TNO has more than twenty years of practical experience with Low Frequency Active Sonars for Anti Submarine Warfare. We began research on the topic of LFAS in 1990 with the experimental ALF system for the benefit of the Dutch Ministry of Defense, in collaboration with Thales Underwater Systems.

This new type of sonar brings new scientific challenges that TNO has been addressing through research. Our research topics include waveform design, array processing, false alarm reduction, wide band sonar signal processing and sonar performance prediction (see hyperlink to Almost under 'Related Items'). We believe that sonar research can only be successful through intense experimentation at sea. LFAS experiments at sea are carried out every year, owing to the close collaboration with the Defense Material Organisation of the Dutch Ministry of Defence. New concepts and algorithms are tested at sea using the successor of the ALF system, the semi-operational Interim Removable LFAS system. This system, comprising the SOCRATES sonar source developed by TNO (see hyperlink to Socrates PDF under 'Related Items') is also used by the Royal Netherlands Navy onboard its operational platforms, to build up operational experience.

This program of research has led to the procurement by the Royal Netherlands Navy of an operational LFAS system (Multistatic Active Passive System) from Ultra Electronics Maritime Systems, with signal processing supplied by TNO.