Enhanced Long-Range Maritime Vessel Classification

OUSD (R&E) MODERNIZATION PRIORITY: General Warfighting Requirements (GWR) TECHNOLOGY AREA(S): Battlespace Environments;Electronics;Sensors OBJECTIVE: Develop techniques to exploit ship structural vibrations appearing as micro-Doppler signatures in remote Inverse Synthetic Aperture Radar (ISAR) imagery for the purposes of improved vessel classification. DESCRIPTION: Significant advancements have been made in the automated classification of ships at long ranges using feature extraction from ISAR imagery. The most capable of these seek to classify a particular ship to the fine naval class level. While physical dimensions of major structural elements of the ship provide the primary classification clues, other micro-Doppler based signatures such as those associated with rotating antennas can provide important additional information to support separation among similar ship classes [Ref 1]. This STTR topic seeks to expand the scope of signatures further. Ship structural vibrations may be another important signature to improve overall classification performance. The sources of structural vibrations are generally understood; however whether they are reliably exploitable for classification clues is unanswered. Multiple authors have shown that radar-sensed micro-Doppler can be used to remotely monitor the vibration of buildings and bridges [Refs 2, 3]. The vibrations generated by an automobile or truck engine has shown to be detectable by radar micro-Doppler signals returned from the surface of the vehicle [Ref 4]. In principle, ship hull and superstructure vibrations primarily driven by propulsion systems should be similarly detectable. Essential to such a technique is the ability to sense the small-scale vibrations of the vessels while they are in motion [Ref 5]. The exploitation of the vessel hull and superstructure vibrations remotely using legacy Navy airborne maritime surveillance radar systems is desired. In addition to single channel monostatic operation, consideration should be given to interferometric and multi-static techniques. If the vibrations are exploitable at long range by these radar systems, they may provide a hull class specific classification feature that in combination with other features will improve overall classification performance. The signatures may also provide information comparable to a fingerprint if it is found that the spectral characteristics are hull specific. PHASE I: Utilizing open-source ship hull and superstructure vibration measurements such as those described in [Ref 6] or simulated data, analyze the feasibility of remote micro-Doppler sensing by x-band maritime surveillance radar systems. Single channel monostatic, multi-channel interferometric, and multi-static operation should be considered. An initial assessment of signal processing approaches should be completed. Develop a Phase II plan. PHASE II: Develop and demonstrate a ship vibration micro-Doppler exploitation mode using collected field data supplied by the Navy sponsor. Assess the performance as a function of range, dwell time, and illumination geometry. Develop mode design and tactical utilization recommendations for radar systems identified by the Navy sponsor. PHASE III DUAL USE APPLICATIONS: Complete development, perform final testing, and integrate and transition the final solution to naval airborne radar systems either through the radar system OEM or through third party radar mode developers. The technology developed from this STTR topic is applicable to Coast Guard Missions. REFERENCES: Chen, V.C. et al. Analysis of micro-Doppler signatures. IEE Proceedings-Radar Sonar Navigation, Vol. 150, No. 4, August 2003. http://www.geo.uzh.ch/microsite/rsl-documents/research/SARlab/GMTILiterature/Ver09/PDF/CLHW03.pdf. Luzi, G. et al. Radar Interferometry for Monitoring the Vibration Characteristics of Buildings and Civil Structures: Recent Case Studies in Spain. Centre Tecn logic de Telecomunicaci ns de Catalunya (CTTC/CERCA), Geomatics Division, Avinguda Gauss, 7, E-08860 Castelldefels (Barcelona), Spain. https://www.mdpi.com/1424-8220/17/4/669/htm. Luzi, G. et al. The Interferometric Use of Radar Sensors for the Urban Monitoring of Structural Vibrations and Surface Displacements. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, Vol. 9, Issue 8, August 2016. https://ieeexplore.ieee.org/document/7493683. Chen, V.C. et al. Micro-Doppler Effect in Radar: Phenomenon, Model, and Simulation Study. IEEE Transactions on Aerospace and Electronic Systems, Vol. 42, No. 1, January 2006. http://www.geo.uzh.ch/microsite/rsl-documents/research/SARlab/GMTILiterature/Ver09/PDF/CLHW06.pdf. Rodenbeck, C. et al. Vibrometry and Sound Reproduction of Acoustic Sources on Moving Platforms Using Millimeter Wave Pulse-Doppler Radar. IEEE Access (Volume 8), 04 February 2020, pp. 27676-27686. https://ieeexplore.ieee.org/document/8981984. Weintz, Brett. Ship vibration. Brabon Engineering Services, 15 June 2021. https://brabon.org/tech-notes/ship-vibration/. KEYWORDS: Inverse Synthetic Aperture Radar; ISAR; Synthetic Aperture Radar; SAR; ship classification; hull and superstructure vibration; radar