was a robotic spacecraft developed by the Japan Aerospace Exploration Agency (JAXA) to return a sample of material from a small near-Earth asteroid named 25143 Itokawa to Earth for further analysis. Hayabusa, formerly known as MUSES-C for Mu Space Engineering Spacecraft C, was launched on 9 May 2003 and rendezvoused with Itokawa in mid-September 2005. After arriving at Itokawa, Hayabusa studied the asteroid's shape, spin, topography, color, composition, density, and history. In November 2005, it landed on the asteroid and collected samples in the form of tiny grains of asteroidal material, which were returned to Earth aboard the spacecraft on 13 June 2010.
The spacecraft also carried a detachable minilander, MINERVA, which failed to reach the surface.
Mission firsts
NASA's Galileo and NEAR Shoemaker spacecraft had visited asteroids before, but the Hayabusa mission was the first one to return an asteroid sample to Earth for analysis.
Hayabusa was the first spacecraft designed to deliberately land on an asteroid and then take off again (NEAR Shoemaker made a controlled descent to the surface of 433 Eros in 2000, but it was not designed as a lander and was eventually deactivated after it arrived). Technically, Hayabusa was not designed to "land"; it simply touches the surface with its sample capturing device and then moves away. However, it was the first craft designed from the outset to make physical contact with the surface of an asteroid. Junichiro Kawaguchi of the Institute of Space and Astronautical Science was appointed to be the leader of the mission.
Despite its designer's intention for momentary contact, Hayabusa landed and sat on the asteroid surface for about 30 minutes (see below).
Mission profile
The Hayabusa spacecraft was launched on 9 May 2003 at 04:29:25 UTC on an M-V rocket from the Uchinoura Space Center (still called Kagoshima Space Center at that time). Following launch, the spacecraft's name was changed from the original MUSES-C to Hayabusa, the Japanese word for falcon. The spacecraft's xenon ion engines (four separate units), operating near-continuously for two years, slowly moved Hayabusa toward a September 2005 rendezvous with Itokawa. As it arrived, the spacecraft did not go into orbit around the asteroid, but remained in a station-keeping heliocentric orbit close by.
Hayabusa surveyed the asteroid surface from a distance of about , the "gate position". After this the spacecraft moved closer to the surface (the "home position"), and then approached the asteroid for a series of soft landings and for the collection of samples at a safe site. Autonomous optical navigation was employed extensively during this period because the long communication delay prohibits Earth-based real-time commanding. At the instant Hayabusa touched down with its deployable collection horn, the spacecraft was programmed to fire tiny projectiles at the surface and then collect the resulting spray. Some tiny specks were collected by the spacecraft for return to Earth and analysis.
After a few months in proximity to the asteroid, the spacecraft was scheduled to fire its engines to begin its cruise back to Earth. This maneuver was delayed due to problems with attitude control (orientation) and the thrusters of the craft. Once it was on its return trajectory, the re-entry capsule was released from the main spacecraft three hours before reentry, and the capsule coasted on a ballistic trajectory, re-entering the Earth's atmosphere at 13:51, 13 June 2010 UTC. It is estimated that the capsule experienced peak deceleration of about 25 G and heating rates approximately 30 times those experienced by the Apollo spacecraft. It landed via parachute near Woomera, Australia.
In relation to the mission profile, JAXA defined the following success criteria and corresponding scores for major milestones in the mission prior to the launch of the Hayabusa spacecraft. As it shows, the Hayabusa spacecraft is a platform for testing new technology and the primary objective of the Hayabusa project is the world's first implementation of microwave discharge ion engines. Hence 'operation of ion engines for more than 1000 hours' is an achievement that gives a full score of 100 points, and the rest of the milestones are a series of world's first-time experiments built on it.
Success criteria for Hayabusa Points Status Operation of ion engines 50 points Success Operation of ion engines for more than 1000 hours 100 points Success Earth gravity assist with ion engines 150 points Success Rendezvous with Itokawa with autonomous navigation 200 points Success Scientific observation of Itokawa 250 points Success Touch-down and sample collection 275 points Success Capsule recovered 400 points Success Sample obtained for analysis 500 points Success
MINERVA mini-lander
Hayabusa carried a tiny mini-lander (weighing only , and approximately tall by in diameter) named "MINERVA" (short for MIcro-Nano Experimental Robot Vehicle for the Asteroid). An error during deployment resulted in the craft's failure.
This solar-powered vehicle was designed to take advantage of Itokawa's very low gravity by using an internal flywheel assembly to hop across the surface of the asteroid, relaying images from its cameras to Hayabusa whenever the two spacecraft were in sight of one another.
MINERVA was deployed on 12 November 2005. The lander release command was sent from Earth, but before the command could arrive, Hayabusa's altimeter measured its distance from Itokawa to be and thus started an automatic altitude keeping sequence. As a result, when the MINERVA release command arrived, MINERVA was released while the probe was ascending and at a higher altitude than intended, so that it escaped Itokawa's gravitational pull and tumbled into space.
Had it been successful, MINERVA would have been the first hopping space rover. The Soviet mission Phobos 2 also encountered a malfunction while attempting to deploy a hopping rover.
Scientific and engineering importance of the mission Scientists' understanding of asteroids depends greatly on meteorite samples, but it is very difficult to match up meteorite samples with the exact asteroids from which they came. Hayabusa helped solve this problem by bringing back pristine samples from a specific, well-characterized asteroid. Hayabusa bridged the gap between ground observation data of asteroids and laboratory analysis of meteorite and cosmic dust collections."Japan's asteroid archaeologist", Sky and Telescope, June 2005, pp. 34–37 Also comparing the data from the onboard instruments of the Hayabusa with the data from the NEAR Shoemaker mission will put the knowledge on a wider level.
Changes in mission plan The Hayabusa mission profile was modified several times, both before and after launch. The spacecraft was originally intended to launch in July 2002 to the asteroid 4660 Nereus (the asteroid (10302) 1989 ML was considered as an alternative target). However, a July 2000 failure of Japan's M-5 rocket forced a delay in the launch, putting both Nereus and 1989 ML out of reach. As a result, the target asteroid was changed to , which was soon thereafter named for Japanese rocket pioneer Hideo Itokawa. Hayabusa was to deploy a small rover supplied by NASA and developed by JPL, called Muses-CN, onto the surface of the asteroid, but the rover was canceled by NASA in November 2000 due to budget constraints. In 2002, launch was postponed from December 2002 to May 2003 to recheck the O-rings of its reaction control system since one of them had been found to be using a different material than specified. In 2003, while Hayabusa was en route to Itokawa, the largest solar flare recorded in historyTen times the solar system reminded us sample collection is hard. Emily Lakdawalla, The Planetary Society. 24 February 2018. damaged the solar cells aboard the spacecraft. This reduction in electrical power reduced the efficiency of the ion engines, thus delaying the arrival at Itokawa from June to September 2005. Since orbital mechanics dictated that the spacecraft still had to leave the asteroid by November 2005, the amount of time it was able to spend at Itokawa was greatly reduced and the number of landings on the asteroid was reduced from three to two. In 2005, two reaction wheels that govern the attitude movement of Hayabusa failed; the X-axis wheel failed on 31 July, and the Y-axis on 2 October. After the latter failure, the spacecraft was still able to turn on its X and Y axes with its thrusters. JAXA claimed that since global mapping of Itokawa had been completed, this was not a major problem, but the mission plan was altered. The failed reaction wheels were manufactured by Ithaco Space Systems, Inc, New York, which was later acquired by Goodrich Company. The 4 November 2005, 'rehearsal' landing on Itokawa failed, and was rescheduled. The original decision to sample two different sites on the asteroid was changed when one of the sites, Woomera Desert, was found to be too rocky for a safe landing. The 12 November 2005, release of the MINERVA miniprobe ended in failure.
Mission timeline
Up to the launch The asteroid exploration mission by the Institute of Space and Astronautical Science (ISAS) originated in 1986–1987 when the scientists investigated the feasibility of a sample return mission to Anteros and concluded that the technology was not yet developed. Between 1987 and 1994, joint ISAS / NASA group studied several missions: an asteroid rendezvous mission later became NEAR, and a comet sample return mission later became Stardust.
In 1995, ISAS selected asteroid sample return as an engineering demonstration mission, MUSES-C, and the MUSES-C project started in fiscal year 1996. Asteroid Nereus was the first choice of target, 1989 ML was the secondary choice. In early development phase, Nereus was considered out of reach and 1989 ML became the primary target. A launch failure of M-V in July 2000 forced MUSES-C's launch to be delayed from July 2002 to November/December, putting both Nereus and 1989 ML out of reach. As a result, the target asteroid was changed to . In 2002, launch was postponed from December 2002 to May 2003 to recheck O-rings of reaction control system since one of it was found using different material than specified. On 9 May 2003 04:29:25 UTC, MUSES-C was launched by an M-V rocket, and the probe was named "Hayabusa".
Cruising Ion thruster checkout started on 27 May 2003. Full power operation started on 25 June.
Asteroids are named by their discoverer. ISAS asked LINEAR, the discoverer of , to offer the name after Hideo Itokawa, and on 6 August, Minor Planet Circular reported that the target asteroid was named Itokawa.
In October 2003, ISAS and two other national aerospace agencies in Japan were merged to form JAXA.
On 31 March 2004, ion thruster operation was stopped to prepare for the Earth swing-by. Last maneuver operation before swing-by on 12 May. On 19 May, Hayabusa performed a Earth swing-by. On 27 May, ion thruster operation was started again.
On 18 February 2005, Hayabusa passed aphelion at 1.7 AU. On 31 July, the X-axis reaction wheel failed. On 14 August, Hayabusa's first image of Itokawa was released. The picture was taken by the star tracker and shows a point of light, believed to be the asteroid, moving across the starfield. Other images were taken from 22 to 24 August. On 28 August, Hayabusa was switched over from the ion engines to the bi-propellant thrusters for orbital maneuvering. From 4 September, Hayabusa's cameras were able to confirm Itokawa's elongated shape. From 11 September, individual hills were discerned on the asteroid. On 12 September, Hayabusa was from Itokawa and JAXA scientists announced that Hayabusa had officially "arrived".
In proximity of Itokawa