A ULA Delta IV Heavy rocket was scheduled to launch the clandestine satellite mission, called NROL-71, on Sunday (Dec. 30) from California's Vandenberg Air Force Base. The launch has been delayed several times due to rocket issues, most recently on Dec. 19 due to a suspected hydrogen leak on the booster.
"The United Launch Alliance Delta IV Heavy carrying the NROL-71 mission will launch no earlier than Sunday, Jan. 6, 2019," ULA representatives said in a statemement."The mission will launch from Space Launch Complex-6 at Vandenberg Air Force Base in California."
ULA's attempts to launch the NROL-71 mission on Dec. 7 and 8 were delayed by technical issues. An attempt on Dec. 18 was thwarted by high winds, leading to the Dec. 19 launch scrub.