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AN/UQQ-2 Surveillance Towed-Array Sensor System (SURTASS)

The Surveillance Towed Array Sensor System (SURTASS) is an element of the Integrated Undersea Surveillance System, providing mobile detection, tracking, and reporting of submarine contacts at long range. SURTASS was developed and deployed in the early 1980s as the mobile, tactical arm of the IUSS, providing long range detection and cuing for tactical weapons platforms against both diesel and nuclear powered submarines. With the SOSUS Arrays being placed in a standby status (data available but not continuously monitored), SURTASS must provide the undersea surveillance necessary to support regional conflicts and sea lane protection.

SURTASS passive surveillance systems, deployed from monohulls and Small Waterplane Twin-Hull (SWATH) platforms provide the Battle Group and Regional Commanders with reliable and continuous maritime picture of their area of responsibility (AOR). SURTASS entered the Fleet as a Strategic Surveillance asset in 1984. Today, in addition to its strategic role, SURTASS provides ASW support to tactical forces as part of the Navy's land warfare support mission.

Current force level is eight ships (4 LANT and 4 PAC).

Existing baseline SURTASS suites on monohull-hull T-AGOS ships are being deactivated and T-AGOS 19 and 23 class vessels replace them. The new vessels feature a small water-plane area twin hull (SWATH) design which provides quieting to enhance performance of the reduced diameter array and greater stability in high sea states for the LFA source array. T-AGOS 23 class ships are larger than T-AGOS 19 ships in order to handle the larger and heavier equipment for the LFA system. Original procurement was projected for up to five T-AGOS 23 class ships; the current program is in flux, but will certainly be more modest, due to extensive delays by shipyard problems with construction of the $60,000,000 lead ship whose delivery has slipped to the end of 1998. The SURTASS block upgrade will back-fit into T-AGOS 19 (currently with a baseline system) and will be the sensor suite (passive receive only) for T-AGOS 20 through 22. Eventually T-AGOS 19 through 22 will also have a capability to receive and process bistatic LFA signals.

SURTASS passive systems have proven their effectiveness against the diesel electric submarine in both deep ocean and shallow water areas. SURTASS with passive automation provides rapid target detection, classification, tracking and reporting of both surface and subsurface vessels. T-AGOS ships, with non-acoustic sensors installed, provide surface ship surveillance capabilities to assist in resolving the undersea classification problem.

Ocean Surveillance Ships conduct submarine hunting patrols and counter drug missions. Ships on Submarine hunting duty employ a towed sonar array. Data is transmitted from the ship to an acoustic processing site ashore via satellite. Stalwart class ships were designed to search for foreign submarines. Several have since been assigned as drug interdiction forces. Victorious class ships are built on a Small Waterplane Twin Hull (SWATH) design for stability at low speeds and in rough waters.

The current, or baseline, sensor is a long array of hydrophones towed by a dedicated non-combatant ship designated T-AGOS. There are two upgrades.

• The SURTASS Block Upgrade expands the capabilities of this towed array passive acoustic data collection and analysis system installed on T-AGOS Monohull and SWATH-P ships. The block upgrade improves the passive-only sensor with advancements against quiet threats including improved sensitivity and signal processing and use of a reduced diameter hydrophone array. The upgrade adds the Reduced Diameter Array (RDA) and a Commercial-Off-The-Shelf (COTS) processing system to provide increased detection capability, more flexible and higher resolution spectrum analysis, and improved target bearing. A communication upgrade will provide additional UHF SATCOM voice and data connectivity between T-AGOS and tactical platforms.

• SURTASS Low Frequency Active (LFA) is the active adjunct to this towed array. The low frequency active (LFA) upgrade is a long-range active sonar designed to detect even quieter threats in the future. The LFA system includes a large source array for active transmissions and the array of the block upgrade as a separate receiver. In its final configuration, SURTASS LFA will include the block upgrade. LFA adds an active transmit array and handling system, power amplification and control systems, an active signal processing and display receive system, and an environmental analysis system to the SURTASS Upgrade. A prototype LFA system has been installed on a leased commercial vessel, Cory Chouest, and operated as an interim fleet LFA asset pending delivery of the T-AGOS-23/SWATH-A, which will be equipped with LFA. New smaller active-source technologies are also under investigation for potential applications in a Compact LFA (CLFA) system suitable for backfitting into existing SURTASS ships. These upgrades provide improved shallow-water operational capability in support of littoral warfare. Open system architecture provides expandability and flexibility while lowering procurement and life cycle costs.

The SURTASS Block Upgrade has been installed on four SWATH-P T-AGOS ships and two Monohull T-AGOS. The remaining monohull received the Block Upgrade in FY 1997-1998.

Other SURTASS development efforts include: twin-line array processing, improved detection and classification/passive automation to counter quieter threats; additional signal processing and bi-static active capability; integrated active and passive operations; improved Battle Group support; and improved information processing.

The twin-line array, which was developed by a joint government-industry team comprised of the John Hopkins University Applied Physics Laboratory, Chesapeake Sciences, and the Navy's Array Technical Support Center, Little Creek, Va. employs COTS telemetry architecture and consists of two short parallel acoustic arrays separated by several meters. The array provides for left-right ambiguity resolution, back lobe rejection, and the flexibility to tow in shallow water.

The baseline Desk Top Computer (DTC II) based system was upgraded with FORCE ® CPU-20/7 CPUs, CSPI Super Card 4 ® Signal Processors, a second 100 mBit Ethernet Local Area Network and the SOLARIS ® operating system. The processing upgrade includes the capability to process bi-static acoustic waveforms when operating with an active SURTASS Low Frequency Active platform. USNS BOLD's communications suite was upgraded to provide connectivity with tactical forces and includes Joint Maritime Command Information Systems, Link 11 and HF, UHF and SHF secure voice. Secret Internet Protocol Router Network, a secure internet, was installed for transfer of classified information, e.g. display snapshots, between the operators of the surveillance ship and tactical forces. Lastly, a Joint Task Force Surveillance (JTFS) upgrade was added to provide a surface ship tracking capability and a fused surface-subsurface display. Using external contact reports and own ship radar, surface-shipping information is correlated with underwater acoustic data to rapidly separate surface from subsurface contacts. Processing and communications upgrades and the JTFS capability were developed, integrated and installed by Raytheon Systems Company.

SURTASS onboard processing system provides the capability for bistatic operations when operating with an active platform. SURTASS is a low frequency passive surveillance system that employs a long array of hydrophones from a surface ship designated T-AGOS. SURTASS is a COTS-based processing and display system, configured in an open architecture. It uses several types of arrays as a passive receiver. SURTASS communications include SHF ship-to-shore data transmission, UHF SATCOM, INMARSAT, SIPRNET and secure voice and GCCS-M 3.1.1 interface for real-time contact reporting.

SURTASS TwinLine is a shallow water variant of the basic SURTASS towed array configuration. Twin-Line is designed to provide vertical directivity, resolve right-left ambiguity, provide for increased tow speeds and provide flexibility in towing in shallow water. T-AGOS, outfitted with SURTASS TwinLine arrays, support operations in littoral areas. A prototype TwinLine array has been operating since 1996, participating in numerous Fleet exercises, in a variety of acoustic environments. The first production TwinLine-R array was deployed in 1999. TwinLine performance has exceeded all design objectives. It's ability to reject back lobe interference in high surface clutter areas makes TwinLine a high value littoral warfare surveillance asset. SURTASS TwinLine is designed for both active and passive receiving. The next generation TwinLine Array is planned for deployment in FY 03. The TwinLine array will use the TB-29A array configuration and is being procured through a NAVSEA omnibus array contract. SURTASS TwinLine is a low frequency surveillance array consisting of two apertures with a variable separation between 2.2 and 8.8 meters. These arrays are made up of HF modules and are approximately 1/5 the length of the standard SURTASS array. TwinLine processing is performed in the SURTASS Next Evolution Upgrade COTS system architecture.

Passive Automation must fill the gap between limited resources and the dramatic increase in data available for processing, analysis and display. To deal with modern ASW threats, SURTASS arrays are being designed with a larger number of beams, and being deployed in littoral areas where clutter from shipping lanes tends to obscure the target. Available manning has also been reduced, resulting in an increased workload for the SURTASS operators. Passive Automation is required to assist the operator in analyzing the increased data output provided by advanced towed arrays such as the A180R and the TwinLine arrays. Passive Automation is intended to assist the operator with handling this increased workload, by allowing the operator to efficiently search for targets of interest. The Passive Automation performs computer-aided detection, classification, and tracking of all surface and subsurface contacts within sensor detection range, significantly improving the timeliness and quality of contact reports to Battle Group and Regional Commanders. This improved performance permits more effective tactical employment of operational forces. Automation also improves the operator's ability to classify and resolve targets from surface clutter in littoral areas with high shipping density. Broadband and Narrowband Energy Trackers in conjunction with the Bearing Time Recorder (BTR) display and automation tools provided by Passive Automation processing greatly enhances the operator's capability to manage the entire surveillance picture by alerting the operator to potential targets of interest and providing tracks of all contacts. Passive Automation algorithms include computer-aided line detection and tracking, signature composition, source detectors, and broadband and narrowband processing. Passive automation displays include the BTR, acoustic gram overlays of automated detector outputs, and tools for contact classification and localization. Algorithms and displays are fully integrated in the SURTASS Commercial-Off-the-Shelf (COTS) architecture.

SURTASS has experienced recent passive and active success against diesel submarines operating in shallow water. A prototype twin-line SURTASS array was tested during 1996 in a variety of locations around the world, with positive results. It is far superior to any other shallow-water passive towed-array system. SURTASS processing is being transferred to the AN/SQQ-89 towed-array sonar system to provide an immediate increase in detection capability without the need to modify or procure additional wet-end hardware. The minimum fleet requirement of eight SURTASS ships is funded through the FYDP.

Functional improvements are delivered to the Fleet in software "Builds". Build #1 (FY 95) includes source-set formulation and analysis tools, automated line trackers and nuclear source auto-detector. Build #2 (FY 96) includes wideband energy trackers, wideband/narrowband feature association, and diesel Full Spectrum Processing (FSP). Build #3 (FY 97) includes automated localization and tracking, diesel automated detection and twin-line integration.

SURTASS is a non-military program staffed by civilian "operations personnel" contracted to SPAWAR, who operate and maintain the mission equipment under the operational command of Commander Undersea Surveillance (CUS). The SURTASS equipment is primarily deployed in Auxiliary Oceanographic Survey ships (T-AGOS) that are staffed by civilian mariners under contract to the Military Sealift Command (MSC). The Military Sealift Command operates ships manned by civilian crews and under the command of a civilian master. These ships, indicated by the blue and gold bands on their stack, are "United States Naval Ships" vice "United States Ships" as is the case of commissioned ships.

SURTASS is comprised of a worldwide network of ship and shore systems designed to do undersea surveillance. This complex network of mission dedicated equipment and systems routinely requires replenishment, upkeep, maintenance, and service to be accomplished by IOSC resident personnel. To this end, several "remote" facilities have been established to provide "bases" of operation in support of the SURTASS mission. Although operations are based in Norfolk Virginia, SURTASS routinely operates from ports in Glasgow Scotland, Rota Spain, Yokohama Japan, Pearl Harbor Hawaii, Port Huneme California, and many other ports of opportunity. SURTASS's Pacific operations are coordinated from the IUSS Operations Support Detachment (IOSD) located at the facility within NRaD Activity, Pacific in Pearl City, Hawaii. SURTASS is greatly reducing costs by consolidating logistics support, using Non-Developmental Items and commercial hardware, and increasing operator efficiency through computer aided detection and classification processing.