4MOST operations will introduce three feedback loops into observations to ensure the highest quality of delivered data. They are summarised in the following:

  1. Quality Control 0 (QC0) verifies whether an Observation Block (OB - field/fibre configuration) has been successfully executed, and in case of failure produces flags that indicate the type of problem concerning the acquired data.
  2. Target progress update will be delivered by Data Management System (DMS) in the form of measured target success per each night of observations. This measure of target success will then be used by the Opeations System (OpSys) to determine whether further exposure time needs to be allocated to a specific target.
  3. Survey progress update in the form of yearly reviews will be conducted by ESO to determine whether surveys progress according to plan and whether Phase 3 data products (return of reduced data to the ESO Archive) are being delivered according to the predefined schedule and quality. The process and scope for intervention in this context is not yet fully defined and will be provided by ESO.