Prime Focus Spectrograph (PFS): The prime focus instrument

Shiang Yu Wang, Pin Jie Huang, Hsin Yo Chen, Masahiko Kimura, Chih Yi Wen, Chi Hung Yan, Jennifer Karr, Richard C.Y. Chou, Chang Yin-Chang, Shu Fu Hsu, Yen Sang Hu, Hung Hsu Ling, Dan J. Reiley, Mitsuko Roberts, James E. Gunn, Craig Loomis, Robert H. Lupton, Hassan Siddiqui, Graham J. Murray, Decio FerreiraLeandro Henrique dos Santos, Ligia Souza Oliveira, Antonio Cesar de Oliveira, Lucas Souza Marrara, Naoyuki Tamura, Yuki Moritani, Naruhisa Takato

Research output: Chapter in Book/Report/Conference proceedingConference contribution

7 Scopus citations


The Prime Focus Spectrograph (PFS) is a new optical/near-infrared multi-fiber spectrograph design for the prime focus of the 8.2m Subaru telescope. PFS will cover 1.3 degrees diameter field with 2394 fibers to complement the imaging capability of Hyper SuprimeCam (HSC). The prime focus unit of PFS called Prime Focus Instrument (PFI) provides the interface with the top structure of Subaru telescope and also accommodates the optical bench in which Cobra fiber positioners and fiducial fibers are located. In addition, the acquisition and guiding cameras (AGCs), the cable wrapper, the fiducial fiber illuminator, and viewer, the field element, and the telemetry system are located inside the PFI. The mechanical structure of the PFI was designed with special care such that its deflections sufficiently match those of the HSC's Wide Field Corrector (WFC) so the fibers will stay on targets over the course of the observations within the required accuracy. The delivery of PFI components started in 2017. After the verification of these components, the mechanical structure of the PFI is fully assembled in early 2019 and all Cobra positioners are integrated in summer 2020. A temperature controlled chamber with precise x-y scanner was setup for the verification of the Cobra fiber positioners. The testing of the target convergence performance of Cobra positioners is now in progress.

Original languageEnglish (US)
Title of host publicationGround-Based and Airborne Instrumentation for Astronomy VIII
EditorsChristopher J. Evans, Julia J. Bryant, Kentaro Motohara
ISBN (Electronic)9781510636811
StatePublished - 2020
EventGround-Based and Airborne Instrumentation for Astronomy VIII 2020 - Virtual, Online, United States
Duration: Dec 14 2020Dec 22 2020

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceGround-Based and Airborne Instrumentation for Astronomy VIII 2020
Country/TerritoryUnited States
CityVirtual, Online

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


  • Guiding camera
  • Mechanical structure
  • Multi-fiber
  • Prime focus
  • Spectrograph


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