WASHINGTON — The U.S. Missile Defense Agency (MDA) plans to contract with Raytheon Missile Systems soon for 20 additional first-generation Standard Missile (SM)-3 interceptors using the nearly $200 million Congress added to the agency’s 2011 budget in April, according to government and industry officials.

The purchase of additional SM-3 Block 1A interceptors is intended as a hedge against technical issues that could delay production of the more advanced Block 1B interceptor that will make its first test flight later this summer, said Wes Kremer, Raytheon’s SM-3 program director.

The SM-3 interceptor and the Lockheed Martin-built Aegis Weapon System are the centerpieces of a revised plan for European missile defense unveiled by the administration of U.S. President Barack Obama in September 2009. For the first phase of the so-called Phased Adaptive Approach, the Aegis-equipped USS Monterey was deployed in March to the Mediterranean Sea. The MDA also plans to deploy a forward-based radar to southern Europe by the end of the year, though it has not yet been announced which nation will host it.

The MDA in its 2011 budget request sought $94.1 million to pay for the final batch of SM-3 Block 1A interceptors. The last of the 137 interceptors bought by MDA were to be delivered in 2012.

Congress was unable to pass any of the 12 annual government spending bills before the beginning of the fiscal year Oct. 1, and instead funded the government with a series of short-term spending measures. In April, a full-year Continuing Resolution was passed that funded most of the U.S. government at 2010 appropriated levels through September.

The final 2011 spending bill provided an additional $189.7 million to purchase more SM-3 Block 1A interceptors, and Raytheon and the MDA are working to define that production contract, Kremer said. This additional funding will allow for the purchase of 20 more interceptors, MDA spokesman Rick Lehner said in a June 16 email.

While Raytheon continues to produce operational Block 1A interceptors, it has been put under contract to deliver 24 SM-3 Block 1B interceptors, all of which will be used for flight testing during the next four years, Kremer said. The Block 1B interceptor uses the same propulsion stack but incorporates an upgraded two-color infrared seeker and a throttleable divert and attitude control system.

The House of Representatives in its version of the 2012 defense authorization bill expressed concern that problems with the new divert and attitude control system could further delay the first Block 1B flight test, and it prohibited the MDA from issuing a production contract until the missile is successfully demonstrated. Kremer has high confidence that the technical issues that caused an April 2010 test failure of the divert attitude control system have been resolved.

“We have implemented a solution for that and this flight test will demonstrate that we understand all those issues,” he said. “At this point I’m highly confident we have that behind us.”

The first SM-3 Block 1B flight test will attempt to intercept a target missile, which is unusual for a new missile, Kremer said. But the performance of the new interceptor is believed to be well understood because it shares some hardware with the Block 1A interceptor and performed well in a January flight simulation in a vacuum chamber, Kremer said.

If the Block 1B flight test is successful, Raytheon expects to receive a production contract in 2012, Kremer said. The MDA requested $565.4 million to purchase 46 of the interceptors next year. The House of Representatives on June 14 passed a 2012 defense appropriations bill that fully funded the program;  the Senate has not yet considered the bill.

Meanwhile, Raytheon is on track with development of the larger SM-3 Block 2A interceptor that the United States is co-developing with Japan. The Block 2A missile is key to the third phase of the Phased Adaptive Approach and will provide a larger coverage umbrella and be able to launch and intercept enemy missiles based entirely on cueing and data from external sources.

The House’s 2012 defense authorization bill also questioned whether the program would be ready for its preliminary design review in late 2011 and its first flight test in late 2014. Some of the subcontractors that work for Raytheon’s Japanese industrial partner, Mitsubishi Heavy Industries of Tokyo, were affected by the March earthquake and tsunami that devastated parts of Japan. But the overall program schedule was not affected and a preliminary design review is expected to be completed by the end of the year, Kremer said.