Introduction and Policy

During a Visitor Mode observing run, observations are expected to follow the scientific programme approved by the Observing Programmes Committee (OPC), including the approved targets and instrument configurations.

Any significant modification to the approved programme must be reviewed and approved in advance. This applies to the following categories:

• Additional Targets: If you wish to observe targets that were not included in the approved proposal, these additional targets must be submitted for approval before the observing run.
• Backup targets: Observers are strongly encouraged to prepare backup targets that can be observed if conditions prevent execution of the primary programme. In particular, strong winds at Paranal frequently originate from the north.
• Instrument set-up changes: Any instrument configuration not included in the approved proposal requires prior approval. This includes changes to instrument modes, filters, gratings, detector configurations, or other observing setups.

If a requested modification is not approved, observations must be limited to the originally approved targets and instrument configurations. If the approved programme cannot be executed because of weather conditions, technical constraints, or target visibility limitations, the observatory may use the telescope for other activities.

Requests for additional targets, backup targets, or setup changes must be submitted at least two weeks before the start of the observing run, via p2. Requests submitted with shorter notice may not be processed in time. In particular, requests received less than 48 hours before the start of the run cannot be guaranteed to receive a decision before observations begin. Please note that observations obtained using unapproved targets or configurations may not be released through the ESO Science Archive until the request has been formally reviewed and approved.

Submission procedure

Programme change requests are submitted directly through p2.

To submit a request:

1. Open the relevant observing run in p2.
2. Select Change Request from the menu in the upper-right corner.
3. Follow the guided submission process.
4. Provide all information necessary to evaluate the requested modification.

Once submitted:

• You will receive an acknowledgement by email confirming receipt of the request.
• The request will be reviewed by ESO staff.
• You will be notified of the outcome by email.
• If approved, the relevant observatory staff and telescope team will be informed.