Airborne Maritime Surveillance Radar Research Articles

The Moonshine Pulse Repeater Jammer

Moonshine was a British airborne pulse repeater decoy jammer, first used in 1942 to counter German air defense radars. It was later developed to be used on ships to spoof airborne maritime surveillance radars, during the allied invasion of Europe in 1944. The development history of this system is described, together with a description of its operating principles and hardware design.

Sea–Land Segmentation in Maritime Surveillance Radars via K-Nearest Neighbor Classifier

Shipborne or airborne maritime surveillance radars at scan mode work at a complex scene consisting of land, sea, and islands. Sea–land segmentation provides a two-class classification of sea clutter versus ground clutter to the surveillance scene as a precondition of adaptive target detection. It is a difficult problem because only a few coherent pulses are available at scan mode. Moreover, due to moving radar platforms and wide dynamic range of ground and sea clutter in power, average amplitude, Doppler offset, and initial phase of radar, the returns vector fails to distinguish sea clutter and ground clutter. In this article, a similarity measure of two radar returns vectors, which is invariant to amplitude, Doppler offset, and initial phase, is constructed, which is closely relevant to the Doppler bandwidth of a returns vector. Based on the similarity measure, a K-nearest neighbor classifier is proposed to yield a pixel-level sea–land segmentation of the scene. Further, the morphological filtering is operated on the pixel-level segmentation to obtain a region-level segmentation. Moreover, the discrete Frechet distances of the main boundaries in successive scan periods are used to assess segmentation quality. The proposed method is verified by measured data from an airborne radar and an island-based radar. The results show that it behaves better than the methods using thresholding phase linearity degree of radar returns and the support vector machine, and back propagation neural network in a three-dimensional feature space.

Clutter Suppression and Target Tracking by the Low-Rank Representation for Airborne Maritime Surveillance Radar

Moving target detection is of vital importance to maritime security and maritime resource protection. However, the detection of slow or weak targets is difficult based on traditional methods. A new detection method is proposed by using the different motion variations of radar moving target and sea clutter in the range-Doppler spectrum sequence. The first step in implementing this method is the separation of moving target and sea clutter by the low-rank representation, in which the target and clutter are modeled as foreground and background components. Subsequently, a sea clutter discriminator is constructed within the sea clutter bandwidth to further remove the sea clutter (false alarms) that exists in the foreground. The proposed method can reduce the sea clutter power while maintaining the target power and improve the detection rate of moving targets, especially slow or weak targets. Data collected with airborne maritime surveillance radar in maritime moving target indication (MMTI) mode are used to validate the performance of the proposed method. The experimental results demonstrate that the improvement in the signal-to-clutter ratio (SCR) obtained with the proposed method is better than that obtained with space-time adaptive processing (STAP, including 1DT-STAP, 3DT-STAP and sparse-STAP) and principal component pursuit (PCP) methods; additionally, the figure of merit (FOM) of the proposed method is higher than that of the constant false alarm rate (CFAR) and PCP method. Furthermore, the tracks of ships are obtained by applying a location constraint to the foreground sequence.

ASV Mark I, the First Airborne Maritime Surveillance Radar

ASV (Air to Surface Vessel) Mk. I was the first operational airborne maritime surveillance radar. It entered service with the Royal Air Force (RAF) in January 1940, in response to urgent operational requirements at the start of WWII. This system was quite experimental, it was unreliable, and its performance was relatively modest. By the start of 1941, it was already obsolete, replaced by ASV Mk. II. Nevertheless, it represented a pioneering engineering endeavor that laid the foundations for the systems that would be developed in the U.K. and USA and which would ultimately play a decisive role in the battle against the U-boats. This paper describes the equipment that was developed, its installations in Lockheed Hudson and Short Sunderland aircraft of RAF Coastal Command, its operation, and performance.

Fast scan‐to‐scan integration algorithm for small target in sea clutter

For small slowly moving targets detection in spiky sea clutter, a fast scan-to-scan integration preprocessing algorithm is proposed. By introducing a velocity steering vector, the scan-to-scan integration is achieved by matrix operations instead of traditional target path searching algorithms. The concept is demonstrated using measured data collected from an airborne maritime surveillance radar. Results show that the computation complexity of the back-end track-before-detect block can be reduced by two orders under the considered scenario.

Asymptotic Performance of the Geometric Mean Detector in Pareto Distributed Clutter

Several independent investigations have demonstrated the validity of the Pareto distribution as a model for X-band high-resolution maritime surveillance radar intensity clutter returns. This has included validation of it for data collected from fixed costal surveillance radars, as well as airborne maritime surveillance radars. Consequently, there has been a steady development of radar detection schemes under such a clutter model assumption, both from a coherent and noncoherent detection perspective. One of the major initiatives at the Australian Defence Science and Technology Group has been to investigate the development of sliding window constant false alarm rate detectors for operation in a Pareto distributed clutter. A transformation approach has provided this capability, and one of the observations has been that a geometric mean detector, derived via this approach, tends to perform ideally when the number of clutter statistics in the clutter range profile is large. This letter examines this phenomenon and provides a mathematical explanation for it.