Live at the Cape: Atlas launch preps under way

Countdown to the planned launch tonight of an United Launch Alliance Atlas 5 rocket is expected to pick up around 2:46 p.m. EST today as the company gears up to launch a clandestine cargo for the super-secret National Reconnaissance Office.

The Atlantis rocket and its payload are scheduled to blast off at 5:03 p.m. from Launch Complex 41 at Cape Canaveral Air Force Station. The exact launch window is classified, but a launch danger zone off the coast will reopen to mariners at 7 p.m.

Launch preparations at this point are continuing without significant problems with the rocket or its payload have been reported.

The rocket rolled out of its assembly building -- the Vertical Integration Facility -- Sunday and headed for the launch pad at complex 41.

Custom-crafted "trackmobiles" pushed the rocket and its mobile launcher platform along rail tracks that link the assembly building and the pad. Thanks to United Launch Alliance and photographer Pap Corkey for these great shots of the Atlas making its way to the pad. Click to enlarge and save any of them.

The Atlas is one of the smaller versions of the venerable rockets -- a so-called 401 configuration with rocket will fly in the 401 vehicle configuration with relatively short nosecone (four meters), no solid rocket boosters and a single Centaur engine.

The standard operating procedure for an Atlas launch would have called for engineers to report to their consoles in the Atlas Space Operations Center near complex 41 early today. Electrical power to the Atlas and Centaur stages of the rocket would have been turned on about 10 a.m., and an initial weather briefing would have been conducted.

The latest weather forecast calls for an 80 percent chance that conditions will be acceptable for flight. Check out the details in the official forecast from meteorologists at the Air Force 45th Space Wing Weather Squadron here: AtlasForecast.pdf.

Atlas launch workers would have started clearing out of the area around the Vertical Integration Facility around 11:15 a.m., and the launch team would have started an operational test of flight control systems shortly after that.

Radar used to track the rocket in flight would have been tested by now, and Air Force security officers also would have cleared a blast danger zone around the complex.

We'll have live updates during the countdown, and we'll also webcast the live United Launch Alliance broadcast here in The Flame Trench starting 20 minutes before liftoff. Check back and refresh this page for periodic updates. More to come.