The Navy is pushing ahead with low-rate initial production of the AQS-20A minehunting sonar system for operations from the new MH-60S Knighthawk multi-mission helicopter and the WLD-1 remote minehunting system (RMS)-both of which will fill key roles in the Fleet's minehunting strategy.
The system, developed and built by Raytheon Integrated Defense Systems, is a towed, ten-foot-long, 1,000-pound body fitted with five active sonars for detection, classification, and identification of mines lying on the sea bed or suspended above the bottom by cables. The system will be hauled by the MH-60S and RMS, both of which will deploy from Arleigh Burke (DDG-51)-class destroyers and new littoral combat ships (LCS).
In the decade since the release of "From the Sea," the Navy has de-emphasized the use of dedicated minehunting assets, mainly the slow-speed deep-water Avengers (MCM-1) and the Osprey (MHC-51 )-class coastal minehunters, in favor of systems carried with faster-moving combat forces. Four of the 14 Avenger-class MCMs and 11 of the 12 Ospreys have been shifted to the Navy Reserve.
The MH-60S will be configured to carry an organic airborne mine countermeasures (OAMCM) mission suite, consisting of the AQS-20, a rapid airborne mine clearance system (RAMICS), an airborne laser mine detection system, and an airborne surface influence sweep system.
Operating from the Burkes and LCSs, the MH-60S and the RMS will provide a forward-deployed capability to find and classify mines in an operating area prior to the arrival of amphibious shipping carrying Marine landing forces, thereby eliminating the need to delay landing while mines are found and cleared.
The AQS-20A is fitted with forward- and side-looking, gap-filler, and volume-search sonars, which provide the capability to find mine-like objects in the turbid, high-noise conditions of shallow littoral waters. The system also is equipped with an electro-optical identification (EO/ID) device, built for Raytheon by Arete Associates of Tucson, Arizona, that performs the mine identification function.
Mike Taylor, Raytheon's AQS-20A program manager, says that the integration of the five sonars and the EO/ID device in the compact towed body presented considerable engineering challenges to ensure precise recording of acoustic signals in noisy littoral waters, avoid interference among the sonars, and maintain the watertight integrity of the towed body. He adds that because the sonars' electronic components generate considerable heat, the body has a liquid cooling system powered by an advanced pump designed for extremely low-noise operation to avoid interfering with acoustic data collection.
Sonar data is transmitted up the tow cable to a computer on board the MH60S. There, data are recorded for playback and prepared for display on the helo's common cockpit display. Taylor points out that in most operational situations the operator uses the real-time information for observation purposes; analysis of the data is conducted later at a workstation. He also notes that while the system has no propulsion capability, it is fitted with wings and essentially "flies" under water while being towed, guided by software that provides roll, pitch, and yaw control.
For LCS operations, the sonar system will be integrated with the ship's mine countermeasures mission module in a package of four towed bodies, two each configured for volume search and EO/ID. When the LCS plans a mine countermeasures operation, an MH-60S will land on board and be fitted with the towed bodies appropriate to the mission.
The Navy has directed Raytheon to build the AQS-20A in a common configuration for helicopter-tow and RMS applications. Operation with the RMS, which hovers slightly below the surface, will be similar to helicopter towing, although the company has modified the control software to allow for differences between the helo and the RMS.
The AQS-20A system has been tested extensively on board the MH-53E Sea Dragon minehunting helicopter, one of several Navy helos that the MH60S will replace. Funding is set for 22 AQS-20A systems through 2007, thanks to a Navy-Raytheon agreement to consolidate procurements for 2005 and 2006 and an option for 2007, a deal that is expected to save the Navy roughly $20 million. Operational testing for the sonar system is set for October 2007, and full-rate production is planned to begin in 2008.