FMOS Instrument Parameters 

Fiber positioner system "Echidna" (see this page for more details)
Field of view 30' diameter (circular FOV at the prime focus)
Fiber diameter 1.2 arcsec (100 microns)
Fiber configuration time ~13 minutes
Patrol field of each spine 87 arcsec in radius (i.e. 6.6 sq. arcmin in area)
Minimal spacing between neighboring spines 12 arcsec
Fiber positioning error 0.2 arcsec rms(1)
Spectrograph (see this page for more details)
Low Resolution (LR) High Resolution (HR)(5)
Spectral coverage 0.9-1.8 μm 0.92-1.12 μm ("J-short")
1.11-1.35 μm ("J-long")
1.40-1.60 μm ("H-short")
1.45-1.67 μm ("H-short prime")
1.60-1.80 μm ("H-long")
Spectral resolution R=600 R=2200
Dispersion ~5 A/pix ~1 A/pix
Image quality FWHM = 4-5 pix
Number of fibers to be extracted as spectra 197(IRS1)(2)
200 (IRS2)
Detector system
IRS1 IRS2
Detector array HAWAII-2 (Sci #55) HAWAII-2 (Sci #90)
Array format 2048 x 2048
Pixel size 18 μm
Readout elesctronics TUFPAC+Messia V SDSU IR Gen III
Readout time (= Minimum exposure time) ~17 sec ~6 sec
Gain ~2.0 e-/ADU ~3.8 e-/ADU
Dark current < 0.1 e-/sec/pix < 0.1 e-/sec/pix
Total background(3) ~0.2 e-/sec/pix ~0.2 e-/sec/pix
Readout noise(4) ~30 e-/pix rms ~15 e-/pix rms
Linearity <1% up to 40,000 ADU ~1% up to 20,000 ADU

(1) This error is based on the measured displacements of the fiber positions from the stars in an open cluster in an engineering observation. Namely, this is a combination of the error in astrometry (the coordinates of the stars were from the UCAC2 catalog) and the purely mechanical error of Echidna in fiber positioning (~10 μm, corresponding to 0.1 arcsec).
(2) The spectra from the three fibers located near the edge of the FOV are focused outside the detector.
(3) This shows the background level including thermal radiation and stray light as well as the dark current of the detector.
(4) These values are error per Fowler sampling.
(5) The wavelength coverage has been changed significantly as of May 2012.

Last updated: May 7, 2012



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