... Most primary visits submitted by HST observers only use one SI, leaving the other SIs free to be requested by ``pure parallel'' observing programs. ... The Parallel Observation Matching System (POMS) has the task of matching parallel visits to primary observations and ``crafting'' appropriate parallel SUs at each opportunity, taking scientific criteria and orbital constraints into account. ... For each parallel visit, POMS then structures the slots into a collection of parallel fields . ... Trans: ....