PIONIER - Precision Integrated-Optics Near-infrared Imaging ExpeRiment


PIONIER is a H-band 4-beam combiner instrument at the VLT interferometer. It is originally a visitor instrument that by agreement with IPAG is offered to the ESO community from P96 onwards as a facility instrument, i.e. without the need for collaborating with the instrument team, and is offered both in visitor and service mode for normal, large, and monitoring programs.

PIONIER combines either beams from the 8.2-m Unit Telescopes or from the 1.8-m Auxiliary Telescopes to provide visibilities of six different baselines, as well as four closure phase measurements, simultaneously.  PIONIER features low resolution spectroscopic optics to measure at six different wavelengths within the H-band, increasing the (u,v) coverage, or can work in integrated light for sensitivity enhancement on faint targets.

Starting from P104 a new imaging optimized scheduling and the mandatory use of the web p2 tool for OB preparation were introduced. Please check instrument news pages for the most uptodate information.

Contact Information

  • Questions related to proposal preparation, service mode, and visitor mode observations should be addressed via the contact form at  ESO Operations Helpdesk.
  • Please, send us your general feedback, comments, suggestions, or report errors and inaccurate statements in the web pages and manuals also via this contact form.
  • For VLTI users needing assistance to prepare their VLTI proposals, the community supported VLTI Expertise Centres - distributed throughout Europe - can offer in-depth support. They also offer support for observation preparation, advanced data reduction and interpretation.

Content of these pages

The following items are available on all the PIONIER pages, using the navigation to the left.

  • News: List of changes affecting the instrument and/or its pages.
  • Overview: All the important parameters of the instrument (must read for proposal preparation).
  • Instrument Description: A short description of the instrument.
  • Manuals: Links to all the documents related to PIONIER, including the data reduction pipeline manual provided by IPAG
  • Tools: A collection of useful tools and informations for preparing and analyzing the PIONIER observations.
  • Instrument Operations Team
  • Links: External links useful for PIONIER users
  • Visitor Instructions: Instrument specific instructions for Visiting Astronomers
  • Science: Links to published papers using PIONIER data

Other Users Information

Important information for Paranal users can be found in the menu items: Site Information and Logistics, Astroclimatology, Information for Visiting Astronomers.


Publications based on data obtained with the PIONIER instrument should quote the following reference paper: LeBouquin, J.B.; et al.: "PIONIER: a 4-telescope visitor instrument at VLTI", 2011, A&A, vol. 535, article id 67