U.S. Approves Sale of Airborne Low Frequency Sonar System and Sonobuoys to Denmark

The U.S. State Department has approved a possible sale of 9 AN/AQS-22 Airborne Low Frequency Sonar (ALFS) systems and 600 AN/SSQ-36/53/62 Sonobuoys to Denmark for an estimated cost of $200 million.

The sale will be conducted through U.S. Foreign Military Sales (FMS) program and the new sensor systems, which will be carried by the MH-60R Seahawk helicopters, will improve Denmark’s capability to perform Anti-Submarine Warfare (ASW) missions. The Defense Security Cooperation Agency (DSCA)), which oversees FMS sales, delivered the required certification notifying Congress of this possible sale on August 27.

The sales package to Denmark also includes spare and repair parts; support and test equipment; communication equipment; publications and technical documentation; personnel training and training equipment; U.S. Government and contractor engineering, technical, and logistics support services; and other related elements of logistical and program support.

The principal contractor will be Lockheed Martin Rotary and Mission Systems in Oswego, New York.


The AN/AQS-22 Airborne Low Frequency Sonar (ALFS) is the primary undersea warfare (USW) sensor of the MH-60R multi-mission helicopter.

The ALFS integrated dipping sonar system, weighing 272 kg, enables the MH-60R to accomplish the assigned anti-submarine warfare (ASW) missions of submarine detection, tracking, localization and classification. It also performs missions relating to acoustic intercept, underwater communications and environmental data acquisition.


The primary purpose of a sonobuoy is to detect acoustic emissions or reflections from potentially hostile submarines and transmit these signals to US Navy airborne antisubmarine warfare forces.

The AN/SSQ-36 Bathythermograph (BT), the AN/SSQ-53 Directional Frequency Analysis and Recording (DIFAR) and the AN/SSQ-62 Directional Command Activated Sonobuoy System (DICASS) are all A-size, expendable and non-repairable sonobuoys.

The AN/SSQ-36 sonobuoy measures the temperature profile of a water column providing sonar propagation and acoustic range prediction. The AN/SSQ-53 sonobuoy is a passive acoustic sensor that is used for detection, classification, and localization of adversary submarines during peacetime and combat operations. The AN/SSQ-62 sonobuoy is an active acoustic sensor that is used in the final localization and attack phase of submarine prosecutions.

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