United Launch Alliance launched a classified National Reconnaissance Office spy satellite on a Delta 4 Heavy rocket June 22 at 5:18 a.m. Eastern from Space Launch Complex-37 (SLC-37) at Cape Canaveral Space Force Station, Florida.

NROL-68 is the Delta 4 Heavy’s 15th and penultimate launch before its expected retirement.

The final launch of the rocket is scheduled for early next year.