Fibre Multi Object Spectrograph

Fibre Multi Object Spectrograph, or FMOS is facility instrument for the Subaru telescope on Mauna Kea 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 spectrographs, each weighing nearly 3000kg. The instrument will be used to look at the light from up to 400 stars or galaxies 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.

Additional recommended knowledge

Weighing the right way

Daily Visual Balance Check

Essential Laboratory Skills Guide

It is currently being built by a consortium of institutes led by Kyoto University and Oxford University with parts also being manufactured by the Rutherford Appleton Laboratory, Durham University and the Anglo-Australian Observatory. The instrument is scheduled for engineering first-light in early 2008.

The Spectrograph 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.