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Staggered SAR: Performance Analysis and Experiments With Real Data

Villano, Michelangelo and Krieger, Gerhard and Jäger, Marc and Moreira, Alberto (2017) Staggered SAR: Performance Analysis and Experiments With Real Data. IEEE Transactions on Geoscience and Remote Sensing, 55 (11), pp. 6617-6638. IEEE - Institute of Electrical and Electronics Engineers. doi: 10.1109/TGRS.2017.2731047. ISSN 0196-2892.

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Official URL: http://ieeexplore.ieee.org/document/8007291/


Synthetic aperture radar (SAR) remote sensing allows high-resolution imaging independent of weather conditions and sunlight illumination and is therefore very attractive for the systematic observation of dynamic processes on the earth's surface. Conventional SAR systems are, however, limited in that a wide swath can only be imaged at the expense of a degraded azimuth resolution. This limitation can be overcome by using systems with multiple receive subapertures displaced in along-track, but a very long antenna is required to map a wide swath. If a relatively short antenna with a single aperture in along-track is available, it is still possible to map a wide area: multiple subswaths can simultaneously be imaged using digital beamforming in elevation, but ``blind ranges'' are present between adjacent swaths, as the radar cannot receive while it is transmitting. Staggered SAR overcomes the problem of blind ranges by continuously varying the pulse repetition interval (PRI). A proper selection of the PRIs, together with moderate oversampling in azimuth, allows an accurate interpolation of the nonuniformly sampled raw data into a uniform grid, so that resampled data can then be focused with a conventional SAR processor. This approach thereby allows high-resolution imaging of a wide continuous swath without the need for a long antenna with multiple subapertures. In this paper, the performance of staggered SAR is thoroughly discussed and novel methods for the evaluation of the range and azimuth ambiguity-to-signal ratios in staggered SAR are proposed. An L-band design example based on a reflector antenna with multiple feeds shows that outstanding ambiguity performance is obtained, provided that data are moderately oversampled in azimuth. As an additional benefit, the energy of range and azimuth ambiguities is spread over large areas: ambiguities therefore appear in the image as a noise-like disturbance rather than localized artifacts. The impact of staggered SAR operation on image quality is furthermore assessed with experiments using real data. As the first step, highly oversampled F-SAR airborne data have been used to generate equivalent staggered SAR data sets and to evaluate the performance for different oversampling factors and interpolation methods. Then, the radar instrument of the German satellite TerraSAR-X has been commanded to acquire data over the lake Constance in staggered SAR mode. Measurements on these data show very good agreement with predictions from simulations. Staggered SAR is currently being considered as the baseline acquisition mode for Tandem-L, a proposal for a polarimetric and interferometric spaceborne SAR mission to monitor dynamic processes on the earth's surface with unprecedented accuracy and resolution.

Item URL in elib:https://elib.dlr.de/113749/
Document Type:Article
Title:Staggered SAR: Performance Analysis and Experiments With Real Data
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Villano, MichelangeloUNSPECIFIEDhttps://orcid.org/0000-0002-1769-6927UNSPECIFIED
Krieger, GerhardUNSPECIFIEDhttps://orcid.org/0000-0002-4548-0285UNSPECIFIED
Moreira, AlbertoUNSPECIFIEDhttps://orcid.org/0000-0002-3436-9653UNSPECIFIED
Date:November 2017
Journal or Publication Title:IEEE Transactions on Geoscience and Remote Sensing
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:Yes
Page Range:pp. 6617-6638
Publisher:IEEE - Institute of Electrical and Electronics Engineers
Keywords:Ambiguities, high-resolution wide-swath imaging, impulse response function (IRF), synthetic aperture radar (SAR), Tandem-L.
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Earth Observation
DLR - Research area:Raumfahrt
DLR - Program:R EO - Earth Observation
DLR - Research theme (Project):R - Vorhaben Tandem-L Vorstudien (old)
Location: Oberpfaffenhofen
Institutes and Institutions:Microwaves and Radar Institute > Radar Concepts
Microwaves and Radar Institute > SAR Technology
Microwaves and Radar Institute
Deposited By: Villano, Dr.-Ing. Michelangelo
Deposited On:18 Aug 2017 08:52
Last Modified:23 Jul 2022 13:44

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