VLTI Configurations Overview

Configurations offered using the Auxiliary Telescopes

The users are requested to provide their chosen AT quadruplet in their proposal at phase 1. The quadruplet cannot be changed after proposal submission.

P102 and P103:

From P102, AMBER is decommissioned and VLTI instruments all use 4 telescopes simultaneously.

As in P101,  the astrometric AT configuration is explicitely scheduled and dual-feed observations are only offered on the small and astrometric configurations.

The astrometric configuration, A0-G1-J2-K0, is a variation of the standard large configuration A0-G1-J2-J3. The astrometric configuration has all its telescopes south of the delay line tunnel, which is mandatory for GRAVITY dual-feed observations. The following table shows which instrument / mode can request which configuration. In order to optimize scheduling, some single-feed observing blocks of service mode runs requesting the large configuration might be executed on the astrometric configuration instead since it offers similar baseline lengths and sky coverage.


AT Configurations PIONIER, MATISSE (from P103),GRAVITY single-feed
GRAVITY dual-feed
Small (A0-B2-C1-D0)
yes yes
Medium (D0-G2-J3-K0)
yes no
Large (A0-G1-J2-J3)
yes no
Astrometric (A0-G1-J2-K0)
no yes

Configurations offered using the Unit Telescopes

PIONIER, MATISSE (from P103) and GRAVITY are offered on the quadruplet UT1-UT2-UT3-UT4.

Configurations from previous periods

For reference, the configurations used in the previous periods can be found on this page.

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.