Complex sentence: Its primary mission is to detect near-Earth objects that threaten impact events and is expected to create a database of all objects visible from Hawaii (three-quarters of the entire sky) down to apparent magnitude 24.
Split into simpler sentences: Its primary mission is to detect near-Earth objects that threaten to cause impact events. It is expected to create a database of all objects visible from Hawaii (three-quarters of the entire sky) down to apparent magnitude 24.