AN/APS-137

AN/APS-137
Name	AN/APS-137
Country	United States
Type	Airborne surveillance radar
Introduced	1990s
Manufacturer	Raytheon
Platform	Maritime patrol aircraft, anti-submarine warfare aircraft, helicopters

AN/APS-137 is an airborne maritime surveillance and surface-search radar developed in the United States for use on patrol aircraft and helicopters. The system entered service during the late 20th century and was integrated into platforms tasked with anti-submarine warfare missions, maritime patrol operations, and littoral surveillance. Designed by a major defense contractor, the radar combined synthetic aperture radar techniques with inverse synthetic aperture processing to provide high-resolution imaging and detection in challenging environments.

Development and Design

The radar was conceived during programs involving United States Navy requirements for improved surface-search and targeting capability, influenced by lessons from Falklands War, Gulf War, and Cold War ASW needs. Development involved corporations with histories tied to Raytheon Technologies, Hughes Aircraft Company, and industrial partnerships connected to General Dynamics and Northrop Grumman supply chains. Design drivers included interoperability with avionics suites certified to standards associated with NATO mission electronics, integration with acoustic processing systems originating from research at Naval Research Laboratory, and compliance with platform constraints similar to those on Lockheed P-3 Orion and derivatives. Engineering teams referenced operational doctrine from United States Pacific Command and United States European Command to set endurance and surveillance performance goals.

Technical Specifications

Hardware architecture used solid-state transmitter modules and digital receiver chains influenced by developments at MIT Lincoln Laboratory, with processor subsystems derived from capacity increases following standards debated at Institute of Electrical and Electronics Engineers conferences. The radar operated in the X-band frequency range and provided modes including synthetic aperture radar (SAR), inverse SAR (ISAR), sea-search, and weather avoidance, echoing capabilities found on systems fielded for operators like Royal Air Force and Royal Canadian Air Force. Antenna designs paralleled those used on maritime patrol radars for platforms such as Boeing P-8 Poseidon and legacy Lockheed P-3 Orion. Signal processing supported high pulse-repetition frequencies and Doppler processing techniques explored in studies at IEEE Radar Conference.

Operational Use and Platforms

The radar was integrated on aircraft used by forces including United States Navy, United States Coast Guard, Royal Canadian Air Force, and export customers aligned with NATO partners. Typical platforms included variants of the Lockheed P-3 Orion, helicopter types akin to Sikorsky SH-60 Seahawk family, and maritime patrol upgrades resembling modernization efforts for the Grumman S-2 Tracker. Operational missions encompassed wide-area surveillance, search and rescue coordination linked to International Maritime Organization guidance, and illicit trafficking interdiction in cooperation with agencies like United States Customs Service (now parts of U.S. Immigration and Customs Enforcement and U.S. Customs and Border Protection).

Variants and Upgrades

Product evolution produced block upgrades incorporating enhanced processors, models with improved clutter suppression influenced by algorithms developed at Cornell University and Stanford University research groups, and missionization kits that interfaced with tactical data links such as Link 16 and command systems used by Allied Command Operations. Incremental improvements paralleled modernization trends seen in radars fitted to Boeing 737 AEW&C and systems retrofitted during Cold War-era platform life extensions. Export variants included mission suites tailored to customer requirements from countries associated with North Atlantic Treaty Organization procurement patterns.

Performance and Capabilities

Performance metrics emphasized surface target detection in littoral and open-ocean environments, high-resolution SAR imaging for ship identification comparable to outputs used in Maritime Domain Awareness programs, and moving target indication capabilities akin to systems fielded for Operation Desert Storm reconnaissance. Capabilities included multi-mode operation for simultaneous moving target tracks, weather mapping analogous to sensors aboard Hawker Siddeley Nimrod upgrades, and low observable detection enhancements inspired by signal-processing research from Massachusetts Institute of Technology. Integration with electro-optical sensors and datalinks allowed cueing of assets like MQ-4C Triton-type systems in cooperative surveillance architectures.

Operators and Deployment History

Operator lists encompassed several Western navies and coast guards, including units under command structures such as United States Fleet Forces Command and national authorities similar to Canadian Forces. Deployments occurred during multinational exercises with participants from NATO and regional partnerships including entities from the Asia-Pacific Economic Cooperation sphere, supporting patrols, fisheries enforcement coordinated with Food and Agriculture Organization, and counter-narcotics operations in coordination with United States Southern Command tasking.

Incidents and Operational Limitations

Operational reports noted limitations when operating in extreme sea states and heavy precipitation, issues also documented in studies commissioned by Congressional Research Service examining maritime surveillance gaps. Incidents involved integration challenges or maintenance deficiencies traced to logistics chains overseen by contractors with ties to Defense Logistics Agency and oversight by Office of the Secretary of Defense. Fielding timelines and capability shortfalls were subjects of reviews similar to those conducted by Government Accountability Office in broader maritime radar modernization programs.

Category:Airborne radars