Scientific exploitation of PAZ products in coastal surveillance and monitoring tasks

Revista oficial de la Asociación Española de Teledetección[EN] PAZ mission appears due to the need of a Spanish SAR satellite able to provide radar image products for security and defense, civil and scientific users. INTA is responsible for the technical direction of the Ground Segment, as well as the development of the Calibration and Validation Centre and the scientific exploitation. The ‘Demonstrator of Maritime SAR Applications’ is proposed as an answer to detection tasks in maritime synthetic aperture radar imagery, which are not completely solved yet. DeMSAR has been developed in the framework of a contract between the Spanish National Institute for Aerospace Technology (INTA) and the University of Alcalá. It is intended to be used as a demonstrator of the capabilities of the airborne SAR prototypes of INTA as well as for PAZ, the Spanish SAR satellite. With two operation modes, an automatic ship detector and a toolboxes mode, DeMSAR offers the user a high flexibility in SAR data processing tasks such as speckle filtering, coastline detection, land mask estimation and ship detection and characterization.[ES] La misión PAZ surge ante la necesidad de un satélite SAR español que pueda proporcionar productos imagen radar para usuarios de seguridad y defensa, civiles y científicos. INTA es el responsable de la dirección técnica del Segmento Terreno, así como del desarrollo y operación del Centro de Calibración y Validación y de la Explotación Científica. Dentro de este ámbito de explotación, se desarrolla un demostrador de aplicaciones SAR marítimas (DeMSAR) como herramienta robusta capaz de llevar a cabo tareas de detección sobre la superficie marina, empleando las imágenes adquiridas por radares de apertura sintética. Se desarrolla bajo un marco de colaboración entre el INTA y la Universidad de Alcalá con el fin de convertirse en un demostrador de las capacidades de los sistemas aerotransportados de INTA y, en el futuro, para procesar los datos adquiridos por el sensor PAZ. Con capacidad de operar en modo automático de detección de barcos o mediante librerías de procesado SAR, DeMSAR ofrece una gran versatilidad al usuario en tareas de procesado tales como filtrado de ruido speckle, detección de líneas de costa, estimación de máscaras de tierra y detección y caracterización de barcos.Jarabo, M.; González, M.; De La Mata, D.; Martín De Nicolás, J.; Del Rey, N.; Bárcena, J.; Peláez, V. (2014). Explotación científica de productos PAZ en tareas de vigilancia y monitorización costera. Revista de Teledetección. (41):97-109. doi:10.4995/raet.2014.2287.SWORD9710941Comaniciu, D., & Meer, P. (2002). Mean shift: a robust approach toward feature space analysis. IEEE Transactions on Pattern Analysis and Machine Intelligence, 24(5), 603-619. doi:10.1109/34.1000236Duda, R. O. & Hart, P. E., 1973. Pattern classification and scene analysis. Wiley.Mallat, S., 2008. A wavelet tour of signal processing. 3rd Edition. Academic Press

DVB-T-based passive radar for silent surveillance of drones

Nowadays, Unmanned Aerial Vehicles (UAVs) and drones are used as threat’s vectors that create personal and public security issues. The unpredictable and complex motion along with the small Radar Cross Section (RCS) and low velocity makes the drone detection a challenging task for any radar system. In the context outlined earlier, the security level enabled by conventional active radar systems could be augmented by the cost-effective, non-intrusive and eco-friendly Passive Radar (PR) technology. As a PR system does not have its own transmitter, this allows reduced costs, intrinsic covert operation capability and the lack of additional electromagnetic pollution. To guarantee complete and continuous coverage, PR can effectively be integrated within conventional active radars not only to extend the surveillance coverage, acting as ‘gap-filler’, but also to reduce the probability of out of service of the surveillance system. Moreover, aiming at the monitoring of airport terminal areas or harbours, where the installation of additional sensors might be limited by regulations related to public safety and risk of interference with pre-existing systems, a network of PRs could easily be deployed to provide continuous and complete coverage. The stationary nature and the isotropic characteristic of many of the employable Illuminators of Opportunity (IoO) provide a persistent illumination of the targets of interest to generate Coherent Processing Intervals (CPIs) of long integration times (Tint) on receive to counteract the limited power density offered by the emitter. This certainly applies to many ground-based transmitters for analogue or digital radio/TV broadcasting. Among them, the emitters of the Digital Video Broadcasting-Terrestrial (DVB-T) are particularly attractive for counter-drone applications. Specifically, the high radiated power of these transmitters and the excellent coverage make them suitable for the detection of these small RCS and low altitude targets. In addition, the continuous emissions and the fine range resolution of about 20 m (equivalent monostatic range resolution yielded by a signal bandwidth of approximately 8 MHz) make them potentially able to continuously detect and discriminate closely spaced targets. Aiming at the detection of the low Signal-to-Noise Ratio (SNR) targets and at widening the DVB-T-based PR coverage area, very long integration times (up to few seconds) can be exploited if the migration effects are properly compensated. It is worth noticing that the use of long integration time allows also to improve the Doppler resolution as well as to discriminate between slowly moving targets and clutter contributions, which is of particular interest in a scenario with a high density of targets. By employing an Orthogonal Frequency-Division Multiplexing (OFDM) modulation, DVB-T signals are noise-like waveforms; thus, they provide ambiguity function with attractive properties that are nearly independent of the signal content and almost time-invariant. Eventually, since a DVB-T transmitter typically broadcasts multiple channels at different carrier frequencies, this provides the desired diversity of information that could be successfully exploited for both target detection and its localization. Recently, different authors have investigated the use of such sensor for counter-drone operations proving the capability of such technology to detect and localize small and medium drones up to a few kilometres from the PR receiver. Moreover, the capability of such sensor in simultaneous detection of drones flying near the airport area along with the conventional civil air traffic at farther ranges has been proved. This chapter reports the latest results of DVB-T-based PR for counter-drone operations obtained by the research groups of the University of Alcala´ and Sapienza University of Rome