UPDATE: Orbital ATK made the announcement official Aug. 12.

WASHINGTON — Orbital ATK has purchased a second Atlas 5 rocket to launch NASA cargo to the International Space Station and could buy a third, the company will announce Aug. 12.

Orbital ATK’s latest Atlas 5 booking is for a mission slated to launch in early 2016, according to a press release slated to hit the wire Aug. 12. The company has already bought one Atlas 5 from Lockheed Martin Commercial Launch Services to launch its Cygnus cargo tug to ISS from Cape Canaveral Air Force Station in Florida in early December. The Atlas 5 is built and operated by United Launch Alliance of Denver, a Boeing-Lockheed Martin joint venture. Lockheed Martin sells the vehicle commercially.

Orbital ATK is counting on Atlas 5 to help fulfill orders NASA placed in 2008 under a $1.9 billion Commercial Resupply Services contract while the company redesigns its Antares rocket following a launch failure last October.  Antares exploded moments after liftoff from the Mid-Atlantic Regional Spaceport in Wallops Island, Virginia.

Orbital ATK has attributed the failure to the rocket’s Soviet-heritage AJ-26 main-stage engine, which was imported and refurbished by Aerojet Rocketdyne of Sacramento, California.  The rebooted Antares will feature a new main-stage engine, the Russian-made RD-181 from NPO Energomash: the same company that makes Atlas 5’s RD-180 core engine.

Both Atlas 5-launched Cygnus tugs will carry their maximum load of  3,500 kilograms of pressurized cargo, Frank Culbertson, president of Orbital ATK’s Space Systems Group, said in the press release.

Besides the mission to be announced Aug. 12, Orbital ATK will conduct “at least three more CRS missions” in 2016, one of which could be launched by a third Atlas 5, the company said. The new Antares, which features two RD-181 engines, will be ready for launch from Virginia “in early 2016,” the company wrote in its press release.

An Antares hot-fire at Wallop’s Pad 0A, which is expected to be repaired and ready for operations by Sept. 30, could happen later this year, Orbital ATK said.

Meanwhile, the pressurized cargo module for the Cygnus launching on Atlas 5 in December arrived at NASA’s Kennedy Space Center in Florida “earlier this week,” according to the press release. The cargo module will next be integrated with Cygnus’ service module, slated to arrive in early October.

NASA has Orbital ATK under contract for the equivalent of eight cargo flights; The company has completed two.

Dan Leone is a SpaceNews staff writer, covering NASA, NOAA and a growing number of entrepreneurial space companies. He earned a bachelor’s degree in public communications from the American University in Washington.