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HAYABUSA-related information Q&A


Hayabusa is an engineering spacecraft developed to prove that planets can be investigated.
The purpose of the Hayabusa project is to establish a technology to enable a sample collected from the asteroid Itokawa to be brought back to Earth.

Asteroids, which are mainly between Mercury and Jupiter, are celestial bodies that are like fossils in that they contain a relatively good record of a planet as it was at the time of its birth. By returning with a sample from Itokawa, an asteroid that is approaching Earth, we can obtain clues to help us answer questions such as the following: What sorts of materials are planets and asteroids made of ? What sorts of elements made up the solar system when planets were born? The answers will help us understand Earth.

Hayabusa is the world's first asteroid probe whose mission is to return a sample from the surface of a celestial body further away than the Moon to Earth.
It accomplishes many feats, including continuously running ion engines and using such engines during an Earth swing-by.

Ion engine refers to an electric propulsion engine that ionizes xenon gas and uses an electrical acceleration system. Due to its super high efficiency, this technology is also expected to be important for future investigation of moons and planets.

The ion engine developed through the combined research of JAXA and NEC has been made suitable for many purposes and had its performance improved based on the results demonstrated by Hayabusa. Therefore, this engine will be used as propulsion equipment for future artificial satellites.

For more than one year after being launched, Hayabusa orbited around the Sun, using its ion engine to continuously accelerate, and then, when it again approached Earth, an Earth swing-by was performed to further accelerate the probe towards the asteroid Itokawa. Hayabusa was the first spacecraft in the world to combine acceleration using an ion engine with an Earth swing-by.

Because Itokawa is so far away that it takes almost 40 minutes for even radio waves to travel to the asteroid and back, there was previously no accurate information even about the asteroid's shape. Therefore, Hayabusa used camera imaging and a laser altimeter to determine the distance from and shape of Itokawa, and then the probe used this data to automatically determine what to do. In this way, Hayabusa approached Itokawa on its own and made various observations of the asteroid as it hovered over the asteroid along the asteroid's orbit.

Hayabusa is equipped with a number of observation devices. These devices include AMICA (Asteroid Multiband Imaging CAmera), a spectrographic camera with a color filter used to obtain color photographs of the asteroid; LIDAR (LIght Detection And Ranging instrument), a laser altimeter used to measure the surface shape; NIRS (Near-InfraRed Spectrometer), a near-infrared spectrometer used to determine which sorts of minerals exist on the surface of the asteroid; and XRS (X-Ray fluorescent Spectrometer), a fluorescent X-ray spectrometer used to study the elemental profile of the surface.

As Hayabusa got close to the asteroid Itokawa, it dropped a sphere that had a diameter of approximately 10 cm (a target marker). The reflective sheet attached to this marker glittered brightly as the light flashed by Hayabusa struck it. Hayabusa used the reflected light as a guide to automatically navigate towards and then touch down on Itokawa.

Due to Itokawa's weak gravitational pull, Hayabusa was not built to stably sit on the asteroid's surface. The probe was supposed use a target marker to touch down on Itokawa, and then use equipment called a sampling horn to collect a surface sample.
Collection was supposed to be accomplished by shooting a metal pellet that weighs several grams into Itokawa's surface and collecting the particles that flew up as a result the instant the probe touched the asteroid.

Hayabusa re-entered the atmosphere at 13:51 p.m. on June 13th, 2010 (UTC). The capsule that separated from Hayabusa was retrieved in the Woomera prohibited area in Australia. (Updated on July 30th, 2010)

It is possible to see an actual-size model of Hayabusa at the Sagamihara campus of JAXA. In addition to Hayabusa, there are also various other ISAS models of historical importance on display. (No reservation is required.)

Under the direction of JAXA, NEC has been deeply involved in the development, manufacturing, testing, and operations of the total system for the Hayabusa project.


Many discoveries were made using the results of Hayabusa's scientific observation. We learned about Itokawa's shape, for example, by analyzing the images sent back by the probe. Images of the face of Itokawa are available at the following website:

Associate professor of space information and energy engineering research Makoto Yoshikawa has commented on Itokawa at the following website:

Other related sites

NEC Online TV provides beautiful videos of Hayabusa's miraculous journey, which was achieved by teamwork between leading-edge technology and humanity, as well as interviews with NEC engineers. These videos clearly explain the unique technologies used for Hayabusa, as well has how the probe's many successes were achieved.

The JAXA channel on YouTube is loaded with videos that can be used in classrooms and for other purposes, including videos of the control room when Hayabusa touched down on Itokawa in November 2005, an overview of Hayabusa, the latest aerospace-related videos, and videos introducing JAXA projects.

The public Hayabusa blog maintained by JAXA is available at the following website:


MUSES-C was the code-name used for Hayabusa during development. MUSES stands for Mu Space Engineering Spacecraft (because the satellite was launched from a Mu rocket) and indicates a particular series of experimental engineering satellites. MUSES-C-Hayabusa-is the third in the MUSES series, which includes MUSES-A, the Hiten probe, and MUSES-B, the Haruka VLBI observation satellite.

An electric propulsion engine that ionizes xenon gas and uses an electrical acceleration system is called an ion engine. Due to its high efficiency, this technology is also expected to be important for future investigation of moons and planets. Hayabusa incorporates four newly developed ion engines that use microwaves.

Asteroid Probe Hayabusa's Return to Earth (PDF file, 6.3 MB)

Itokawa is a solar system asteroid that belongs to the Apollo group of near-Earth asteroids (celestial bodies that have orbits near Earth). Itokawa was discovered on September 26th, 1998, by an American team of aerospace researchers belonging to the LINEAR (Lincoln Near-Earth Asteroid Research) project.
After the asteroid was selected as Hayabusa's investigative target, the ISAS requested that the LINEAR team name the asteroid after Hideo Itokawa, a pioneer of Japanese rocket development, and the name was approved by the International Astronomical Union on August 6th, 2003, and announced as the official name.

A chemical propulsion thruster is a device used to eject gas from a small rocket engine and use the resulting reaction force for attitude control and fine position control of the satellite. Hayabusa uses 12 chemical propulsion thrusters arranged into two systems.

The re-entry capsule is a small collection capsule that has a diameter of 40 cm and was used to carry the sample from Itokawa. After the capsule separates from Hayabusa, it will directly re-enter Earth's atmosphere from interplanetary orbit at a velocity of more than 12 km/s. The maximum amount of aerodynamic heat the capsule will be dozens of times stronger than the Space Shuttle and several times more intense than the heat Apollo was subject to upon returning from the moon. The surface temperature will reach several thousand degrees Celsius. One of the greatest challenges for the Hayabusa design team was to develop heat shielding materials that could withstand these kinds of temperatures.

Asteroid Probe Hayabusa's Return to Earth (PDF file, 6.3 MB)

Swing-by refers to a technique for using the gravity of a celestial body to change the direction or speed of a satellite. The orbital motion of celestial bodies can be used to increase or reduce the speed of a satellite. Hayabusa is the first spacecraft ever to demonstrate the ability to use both the usual Earth swing-by and ion engine propulsion.

The solar array paddle is an important part that generates the power essential for operating the equipment on the probe. During the launch, the paddle is attached to the satellite in a folded state, then the metal fittings are severed following the initial orbit injection to unfold the paddle. The attitude of the paddle is generally controlled so that the surface to which the solar array is fixed faces the sun. The Hayabusa solar paddle is approximately 5.7 m from tip to tip, and it generates approximately 2.6 kW of power at a distance of 1.0 AU*.

* AU is the abbreviation for Astronomical Unit, a measure of distance. 1.0 AU indicates the average distance between Earth and the sun.

The target marker is a device that served as a beacon guiding the way to the asteroid surface. Hayabusa dropped the target marker as the probe got close to the asteroid Itokawa. The target marker had a diameter of approximately 10 cm, and the reflective sheet attached to the marker glittered brightly, reflecting the light flashed by Hayabusa. Based on images of the marker taken by its camera, Hayabusa detected the horizontal speed and canceled the same speed to touch down on Itokawa.On November 20th, 2005, Hayabusa dropped the target marker, which was signed by 880,000 people from 149 countries.

Touchdown refers to the landing of Hayabusa on Itokawa, which has a weak gravitational pull, for a very short time (approximately one second) to obtain a sample.
To obtain this sample, the instant a piece of Hayabusa equipment called a sampling horn touched the surface of Itokawa, Hayabusa was supposed to shoot a metal pellet that weighs several grams into Itokawa's surface and collect the particles that flew up as a result. This was an extremely inventive concept.

The term "beacon" commonly refers to a radio transmitter, but in reference to satellites, this term is sometimes used to refer to a radio wave not carrying much information that is emitted from a satellite to Earth to simply indicate its existence (by the fact that it emits a radio wave).

Specific impulse is an indicator of the performance of a rocket engine. It indicates the fuel efficiency of a rocket engine and is defined as the number of seconds for which a rocket engine can produce 1 N of power from one 1 kg of propellant. The larger this value is, the less propellant is needed to achieve acceleration to a high velocity.

The Hiten engineering satellite was launched in 1990 and used to gain orbit control skills such as the swing-by information required for investigating moons and planets.

The newton (N) is a unit of force. One newton is defined as the amount of force necessary to accelerate a mass of 1 kg at a rate of 1 m/s² and is equal to force of gravity exerted on a mass of 98 grams (equivalent to a small apple). One micronewton (µN) is one 1 millionth of one newton.

This equipment is used to stabilize the attitude or change the direction of a satellite without using rocket or jet propulsion. The satellite attitude is controlled using a flywheel. When the fly wheel is rotated one way, the spacecraft turns the other way (due to the conservation of angular momentum). Hayabusa was equipped with three reaction wheels.

The laser altimeter emitted laser pulses to measure the distance between the probe and the asteroid. In addition to being an extremely important navigation sensor for Hayabusa to touch down on Itokawa, the laser altimeter carried out scientific observation such as measuring the shape of the asteroid surface and its gravity based on the force of rotation. Hayabusa's laser altimeter was capable of measuring distances in the extremely wide range of 50 m to 50 km, making it usable both for approaching and touching down on the asteroid.

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