ESO User Support and Observation Preparation for VLTI Operations

Abstract

We present recent enhancements to VLTI observing capabilities from a user-oriented perspective, together with new developments in ESO's Observation Handling Tools and end-to-end operations model for VLTI. Key upgrades include GRAVITY+ Coudé guiding with laser guide stars at the UTs, improved limiting magnitudes for GRAVITY and MATISSE, and a new MATISSE narrow-field off-axis mode, all supported by a streamlined, uniform template structure. Phase 2 tools now enable finding-chart generation and the selection of Coudé guide stars and fringe-tracker targets, and will soon offer expanded preparation features and uv-coverage visualisation. We summarise usage statistics for snapshot, astrometric, imaging, and time-series observations, outline VLTI scheduling considerations, and present new video tutorials. Starting in 2026, an archive data stream of reduced GRAVITY dispersed visibilities has become available. Complementary community engagement in VLTI operations continues to grow. We close by identifying operational lessons for future interferometric facilities, including the importance of an end-to-end data-flow and user-support model, flexible scheduling, high-level observation-preparation tools, and coordinated community support to keep complex interferometric facilities usable by a broad community.