Photos: News media images of Atlas 5 launch

After unusual concentrations of hydrogen around the rocket foiled a launch attempt Dec. 19, United Launch Alliance said Friday that the company’s powerful Delta 4-Heavy launcher and a U.S. government spy satellite will remain grounded in California until at least Jan. 6 as engineers troubleshoot a small fuel leak.

United Launch Alliance kicked off its 2018 launch campaign with a Delta 4 rocket flight at 2:11 p.m. PST (5:11 p.m. EST; 2211 GMT) Friday from Vandenberg Air Force Base in California. Gusty winds forced officials to call off a launch attempt Wednesday, and technical problems halted a countdown Thursday multiple times. The Delta 4 launched with a top secret spy satellite for the National Reconnaissance Office.

A Chinese Long March 3B rocket deployed the Tiantong 1-03 satellite to provide mobile communications services after a successful launch Tuesday, the first of more than 40 Chinese space missions set for liftoff in 2021.