Sending multiple preliminary notices
At the O3 run call this morning (9/16/19( we had a discussion about sending multiple preliminary notices for a single event. No one was opposed to doing this, in fact we expect this will become necessary in the future with (for example), early warning alerts for BNS mergers. There was a consensus that we don’t want to send a preliminary alert after the initial notice/circular has been sent. Again, I think this matches the wider opinion in the emfollow group, but correct me if I’m wrong.
One issue with sending multiple preliminary alerts for a single event is that while the documentation at present hints that this can happen, it doesn’t explicitly state it. For example at
https://emfollow.docs.ligo.org/userguide/analysis/index.html
it is written that "the first preliminary notice will be sent fully autonomously”, which by implication suggests that there could be more than one.
If we are to start sending multiple preliminary notices for a single event (note that we have done so already during O3, but generally for some special or corner-cases), then I suggest we make this explicit in the documentation. I also think we should change the “Alert Timeline” figure to include possible generation ofpreliminary alerts during the “Human Vetting” stage, i.e. before the "Initial Alert or Retraction Sent” stage.