Observational Instruments

Subaru's mission is to explore as wide range of astronomical phenomena as possible, from the birth and death of individual stars to the catastrophic collisions of large galaxies.

Astronomical observations can be classified into two groups: one is imaging objects to investigate their structure and brightness, and the other is spectroscopy which spreads light into its constituent colors to study temperature, composition, and other physical characteristics. Optical (visible) light and infrared light each probe different astronomical phenomena. We can see stars and galaxies in visible light, but we can only see into star-forming regions enshrouded in thick dust by observing in infrared light.

Observational instruments are mounted at various foci of the telescope and detect the light collected by the primary mirror. Each instrument has special functions to explore specific areas of frontier research. There are seven instruments and an adaptive optics system that comprise the first-generation instruments.

Subaru Telescope currently has seven observational instruments and an auxiliary in operation. Subaru Telescope's observational abilities, in visible light to infrared, are further more extended by MOIRCS, Multi-Object Infrared Camera and Spectrograph had first light in February 2006, and other four focus units.


For Scientists

Current Subaru Instruments

Fiber Multi-Object Spectrograph (FMOS)

FMOS is a powerful wide-field spectroscopy system that enables near-infrared spectroscopy of over 100 objects at a time. It is composed of three subsystems: 1) an infrared unit at prime focus (PIR) that includes a wide-field corrector lens system and fiber positioning system ("Echidna"), 2) a fiber bundle unit of 400 optical fibers, and 3) two spectrographs. Echidna can precisely position all 400 fibers in just 15 minutes. This high speed for repositioning allows observers to reconfigure Echidna, observe multiple fields during a night and rapidly observe hundreds of faint targets that can be compiled as data for statistical analysis.



Multi-Object Infrared Camera and Spectrograph (MOIRCS)

MOIRCS, a wide-field near-infrared instrument using 8 megapixel detectors, has the widest field of view of all the infrared instruments among 8-meter class telescopes. It has the capability to obtain spectra of multiple astronomical objects at the same time, dramatically increasing its observational efficiency.


Topics (February 2006) MOIRCS First Light !

Infrared Camera and Spectrograph (IRCS)

IRCS is a workhorse infrared instrument for the Subaru telescope, providing high angular resolution and sensitivity. It is used in conjunction with the Adaptive Optics unit. This instrument has the ability to separate light with a wavelength difference of 1 part in 20,000. It was developed under collaboration with the University of Hawaii. This photograph shows the imaging optics. IRCS mounts at the infrared Nasmyth focus.


Topics (June 2000) IRCS First Light !

Cooled Mid Infrared Camera and Spectrometer (COMICS)

Because the air over Mauna Kea is thin and dry, Subaru is able to more easily detect mid-infrared light from astronomical objects. COMICS is a camera and spectrograph that can take advantage of the unique observing conditions at Subaru. It can be used to study the formation of individual stars in our own galaxy and large-scale star formation in others. It can also be used to examine the formation of interstellar dust, the raw material of planets.



Topics (January 2000) COMICS First Light !

Faint Object Camera And Spectrograph (FOCAS)

FOCAS is Subaru's workhorse instrument for high-sensitivity optical observations. It is equipped with a multi-slit system which allows spectra of up to 100 objects to be taken simultaneously. This is a powerful capability when measuring the distances to faint galaxies near the edge of the Universe. FOCAS attaches to the Cassegrain focus.


Topics (March 2000) FOCAS First Light !

Subaru Prime Focus Camera (Suprime-Cam)

Because of its shorter focal length, the prime focus allows the instrument to capture objects in a fi eld of view fi ve times wider than the Cassegrain focus. Suprime-Cam is an 80-megapixel digital camera designed to take advantage of Subaru's prime focus for effi cient deep imaging of a large area of sky. With a 30- by 24-arcminute fi eld of view, each image covers an area comparable to the size of the full Moon. Suprime-Cam is an eff ective tool for detecting small bodies at the outskirts of the solar system, studying the birth and evolution of galaxies, and probing the large-scale structure of our universe.

Topics (July 2000) Suprime-Cam at Prime Focus

High Dispersion Spectrograph (HDS)

HDS splits light into its constituent colors with an accuracy of 1 part in 100,000. With this precision, we can investigate the evolution of elemental abundances by observing old stars, as well as learn about the physical and chemical state of intergalactic gas from quasar absorption line studies. The instrument weighs 6 metric tons and sits at the optical Nasmyth focus.


Topics (August 2000) HDS First Light !

188-Element Adaptive Optics (AO)

Subaru’s 188-element AO system includes laser guide star technology, which allows observers to use a laser as an artificial star when there is no bright guide star illuminating an object-star. The development of the 188-element system was a product of continual improvements to Subaru’s earlier 36-element AO system, which was designed, produced, and then made available to astronomers worldwide in 1990. The current 188-element AO system successfully passed its first test on October 9, 2006 and replaces the older system. This 188-element AO mounts at the infrared Nasmyth focus.


Science Results (2006. Nov.) First light of laser guide system of adaptive optics system

Wavelength Regime

Larger Image (69KB)

Each of Subaru's seven instruments detects light of either the optical or the infrared. Instruments like FOCAS and IRCS function as both a camera and a spectrograph. HDS specializes in high resolution spectroscopy. The figure on the left shows the wavelength regime detected by the instruments above and how finely each can divide that light into component of wave-lengths or colors (spectral resolution). Instruments with different fields of view or special features optimized for particular scientific targets sometimes have overlapping wavelength and resolution coverage.

Former Generation Instruments

Coronagraphic Imager with Adaptive Optics (CIAO)

CIAO is an infrared imager, designed to detect fainter objects near bright ones by blocking out the light of the brighter ones. It can image the immediate neighborhood of stars where planets may be forming and study stars that are ejecting gas and dust into interstellar space as they die.


Topics (April 2000) CIAO First Light !

36-Element Adaptive Optics (AO)

The Subaru telescope has achieved an angular resolution of 0.2 arcsec at wavelength of 2 μm by minimizing air turbulence inside the enclosure. This resolution is, however, still limited by atmospheric turbulence. With the Adaptive Optics system, which can compensate for the distorted wavefront very rapidly, the light can be focused still further, limited only by the diameter of the primary mirror. For many observations, this limit of 0.06 arcsec exceeds the resolution of the Hubble Space Telescope. The 36-Element AO is mounted at the Cassegrain Focus of the Subaru Telescope.


Scientific Results (December 2000) Adaptive Optics First Light !

OH-Airglow Suppressor (OHS)

By eliminating infrared light emitted by OH airglow in the upper atmosphere, OHS achieves the high sensitivity required to obtain spectra of faint objects such as distant galaxies and brown dwarfs. It sits at the IR Nasmyth focus. This picture shows CISCO, the imaging camera for OHS, which has been working excellently since First Light.


Topics (May 2000) OHS First Light !

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