In order to meet the urgent requirements of building a maritime power for China, and promoting the implementation of "the 21st Century Maritime Silk", it is necessary to turn the marine information, from the "digital ocean" to the "mart ocean". This paper analyzes the successful experience of the foreign marine information construction and the main problems of our country. The concept of the "smart ocean"and its connotation and system composition are proposed, to comprehensively enhance the capability of China's marine information system. The smart ocean is to be constructed based on the systems engineering, This paper proposes the direction for the deep integration of the marine informatization and industrialization in China.

As the main equipment of target detection and surveillance, the radar plays an important role in the air and sea target monitoring, early warning detection and other public and defense security applications. Due to the complex detection environment and the variety of the targets, the echo has a low observability. It is dificult for the radar detection performance to meet the actual demand, and we face the weak target detection problem in a complex environment. In recent years, with the development of the radar system and the radar signal processing technology, the radar gains the ability to obtain fine target characteristics, and by extending the signal dimension, a new way is provided for the radar target detection and recognition. This paper reviews the connotation and the characteristics of the low observable moving target, the challenge of the radar detection and the key technology of fine processing, focusing on the engineering applications based on the measured data of the radar. Finally, the development direction of fine processing is discussed.

The airborne radar sees a technology leap forward from single pulse, pulse Doppler to phased array. The advancement of each generation of the naval aviation facilitiy involves breakthroughs of functions and performances of the maritime detection radar. Based on the analysis of the airborne radar and the development of the radar form, the technological development of the airborne maritime detection radar is reviewed, including the main characteristics, the system architecture, and the development direction. The cutting-edge scientific achievements in recent years, with respect to the airborne maritime detection radar promote the technology of the naval aviation equipment.

As one of the most widely-used methods for target detection and recognition, the radar has been intensively studied since it was proposed. In the past few decades, great efforts were devoted to improve radar's functionality, high precision and real-time performance, of which the key is to generate, control and process a wideband signal with a high speed. However, due to the well-known "electronic bottleneck", it is extremely difficult for electrical systems to handle a signal with a high frequency and large bandwidth. The optical technologies, with the intrinsic characteristics of high frequency, large bandwidth, low loss transmission and electromagnetic immunity, were considered as the keys to "illuminate the future of radar". In addition, photonic systems are light, small and integratable, which would significantly reduce the load of aircraft, satellites and ships when carrying the radar. Therefore, photonic technologies would change the existing radar systems, making radar systems more sustainable. In this paper, an overview of the microwave photonic radars is presented. The recent progresses of the key technologies and the future developments of the microwave photonic radars are discussed.

Ship targets are very important for the matine law enforcement and military operations. The radar imaging of ships plays an important role in the surveillance and reconnaissance of ship targets. This paper analyzes the key steps in the ship-target imaging and the corresponding technologies, including the related principles and algorithms. The new technologies which may emerge in the future for the ship-target imagery are discussed.

The lack of feature data and the poor extending capability of the radar target recognition algorithms are two main problems for the radar sea target recognition, which have attracted many researches. This paper reviews the studies of the radar sea target recognition in two aspects, namely, the electro-magnetic modeling and the radar target classification algorithms. For the analysis of sea target electromagnetic behaviors, the review is focused on both the measurement and the modeling of the electro-magnetic scattering. For the radar sea target recognition technologies, the review covers the methods based on the narrow band, the high resolution range, and the high resolution images. The developments of the radar sea target recognition technologies are predicted based on the available researches.

In order to satisfy the increasing demand for ocean surveillance, the spaceborne SAR system should have the capacity of High Resolution and Wide Swath (HRWS). The HRWS spaceborne SAR system can not only obtain the ocean environment parameters (such as current, wave, wide speed and direction and internal wave), but also extract a variety of target information (such as ships, oil spills and sea ice) on the surface of the sea. Therefore, the HRWS spaceborne SAR system plays an important role in the national economic development and the national defense construction. This paper reviews the applications of the spaceborne SAR system in ocean surveillance and the key techniques of the spaceborne SAR system for ocean surveillance. Finally, a possible HRWS SAR satellite constellation is designed, which can meet the demand of ocean surveillance in the future.

Ship detection based on optical remote sense images is an important application direction in the marine information perception. Its primary tasks include the fast detection of ship targets in a large view field and the further extraction and classification of the targets based on the ship detection. It is of great significance both in civilian and military applications. This paper reviews the main achievements in that field, focusing on the difficulties involved. Finally, the existing problems and the future development are discussed.

The SAR is an active microwave imaging sensor, which can work day and night, under all weather conditions, and with a highresolution earth observation capability. It is widely used for ship detection and classification. With the development of the SAR imaging technology, the resolution of the SAR image is becoming higher and higher, thus the robust and efficient ship detection and classification methods are very important for military and civil applications. This paper reviews the current ship detection and classification based on single-polarization SAR images, analyzes their features and shortcomings, and make aprediction of the future developments.

The ship geometric parameter extraction is an essential basis for the marine target detection and classification for the Synthetic Aperture Radar(SAR) images. With the assistance of the ground true value sample of the marine target size, the improvement of the geometric dimension extraction can be achieved by the parameter optimization and regression, as verified in TerraSAR-X datasets. Taking into consideration of the typical characteristics of the dual-polarization for the sentinel-1 products, this paper explores the usefulness of the dual-polarization fusion information. Based on the OpenSARShip, firstly we utilize a two-dimensional filter method for image processing. The parameters in the image processing are optimized by a cross-entropy method based on the large dataset. Next, with the preliminary extraction results, we combine the information from the sensors, the environment and the target, and especially the information from the dual-polarization. We employ a multiple linear regression model to obtain the precise physical dimensions. The size extraction performance by the dual-polarization fusion information is much better than merely using the single-polarization information, which proves the usefulness of the dual polarization information.

For an active sonar, the reverberation is the main interference in shallow water, and the reverberation suppression is a complicated problem in the sonar signal processing, especially when the sonar carrier moves with a certain velocity to cause the space-time coupling in the reverberation. The space-time adaptive processing (STAP) is an effective way to solve this problem, with the implicit compensation for the motional platform and it allows to obtain the most optimal performance for the reverberation suppression in the theory. This paper reviews the reverberation suppression and target detection methods for the traditional active sonar. By analyzing the difference between the sonar and the radar, the space-time adaptive processing model suitable for a moving sonar is proposed. Based on this model, the design of the robust space-time adaptive detection method is discussed. At last, the paper summarizes the prospects of the reverberation suppression and target detection methods of the moving sonar.

Unlike the radar target detection in a noise background, for the target detection in the background of the sea clutter, the increase of the transmitting power would not bring about a significant performance improvement and thus a refined modeling of the sea clutter and a full exploitation of the characteristics of the sea clutter become very important to improve the performance of the target detection in the background of the sea clutter. The compound-Gaussian model is a widely recognized model to characterize the sea clutter, which provides a powerful tool to implement a refined description of the sea clutter. Moreover, the related optimum detection theory and methods with regard to this model provide the technique for improving the target detection performance in the background of the sea clutter. This paper reviews three compound-Gaussian sea clutter models, including the K distribution, the generalized Pareto distribution and the inverse Gaussian texture and the existing optimum coherent detection and the near-optimum coherent detection with these models. The current development of the optimum coherent detection in the compound-Gaussian clutter plus noise is addressed and their ‘bottleneck’ in practical applications is analyzed. At last, we discuss several possible approaches to develop near-optimum and computationally implementable detection methods.

Wideband digital phased array radar is a promising technology to monitor ocean environment. It can realize wide sea area, multi targets and high precision sea area monitoring. The key component of wideband digital phased array radar is digital RF transceiver chips. This paper briefly introduces the development and technology of integrated digital RF transceiver chips. In this paper, we discuss and analyze several key technical problems. The analysis results suggest that broadband digital phased array radar could be the best candidate for the next generation ocean surveillance.

With the rapid development of China's sea observation technologies and data collection methods, we have an ever expanding amount of observed data with more and more complexity. Therefore, the traditional data storage and processing techniques cannot effectively manage and analyze the big ocean data. Meanwhile, the regionalization and the distribution of these data become an challenge for a unified data management, during the data mining process. From the perspective of the big data life cycle, this paper reviews the technical principles of the existing open source big data framework in areas of data acquisition, storage, processing, intelligent analysis, security protection and data governance, focusing on their applications for the big ocean data.