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 ⁽³⁾	∼130 sec
Number of fibers⁽⁴⁾	Science fibers		Fixed fiducial fibers
Number of fibers⁽⁴⁾	2386 (2394)		92 (96)
Fiber density	∼2000 deg^-2 / ∼0.6 arcmin^-2
Number of A&G camera ⁽⁵⁾	6
Field of view of A&G camera	∼5.1 arcmin² per one camera
Sensitivity of A&G camera ⁽⁶⁾	gaia 21.7 AB mag for S/N∼5 in 5 sec exposure
Spectrograph System
Number of Spectrograph	4
Spectral arms	Blue	Red		NIR
Spectral arms	Blue	Low Res.	Mid. Res.	NIR
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 ⁽⁷⁾	∼2500 (@500nm)	∼3000 (@800nm)	∼5500 (@800nm)	∼4500 (@1100nm)
Spectrograph throughput ⁽⁸⁾	∼49% (@500nm)	∼52% (@800nm)	∼48% (@800nm)	∼39% (@1100nm)
Metrology Camera System
Magnification factor	0.037
Camera	8960 × 5778 CMOS sensor (3.2 μm pixel)
Filter	MidOpt BP635
Fiber Cable
Length	∼ 53.5 m

Notes:
(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) For typical fiber configuration using 8 iterations, skipping going home position at the beginning, and taking 4.8-sec MCS image. (As of May 2024)
(4) Excluding the broken fibers. Number in parentheses is from the design.
(5) The A&G cameras are mounted surrounding the hexagonal shaped array of fiber positioners.
(6) Before installing extra window to compensate focus shift. (in 2022)
(7) As of July 2024. These are based on measurement before shipping to Subaru Telescope.
(8) As of July 2024. These values include detector QEs.

System Throughput

The prediction of 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 ∼20% (@500nm), ∼26% (@800nm), ∼22% (@1100nm), and ∼24% (@800nm), respectively. See Fig. 1 (left) below. Note that the telescope primary mirror reflectivity is the expected value at 1.5 years after re-coating.

The total throughput measured using standard stars during the commissioning in blue, red, NIR, and mid. resolution arms are ∼18% (@500nm), ∼26% (@800nm), ∼19% (@1100nm), and ∼25% (@800nm), respectively. See Fig.1 (right) below.

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.