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Airborne Synthetic Aperture Radar: Systems, Processing, New Challenges and Opportunities

A special issue of Remote Sensing (ISSN 2072-4292). This special issue belongs to the section "Remote Sensing Image Processing".

Deadline for manuscript submissions: closed (30 December 2022) | Viewed by 9027

Special Issue Editors

1. ETH Zurich, Earth Observation and Remote Sensing Institute of Environmental Engineering, Leopold-Ruzicka-Weg 4, HCP G31.1, CH-8093 Zurich, Switzerland
2. Gamma Remote Sensing AG, Worbstrasse 225, CH-3073 Gümligen, Switzerland
Interests: synthetic aperture radar (SAR) remote sensing techniques and applications; SAR imaging algorithms; SAR signal processing; SAR tomography; SAR interferometry techniques and applications

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Guest Editor
Institute for Electromagnetic Sensing of the Environment (IREA), National Research Council (CNR) of Italy, Via Diocleziano 328, 80124 Naples, Italy
Interests: microwave remote sensing and electromagnetics; signal processing; estimation of parameters from SAR data; SAR polarimetry; airborne SAR data processing; modeling of electromagnetic scattering from natural surfaces

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Guest Editor
Embraer, Campinas, Brazil( electronic engineer, Dr.-Ing., Rua Sergio Fernandes Borges Soares 1000, Postal Code 130054-709, Brazil)
Interests: airborne and satellite-borne SAR design; interferometry; ground based radars

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Guest Editor
1. Department of Engineering (DI), Università degli Studi di Napoli “Parthenope”, 80143 Napoli, Italy
2. Institute for Remote Sensing of Environment (IREA), National Research Council (CNR), 80124 Napoli, Italy
Interests: SAR; airborne SAR data modeling and processing; modeling of electromagnetic scattering from natural surfaces; synthesis of antenna arrays, antenna measurements
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Synthetic aperture radar (SAR) systems mounted onboard aerial platforms, such as fixed-wing aircraft, helicopters, and unmanned aerial vehicles (UAV), are gaining increasing interest within the remote sensing community, since they offer complementary properties compared to spaceborne SAR systems, in terms of revisit time, operational flexibility, and observation capabilities. In addition, airborne SAR systems allow assessing the potentialities of novel technologies and/or measurement modalities before these are deployed operationally on spaceborne SAR missions.

These appealing features, along with the recent advancements in radar, navigation, and aeronautical technologies, are pushing the scientific community toward new challenges and opportunities in the field of airborne SAR. Emerging lightweight and compact SAR sensors can indeed be mounted onboard ever smaller, highly flexible, aerial platforms. This offers the opportunity to design new observation configurations based, for instance, on multifrequency, multiantenna or even multiplatform SAR systems.

Small aircraft are of key interest for new applications like high resolution, vegetation and subsurface tomography, with monostatic and bistatic SAR. Since the sensor trajectory of small aircraft can be strongly nonlinear, either due to turbulent tropospheric conditions, or even on purpose—e.g., to more closely follow a curvilinear feature of interest, or for circular and helicoidal SAR applications—SAR processing strategies need to be able to handle such flight paths. In addition, residual unknown platform motion beyond the accuracy provided by the navigation system may require adequate SAR-data-driven correction approaches.

The goal of this Special Issue is to gather recent scientific and technological advancements in the field of airborne SAR, in terms of system development, signal modeling, image formation, data processing, and resulting new applications.

Potential topics include but are not limited to:

  • New airborne SAR systems;
  • Navigation sensors and algorithms;
  • Frequency-domain and/or time-domain approaches for airborne SAR focusing;
  • Real-time SAR processing hardware and algorithms;
  • Airborne monostatic and bistatic SAR imaging in nonconventional acquisition modes;
  • Innovative data processing approaches;
  • Airborne single-pass cross-track, along-track SAR interferometry;
  • Airborne repeat-pass SAR interferometry and tomography;
  • Cutting-edge airborne SAR applications;
  • Experimental results based on airborne SAR data acquired in challenging operative scenarios;
  • Curvilinear, circular and helicoidal SAR;
  • Integration of multifrequency SAR data;
  • Integration of spaceborne and airborne SAR data.
Dr. Othmar Frey
Dr. Antonio Natale
Dr. Joao Roberto Moreira Neto
Dr. Stefano Perna
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Remote Sensing is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Synthetic aperture radar (SAR)
  • Airborne SAR
  • SAR processing
  • Bistatic SAR
  • SAR interferometry
  • SAR tomography
  • SAR applications

Published Papers (4 papers)

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Research

32 pages, 23560 KiB  
Article
Airborne Millimeter-Wave InSAR Terrain Mapping Experiments Based on Automatic Extraction and Interferometric Calibration of Tie-Points
by Bin Zhang, Futai Xie, Liuliu Wang, Shuang Li, Lideng Wei and Liang Feng
Remote Sens. 2023, 15(3), 572; https://doi.org/10.3390/rs15030572 - 18 Jan 2023
Cited by 1 | Viewed by 1232
Abstract
Limited by meteorological conditions, airspace, complex terrain and other factors, airborne millimeter-wave InSAR will inevitably face the situation of no control point layout when acquiring terrain data in the difficult mapping areas in Southwest China, which increases the difficulty of subsequent data processing. [...] Read more.
Limited by meteorological conditions, airspace, complex terrain and other factors, airborne millimeter-wave InSAR will inevitably face the situation of no control point layout when acquiring terrain data in the difficult mapping areas in Southwest China, which increases the difficulty of subsequent data processing. Moreover, the layout of control points in difficult mapping areas consumes a lot of manpower and time, which is not suitable for large-scale high-precision topographic mapping. To solve these problems, this paper proposes an automatic extraction of tie-points and interferometric calibration technology based on tie-points. This technology develops the automatic extraction algorithm of tie-points based on SAR + SIFT + RANSAC to obtain evenly distributed tie-points of adjacent images, and uses the evenly distributed tie-points as real known points to recalibrate the interference parameters, then carries out elevation transfer and elevation inversion through the tie-points of overlapping areas, thus realizing high-precision mapping without control points for airborne millimeter-wave InSAR. This paper uses measured data to verify the technology, and compares it with the areas with control points and marking points. The comparison results of elevation accuracy prove the feasibility and effectiveness of this method. This paper also discusses the difficulties in the treatment of typical areas, such as water areas, urban areas and mountain areas, and gives reasonable solutions that have good engineering application value. Full article
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24 pages, 7022 KiB  
Article
Predicting Sugarcane Harvest Date and Productivity with a Drone-Borne Tri-Band SAR
by Gian Oré, Marlon S. Alcântara, Juliana A. Góes, Bárbara Teruel, Luciano P. Oliveira, Jhonnatan Yepes, Valquíria Castro, Leonardo S. Bins, Felicio Castro, Dieter Luebeck, Laila F. Moreira, Rodrigo Cintra, Lucas H. Gabrielli and Hugo E. Hernandez-Figueroa
Remote Sens. 2022, 14(7), 1734; https://doi.org/10.3390/rs14071734 - 04 Apr 2022
Cited by 6 | Viewed by 2770
Abstract
This article presents a novel method for predicting the sugarcane harvesting date and productivity using a three-band imaging radar. Taking advantage of working with a multi-band radar, this system was employed to estimate the above-ground biomass (AGB), achieving a root-mean-square error (RMSE) of [...] Read more.
This article presents a novel method for predicting the sugarcane harvesting date and productivity using a three-band imaging radar. Taking advantage of working with a multi-band radar, this system was employed to estimate the above-ground biomass (AGB), achieving a root-mean-square error (RMSE) of 2 kg m−2 in sugarcane crops, which is an unprecedented result compared with other works based on the Synthetic Aperture Radar (SAR) system. By correlating the field measurements of the ripening index (RI) with the AGB measurements by radar, an indirect estimate of the RI by the radar is obtained. It is observed that the AGB reaches its maximum approximately 280 days after planting and the maximum RI, which defines the harvesting date, approximately 360 days after planting for the species IACSP97-4039. Starting from an AGB map collected by the radar, it is then possible to predict the harvesting date and the corresponding productivity with competitive average errors of 8 days and 10.7%, respectively, with three months in advance, whereas typical methods employed on a test site achieve an average error of 30 days with three months in advance. To the best of our knowledge, it is the first time that a multi-band radar is employed for productivity prediction in sugarcane crops. Full article
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17 pages, 4232 KiB  
Article
Down-Looking Airborne Radar Imaging Performance: The Multi-Line and Multi-Frequency
by Ilaria Catapano, Carlo Noviello and Francesco Soldovieri
Remote Sens. 2021, 13(23), 4897; https://doi.org/10.3390/rs13234897 - 02 Dec 2021
Cited by 1 | Viewed by 1140
Abstract
The paper proposes an analytical study regarding airborne radar imaging performances and accounts for a down-looking radar system moving along parallel lines far, in terms of probing wavelength, from the investigated domain and collecting multi-frequency and multi-monostatic data. The imaging problem is formulated [...] Read more.
The paper proposes an analytical study regarding airborne radar imaging performances and accounts for a down-looking radar system moving along parallel lines far, in terms of probing wavelength, from the investigated domain and collecting multi-frequency and multi-monostatic data. The imaging problem is formulated in a constant depth plane by exploiting the Born approximation. Hence, a linear inverse scattering problem is faced by considering both the Adjoint and the Truncated Singular Value Decomposition reconstruction schemes. Analytical and simulated results are provided to state how the achievable performances depend on the measurement configuration. These results are of practical usefulness because, in operative conditions, it is unfeasible to plan a flight grid made up by a high number of closely (in terms of probing wavelength) spaced lines. Hence, the understanding of how the availability of under-sampled data affects the radar imaging allows for a trade-off between operative data collection constrains and reliable reconstructions of the scenario under test. Full article
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20 pages, 5872 KiB  
Article
On the Frequency Sweep Rate Estimation in Airborne FMCW SAR Systems
by Carmen Esposito, Paolo Berardino, Antonio Natale and Stefano Perna
Remote Sens. 2020, 12(20), 3448; https://doi.org/10.3390/rs12203448 - 20 Oct 2020
Cited by 3 | Viewed by 2219
Abstract
Use of Frequency Modulated Continuous Wave (FMCW) Synthetic Aperture Radar (SAR) systems requires to accurately know the electronic parameters of the system. In particular, the use of an incorrect value of the Frequency Sweep Rate (FSR) introduces geometric distortions in the focused images. [...] Read more.
Use of Frequency Modulated Continuous Wave (FMCW) Synthetic Aperture Radar (SAR) systems requires to accurately know the electronic parameters of the system. In particular, the use of an incorrect value of the Frequency Sweep Rate (FSR) introduces geometric distortions in the focused images. Recently, a method, that we name FSR Estimate Through Corner reflectors (FSRETC), has been proposed to estimate the FSR value actually employed by the radar. The method is based on the use of the SAR image focused with the available erroneous FSR. Moreover, it exploits a number of Corner Reflectors (CRs) deployed over the illuminated area. In this work, we provide an assessment of the capabilities of the FSRETC algorithm. The overall analysis is performed through the use of a real dataset consisting of 10 acquisitions carried out in 2018 (5 acquisitions) and 2019 (5 acquisitions) with an airborne FMCW SAR system. The presented experimental analysis shows that even with a single acquisition, use of two CRs sufficiently far from each other in the range direction, allows achieving an accurate estimate of the searched FSR. Moreover, it is shown that the obtained estimate is very stable over the time. Therefore, the overall procedure can be applied only once, since the estimated values can be safely used for the subsequent missions, at least for the time interval considered in the work, that is, 14 months. In addition, the presented results pose the basis for an enhanced measurement strategy that allows effective application of the FSRETC algorithm through the use of only one CR. Full article
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