Exploring the distant universe

CCD image sensors in the Subaru Telescope's ultra-wide-field prime focus camera
Unraveling the mysteries of the birth of the universe

The Subaru Telescope sits at an elevation of 4205 m at the peak of Mauna Kea on the island of Hawaii. Its ultra-wide-field prime focus camera contains CCD area image sensors made by Hamamatsu Photonics that boast the highest sensitivity in the world.
Here breathes the spirit of Hamamatsu Photonics, to do what others cannot, to create what has never been.

CCDs installed in the HSC

Keyman Interview

To observe farther in the universe
Hisanori Suzuki
Responsible for CCD development for the Subaru Telescope, Solid State Division of Hamamatsu Photonics

What is the Subaru Telescope?

The Subaru Telescope is a large national optical/infrared telescope at the peak of Mauna Kea on the island of Hawaii. It is a next-generation telescope with revolutionary observational power. The purpose of the Subaru Telescope is to measure dark energy and the history of the universe's expansion. It uses gravitational lens effects to directly observe distribution of dark matter. Thus, it needs to be able to measure an extremely wide range, so, in 2001, development began for a new ultra-wide-field prime focus camera, the Hyper Suprime-Cam (HSC). Test operation began in 2012.

Subaru Telescope at the peak of Mauna Kea (courtesy of NAOJ)

CCDs in the new Hyper Suprime-Cam (HSC) on the Subaru Telescope: 116

The CCD image sensors for the HSC newly installed on the Subaru Telescope were developed by Hamamatsu Photonics in collaboration with the National Astronomical Observatory of Japan (NAOJ), Osaka University, and Kyoto University.
There are 116 CCDs in the HSC, which give the camera the world's greatest wide-field performance, capable of photographing a breadth nine times the size of the full moon all at once.

Pixels in the Hyper Suprime-Cam (HSC): 870,000,000

The HSC was first installed on the Subaru telescope in Aug. 2012. Since then, observations have been done as performance tests. In the first light*, the HSC succeeded in capturing about the entirety of the Andromeda Galaxy in one field. The Andromeda Galaxy, at approximately 2.3 million light-years from Earth, is the closest spiral galaxy to the Milky Way Galaxy and has a diameter of over 200,000 light-years. Never before has a large telescope on Earth been able to capture it all at once.
* First light: The initial observation to confirm that optical equipment, such as of a completed telescope, achieves its predicted performance.

The Andromeda Galaxy (M31), captured by the Subaru Telescope (courtesy of NAOJ)

Flatness expected of the sensor area of the CCDs for the Subaru Telescope: 20 µm for 3 cm (6.6 mm for 100 m) (1 µm = 1/1000 mm)




CCD flatness: Flatness of about 10 µm achieved while CCDs cannot be ground after manufacturing

Large-area CCDs tend to have poor flatness due to warpage, etc. However, we established assembly technology to minimize warpage, keeping the variation in height in the whole area tiled together down to about 40 µm. This CCD technology is being pushed into soft X-ray direct detectors, Raman spectroscopic analysis, etc., so there should also be useful applications for NIR, soft X-rays, electron beams, etc. in the future.

Quantum efficiency with a wavelength of 1 µm: 40%


Higher NIR sensitivity in CCDs is optimal for observation of distant astronomical objects

The CCDs used in the Subaru Telescope use a fully-depleted, back-illuminated structure with thick silicon to achieve high sensitivity in the near-infrared (NIR) range. Since the light from astronomical objects that are moving away is shifted to longer wavelengths (red), by observing the shift in wavelengths in galactic spectral lines, the speed of an object can be deduced. The CCDs in the HSC have silicon thickness of 200 μm, five times that of previous CCDs, to improve quantum efficiency in the NIR range, and a back bias is applied to N-type silicon with ultra-high resistance without crystal defects to achieve full depletion, to control degradation of resolution.

Furthest galaxy detected, 12.91 billion light-years away, by the Subaru Telescope's prime focus camera


Red object enlarged at lower left: A galaxy 12.91 billion light-years away, SXDF-NB1006-2 (courtesy of NAOJ)

Using the prime focus camera and such of the Subaru Telescope, the universe 12.91 billion years ago (750 million years after the Big Bang) has been observed. The Subaru's Telescope's prime focus camera, with our CCDs, can observe a wide field at once and discover dark, scant distant galaxies.