FMOS: Fiber Multi Object Spectrograph

ATTENTION - Operation

[1] FMOS will be decomissioned at the end of May 2016, and it is offered for open-use only until May 2016.
[2] The Low Resolution mode (LR) and the High Resolution mode (HR) are available on both IRS1 and IRS2 spectrographs while FMOS is still operated in a shared-risk mode.

[3] Important for the applicants/observers who want to use HR: There are a few important restrictions applid in the operation of HR. Applicants/observers should go to this page and keep the notes there in mind about the use of HR.

[4] A new HR mode is open as 'H-short prime' covering 1.45 - 1.67 micron.


FMOS is a fiber-fed multi-object spectrograph. The Echidna fiber positioner system configures 400 fibers with an accuracy of 0.2 arcsec rms in the 30-arcmin diamter field of view at the Subaru prime focus and these fibers are extracted as spectra by the two spectrographs (IRS1 & IRS2). A mask mirror is installed in these spectrographs for OH airglow suppression (OHS). The spectral coverage is from 0.9 μm to 1.8 μm. This is observed at one exposure entirely with R=600 in the Low Resolution mode (LR), while it is divided into four bands ("J-short", "J-long", "H-short", "H-short prime" & "H-long") with a ~0.25 μm coverage and one of them is observed at one exposure with R=2200 in the High Resolution mode (HR).

!! Important notes for S14A or later observers !!

  • We request S14A or later observers to download the latest version (20130311 version) from the link below and prepare s2o files using it. We beieve the known issues on the previous version have been solved.


Further information

Questions regarding these pages should be directed to Kentaro Aoki ( ). Please note that all numbers on these pages are subject to change as the characteristics and performance of FMOS are better determined.


Readers can also refer to the papers as listed below and references therein for more details of this instrument:

"The Fibre Multi-Object Spectrograph (FMOS) for Subaru Telescope"
Kimura, M., et al. 2010, Publication of The Astronomical Sciety of Japan, Vol. 62, 1135
"FIBRE-pac: FMOS image-based reduction package"
Iwamuro, F., et al. 2012, Publication of The Astronomical Sciety of Japan, Vol. 64, 59
"FMOS: the fiber multiple-object spectrograph: Part VI. Onboard performances and results of the engineering observations"
Iwamuro, F. et al. 2008, Proc. of SPIE, Vol. 7014, 26
"Performance of Echidna fiber positioner for FMOS on Subaru"
Akiyama, M., et al. 2008, Proc. of SPIE, Vol. 7018, 94
"Echidna: the engineering challenges"
Brzeski, J., et al. 2004, Proc. of SPIE, Vol. 5492, 1228
"Integration, commissioning, and performance of the UK FMOS spectrograph"
Dalton, G., et al. 2008, Proc. of SPIE, Vol. 7014, 127
"Design and construction of the fibre system for FMOS"
Murray, G., et al. 2008, Proc. of SPIE, Vol. 7014, 186
"Cryogenic tests of volume-phase holographic gratings: results at 100 K"
Tamura, N. et al. 2006, Applied Optics, Vol. 45, 5923

Last updated: August 10, 2015

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