VI. Operations

Tracking station locations ・Usuda is used for normal operations (with Uchinoura also used during launch) Uplink: CMD, RNG (7GHz band) Critical operations also performed by the NASA ・ Downlink: TLM, RNG (8GHz band) Deep Space Network (DSN) (DSN: Goldstone, Madrid, Canberra) Downlink: TLM, RNG (32GHz band) ・We are also trying to arrange use of the Weilheim tracking station with support of the German Aerospace Center (DLR) and the European Space Agency Tracking Station Network (ESTRACK) (Malargüe presumed).

Tracking Stations

JAXA Sagamihara Campus Usuda 64m Uchinoura 34m Uchinoura 20m DSN 34m, 70m ESA / DLR Telemetry reception, confirmation, analysis. Main stn Sub stn Launch support NASA tracking DLR tracking support support Command transmission X-band Trajectory determination and prediction Ka-band Main stn Trajectory planning

East経度longitude（東経） 340 0 20 40 340 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 0

セブレロス（ ESA ） DLR, Weilheim ゴールドストーン（ NASA ） 50 臼田（ＪＡＸＡ） NASA Cebrerosマドリー (ESA) ド（） Usuda 64m (JAXA) 40 Madrid (NASA) Goldstone (NASA) North latitude 緯 Uchinoura 34m (JAXA) 30

度 20

（北緯） 10

-10 -20 ニューノーシア（ ESA ） -30 サンチャゴ（案） NewNorcia(ESA） Canberra (NASA) Malargüe (ESA) -40 キャンベラ（ NASA ） -50

-60 Operations 35 Trajectory planning and determination

Spacecraft trajectory operations are conducted under cooperation between the orbit planning group and the orbit determination group.

Trajectory planning Trajectory determination

Before launch Before launch Plan spacecraft trajectories from launch to Earth Confirm precision of trajectory determination from return (considering various conditions such as launch to Earth return. Perform analysis presuming rockets, ion engines, communications, and heat). data error.

After launch After launch ・Trajectory plans are corrected based on orbit ・Based on actually acquired data*, estimate spacecraft determination values, in particular adjustments to trajectory (positioning and velocity). ion engine operations. ・ Attitude systems group supports trajectory ・ Cooperation with the attitude systems group for estimations for trajectories near the asteroid. trajectories near the asteroid.

Data used for orbital determination

1-way 2-way 3-way

Normally, range and range Range Range rate (Doppler) rate (Doppler) data are used We can know the distance to Both the spacecraft and the ground station are moving, so the frequencies for spacecraft trajectory the spacecraft by sending radio of radio waves traveling between them change due to the Doppler effect, waves from a ground station like any other wave. In other words, by examining changes in transmitted determinations and measuring the return time and received radio wave frequencies, the line-of-sight speed of spacecraft of radio waves sent back. This is with respect to the ground station can be known. This is called the “range called the “range.” rate” or “Doppler.” Distances can be measured using methods called 1-way, 2-way, or 3-way Doppler.

“Radio navigation” refers to estimating position and velocity (trajectory) of the spacecraft using the range and range rate.

QSO waves from the quasar Radio navigation Asteroid imaged by cameras

DDOR : A technique called Delta Differential One-way Optical navigation: Optical navigation, in which data Ranging is used to more accurately determine trajectories. from spacecraft cameras supplement radio navigation, is At least two ground stations simultaneously receive radio waves from performed immediately before arrival at the asteroid. the spacecraft. In addition, we receive radio waves emitted from a By imaging the asteroid using onboard cameras, we can determine the visible celestial body (a quasar) that is visually as close as possible to the direction to the asteroid as seen from the spacecraft. The spacecraft spacecraft. By interfering data received at two or more ground stations, position can be accurately determined through DDOR, but uncertainty the probe trajectory can be determined with high accuracy. (Radio waves regarding the asteroid’s position remains. Accurately approaching the from the probe and those from the quasar are received alternately.) asteroid while verifying its position from the spacecraft is called optical navigation.

Operations 36 VII. Target body

Ryugu( リュウグウ )

162173 Ryugu (1999 JU3) near-Earth asteroid (Apollo group)

Physical parameters Type - Type C (assumed to comprise materials containing water and organics) Size ans Shape - 865 ± 15 m ≒ 900 m, nearly spherical [Müller+ 2017] Reflectivity - Geometric 0.047±0.003 ≒ 0.05(blackish); Bond 0.014±0.002 [Ishiguro+2014] Cg [Binzel+ 2001] ; The reflection spectrum gradient is nearly flat. but slightly reddened in the near-infrared region and with a slight drop in the ultraviolet region. This resembles the reflection spectra of CM and CI meteorites that have experienced heating. [Perna+2017] Density and mass - Density is currently unknown, but presumed to be 0.5-4.0g/cm3 ; Mass is approx. 1.7×1011kg ～ 1.4×1012kg Thermal inertia - 150~300 J m-2 s-1/2K-1, extremely low surface roughness [Müller+ 2017] Rotation period - 7.6326 h ≒ approx. 7h 38min Rotation orientation - Ecliptic longitudeλ = 325±15°Ecliptic latitude β = -40±15° Perihelion distance - 13.25148 Feb 2017; Perihelion distance 0.96321 au; aphelion distance 1.41592 au argument of perihelion 211.447; Ascending node long. 251.591° Orbit Orbital elements - epoch 2458000.5 TDB ( 4 Sep 2017 0:00 UTC ) JPL Small-Body Database Browser ※https://ssd.jpl.nasa.gov/sbdb.cgi#top, accessed 10 Dec 2017 Minimum orbit intersection distance 0.00112 au (potentially dangerous asteroid) Revolution cycle - 473.8908 days ≒ 1.29747 years Orbital radius - Approx.180million km / 1.18956 au; eccentricity 0.19028; inclination 5.8839°

Ryugu Approx. 900m

Tokyo Skytree 634m Itokawa 535m

Tokyo Tower 333m

Asteroid Ryugu imaged with the ONC-T. The photograph was taken on June 26, 2018 at around 12:50 JST. The distance to Ryugu is about 22 km. Image credit : JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University, University of Aizu, AIST.

Target body 37 History of Ryugu naming 10 May 1999 - U.S. LINEAR team discovers asteroid 1999 JU3 (provisional name) at the Socorro observatory. Oct 2006 - 1999 JU3 is listed as a candidate exploration target in the “Hayabusa Successor Spacecraft” proposal. Aug 2013 - Request for naming 1999 JU3 in the Hayabusa 2 project submitted to the LINEAR team, and approval received. 22 Jul 2015 - A campaign for collecting proposed names is conducted. ~31 Aug Approximately 7,300 suggestions are received, from which “Ryugu” is selected. Sep 2015 - LINEAR team submits the name “Ryugu” to the International Astronomical Union. 28 Sep 2015 - Ryugu is published in the Minor Planet Circulars as (162173) Ryugu = 1999 JU3.

Selection of asteroids for exploration

Conditions for selecting an asteroid for exploration

・Scientific objectives : In the Hayabusa 2 project, a C-type asteroid ・Engineering requirements - Ability to return within Hayabusa 2 capabilities ➡ Limits on trajectory size and inclination - Ability for touchdown within Hayabusa 2 capabilities ➡ Limits on asteroid size and revolution period Explorable asteroids ・Orbit between those of Earth and Mars, low inclination from Earth orbit ➡ From spacecraft trajectory control capabilities ・Revolution period of at least about 6 hours ➡ From navigational capabilities at touchdown ・Diameter of at least several hundred meters ➡ To allow for crater creation by impactor ※ We also searched for backup targets, but only 1999 JU3/Ryugu was found to be appropriate. Required acceleration from Earth to asteroid and asteroid absolute magnitude © Y.Tsudaetal. ActaAstronautica 91 (2013) 356–362

(162173) 1999 JU3 (Ryugu) spectrum (162173) 1999 JU3 (Ryugu) light curve from Kim, Choi, Moon et al. A&A 550, L11 (2013) Data from Viras (2008), Sugita et al. (2012), Abe et al. (2008)

Belongs to another low-albedo family Relative reflectance

1999 JU3 = Ryugu

The largest member of Erigone Family

Wavelength [µm] Target body 38 Reference information

Asteroid naming Categorization by asteroid spectral type -Asteroid discoverer receives naming rights. -Here, “discoverer” means the person making first observations allowing for estimation of orbit. -When asteroids are discovered, they are assigned a provisional name. -After a number of observations allowing for sufficiently precise determination of orbit, asteroids are assigned a permanent designation. -Names can be proposed after a permanent designation is assigned. -Proposed names are approved by the International Astronomical Union’s Committee on Small Body Nomenclature.

Naming requirements ・A pronounceable (preferably single) word of 16 or fewer characters ・Names from political or military events or persons allowed only 100 years after occurrence (for persons, 100 years after death) ・Pet names are not allowed ・Restrictions on names of asteroids in special orbits ・Names similar to those of existing celestial bodies are not allowed ・Names for advertising or commercial purposes are not allowed

Asteroid provisional names Broadly S-type 1999 JU 3

Year of discovery・Month of discovery・Order of discovery D Month of discovery : A / B = Jan.1~15 / Jan.16~31, C / D = Feb.1~15/ Feb.16~29...X / Y = Dec.1~15 / Dec.16~31 S Order of discovery : A = 1st, B = 2nd...Z = 25th ( A1 = 26th, B1 = Broadly C-type

2nd...A2 = 51th... ) ※ "I" is not used

C Meteorite classifications

Classified Rocky meteorites Chondrites 86％ Undifferentiated from ratios of Achondrites 8％ meteorites silicate and Stony-iron meteorite 1 Differentiated metallic iron ％ Distance from sun Classification of asteroids by components Iron meteorites (meteoric iron) 5％ meteorites Enstatite chondrites (EH, EL) by T.Hiroi reflective spectrum Chondrites Ordinary chondrites (H, L, LL) by D. Tholen in ASTEROID II Carbonaceous chondrites (CI, CM, CO, CV, CR, CK, CH) S-type - Rocky - Ordinary chondrites C-type - Rich in organics and hydrated minerals - Carbonaceous chondrites D-type - More primitive - Tagish Lake meteorite?

Target body 39 Compound Primitive rocky meteorites Italics indicat names of Metachondrites chondrites Chondrites containing chondrules representative meteorites (spherical grains)

Carbonaceous Ordinary Ungrouped Kakangari Rumuruti Enstatite

Chondrule-free differentiated CI H EL Achondrites rocky meteorites Ivuna High metal Fe Low metal Fe

*1There are other CM L EH Primitive*1 Enstatite categories in addition Murchison Low metal Fe High metal Fe to the two below

Differentiated meteorites in which CO LL nearly same amounts of iron-nickel Acapulcoites Aubrites Ornans Very low m-Fe alloys and silicate minerals coexist

Itokawa particles Stony-Iron Meteorites CV *2 Howardites, Lodranites Angrites Vigarano Eucrites, Diogenites Pallasites Mesosiderites CK HED *2 CHHigh metal Ureilites Karoonda Vesta origin Considered as the origin of metal cores in planetesimals

CR CB Lunar Met. Mars Met. Iron Meteorites Renazzo Bencubbin

Features of each type

Type Spectral form Distribution Correlation with meteorites

C Flat from 0.45 - 0.9 µm. Often outside of the Carbonaceous chondrites Absorption of hydrous mineral origins in 3-µm band in asteroid belt. most cases.

S Reflectance increases from 0.4 to 0.7 μm, but decreases Often inside of the asteroid Ordinary chondrites to 0.7 to 0.9 μm. There is an absorption band around belt. However, reflectance on 0.8 - 1.4 μm and 2 μm. This is consistent with the the short wavelength side absorption bands of pyroxene and olivine. is lowered due to space weathering.

X Reflectivity gently increases at 0.4 - 0.9 μm. Exist throughout the Iron meteorite Those with low reflectance of - 0.04 at 0.55 μm are also asteroid belt. Metamorphic Tagish Lake called P-type. meteorite M-type have reflectance of - 0.1. Enstatite chondrites E-type have reflectance of - 0.4. Achondrite Aubrite

D Reflectance sharply increases at 0.45 - 0.9 μm. Near the Jupiter Trojans Tagish Lake meteorite

V Reflectance increases at 0.4 - 0.7 μm, and abruptly Several percent of asteroids Similar to HED meteorites, drops at 0.7 - 0.9 μm. in the asteroid belt which are basaltic meteorites. Absorption bands are observed around 0.8 - 1.4 μm Asteroid Vesta origin? and 2 μm (absorption bands of pyroxene).

Target body 40 VIII. Science

Component materials Space In addition to science and internal structure weathering Comparison with other asteroids from Itokawa… Molecular LL chondrites? Positioning with regard to Itokawa cloud Rubble pile? Meteoroid impacts Organics, water Primitive solar Crater formation system nebula micrometeoroid descent 2 interplanetary dust Hayabusa 2 1 (comet/ asteroid)

Solar system Ryugu Rubble origins? Hayabusa Regolith science Cosmic ray irradiation Interactions with Solar wind exposure space environment New dating indices Surface exploration through impact experiment

1 Solar system’s past Cross sections Elucidating the birth and evolution of the solar system ・What substances existed, and in what state? Primitive solar system disk ・How did the planets arise and evolve? ( gas + dust ) ・What were the raw materials (organic matter, water) for life? 2 Solar system’s present Calibration of meteorites ・ How are meteorites and asteroid samples related? ※ Many meteorites have been collected, but they are contaminated by the Earth’s atmosphere, water, etc., making it difficult to determine their situation when they were in space. Through comparisons with asteroids, meteorites can become Planetoid valuable samples. Dust ➡ Planetoid formation

Primitive planets

Coalescence of planets

Terrestrial planet formation

Gas giant formation Science from an asteroid sample return - Investigating the materials that formed the planets What materials existed in the primitive solar system disk, and how did they change up to the formation of planets? - Investigating the formation processes of the planets Loss of solar disk, completion of solar How do celestial bodies grow from planetoids to planets? system

Science 41 Science from an asteroid sample return

Investigating the materials that formed the planets

The universe is thought to have been created 13.8 billion Molecular cloud → Primitive solar disc Planetoid Asteroid years ago. Following that, stellar evolution produced various CO CO H H2 elements, which were scattered into space. The solar system Dust Dust Dust Dust

was formed from these materials approximately 4.6 billion D H2O, NH3, Organics CH OH Metamorphosis years ago, but the materials that were present in space at 3 Accumulation Transition of carbon that time remain unknown. We will clarify the distribution of materials on dust surfaces substances in the original solar system disk. We will clarify

how these substances changed on celestial bodies after Interactions between materials, Chirality of water,Minerals and organics their initial formation. amino acids Life on Earth almost Finally, we will elucidate the materials that Earth exclusively formed the planets, oceans, and life. Ice Oceans uses left- Organic Life handed amino acids. Elucidation of organics by Hayabusa2 → But why? Water in minerals Volatile substances, such as water and organic matter, Left-handed right-handed form on dust surfaces in molecular clouds. It is thought (L-configuration) (D-configuration) that these change due to aqueous metamorphism and thermal denaturation in primitive solar system discs and planetoids, eventually accumulating on Earth and providing materials for life. We will clarify what kinds of substance existed during this process.

Topics for Hayabusa 2 What kind of organics were present in the primitive solar discbefore the creation of Earth? Reference: Molecules containing carbon found in space Keywords From Sakai (2011), Yuseijin ・Pre-solar particles : Particles from the interstellar molecular cloud brought into the solar system ・Calcium–aluminum-rich inclusions (CAI) : Substances that record high-temperature states in the early solar system ・Interactions between minerals, water, and organics : Diversification of organic matter on early celestial bodies ・Thermal metamorphism, space weathering : Material changes occurring within or on the surface of celestial bodies after their formation

Investigating planetary formation

Elucidate the structure of planetoids that eventually became planets. Elucidate what processes occurred during the collisions, coalescence, and accumulation of celestial bodies.

Elucidate formation processes from planetoid to planet

Keywords ・Rubble pile body : A celestial body formed from accumulated rubble ・Impacts and coalescence : When celestial bodies collide, the resulting fragments can combine to form a new body ・Accumulation : Accumulation of fragments resulting from a collision via the force of gravity Rubble pile body

Metal core Planet

Dust Planetoid Impact Minerals, water, Differentiated body organic Science 42 Reference

Hayabusa & Hayabusa2 ➡We will investigate events in the early solar system as recorded in asteroids, thereby elucidating the process by which planets formed. ➡ Elucidation of the Missing Zone

Sun Planetoids Earth

Accumulation of Contraction of molecular cloud core, star formation (Ma = 1 million years) gas and dust from molecular cloud core Primordial star Formation of primordial solar disc CAI formation CTTS 4568Ma CAI solidification Gas Adhesion / destruction Bipolar molecular flow Water ice Evaporation/ condensation / Organics melting 4565Ma Silicate dust Metamorphism / alteration Allende chondrule etc. Material mixing and circulation etc. Planetoid Chondrule WTTS (virtual body) formation 4564Ma Accumulation into central star / Collision / destruction / HED differentiation Dispersion of disc gas dissipation outside the system re-accumulation Missing Zone Metamorphism / melting (planetoid = differentiation by (parent virtual body) 4563Ma body) internal heat CM chondrite generation carbonate minerals Aqueous metamorphism (–200 ℃ ) Thermal metamorphism (–800 ℃ ) Collision, Asteroid destruction, Primordial planet Main sequence star accumulation accumulation formation

Appearance of Space Collision, destruction, Accumulation of main sequence weathering, orbit alteration primordial Earth stars: –10 Myr. surface thermal metamorphism Solar radiation, wind Magma oceans Galactic cosmic rays Birth of ocean & life? Oldest sedimentary rock Near-Earth asteroid Meteorites, dust 3800Ma Birth of life? Life (–10 Myr.) First humans

0.2Ma

Present

Science 43 IX. International cooperation

USA - NASA OSIRIS-REx (101955) Bennu

Europe - DLR, CNES

Japan -1999 JU3 U.S. - Bennu EU - 2008 EV5 2014 launch 2016 launch Proposed but not selected Feb 2014

EU/US sample return missions

Hayabusa2 OSIRIS REx Marco Polo - R Cooperation Solar system origins Comparison of mission target asteroids

(101955) Bennu 1999 RQ36 (341843)2008 EV5 (65803) Didymos 1996 GT Mission OSIRIS-RE x Sample return MarcoPolo-R Sample return (not selected) DART Impact Type B C Xk Size 492 m 400 m 780 m Period 4.297 h 3.725 h 2.2593 h Axis RA/Dec : 87/-65 RA/Dec : 105/-66 Albedo 0.046 0.137 0.15 Note binary

International cooperation 44