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Advanced Enclosed Mast/Sensor System Installed on San Antonio

NAVSEA News Wire

Release Date: 5/30/2003

By Naval Sea Systems Command Office of Congressional and Public Affairs

AVONDALE, La. The future USS San Antonio (LPD 17) now shows its distinctive appearance. When shipyard workers lifted the 83.7-foot high aft Advanced Enclosed Mast/Sensor system (AEM/S) into place on the amphibious transport dock's superstructure, San Antonio became the first ship to have two of the revolutionary masts.

The AEM/S serves the dual-purpose of both supporting and protecting ship sensors. It provides the structural support of a traditional mast while providing protection from the elements and threat radar. Its new function is enabled by the mast's composite hybrid frequency selective surface that blocks threat radar and allows non-threat radar and communication signals to pass through.

The AEM/S replaces traditional navy stick masts that have been standard on navy ships for over a hundred years. The mast is now an integral part of the radar and communication antennas suite, which improves system performance and reduces maintenance while maximizing the ship's ability to safely support expeditionary warfare missions in the littoral.

Northrop Grumman Ship Systems fabricated both the forward and aft AEM/S systems at their Gulfport, Miss. facility and then barged them separately through the Gulf of Mexico and up the Mississippi River to the Avondale shipyard. The forward AEM/S was landed on San Antonio on April 28, 2003.

The forward mast will support the SPQ-9B horizon search radar and enclose various communications antennas, reducing wear and tear from exposure to weather and sea spray. The aft, taller AEM/S encloses the SPS-48 E 3D air search radar as well as additional sensors and antennas. Northrop Grumman suspended the after mast from two cranes as they moved this, the largest composite material structure ever mounted aboard a surface ship, into place.

With the AEM/S installation, 208 of 210 ship units have been erected and San Antonio is approximately 70 percent complete. The new LPD will be a Norfolk based ship and remains on track for christening in July of this year. Construction also continues for the LPD 17's sister ships, New Orleans (LPD 18) and Green Bay (LPD 20) in the Avondale shipyard, while Mesa Verde (LPD 19), progresses at Northrop Grumman's facility in Pascagoula, Miss.