Fibre multi-object spectrograph (FMOS) is facility instrument for the

Subaru telescope is the telescope of the National Astronomical Observatory of Japan, located at the Mauna Kea Observatory on Hawaii. It is named after the open star cluster known in English as the Pleiades. It had the largest monolithic primary mirror in the wo ...

Mauna Kea Mauna Kea ( or ; ; abbreviation for ''Mauna a Wākea''); is a dormant volcano on the island of Hawaii. Its peak is above sea level, making it the highest point in the state of Hawaii and second-highest peak of an island on Earth. The peak is ...

in Hawaii. The instrument consists of a complex fibre-optic positioning system mounted at the prime focus of the telescope. Fibres are then fed to a pair of large

spectrograph An optical spectrometer (spectrophotometer, spectrograph or spectroscope) is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify mate ...

s, each weighing nearly 3000 kg. The instrument will be used to look at the light from up to 400

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

s or

galaxies A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. ...

simultaneously over a field of view of 30 arcminutes (about the size of the full moon on the sky). The instrument will be used for a number of key programmes, including galaxy formation and evolution and dark energy via a measurement of the rate at which the universe is expanding.

Design, construction, operation

It is currently being built by a consortium of institutes led by

Kyoto University , mottoeng = Freedom of academic culture , established = , type = National university, Public (National) , endowment = ¥ 316 billion (2.4 1000000000 (number), billion USD) , faculty = 3,480 (Teaching Staff) , administrative_staff ...

and Oxford University with parts also being manufactured by the Rutherford Appleton Laboratory,

Durham University , mottoeng = Her foundations are upon the holy hills (Psalm 87:1) , established = (university status) , type = Public , academic_staff = 1,830 (2020) , administrative_staff = 2,640 (2018/19) , chancellor = Sir Thomas Allen , vice_chan ...

and the Anglo-Australian Observatory. The instrument is scheduled for engineering first-light in late 2008.{{update after, 2009

OH-suppression

The spectrographs use a technique called OH-suppression to increase the sensitivity of the observations: The incoming light from the fibres is dispersed to a relatively high resolution and this spectrum forms an image on a pair of spherical mirrors which have been etched at the positions corresponding to the bright OH-lines. This spectrum is then re-imaged through a second diffraction grating to allow the full spectrum (without the OH lines) to be imaged onto a single infrared detector.

References

FMOS

Telescope instruments Spectrographs Electronic test equipment Signal processing Laboratory equipment