Stats: Atlas 5 and Delta 4 histories and backlogs (updated April 20)

United Launch Alliance’s Atlas 5 rocket made its way back to the pad at Space Launch Complex 41 at Cape Canaveral Space Force Station on Thursday morning for a mission carrying national security mission payloads, collectively codenamed Silentbarker. Liftoff has been rescheduled for at 8:47 a.m. EDT (1247 UTC).

The 75th Atlas 5 rocket rolled to its launch pad at Cape Canaveral on Wednesday, a day before it was scheduled to lift off with a U.S. Air Force satellite to provide warnings of missile launches that might threaten U.S. territories and allies.

Final preparations began this weekend at NASA’s Stennis Space Center in Mississippi to load super-cold liquid hydrogen and liquid oxygen into the massive core stage of the Space Launch System heavy-lift rocket for the first time as soon as Monday.