Move isolatedStarAssociation task to DECam step2a

ingredients/DECam/DRP.yaml

@@ -145,23 +145,31 @@ subsets:
     subset:
       - consolidatePreSourceTable
       - consolidateVisitSummary
+      - isolatedStarAssociation
     description: |
-      Visit-level tasks
-      Allowed data query constraints: visit
+      Global tasks: This is a mix of visit-level and tract-level tasks that
+      must be run with a skymap data query constraint only (an instrument
+      constraint is fine, but generally unneccessary).  For example, running
+      with 'tract' (and 'patch') constraints will select partial visits that
+      overlap that region.  A skymap constraint is necessary to prevent
+      isolatedStarAssociation from producing results for all skymaps in the
+      data repository. This only works with small to medium jobs.
+      The isolatedStarAssociation task uses PreSources, generated by
+      consolidatePreSourceTable, for all visits that overlap a tract.
 
-      Tasks aggregate all detectors for a given visit.
+      Visit-level: consolidatePreSourceTable, consolidateVisitSummary
+      Tract-level: isolatedStarAssociation
   step2b:
     subset:
-      - isolatedStarAssociation
       - jointcal
     description: |
       Tract-level tasks
       Allowed data query constraints: tract
 
-      Jointcal and isolatedStarAssociation both use PreSources, generated
-      by consolidatePreSourceTable, for all visits that overlap a tract.
-      jointcal produces solutions per-tract, per-visit
-      isolatedStarAssociation produces solutions per-tract.
+      Jointcal uses PreSources, generated by consolidatePreSourceTable,
+      for all visits that overlap a tract. It also produces solutions
+      per-tract, per-visit isolatedStarAssociation produces solutions
+      per-tract.
   step2d:
     subset:
       - finalizeCharacterization