VLTI Configurations Overview

P96 and following periods

The offered AT quadruplets available for service and visitor mode in P96 are different from the ones offered in P94. The new configurations were chosen combining operational constraints and an optimized sky and u,v coverage. For periods following P96, the quadruplets are presented in the figure below, alongside two figures showing the sky and uv coverage for a 4h observation of a star at -15º.

P98 and following periods

The introduction of GRAVITY comes with a slight complication: in dual feed mode, GRAVITY can only be operated with AT all south of the delay line tracks. As such, the current Large (A0-G1-J2-J3) and Medium (K0-G2-D0-J3) *cannot* be used in dual feed. As such, dual feed observations of GRAVITY will be executed either with the Small (A0-B2-D0-C1) or the "all south" Large (A0-G1-J2-K0) configurations. 




For reference, the old configuration (available up to P94) can be found here. The previous version of this page (pre-P95) can be found here.

Observations preparations


For details on the offered modes please refer to the current Call for Proposals and the VLTI manual.

In all cases, please verify your observations with ESO tool VisCalc, or alternatively, with the third party preparation software Aspro2, developped with inputs from ESO.

Configurations offered using the Unit Telescopes:

PIONIER and GRAVITY are offered on the quadruplet UT1-UT2-UT3-UT4.

AMBER is offered on all four available UT triplets:

  • UT1-UT2-UT3
  • UT1-UT2-UT4
  • UT1-UT3-UT4
  • UT2-UT3-UT4
  • Configurations offered using the Auxiliary Telescopes:

    The users are requested to provide their preferred AT quadruplet in their proposal at phase 1. The quadruplet cannot be changed after proposal submission. In case of the 3 telescope instrument AMBER, the triplet used on sky is set by the OB preparation process in phase 2 (for service mode proposals) and during the run itself for visitor mode observations.

    PIONIER and GRAVITY are offered on the 3 following quadruplets:

  • "large": A0-G1-J2-J3. Note that in the case of GRAVITY dual feed, there is a yet uncharacterized visibility loss due to the mix of North and South to the delay line tunnel Stations. ESO might execute your OBs on A0-G1-J2-K0 in case the loss is deemed too large to be acceptable.
  • "medium": D0-G2-J3-K0, except for GRAVITY in dual feed mode
  • "small": A0-B2-C1-D0

    AMBER is offered with the 12 unique triplets: