The FMOS instrument is being built as a 2nd generation instrument for the Subaru telescope in Mauna Kea, Hawaii.
The FMOS instrument is made up of a number of major components:
- Fibre positioner and Autoguider (collectively known as Echidna)
- 2 Spectrographs
The fibre positioner is located at the prime focus of the telescope and can position up to 400 spines in a 0.5° diameter field of view. Each spine is separated by ~7.2mm from each of its 6 neighbours and can be tilted up to 7.2mm radially in any direction. This ensures any (non-peripheral) position on the field plate can be reached by at least 3 spines.
Each individual spine is positioned by a piezo-electric actuator which each spine is inserted into.
Control of the positioning of each spine is achieved by sending signals from the Echidna Control Computer. Signals are routed through a set of switching boards which allow each individual spine to be addressed whilst also allowing multiple spines to be driven in parallel.
A CCD camera mounted on an XY gantry (called the Focal Plane Imager) is able to image the spine tips for the purposes of spine position feedback. Each of the fibres can be back-illuminated so as to make the spine tip visible to the CCD camera.
The FMOS instrument uses a 3-element prime focus corrector to convert the ~f/1.8 beam coming off the primary mirror of the Subaru telescope to an ~f/2.1 beam for the spine tips constituting the Echidna field plate. (The high NA optical fibres are just able to handle this fast beam.)
The 400 science fibres from the Echidna positioner are fed to 2 separate spectrographs. The Echidna fibres are interfaced to the spectrographs via a special connector being developed at Durham University, UK.
The FMOS-Echidna instrument will be completed in late 2006. Instrument commissioning is expected to commence in Hilo, Hawaii in early 2007.