WASHINGTON — The U.S. Missile Defense Agency (MDA) and the U.S. Navy executed a second consecutive successful intercept test June 26 of a new variant of the sea-based Standard Missile 3 (SM-3) interceptor after a first attempt failed last fall.

The successful test of the SM-3 Block 1B interceptor also was the second for the Aegis Ballistic Missile Defense (BMD) 4.0.1 weapon system upgrade, the MDA said in a June 26 press release.

An industry official characterized the test as more operationally realistic than the previous test, which was carried out May 9.

In the latest test, an SM-3 Block 1B interceptor was launched from the deck of the USS Lake Erie and destroyed a target missile that was launched at 11:15 p.m. local time from the Pacific Missile Range Facility at Kauai, Hawaii, the MDA said. The target missile was tracked by the Lake Erie’s AN/SPY-1 radar, and the onboard Aegis BMD weapon system developed a fire control solution.

The Aegis weapon system sent course-correction information to the interceptor in flight. The interceptor then released a kinetic warhead that destroyed the target missile via impact, a technique known as a hit-to-kill.

Wes Kremer, vice president of air and missile defense at SM-3 prime contractor Raytheon Missile Systems of Tucson, Ariz., said the May test was considered a pure developmental test in which the crew aboard the Lake Erie knew when the target missile was going to launch. The latest test was a combined operational and development test where the Lake Erie crew “did not have knowledge of the exact launch time or the specifics on the threat,” he said.

Speaking with reporters in a conference call June 27, Kremer also said the target was more complex than the one used previously. He declined to be more specific other than to make an oblique reference to the SM-3 Block 1B’s two-color infrared seeker, which guides the interceptor’s kill vehicle to final impact with the target.

Riki Ellison, founder and chairman of the Missile Defense Advocacy Alliance here, said the separating stage of the solid-fuel, medium-range target missile produces debris that makes it difficult to pick out the actual target. The two-color infrared seeker is better able to distinguish missile warheads not only from debris but also from decoys and other countermeasures likely to be deployed by sophisticated offensive missiles, Ellison said June 27 in a post-intercept press release.

In addition to the two-color seeker, SM-3 Block 1B features an upgraded onboard signal processor and a more flexible throttleable divert and attitude control system. The interceptor, along with the Aegis BMD 4.0.1, is expected to extend the range of the SM-3 Block 1A, designed to counter short- and medium-range missiles.

The Block 1B failed in its first intercept test in September 2011 and also had problems in a nonintercept test conducted the previous April. These issues have raised concerns among U.S. lawmakers and from the U.S. Government Accountability Office, which in an April 20 report criticized the MDA for approving production of the SM-3 Block 1B before completing developmental testing. The report said this concurrency has led to production halts and expensive hardware retrofits.

Cristina Chaplain, director of acquisition and sourcing management at the Government Accountability Office, said via email June 27 that concurrency is justified as a means of fielding capabilities quickly and sustaining the industrial base, but can “backfire” when resulting technical problems cause disruptions to production schedules.

“The successful flight test is encouraging news for MDA as it recovers from problems experienced in past tests,” Chaplain said of the June 26 test. “More testing is needed to fully verify key technologies but the MDA is now one step closer to resuming production of the 1B.”

Both the MDA and Ellison said the latest successful test was critical to U.S. President Barack Obama’s Phased Adaptive Approach for defending Europe against ballistic missile attacks. The initial phase of that approach features SM-3 interceptors aboard ships operating in or near European waters, but plans call for installing SM-3 Block 1B interceptors on the ground in Romania starting in 2015 as part of the “Aegis Ashore” program.