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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 it has been decided that only a fixed number of OUS levels will be allowed and that each level will always appear, even if all are in theory not necessary. It has been decided that for all observations the same OUS/SB structure will be used.
The OUS levels in a project are shown in Figure 3.1 and comprise the following (from bottom to top):
- Member OUS - this level, and only this level, will contain the SBs. Once an SB within a Member OUS has been fully observed, the OUS will trigger the data reduction of the resulting ASDMs.
- Group OUS - this OUS contains one or more Member ObsUnitSets. If there is more than one Member OUS, usually when both ALMA and the ACA are required, this indicates that these should be combined during subsequent data processing. This will be triggered by the Group OUS once reduction of all the individual Member ObsUnitSets is complete. Even if the Group OUS only contains a single Member OUS, it will still be present, even though it strictly speaking isn't necessary
- Science Goal OUS - all Group OUSs for a given Science Goal are contained in the corresponding Science Goal OUS. No pipeline processing happens at this level.
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.
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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.
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The ALMA OT Team, 2018 Sep 25