The User Support Department (USD) of the ESO Data Management and Operations Division is based in Garching bei München, Germany. Its main activities consist in providing support to users of ESO La Silla Paranal Observatory (LPO) facilities:

• Support for Phase 1 proposal preparation, mainly concerning technical questions on instruments, strategies, etc. at the time of writing observing proposals;
• Support, review and optimization during the preparation of Phase 2 material. The purpose is to ensure that the material submitted by the users for the execution of their programmes is compliant with the principles of Service Mode observing and with the Service Mode guidelines, and that the observing strategy is both efficient and adequate for the scientific goals;
• Maintenance of a Web-based Service Mode status information service, where users can obtain up-to-date information on the progress of their Service Mode programmes.
• Operation of a helpdesk system (support.eso.org) where users can address questions and request assistance on all aspects of ESO telescope Service Mode operations.

It also provides assistance to Science Operations Teams at ESO's observatories in the areas of:

• LPO telescopes long-term schedule preparation and maintenance: https://www.eso.org/LPOschedule/public 
• Program mid-term scheduling and tracking services;
• Providing a link between the observatory and the users when actions are needed during the execution of service mode programmes;
• On-site assistance for the execution of Service Mode programmes;
• Maintenance of the User Portal database content;
• Definition and maintenance of operations metrics;
• Definition of requirements for observation preparation tools and feedback on operational requirements for new instruments.

The User Support Department currently provides support for all the instruments available at the VLT and VLTI (Paranal). VISTA is getting ready to be used for surveys with 4MOST and is currently not operational. The VST is operated by INAF as a hosted facility as of October 2022. Users having obtained Visitor Mode time at the La Silla telescopes (NTT and 3.6m telescopes) should contact the La Silla Science Operations Group directly.

The User Support Department is headed by Marina Rejkuba. The deputy head is Markus Wiittkowski. The USD Phase 1 and Phase 2 support for the VLT and VLTI instruments is distributed among the USD staff astronomers as follows (in alphabetical order with the main astronomer responsible in bold):

• CRIRES: Carlo Manara, Mario van den Ancker
• ERIS: Carlo Manara, Monika Petr-Gotzens
• ESPRESSO: John Pritchard, Markus Wittkowski
• FLAMES: Giacomo Beccari, John Pritchard
  
• FORS2: Henri Boffin, Christian Hummel, John Pritchard, Paula Sánchez Sáez
• GRAVITY: Christian Hummel, Johan Olofsson, Markus Wittkowski
• HAWK-I: Monika Petr-Gotzens
  
• KMOS: Paola Popesso
• MATISSE: Christian Hummel, Johan Olofsson, Markus Wittkowski
• MUSE: Giacomo Beccari, Carlo Manara, Monika Petr-Gotzens, Paula Sánchez Sáez
• PIONIER: Christian Hummel, Markus Wittkowski
• SPHERE: Henri Boffin, Johan Olofsson, Monika Petr-Gotzens, Mario van den Ancker
  
• UVES: Christian Hummel, Carlo Manara, John Pritchard
• VISIR: Mario van den Ancker
  
• X-SHOOTER: Giacomo Beccari, Carlo Manara, Paula Sánchez Sáez, Mario van den Ancker, Miguel Vioque
  

The USD operations support scientists, Stéphane Marteau and Sangeeta Mysore, are responsible for a variety of operations tasks, including maintaining the Service Mode run status pages, managing the USD helpdesk (support.eso.org), maintaining the external report and verification modules for instrument packages implemented in the p1 and p2 web tool, delivery of instrument specific observation preparation tools and operations metrics. Matheus Brito is taking care of travel arrangements for visiting astronomers. The techical scheduling assistant Nelma Silva provides support for telescope schedule preparation and its maintenance.