The Subaru Prime Focus Spectrograph (PFS) Project
About the Subaru Prime Focus Spectrograph (PFS) Project
This project aims to develop a new powerful spectrometer to be installed on the Subaru Telescope. By exploiting the Subaru Telescope’s superior light collecting power and wide field of view, this instrument will allow simultaneous spectral observation of up to about 2400 celestial objects across a wide field of view of 1.3-degree diameter. It will also cover a wide range of wavelengths in one exposure: 380-1260 nm, that is to say from optical to near-infrared. Its resolving power varies based on the observed wavelength, from 2300 at 380-650 nm to the highest resolving power of about 5000 achievable at 710-885 nm by using a medium resolution grating . Compared to current optical spectroscopy, this multi-object spectrograph is expected to offer a 50-fold increase in field of view and 20-fold increase in number of simultaneously observable celestial objects. By observing the spectra of many objects at the same time, this instrument can measure the distances and chemical compositions of galaxies and stars very efficiently.
PFS is being developed through international collaboration among 12 institutions and consortia from 7 countries and regions led by the Kavli Institute for the Physics and Mathematics of the Universe. Among these institutions, the National Astronomical Observatory of Japan is playing major roles in the installation and commissioning of the instrument, the development of the data reduction pipeline, the science platform to analyze spectra, and the construction and the operation of the science observation system.
Figure 1: Four spectrograph modules installed in the dedicated temperature-controlled clean room (SCR) at the Subaru Telescope summit facility. Each module employs three cameras to cover the wide wavelength range of observed spectra with about 600 fibers at once.
Figure 2: Many tiny spots are lined up in the hexagonal area. These are the tips of about 2400 science fiber optics placed on the primary focal plane of the Subaru Telescope. Meanwhile, the six red squares around the hexagon are the windows of 6 AG cameras. A robotic fiber positioner (see Figure 3 below) precisely places each fiber tip within its patrol area to match the position of an astronomical objects on the night sky to receive light from it. In this picture, color-filtered lights were injected into the fibers to indicate the individual spectrograph modules to which each fiber is connected.
Figure 3: These actuators for PFS, designed to maintain optical fibers at the desired positions, were developed through a collaboration led by NASA’s Jet Propulsion Laboratory and the California Institute of Technology. By accurately pointing each optical fiber at a different celestial object, the light from many objects can be fed into the spectrograph at one time.