Located in one of the pieces of the wreckage of the Dawn at the beginning of the level Requiem is a computer monitor on its side with a prompt to "access log entry." I took pictures of the entire entry subtitles and will transcribe them here, and I recommend that the rest of you also keep an eye out for this and any other log entries that we may find. It pertains directly to what I can only assume is Cortana, yet Halsey only refers to her as H-1. You'll see what I mean when I post the transcription.
Spoiler in this next line, so unless you've finished the campaign, look at your own risk!
It may even be possible to unlock a separate ending and save Cortana from rampancy if we find all of the logs, similar to the audio logs in ODST. Just my thoughts.