Symmetry Applied in Remote Sensing Technology

Dear Colleagues, 

In recent years, remote sensing technology has been developed rapidly to provide support for emerging applications and to enable better localization of targets. The localization of ships and sea traffic monitoring have always been a focus of coastal countries. Also, of particular interest is air monitoring and early warning systems. This has been particularly pronounced in recent years, primarily due to security reasons. 

To monitor activities on a sea surface, radars operating in the microwave frequency band have been primarily used. However, they generally cover only the territorial waters, as they are based on direct propagation of waves. Unfortunately, many illegal activities can be carried out beyond the horizon, which is well beyond the detection range of these radars. In order to monitor the entire EEZ, over-the-horizon radars (OTHR) are used, especially those that operate in the high-frequency (HF) band. Similarly, monitoring activities in the air often relies on radars operating in the VHF frequency band, while other systems of particular interest include SAR systems and ionospheric radars.  

In such radar systems, different symmetry models are developed to address various challenges and issues. Symmetry arises in many radar subsystems—including waveforms, codes, antenna arrays, and signal processing—and is employed to simplify design, improve ambiguity properties, cancel sidelobes, enforce reciprocity, and enhance the robustness of hardware and algorithms. Additional topics of interest include symmetric beam control, simple calibration, the effects of realistic asymmetries (such as phase and amplitude errors, Doppler shifts, and coupling), and interference suppression. The mechanical construction of these systems and their correspondinh symmetry-based models also offer valuable research directions, making this topic relevant to mechanical engineers. Real-time signal processing poses further challenges, inviting contributions from software engineers, while the integration of AI methods is likewise encouraged. 

In this Special Issue, we welcome novel ideas, advanced techniques, comparative analyses of different methodologies, as well as surveys and technical reviews covering all aspects of existing results in remote sensing.  

Potential topics include, but are not limited to, the following:

• OTHR (over-the-horizon radars);
• HFSWR (high-frequency surface wave radars);
• VHF radars;
• Early warning systems;
• SAR (Synthetic-aperture radar);
• Ionospheric radars;
• Microwave radars.

Symmetry is a fundamental property that has been extensively applied in the study and development of diverse radar systems. This Special Issue invites original research exploring symmetry and asymmetry characteristics in remote sensing technology. Through this Issue, we aim to share knowledge and foster collaboration among researchers, designers, manufacturers, and users in this dynamic field.

We look forward to receiving your contributions. 

Dr. Dragan Golubović
Prof. Dr. Mirjana I. Simić
Guest Editors

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• symmetry
• OTHR
• HFSWR
• VHF radars
• SAR
• ionospheric radars
• waveform symmetry
• antenna array symmetry
• ambiguity properties
• sidelobes cancellation
• interference suppresion