| Popis: |
This paper is dedicated to the work of Pieter Schippers and gives an overview of his achievement in sonar performance modelling over his career. This publication is the last of a long list, many of which published at UDT [1-5]. A historical review is presented of the sonar performance modeling work at TNO in Underwater Acoustics since the mid-seventies. At that time, sonar performance was a hot topic for the upcoming receiver technique using passive low frequencies towed arrays. The aim was entirely focused on detection of hostile submarines, being practically undetectable with other systems. The main challenge was the modeling of propagation, first for deep water, and later also for shallow water. The developed propagation modeling is based on eigenrays. This enabled fast semi-analytical solutions, which was a strong requirement at that time. In the late eighties active sonar regained interest [1,2], and the active and passive sonar performance model ALMOST of TNO got under development. Sonar modeling got included and source and receiver vertical directivity patterns are applied. Furthermore, ambient noise and reverberation were modelled, based on noise sources at the sea surface, and scatterers at sea surface, volume and bottom, respectively. For active and passive detection performance, detection probability is computed from the modelled SNR for different types of signal processing in the receiver. After the Cold War the sonar bandwidth increased to enable shallow water operations [3]. Targets could no longer be considered as point targets and extended target modeling was started [4]. More attention was paid to input parameters, to properly model the complex environments is shallow water. Recently, graphical user interfacing got more attention [5]. This allows even unskilled operators to get their sonar performance prediction in due time and presented in an intuitive way. The future of sonar performance modeling is both in improving models and inputs, at the same time evaluating errors and uncertainty in the modeling. Pieter will watch this development from this lazy chair. |
