is an asteroid sample-return mission operated by the Japanese state space agency JAXA. It is a successor to the Hayabusa mission, which returned asteroid samples for the first time in June 2010. Hayabusa2 was launched on 3 December 2014 and rendezvoused in space with near-Earth asteroid 162173 Ryugu on 27 June 2018. It surveyed the asteroid for a year and a half and took samples. It left the asteroid in November 2019 and returned the samples to Earth on 5 December 2020 UTC. Its mission was extended through at least 2031, during which it flew by the asteroid 98943 Torifune in July 2026, and has a planned rendezvous with the small, rapidly rotating asteroid in July 2031.
Hayabusa2 carries multiple science payloads for remote sensing and sampling, and four small rovers to investigate the asteroid surface and analyze the environmental and geological context of the samples collected.
Mission overview
Asteroid 162173 Ryugu (formerly designated ) is a primitive carbonaceous near-Earth asteroid. Carbonaceous asteroids are thought to preserve the most pristine, untainted materials in the Solar System, a mixture of minerals, ice, and organic compounds that interact with each other. 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, all relevant to the origin of life on Earth.
Initially, launch was planned for 30 November 2014, but was delayed to 3 December 2014 at 04:22:04 UTC (3 December 2014, 13:22:04 local time) on a H-IIA launch vehicle. Hayabusa2 launched together with PROCYON asteroid flyby space probe. PROCYON's mission was a failure. Hayabusa2 arrived at Ryugu on 27 June 2018, where it surveyed the asteroid for a year and a half and collected samples. It departed the asteroid in November 2019 and returned the samples to Earth in December 2020.
Compared to the previous Hayabusa mission, the spacecraft features improved ion engines, guidance and navigation technology, antennas, and attitude control systems. A kinetic penetrator (a high-explosive shaped charge) was shot into the asteroid surface to expose pristine sample material which was later collected for return to Earth.
Funding and history Following the initial success of Hayabusa, JAXA began studying a potential successor mission in 2007. 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$).
Hayabusa2 was launched on 3 December 2014, arrived at asteroid Ryugu on 27 June 2018, and remained stationary at a distance of about to study and map the asteroid. In the week of 16 July 2018, commands were sent to move to a lower hovering altitude.
On 21 September 2018, the Hayabusa2 spacecraft ejected the first two rovers, Rover-1A (HIBOU) and Rover-1B (OWL), from about a altitude that dropped independently to the surface of the asteroid. They functioned nominally and transmitted data. The MASCOT rover deployed successfully on 3 October 2018 and operated for about 16 hours as planned.
The first sample collection was scheduled to start in late October 2018, but the rovers encountered a landscape with large and small boulders but no surface soil for sampling. Therefore, it was decided to postpone the sample collection plans to 2019 and further evaluate various options for the landing. The first surface sample retrieval took place on 21 February 2019. On 5 April 2019, Hayabusa2 released an impactor to create an artificial crater on the asteroid surface. However, Hayabusa2 initially failed on 14 May 2019 to drop reflective markers necessary onto the surface for guiding the descent and sampling processes, but later it successfully dropped one from an altitude of on 4 June 2019. The sub-surface sampling took place on 11 July 2019. The spacecraft departed the asteroid on 13 November 2019 (with departure command sent at 01:05 UTC on 13 November 2019). It successfully delivered the samples back to Earth on 6 December 2020 (JST), dropping the contents by parachute in a special container at a location in southern Australia. The samples were retrieved the same day for secure transport back to the JAXA labs in Japan.
After Hayabusa2 completed its primary mission, its mission was extended, and it continued orbiting the Sun using its remaining propellant so that it could visit more asteroids along its flight path. The probe successfully flew-by asteroid 98943 Torifune in July 2026, and it will flyby the micro-asteroid in July 2031.
Spacecraft Hayabusa2 Performance Propulsion Number of thrusters Total thrust (ion drive) Specific impulse (Isp) Acceleration Power Spacecraft wet mass Ion engine systemdry mass Ion engine systemwet mass Solar array Xenon propellant Hydrazine/MON-3 propellant Thrust (chemical propellants)
The design of Hayabusa2 is based on the first Hayabusa spacecraft, with some improvements. It has a mass of including fuel, and electric power is generated by two sets of solar arrays with an output of 2.6 kW at 1 AU, and 1.4 kW at 1.4 AU. The power is stored in eleven inline-mounted 13.2 Ah lithium-ion batteries.
Propulsion The spacecraft features four solar-electric ion thrusters for propulsion called μ10, one of which is a backup. These engines use microwaves to convert xenon into plasma (ions), which are accelerated by a voltage applied by the solar panels and ejected out the back of the engine. The simultaneous operation of three engines generates thrusts of up to 28 mN. Although this thrust is very small, the engines are also extremely efficient; the of xenon reaction mass can change the speed of the spacecraft by up to 2 km/s.
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. The chemical thrusters use hydrazine and MON-3, with a total mass of of chemical propellant.
Communication The primary contractor NEC built the spacecraft, its Ka-band communications system and a mid-infrared camera. The spacecraft has two high-gain directional antennas for X-band and Ka-band. Bit rates are 8 bit/s to 32 kbit/s. The ground stations are the Usuda Deep Space Center, Uchinoura Space Center, NASA Deep Space Network and Malargüe Station (ESA).
Navigation The optical navigation camera telescope (ONC-T) is a telescopic framing camera with seven colors to optically navigate the spacecraft. It works in synergy with the optical navigation camera wide-field (ONC-W2) and with two star trackers.
In order to descend to the asteroid surface to perform sampling, the spacecraft released one of five target markers in the selected landing zones as artificial guide marks, with highly reflective outer material that is recognized by a strobe light mounted on the spacecraft. The spacecraft also used its laser altimeter and ranging (LIDAR) as well as Ground Control Point Navigation (GCP-NAV) sensors during sampling.
Firsts The Hayabusa2 spacecraft was the first to deploy operating rovers on an asteroid.
Science payload
The Hayabusa2 payload is equipped with multiple scientific instruments: 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 sensing The Optical Navigation Cameras (ONCs) were used for spacecraft navigation during the asteroid approach and proximity operations. They also remotely imaged the surface to 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 with nadir and oblique views, respectively.
The Near-Infrared Spectrometer (NIRS3) is a spectrograph operating at a wavelength of 1.8–3.2 μm. NIRS3 was used 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 (70 ft at 12 mi, or 2 in at 160 ft). It was used to determine surface temperatures in the range .
The Light Detection And Ranging (LIDAR) instrument measured the distance from the spacecraft to the asteroid surface by measuring the reflected laser light. It operated over an altitude range between 30 m and 25 km (100 ft and 16 mi).
When the spacecraft was closer to the surface than during the sampling operation, the Laser Range Finders (LRF-S1, LRF-S3) were used to measure the distance and the attitude (orientation) of the spacecraft relative to the terrain. The LRF-S2 monitored the sampling horn to trigger the sampling projectile.
LIDAR and ONC data are being combined to determine the detailed topography (dimensions and shape) of the asteroid. Monitoring of a radio signal from Earth allowed measurement of the asteroid's gravitational field.
Rovers Hayabusa2 carried four small rovers to explore the asteroid surface in situ, and provide context information for the returned samples. Due to the minimal gravity of the asteroid, all four rovers were designed to move around by short hops instead of using normal wheels. They were deployed at different dates from about altitude and fell freely to the surface under the asteroid's weak gravity. The first two rovers, called HIBOU (previously Rover-1A) and OWL (previously Rover-1B), landed on asteroid Ryugu on 21 September 2018. The third rover, called MASCOT, was deployed 3 October 2018. Its mission was successful. The fourth rover, known as Rover-2 or MINERVA-II-2, failed before release from the orbiter. It was released on 2 October 2019 to orbit the asteroid and perform gravitational measurements before being allowed to impact the asteroid a few days later.
MINERVA-II
MINERVA-II is a successor to the MINERVA lander carried by Hayabusa. It consists of two containers with 3 rovers.
MINERVA-II-1 is a container that deployed two rovers, Rover-1A (HIBOU) and Rover-1B (OWL), on 21 September 2018. It was developed by JAXA and the University of Aizu. The rovers are identical having a cylindrical shape, diameter and tall, and a mass of each. They move by hopping in the low gravitational field, using a torque generated by rotating masses within the rovers. 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-1 rovers were successfully deployed 21 September 2018. Both rovers performed successfully on the asteroid surface, sending images and video from the surface. Rover-1A operated for 113 asteroid days (36 Earth days) returning 609 images from the surface, and Rover-1B operated for 10 asteroid days (3 Earth days) returning 39 images from the surface.
The MINERVA-II-2 container held the ROVER-2 (sometimes referred to as MINERVA-II-2), developed by a consortium of universities led by Tohoku University in Japan. This was an octagonal prism shape, diameter and tall, with a mass of about . It had two cameras, a thermometer and an accelerometer. It was equipped with optical and ultraviolet LEDs to illuminate and detect floating dust particles. ROVER-2 carried four mechanisms to move around using short hops. Rover-2 had problems prior to deployment from the orbiter but was released on 2 October 2019 to orbit the asteroid and perform gravitational measurements. It was then crashed onto the asteroid surface a few days later on 8 October 2019.