Live coverage: Atlas 5 countdown and launch journal

Watch the briefing to learn what is aboard the Orbital ATK Cygnus OA-6 resupply freighter launching to the International Space Station on March 22 aboard a United Launch Alliance Atlas-5 rocket.

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.

The newest Global Positioning System replenishment satellite went into operation Tuesday night, five weeks after ascending to space from Cape Canaveral atop a United Launch Alliance Atlas 5 rocket.