( - A 19-story Atlas V rocket is scheduled to roll to its pad today in preparation for a Thursday morning blastoff from Cape Canaveral Air Force Station — United Launch Alliance's second countdown in six days.

Liftoff from Cape Canaveral Air Force Station with a classified intelligence satellite is planned at 9:05 a.m. The launch period extends to 10:15 a.m.

Forecasters expect nice weather, with an 80 percent chance of favorable conditions Thursday and again Friday, if the mission slips a day.

Managers on Monday reviewed their readiness for the countdown and concluded with a "go" to roll the rocket from its vertical processing tower a quarter-mile to the pad at Launch Complex 41.

The Atlas V is flying in a "401" configuration with a four-meter diameter payload fairing, no solid rocket motors and a single Centaur engine powering the upper stage.

The rocket's Russian-made RD-180 main engine has been the subject of controversy of late. Rival SpaceX claimed its use violates sanctions imposed on Russia for its annexation of Crimea — U.S. officials say it doesn't — and Russian has threatened to cut off its supply.

The national security launch would be ULA's fourth this year by an Atlas V, including the April 10 launch of another NRO satellite from the Cape, and sixth overall in 2014.

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