Guillaume Hajduch

Airborne high-resolution ISAR imaging of ship targets at sea

We address the problem of airborne high resolution two-dimensional inverse synthetic aperture radar (ISAR) side-view imaging of ship targets. Using a simple model of the ship motions avoids the use of advanced joint-time frequency (JTF) transforms. A robust processing scheme including motion estimation and correction, optimal processing time and duration estimation and target shape extraction are developed. We stress the fact that the robustness of this processing leads to a single ISAR image analysis and that no merging of data from a set of radar images is necessary.

Vessel Refocusing and Velocity Estimation on SAR Imagery Using the Fractional Fourier Transform

This paper studies the effects of stationary-based processing of moving ship signatures in synthetic aperture radar (SAR) imagery and introduces a methodology to estimate and compensate for them. SAR imaging of moving targets usually results in residual chirps in the azimuthal SLC processed signal. The fractional Fourier transform (FrFT) makes it possible to represent the SAR signal in a rotated joint time-frequency plane and performs optimal processing and analysis of these residual chirp signals. The along-track defocus can thus be compensated for and the targets azimuthal speed estimated. The impact of higher order motion terms (e.g., acceleration) has been also considered. Experiments were conducted on a large number of ship signatures extracted from Radarsat-2 Multi Look Fine and Ultra Fine SAR images. An intercomparison with a standard Doppler Sublook Decomposition Method (SDM) is carried out, as well as a complete performance analysis with AIS data as ground truth.

Performance evaluation of Sentinel-1 data in SAR ship detection

This study addresses the performances of ship detection with data acquired by the newly launched Sentinel-1 SAR sensor. An automatic validation approach based on coastal AIS data is employed for measuring the detection efficiency. Results are compared with ship detection capabilities conducted on Radarsat-2 and CosmoSkymed datasets. The influence of different key parameters, such as SAR imaging characteristics (polarization, incidence angle) or meteorological conditions, is addressed. Such an analysis is useful for operational services to determine data specifications that assure optimum vessel detection for maritime surveillance applications.

The Sentinel-1A instrument and operational product performance status

This paper addresses the results of the instrument and product performance verification, radiometric and geometric calibration achieved during the since commissioning and routine phase.

Completing fishing monitoring with spaceborne Vessel Detection System (VDS) and Automatic Identification System (AIS) to assess illegal fishing in Indonesia

The Indonesian fisheries management system is now equipped with the state-of-the-art technologies to deter and combat Illegal, Unreported and Unregulated (IUU) fishing. Since October 2014, non-cooperative fishing vessels can be detected from spaceborne Vessel Detection System (VDS) based on high resolution radar imagery, which directly benefits to coordinated patrol vessels in operation context. This study attempts to monitor the amount of illegal fishing in the Arafura Sea based on this new source of information. It is analyzed together with Vessel Monitoring System (VMS) and satellite-based Automatic Identification System (Sat-AIS) data, taking into account their own particularities. From October 2014 to March 2015, i.e. just after the establishment of a new moratorium by the Indonesian authorities, the estimated share of fishing vessels not carrying VMS, thus being illegal, ranges from 42 to 47%. One year later in January 2016, this proportion decreases and ranges from 32 to 42%.

Ship detection with the Hölder moments and SAR dual-pol data

This study addresses the use of the Hölder moments for ship detection from SAR dual polarization data. In the proposed methodology we first merge the two images from the dual polarization data and then perform the detection. The discrimination between the vessel samples and the ones of the sea clutter is achieved via a joint PDF of the geometric and quadratic means from the two polarization channels. Results with Sentinel-1 data demonstrate the effectiveness of this methodology. Such a study is useful to investigate the advantages of detecting vessels from the joint information of the dual polarization data with respect to a detection performed independently on each polarization channel.

Taking advantage of Sentinel-1 acquisition modes to improve ocean sea state retrieval

Sentinel-1s SAR instrument offers a number of improvements with respect to its predecessor ENVISAT/ASAR such as a much better Wave Mode imagette coverage, improved Doppler estimator allowing higher resolution Doppler grid, more systematic dual-polarizations and a new TOPSAR acquisition mode. In the context of SEOM program, the Sentinel-1 ocean study offers to take advantage of these new capabilities to improve the retrieval of ocean sea state parameters: surface wind fields, directional wave spectrum, total significant wave height and surface currents. The study also tackles the ability to conduct a synergetic retrieval scheme in which the mutual effects of sea state components are taken into account.

Refocusing of ship signatures and Azimuth speed estimation based on FRFT and SAR SLC imagery

This paper considers the impact of dynamical targets on SAR imagery, when processed with stationary based techniques. We propose to employ the Fractional Fourier Transform as a tool for estimating the residual Doppler rate corresponding to moving vessels. Hence, the defocusing effect can be corrected and the associated azimuthal velocity can be estimated. The capabilities of the proposed methodology are illustrated with moving vessels extracted from Radarsat-2 Multilook Fine images and AIS data flows as ground truth.