Observing Unit Sets

Depending on the user inputs in a Science Goal, multiple Scheduling Blocks might result e.g. both the 12-m Array and the ACA might be required and these cannot be observed with the same SB. SBs are contained within folders called Observing Unit Sets (usually abbreviated to ObsUnitSet or OUS) which can in turn be contained within other ObsUnitSets. In principle, an arbitrarily complicated nested OUS/SB structure could be created, but ALMA uses a fixed number of OUS for all observations.

The OUS levels in a project are shown in Figure 3.1 and comprise the following (from bottom to top):

Figure 3.1: The Project Structure pane for a project involving two sources, each of which requires the 12-m Array and the ACA. For each source, the SBs for each array live in their own Member OUS, and these are contained within a Group OUS. The two Group OUSs are contained within their common Science Goal OUS. The two sources are in separate Group OUSs because the data will not be combined.
Image OUSNest

As can been seen, one of the main purposes of an OUS is to define relationships between different SBs for data processing purposes. The data processing pipeline is only triggered when all of the SBs inside an individual OUS are marked as completed, unless other conditions apply to finish the observation.

The ALMA OT Team, 2024 May 21