4MOST passes full end-to-end rehearsal — Operations Rehearsal 4 complete

Operations Rehearsal 4 (OpR4) — described as a full "dress rehearsal" for 4MOST — has concluded successfully, verifying the complete operational ecosystem from observation planning through data processing and feedback into future observing decisions.

The exercise demonstrated autonomous nightly operations end-to-end: the system automatically generated and scheduled Observing Blocks (OBs), selected targets, and optimised observations based on live site conditions at Paranal. For ESO, which operates some of the world's foremost observatories, an autonomous remote scheduler of this kind represents a significant operational milestone.

Cambridge DMS team confirms end-to-end functionality

Nic Walton and David Murphy, who lead the 4MOST Data Management System (DMS) team at the Cambridge Astronomical Survey Unit (CASU), confirmed that OpR4 demonstrated full end-to-end functionality of the processing system and verified that observations are successfully transformed into science-ready products.

CASU leads the core 4MOST DMS and hosts the 4MOST Data Processing Centre (4DPC) at Cambridge, performing all Level 1 processing, integrating the galactic and extragalactic Level 2 pipelines, and ensuring Phase 3 delivery of validated science products to the ESO Science Archive.

Next steps: Science Program Verification

With OpR4 complete, the project has advanced to the Science Program Verification (SVP) phase, the final stage before routine survey operations begin. Full science operations are expected in Q2 2026, when the nightly DMS data flow will run continuously, turning every night of VISTA/4MOST observations into archived, publicly accessible spectra.

Jakob Walcher, 4MOST Operations Manager, noted: "For me the most impressive thing to see was the enthusiasm, competence, and hard work of everyone involved."

Source: Reflections on OpR4 — 4MOST project website, 2 March 2026