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Hayabusa2 (Japanese: はやぶさ2, "Peregrine falcon-2") is an asteroid sample-return mission operated by the Japanese space agency, JAXA. It follows on from Hayabusa and addresses weak points identified in that mission.[5] Hayabusa2 was launched on 3 December 2014 and rendezvoused with near-Earth asteroid 162173 Ryugu on 27 June 2018.[6] It is in the process of surveying the asteroid for a year and a half, departing in December 2019, and returning to Earth in December 2020.

Hayabusa2
Hayabusa probe
Artist's impression of Hayabusa2
Mission typeAsteroid sample return
OperatorJAXA
COSPAR ID2014-076A
SATCAT no.40319
Websitewww.hayabusa2.jaxa.jp/en/
Spacecraft properties
ManufacturerNEC[1]
Launch mass609 kg (1,343 lb)
DimensionsSpacecraft bus: 1 × 1.6 × 1.25 m (3.3 × 5.2 × 4.1 ft)
Solar panel: 6 m × 4.23 m (19.7 ft × 13.9 ft)
Power2.6 kW (at 1 au), 1.4 kW (at 1.4 au)
Start of mission
Launch date3 December 2014, 04:22 UTC (2014-12-03UTC04:22Z)[2]
RocketH-IIA 202
Launch siteLA-Y, Tanegashima Space Center
End of mission
Landing dateDecember 2020 (planned)
Landing siteWoomera, Australia
Flyby of Earth
Closest approach3 December 2015
Distance3,090 km (1,920 mi)[3]
(162173) Ryugu orbiter
Orbital insertionJune 27, 2018, 09:35 UTC[4]
Orbital departureDecember 2019 (planned)
Animation of Hayabusa2 orbit from 3 December 2014 to 29 December 2019
  Hayabusa2   162173 Ryugu   Earth   Sun

Hayabusa2 carries multiple science payloads for remote sensing, sampling, and four small rovers that will investigate the asteroid surface to inform the environmental and geological context of the samples collected.

Contents

Mission overviewEdit

Asteroid 162173 Ryugu (formerly designated 1999 JU3) is a primitive carbonaceous near-Earth asteroid. Carbonaceous asteroids are expected to preserve the most pristine materials in the Solar System, a mixture of minerals, ice, and organic compounds that interact with each other.[7] Studying it is expected to provide additional knowledge on the origin and evolution of the inner planets and, in particular, the origin of water and organic compounds on Earth,[8][7] all relevant to the origin of life on Earth.[9]

Initially, launch was planned for 30 November 2014,[10][11][12] but was delayed to 3 December 2014 04:22 UTC (4 December 2014 13:22:04 local time) on a H-IIA launch vehicle.[13] Hayabusa2 arrived at Ryugu on 27 June 2018,[6] and it is expected to survey the asteroid for a year and a half during which time it will collect samples three times.[7] The mission plan calls for it to depart in December 2019, and return the samples to Earth in December 2020.[12]

Compared to the previous Hayabusa mission, the spacecraft features improved ion engines, guidance and navigation technology, antennas, and attitude control systems.[14] A kinetic penetrator will be shot into the asteroid to expose pristine sample material.[12][8]

Funding and historyEdit

Following the partial success of Hayabusa, JAXA began studying a potential successor mission in 2007.[15] In July 2009, Makoto Yoshikawa of JAXA presented a proposal titled "Hayabusa Follow-on Asteroid Sample Return Missions". In August 2010, JAXA obtained approval from the Japanese government to begin development of Hayabusa2. The cost of the project estimated in 2010 was 16.4 billion yen (US$146 million).[5][16]

The primary contractor NEC built the 590 kg (1,300 lb) spacecraft, its Ka band communications system and a mid-infrared camera.[17]

Hayabusa2 was launched on 3 December 2014, arrived at asteroid Ryugu on 27 June 2018, and remained at a distance of about 20 km to study and map the asteroid. In the week of 16 July 2018, operations were begun to lower this hovering altitude.[18] On 21 September 2018, Hayabusa2 ejected the first two rovers, Rover-1A and Rover-1B, from about 55 meters altitude that fell independently to the surface of the asteroid.[19][20]

SpacecraftEdit

Hayabusa2 Performance[21][22]
Ion thruster name μ10
Number of thrusters 4 (one is a spare)
Total thrust 30 mN
Specific impulse (Isp) 3,000 sec
Acceleration 49 μm/s2
Power 1,250 W
Spacecraft wet mass 610 kg
Ion engine system
dry mass
66 kg
Ion engine system
wet mass
155 kg
Solar array 23 kg
Xenon propellant 66 kg
Hydrazine/MON-3 propellant 48 kg

The design of Hayabusa2 is based on the first Hayabusa spacecraft, with some matured improvements. [23][24] It has a mass of 610 kg (1,340 lb) with fuel,[24] and electric power is generated by bilateral solar arrays with an efficiency of 2.6 kW at 1 AU, and 1.4 kW at 1.4 AU.[24] The power is stored in eleven inline-mounted 13.2 Ah lithium ion batteries.[24]

Propulsion

The spacecraft features four solar-electric ion thrusters for propulsion called μ10,[21] one of which is a backup. These engines use microwaves to convert xenon into plasma (ions), which is accelerated by applying a voltage from the solar panels and ejected out the back of the engine. The simultaneous operation of three engines generates thrusts of up to 28 mN.[24] Although this thrust is very small, the engines are also extremely efficient; the 66 kg of xenon[21] reaction mass can change the speed of the spacecraft by up to 2 km/s (4,500 mph).[24]

The spacecraft has four redundant reaction wheels and a chemical reaction control system featuring twelve thrusters for attitude control (orientation) and orbital control at the asteroid.[24][21] The chemical thrusters use hydrazine and MON-3, with a total mass of 48 kg of chemical propellant. [24]

Communication

The spacecraft has two high-gain directional antennas for X band and Ka band.[21] Bit rates are 8 bps–32 Kbps.[24] The ground stations are the Usuda Deep Space Center, Uchinoura Space Center, NASA Deep Space Network and ESA's Malargü Station.[24]

Navigation

The optical navigation camera telescope (ONC-T) is a telescopic framing camera with seven colors to optically navigate the spacecraft. [25] It works in synergy with the optical navigation camera wide-field (ONC-W2) and with two star trackers.[24]

In order to descend to the asteroid surface for sampling, the spacecraft will first release up to five target markers in the selected landing zones as artificial landmarks with highly reflective outer material that is recognized by a strobe light mounted on the spacecraft.[24] The spacecraft will also use its laser altimeter and ranging (LIDAR) and other sensors during sampling.

InstrumentsEdit

The Hayabusa2 payload incorporates multiple scientific instruments:[26][27]

  • Remote sensing: Optical Navigation Camera (ONC-T, ONC-W1, ONC-W2), Near-Infrared Camera (NIR3), Thermal-Infrared Camera (TIR), Light Detection And Ranging (LIDAR)
  • Sampling: Sampling device (SMP), Small Carry-on Impactor (SCI), Deployable Camera (DCAM3)
  • Four rovers: Mobile Asteroid Surface Scout (MASCOT), Rover-1A, Rover-1B, Rover-2.

Remote sensingEdit

The Optical Navigation Cameras (ONCs) are used for spacecraft navigation during the asteroid approach and proximity operations. They will also remotely image the surface and search for interplanetary dust around the asteroid. ONC-T is a telephoto camera with a 6.35°×6.35° field of view and several optical filters carried in a carousel. ONC-W1 and ONC-W2 are wide angle (65.24°×65.24°) panchromatic (485–655 nm) cameras of nadir and oblique views, respectively.

The Near-Infrared Spectrometer (NIRS3) is a spectrograph operating at wavelengths 1.8–3.2 μm, intended for analysis of surface mineral composition.

The Thermal-Infrared Imager (TIR) is a thermal infrared camera working at 8-12 μm, using a two-dimensional microbolometer array. Its spatial resolution is 20 m at 20 km distance or 5 cm at 50 m distance. It will be able to determine surface temperatures in the range -40 – 150°C.[26]

The Light Detection And Ranging (LIDAR) instrument will measure the distance from spacecraft to the asteroid surface by measuring the time of flight of laser light reflection. It operates over the altitude range 30 m–25 km.[26]

When the spacecraft is closer to the surface than 30 m during the sampling operation, Laser Range Finders (LRF-S1, LRF-S3) are used to measure the distance and the attitude of spacecraft relative to the terrain.[28][29] Another device LRF-S2 monitors the sampling horn to trigger the sampling projectile.

LIDAR and ONC data will be combined to determine the detailed topography (dimensions and shape) of the asteroid. Monitoring of a radio signal from Earth will allow measurement of the asteroid's gravitational field.

RoversEdit

Hayabusa2 carries four small rovers to investigate the asteroid surface in situ,[30] and provide context information for the returned samples. All four rovers will move around by short hops, and none is equipped with wheels due to the minimal gravity of the asteroid. They will be deployed at different dates from about 60 m altitude and fall freely to the surface under the asteroid's weak gravity.[31] The first two rovers landed on asteroid Ryugu on 21 September 2018.[32]

MINERVA-IIEdit

 
The first photograph from the surface of an asteroid, taken by HIBOU on 22 September during one of its "hops".

MINERVA-II is a successor to the MINERVA lander carried by Hayabusa. It consists of several separate subsystems.

MINERVA-II-1 is a container that deployed two rovers, Rover-1A (HIBOU) and Rover-1B (OWL), on 21 September 2018.[33][34] It was developed by JAXA and the University of Aizu. The rovers are identical with a cylindrical shape, 18 cm diameter and 7 cm tall, and a mass of 1.1 kg (2.4 lb) each.[26][35] They move by hopping in the low gravitational field, using a torque generated by rotating masses within the rovers.[36] Their scientific payload is a stereo camera, wide-angle camera, and thermometers. Solar cells and double-layer capacitors provide the electrical power.

The MINERVA-II-2 container holds the ROVER-2, developed by a consortium of universities led by Tohoku University in Japan. This is an octagonal prism shape, 15 cm diameter and 16 cm tall (5.9 × 6.3 in), with a mass of about 1 kg (2.2 lb). It has two cameras, a thermometer and an accelerometer. It has optical and ultraviolet LEDs for illumination to detect floating dust particles. ROVER-2 carries four mechanisms to hop and relocate.

MASCOTEdit

The Mobile Asteroid Surface Scout (MASCOT) was developed by the German Aerospace Center in cooperation with the French space agency CNES.[37] It measures 29.5 cm × 27.5 cm × 19.5 cm and has a mass of 9.6 kg (21 lb).[38] MASCOT carries four instruments: an infrared spectrometer (MicrOmega), a magnetometer (MASMAG), a radiometer (MARA), and a camera (MASCAM) that imaged the small-scale structure, distribution and texture of the regolith.[39] The rover is capable of tumbling once to reposition itself for further measurements.[30][40] It collected data on the surface structure and mineralogical composition, the thermal behaviour and the magnetic properties of the asteroid.[41] It has a non-rechargeable battery that allowed for operations for approximately 16 hours.[42] The infrared radiometer on the InSight Mars lander, launched in 2018, is based on the MASCOT radiometer.[43][44]

Rover Mass Dimensions Power Science payload Landing date Status
Rover-1A
(HIBOU)
Rover-1B
(OWL)
1.1 kg Diameter: 18 cm
Height: 7 cm
Solar panels Wide-angle camera, stereo camera, thermometers
21 September 2018
Successful landing. Operational.
Rover-2 1.0 kg Diameter: 15 cm
Height: 16 cm
Solar panels Two cameras, thermometer, accelerometer. Optical and ultraviolet LEDs for illumination To land in July 2019[24]
MASCOT 9.6 kg 29.5 × 27.5 × 19.5 cm Non-rechargeable
battery[42]
Camera, infrared spectrometer, magnetometer, radiometer
3 October 2018[45]
Successful landing. Operated on battery for more than 17 h[46]

SamplingEdit

 
Artistic rendering of Hayabusa collecting a surface sample

The spacecraft will collect three samples and store them in separate sealed containers inside the sample return capsule. The three desired samples are surface regolith that exhibits traits of hydrous minerals, regolith with either unobservable or weak evidence of aqueous alterations, and excavated sub-surface material.[47] The minimum desired amount per sampling is 0.1 g, but the system has capacity to collect up to 10 g per sample.[47] The first two samples were scheduled to start in late October 2018, but the rovers show a scenery of large and small boulders and no regolith to sample, so the mission team decided to postpone them to 2019 and evaluate several options.[48] The third sampling will be on excavated material dislodged by a kinetic impactor shot from a distance.[49]

Surface samplesEdit

Hayabusa2's sampling device is based on Hayabusa's. In 2019,[48] the spacecraft will approach the surface of the asteroid with a sampling horn. When the horn touches the surface, a projectile (5-gram tantalum bullet) will be fired at 300 m/s into the surface. The resulting ejecta particles are collected by a catcher at the top of the horn, which the ejecta will reach under their own momentum under microgravity conditions.

Subsurface sampleEdit

The third and last sample collection will acquire material deeper into the subsurface, which has not been subjected to space weathering. This requires removing a large volume of surface material with a substantial impactor. For this purpose, Hayabusa2 will deploy what can de described as a free-flying gun with one "bullet", called Small Carry-on Impactor (SCI); the system consists of a 2.5 kg (5.5 lb) copper projectile shot to the surface by an explosive propellant charge. Following SCI deployment, Hayabusa2 will also leave behind a deployable camera (DCAM3)[Note 1] to observe and map the precise location of the SCI impact, while the orbiter maneuvers to the far side of the asteroid in order to avoid debris from the impact.

Approximately 40 minutes after separation, when the spacecraft is at a safe distance, the penetrator will be fired into the asteroid surface by the detonation of 4.5 kg (9.9 lb) shaped charge of plasticized HMX for acceleration.[40][50] The copper impactor will be shot to the surface from an altitude of about 500 meters and it is expected to excavate a crater of about 2 meters in diameter and expose pristine material.[8] Hayabusa2 will wait about two weeks for the floating debris to clear from the site before descending into the newly-formed crater to retrieve a sample.[51]

Sample-returnEdit

 
Replica of Hayabusa's sample-return capsule (SRC) used for re-entry. Hayabusa2's capsule is of the same size, measuring 40 cm in diameter and will deploy a parachute.

The spacecraft will collect three samples and store them in separate sealed containers inside the sample-return capsule (SRC), which has a thermal insulation, 40 cm external diameter, 20 cm in height, and a mass of ~16 kg.[24]

At the end of the science phase in December 2019,[12] Hayabusa2 will use its ion engines for changing orbit and return to Earth.[52] When Hayabusa2 flies past Earth in December 2020, it will release the capsule spinning at one revolution per three seconds. The capsule will re-enter the Earth's atmosphere at 12 km/s and it will deploy a radar-reflective parachute at an altitude of about 10 km, and eject its heat-shield, while transmitting a position beacon signal.[24][52] The sample capsule will land in the Woomera Test Range in Australia.[53] The total flight distance would be 5,240,000,000 km.[24]

Once on Earth, any volatile substance will be collected before the sealed containers are opened.[47] The samples will be curated and analyzed at JAXA's Extraterrestrial Sample Curation Center,[54] where international scientists can request a small portion of the samples.

StatusEdit

On 21 September 2018, the Hayabusa2 spacecraft ejected the first two rovers, Rover-1A and Rover-1B, from about 55 meters altitude that fell independently to the surface of the asteroid.[19][20] They functioned nominally and transmitted data.[32] The MASCOT rover deployed successfully on 3 October 2018 and operated for about 16 hours as planned.[55]

The first sample collection was scheduled to start in late October 2018, but the rovers show a scenery of large and small boulders and no regolith to sample, so the mission team decided to postpone the sample acquisition to 2019 and evaluate several options.[48] The third and last sample will be on excavated material dislodged by an impactor.[49]

Potential mission extensionEdit

When the spacecraft returns to Earth and delivers the sample capsule in December 2020, it is expected to retain 30 kg of xenon propellant, which can be used to extend its service and flyby new targets to explore.[56] One prime candidate is asteroid 2001 WR1 for a flyby on 27 June 2023.[56]

See alsoEdit

Japanese minor body probes

NotesEdit

  1. ^ DCAM3 is numbered as such because it is a follow-on to the DCAM1 and DCAM2 used for the IKAROS interplanetary solar sail

ReferencesEdit

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External linksEdit