Narrated video packages show the shrouded NROL-37 payload being hoisted atop the United Launch Alliance Delta 4-Heavy rocket and the retraction of the mobile service gantry.

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.

With its liftoff just 18 days away to deploy a new Global Positioning System satellite, stacking of the next United Launch Alliance Atlas 5 rocket began Monday at the vertical assembly building outside Complex 41.