	  merit	  Landing Site Selection(LSS). Conducted atconference.

Operationalproficiency
@Gather informationAb

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

High resolution
surface images
Landing gear
operational data@Landing (trial) operationA

Landing attempt. Depending on
circumstances, stop half-way anduse data to analyze landing area. Repeat	  while	  reﬁning	  landing	  technique	  and	  improving	  this	  sequence.

