AESOP: the 4MOST fiber positioner

Jurek Brzeski*, Gabriella Baker, Sufyan Baker, Rebecca Brown, Scott Case, Tony Farrell, Peter Gillingham, Urs Klauser, Jon Lawrence, Slavko Mali, Rolf Muller, Vijay Nichani, Naveen Pai, Scott Smedley, Sudharshan Venkatesan, Lew Waller

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference proceeding contributionpeer-review

4 Citations (Scopus)


The Australian Astronomical Observatory's (AAO's) AESOP project is part of the 4 metre Multi-Object Spectrograph Telescope (4MOST) system for the VISTA telescope. It includes the 2436-fiber positioner, space frame and electronics enclosures. The AESOP concept and the role of the AAO in the 4MOST project have been described in previous SPIE proceedings. Prototype tests, which were completed early in 2017 demonstrated that the instrument requirements are satisfied by the design. The project final design stage has recently been completed. In this paper, key features of the AESOP positioning system design, along with the techniques developed to overcome key mechanical, electronic, and software engineering challenges are described. The major performance requirement for AESOP is that all 2436 science fiber cores and 12 guide fiber bundles are to be re-positioned to an accuracy of 10 μm within 1 minute. With a fast prime-focus focal-ratio, a close tolerance on the axial position of the fiber tips must be held so efficiency does not suffer from de-focus losses. Positioning accuracy is controlled with the metrology cameras installed on the telescope, which measures the positions of the fiber tips to an accuracy of a few μm and allows iterative positioning until all fiber tips are within tolerance. Maintaining co-planarity of the fiber tips requires accurate control in the assembly of several components that contribute to such errors. Assembly jigs have been developed and proven adequate for this purpose. Attaining high reliability in an assembly with many small components of disparate materials bonded together, including piezo ceramics, carbon fiber reinforced plastic, hardened steel, and electrical circuit boards, has entailed careful selection and application of cements and tightly controlled soldering for electrical connections.

Original languageEnglish
Title of host publicationGround-based and Airborne Instrumentation for Astronomy VII
EditorsChristopher J. Evans, Luc Simard, Hideki Takami
Place of PublicationBellingham, Washington
Number of pages17
ISBN (Electronic)9781510619586
ISBN (Print)9781510619579
Publication statusPublished - 8 Jul 2018
EventGround-based and Airborne Instrumentation for Astronomy VII 2018 - Austin, United States
Duration: 10 Jun 201814 Jun 2018

Publication series

NameProceedings of SPIE
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceGround-based and Airborne Instrumentation for Astronomy VII 2018
Country/TerritoryUnited States


  • 4MOST
  • Fiber positioner
  • piezoelectric actuators


Dive into the research topics of 'AESOP: the 4MOST fiber positioner'. Together they form a unique fingerprint.

Cite this