United Launch Alliance on Tuesday announced it had rescheduled a Delta IV Heavy launch carrying a classified payload for the National Reconnaissance Office for Jan. 19.

The launch, dubbed NROL-71, was previously scheduled to launch in December from Vandenberg Air Force Base, California, but was scrubbed multiple times due to technical and weather conditions. The latest attempted launch on Dec. 19 was postponed due to elevated hydrogen levels in the port engine.

A Delta IV rocket lifts GPS IIF-6 into space from Cape Canaveral Air Force Station, Fla., May 16, 2014. Photo: ULA.

At that point, the

Boeing [BA] and Lockheed Martin [LMT] conglomerate ULA determined a new launch attempt would not be made until after Dec. 30 to allow engineers to determine the cause of the elevated hydrogen levels, the alliance said Dec. 28.

The new launch window is set for Jan. 19 at 11:05 a.m. Pacific Standard Time from Vandenberg’s Space Complex 6, ULA said Jan. 15.

This will be ULA’s 132nd mission the second Delta IV Heavy launch in less than four months. It is the 382nd Delta launch since 1960, the 38th for a Delta IV rocket since 2002 and the 11th Delta IV Heavy, ULA said.

United Launch Alliance was one of three entities awarded an Air Force contract to develop a new launch system prototype by 2021 for the Evolved Expendable Launch Program (Defense Daily, Oct. 10). It plans to build its Vulcan Centaur launch system, while Blue Origin and Northrop Grumman Innovation Systems [NOC] will develop the New Glenn vehicle and OmegA launch system under the contract, respectively. Each company will next compete for a follow-on contract under the Air Force’s launch service agreement program. If selected for that contract, ULA could receive up to $967 million in government development funds.