PFS Instrument Parameters

Prime Focus Instrument
Field of view ∼1.38 deg (hexagonal - diameter of circumscribed circle)
Field of view area ∼1.25 deg2
Input F number to fiber 2.8
Fiber core diameter (1) 127 μm (1.12 arcsec at the FoV center, 1.02 arcsec at the edge)
Positioner pitch 8 mm (90.4 arcsec at the FoV center, 82.4 arcsec at the edge)
Positioner patrol field 9.5 mm diameter (107.4 arcsec at the FoV center, 97.9 arcsec at the edge)
Fiber minimum separation (2) ∼30 arcsec
Fiber configuration time ∼60-120 sec. [TBC]
Number of fibers Science fibers Fixed fiducial fibers
2394 96
Fiber density ∼2000 deg-2 / ∼0.6 arcmin-2
Number of A&G camera (3) 6
Field of view of A&G camera ∼5.1 arcmin2 per one camera
Sensitivity of A&G camera r'∼20.0 AB mag for S/N∼30 (100) in 1 (10) sec. exposure
Spectral arms Blue Red NIR
Low Res. Mid. Res.
Spectral coverage 380 - 650 nm 630 - 970 nm 710 - 885 nm 940 - 1260 nm
Dispersion ∼0.7 Å/pix ∼0.9 Å/pix ∼0.4 Å/pix ∼0.8 Å/pix
Spectral resolution ∼2.1 Å ∼2.7 Å ∼1.6 Å ∼2.4 Å
Resolving power ∼2300 ∼3000 ∼5000 ∼4300
Spectrograph throughput (4) ∼52% (@500nm) ∼52% (@800nm) ∼47% (@800nm) ∼35% (@1100nm)

(1) This is a diameter of the sky projected on to the fiber core not directly but through a miclolens with a magnification of 1.28. According to the plate scale without microlens, 100um subtends ∼ 1.1 arcsec on the sky.
(2) The minimum separation includes a physical limitation and a margin for collision avoidance.
(3) The A&G cameras are mounted surrounding the hexagonal shaped array of fiber positioners.
(4) As of Dec. 2021. These values include detector QEs. The typical total throughput including primary mirror reflectivity, WFC, fiber systems, spectrograph optics, detector QE, etc. in blue, red, NIR, and mid. resolution arms are ∼21% (@500nm), ∼26% (@800nm), ∼19% (@1100nm), and ∼23% (@800nm), respectively. See Fig. 1 below. Note that the telescope primary mirror reflectivity is the expected value at 1.5 years after re-coating.

Throughput1 Throughput2

*Fig. 1. (Left) The throughput of each component as a function of wavelength. (Right) The total throughput as a function of wavelength. Note that the fiber aperture effect and vignetting effect are not included. *