WASHINGTON — With a nearly $1 billion contract award to Raytheon Co., the U.S. Missile Defense Agency (MDA) has ushered a U.S.-Japanese missile interceptor development program into its final phase, the highlight of which is an intercept attempt tentatively scheduled for mid- to late 2016, a company official said.

Raytheon Missile Systems will finalize the design of the Standard Missile (SM)-3 Block 2A interceptor and begin nonintercept flight testing in 2015 under the $925 million contract modification, according to Mitch Stevison, the company’s senior SM-3 program director. The MDA awarded the modification July 25, bringing the total value of Raytheon’s work on the program to $1.5 billion.

The contract runs through February 2017. A critical design review of the interceptor is scheduled for September 2013, Stevison said.

The SM-3 Block 2A is a larger and more capable version of the Raytheon-built SM-3, the munition for the sea-based Aegis Ballistic Missile Defense system. The first-generation SM-3 interceptor, designed to knock down short- and medium-range ballistic missiles, is operational and deployed aboard U.S. and Japanese navy ships; an upgraded variant known as the Block 1B is undergoing flight testing.

Japan and the United States agreed in 2006 to jointly develop the SM-3 Block 2A, designed to intercept short-, medium- and intermediate-range ballistic missiles during the midcourse portion of flight. Though the new variant will be bigger and have more range than the current SM-3, it can be fired using the same ship-based launching systems.

Japan has committed $1 billion for its portion of SM-3 Block 2A development-phase work, with Tokyo-based Mitsubishi Heavy Industries as prime contractor. Mitsubishi is responsible for the interceptor’s second- and third-stage motors and nose cone.

Raytheon is developing the other elements of the interceptor, including the kill vehicle, and is responsible for overall system integration, according to MDA spokesman Rick Lehner.

The SM-3 Block 2A is scheduled for deployment in 2018. U.S. President Barack Obama’s Phased Adaptive Approach to European missile defense calls for placing 24 of the interceptors in Poland starting in 2018, but it has yet to be decided whether the initial versions will be sea- or land-based, Lehner said.

Work on the Block 2A, characterized by the MDA as one of the most complex weapon codevelopment programs with Japan ever undertaken, began in 2007. Initial plans called for flight testing to begin as early as 2012, with deployment to follow in 2015, but the program has since been stretched out to better align it with the schedule of the European Phased Adaptive Approach, Lehner said via email.

The MDA built in more time between subsystem and system level design reviews in fiscal year 2011 to try to reduce risk and incorporate lessons from the SM-3 Block 1B development program, Lehner said. Program officials also changed the propellant formulation in Block 2A’s divert and attitude control system, which maneuvers its kinetic warhead to its target, and had to take measures to reduce the weight of the third-stage motor, “all typical things that are examples of good engineering practices,” he said.

Raytheon and Mitsubishi Heavy Industries do not have a direct contractual relationship on the SM-3 Block 2A program but there has been dialogue between the two companies, according to Stevison. One advantage of the joint development is cost-sharing, but there are communication delays, he said. However, the companies have mitigated most of the potential pitfalls of the situation and are working to see if a more formal partnership can be forged for production work, he said.

“I think we learn a lot from the Japanese with respect to the way that they execute their quality on the programs, the way that they execute their engineering, the way that they deliver and look at programs,” Stevison said. “We learn from them and they learn from us, so it is a very mutually beneficial academic investment in learning together to be successful together.”

Meanwhile, U.S. Defense Secretary Leon Panetta announced in Tokyo Sept. 17 that the United States and Japan will install an additional AN/TPY-2 X-band missile tracking radar on Japanese territory as part of expanded missile defense ties between the two nations. The radar system, built by Raytheon, will bolster the protection of Japanese and U.S. territory, along with forward-deployed U.S. troops, against the North Korean missile threat, he said.

“This continued close cooperation on ballistic missile defense reflects our joint commitment to this alliance and to promoting peace and security in the Asia-Pacific region,” Panetta said during a joint press conference with Japanese Defense Minister Satoshi Morimito. “Our new defense strategy for the United States clearly articulates America’s rebalance to the Asia-Pacific region, which we recognize is of growing importance to the international security and the global economy.”