Overview
Recall that the motivation for doing the overlays in the first place is a result of the differing windows for latching trigger data as opposed to event data, and the resulting overlay scheme needs to provide for not only overlaying event data from the Periodic Trigger events, but also properly handling the event's raw trigger data.
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This scheme for including the trigger information was included in the overlays with GlastRelease v15r50p7 and later.