Exploring asteroids

Image sensors on the asteroid explorer Hayabusa
Measuring the surface of Itokawa and tracing the memories of the birth of the asteroid

In 2010, the asteroid explorer Hayabusa made a miraculous return, attracting attention from all over the world. Image sensors developed by Hamamatsu Photonics were chosen for two devices used to investigate the composition of the surface of the asteroid Itokawa. The InAs image sensor was also used in Hayabusa2, which was launched in 2014, to measure moisture on the surface of an asteroid.


From Hamamatsu to the World: and then to space. Hamamatsu Photonics' optical technology shows unlimited expansion.

InGaAs image sensor used for Hayabusa's NIR spectrometer

CCD image sensor used for Hayabusa's fluorescent X-ray spectrometer

CCD image sensor used for Hayabusa's fluorescent X-ray spectrometer

InAs image sensor used for Hayabusa2's NIR spectrometer

The asteroid explorer Hayabusa

Hayabusa was launched on May 9, 2003 with the purpose of bringing back samples of matter from the surface of the asteroid Itokawa. After successfully collecting fine particles on the surface of Itokawa, it safely returned to Earth on June 13, 2010. Hayabusa dropped its on-board capsule over Australia and finished its mission. Asteroids are celestial bodies similar to fossils, in that they serve as a relatively good record of the time when planets were formed. Hayabusa collected samples to obtain clues about what kind of material the planets were formed of, and what was inside the solar system nebula when the planets were formed.


Hayabusa returns

Distance traveled by Hayabusa: 6,000,000,000 (6 billion) km

Hayabusa, launched in 2003, reached the asteroid Itokawa in 2005. Overcoming many problems that arose, it returned to Earth in Jun. 2010. The distance traveled with the ion engine totaled about 6 billion km. Our CCD and InGaAs image sensors used on Hayabusa operated normally despite the harsh conditions of space to measure data.


Observation time of Hayabusa's fluorescent X-ray spectrometer: 700 hours

The fluorescent X-ray spectrometer was a device to study the matter on the ground of the asteroid from the space above.

Elements in matter on the ground emit fluorescent X-rays of a certain wavelength in response to energy from X-rays from the sun. The wavelengths of the fluorescent X-rays are defined for each element, so, by measuring the fluorescent X-rays emitted from the surface of an asteroid, it is possible to determine about how much of what elements are there.

The fluorescent X-ray spectrometer succeeded in measuring the material composition of Itokawa's surface, which included magnesium, aluminum, and silicon, etc. This owed to our CCDs' features of large photosensitive area and high energy resolution.


Locations on Itokawa's surface measured by Hayabusa's NIR spectrometer: 75,000

The near-infrared spectrometer (NIRS) on Hayabusa was a device to disperse and detect infrared rays from the sunlight reflected off the surface of the asteroid, in order to analyze the minerals on the ground and the form of the terrain. Our InGaAs image sensor was used for the NIRS, as the NIRS required high sensitivity in the NIR range and high reliability and durability.

Olivine and pyroxene

These were the minerals measured on Itokawa's surface by the near-infrared spectrometer using our InGaAs image sensor. When 0.8 to 2.1 μm light reflected from Itokawa was spectroscopically measured, it was found that reflectance dropped at the regions of 1 μm and 2 μm. Thus, it was concluded that the minerals on the surface include olivine and pyroxene.


The asteroid explorer Hayabusa2

Hayabusa2 is equipped with a near-infrared spectrometer (NIRS3) that measures moisture on the surface of asteroids with remote sensing, making observation from the sky during the operation. The detection unit incorporates Hamamatsu’s InAs linear image sensor specially designed to have sensitivity in the 3 μm band of the infrared absorption wavelength of water. It contributed to the analysis of the composition and moisture content of the surface of the asteroid Ryugu, as well as the selection of landing points for sample collection.


Conceptual image of remote sensing (near-infrared specrisciouc observation) of the asteroid by Hayabusa2)  ©JAXA