Loading [MathJax]/extensions/MathMenu.js
Alberto Moreira - IEEE Xplore Author Profile

Showing 1-25 of 287 results

Filter Results

Show

Results

High-Resolution Wide Swath (HRWS) Synthetic Aperture Radar (SAR) systems are normally designed to have identical antenna patterns in each receive channel. Nevertheless, due to different factors, this condition might not be satisfied, resulting in a multichannel radar system with different antenna patterns. This paper studies the impact of these relative antenna differences on the performance of a ...Show More
The use of airborne synthetic aperture radar (SAR) to demonstrate high-resolution wide swath (HRWS) operational modes in spaceborne SAR missions has supported the development of advanced digital beamforming (DBF) techniques. In doing so, one of the challenges to overcome is the temporal variation of the antenna phase centers in the airborne DBF SAR scenario, which significantly degrades the perfor...Show More
The recently proposed frequency scanning (F-Scan) technique, together with the new International Telecommunication Union (ITU) allocation of 1200 MHz in X-band, enables the improvement of important performance parameters of synthetic aperture radar (SAR) acquisitions, such as the swath width, the signal-to-noise ratio, and the range ambiguity-to-signal ratio. The concurrent imaging technique, in t...Show More
The feasibility of single-pass interferometric or multistatic synthetic aperture radar (SAR) mission concepts largely relies on the ability to achieve the matching of the carrier phase of the different radar instruments of the constellations within a few degrees. We put forward a phase synchronization scheme in which the global navigation satellite system (GNSS) receiver and the radar payload shar...Show More
A significant level of range ambiguity disturbance may affect high-resolution wide-swath spaceborne synthetic aperture radar (SAR) systems with multiple elevation receive beams. To overcome this limitation, a promising approach, based on the higher order blind source separation (BSS), was recently proposed. This method, denoted as range ambiguity BSS (RABSS), demonstrates outstanding range ambigui...Show More
Advanced multichannel spaceborne synthetic aperture radar (SAR) systems with multiple elevation beams allow for obtaining high-resolution and wide-swath SAR images. However, the degradation of the SAR image quality due to range ambiguities is still an issue. In this article, the range-ambiguity problem is analytically modeled and solved by employing a range-time and Doppler-frequency dependent mix...Show More
High Earth orbit synthetic aperture radar (SAR) systems offer high temporal sampling and moderate spatial resolution on a global scale, potentially outperforming conventional low Earth orbit (LEO) systems in revisit times. However, this requires complex system architectures such as burst operation modes with multiple subswaths, large antennas, and digital beamforming. Similar temporal sampling and...Show More
Spaceborne synthetic aperture radar (SAR) is an essential tool for Earth observation applications. By combining multiple SAR images taken from different viewing angles, precise digital elevation models and high-resolution tomograms can be created, revealing the three-dimensional structure of vegetation, ice, and dry soil. Currently, such images are typically acquired sequentially, impacting produc...Show More
The Venus Interferometric Synthetic Aperture Radar (VISAR) is one of two instruments carried by the VERITAS Discovery Mission to Venus that was selected by NASA in 2021 [1] , [2] . VERITAS (Venus Emissivity, Radio Science, Insar, Topography And Spectroscopy) is a partnership between scientists and engineers at NASA/JPL in an international cooperation with the Germany Aerospace Center (DLR), the It...Show More
Spaceborne synthetic aperture radar (SAR) is an essential tool for Earth observation. The combination of multiple SAR images taken from different viewing angles allows forming accurate digital elevation models and high-resolution tomograms that unveil the three-dimensional structure of vegetation, ice, and dry soil. Whereas nowadays such images are mostly acquired sequentially, compromising produc...Show More
Synthetic aperture radar (SAR) interferometry is an essential remote sensing technique with a wide range of applications. Studying and monitoring dynamic processes on the Earth’s surface requires digital elevation models (DEMs) at short time intervals, making distributed and multi-static SAR systems a very promising solution to this need. This work introduces a concept for distributed SAR interfer...Show More
This paper provides an overview of the state of the art and an outlook on future developments of spaceborne Synthetic Aperture Radar (SAR) systems with multi-baseline imaging capability, such as 3D differential SAR interferometry (3D-DinSAR), polarimetric SAR interferometry (Pol-InSAR), tomography (TomoSAR), and holography (HoloSAR). The goal is to fill the multidimensional data space with additio...Show More
The effectiveness of swath reconstruction algorithms in cross-track multistatic synthetic aperture radar (SAR) constellations heavily relies on the precise positioning of individual spacecrafts. Ideally, a static array configuration is desired, where the satellites are evenly distributed in a Local Vertical Local Horizontal (LVLH) frame, emulating a fixed antenna. However, achieving this ideal con...Show More
Geosynchronous synthetic aperture radar (SAR) missions offer the advantage of conducting multiple sub-daily interferometric acquisitions using a single platform. However, this comes at the expense of increased fuel and power budgets, due to the significant distance to Earth’s surface. Consequently, such missions are suited for delivering SAR products with relatively lower spatial resolutions, typi...Show More
We present in this paper an algorithm for the estimation of synchronisation phase errors in bistatic and multistatic SAR systems with azimuth diversity, such as multi-channel architectures or azimuth constellations, solely based on the evaluation of the received bistatic data. The suggested algortihm working with unfocussed SAR data shows more robustness against processing errors when compared to ...Show More
In the last decade we entered into a golden age for spaceborne synthetic aperture radar (SAR) systems with the number of satellites increasing in a quasi-exponential way. The reason is obvious: SAR data utilization and associated services are making a most important contribution in addressing societal challenges of global dimension since spaceborne SAR is the only sensor technology that is able to...Show More
Highly accurate digital elevation models (DEMs) from spaceborne synthetic aperture radar (SAR) interferometry are often affected by phase unwrapping errors. These errors can be resolved by the use of additional interferograms with different baselines, but this requires additional satellites in a single-pass configuration, resulting in higher cost and system complexity, or additional passes of the ...Show More
Synthetic aperture radar (SAR) interferometry is a well-established technique for producing high-resolution digital elevation models (DEMs) of the Earth’s surface and measuring displacements on different time scales. Observations of SAR interferograms, however, show that azimuth ambiguities can be coherently imaged and may lead to phase biases and coherence losses that significantly degrade the in...Show More
The synthetic aperture radar (SAR) imaging mode described in this article utilizes the available signal bandwidth to form a narrow frequency-scanning transmit antenna beam illuminating the swath of interest from far to near range. The imaging technique is named frequency scan for time-of-echo compression (f-STEC), because, for a proper choice of mode parameters, the radar echo duration is reduced,...Show More
Utilizing digital beamforming (DBF) techniques in conjunction with the feed array of large deployable reflector antennas can boost the performance of synthetic aperture radar (SAR) systems. Multichannel SAR overcomes the constraints of classical single-channel SAR, allowing for wide-swath imaging at fine azimuth resolution. Part 1 of this tutorial provided an introduction to the instrument structu...Show More
Radio Frequency Interference (RFI) is a growing problem for future Synthetic Aperture Radar (SAR) missions, resulting in data loss, image artifacts and undetected biases. A new approach for mitigating RFI is digital beamforming (DBF), which is possible with the next generation of multichannel SAR systems and allows for a spatial filtering of signals from different directions. While on-board RFI re...Show More
The paper provides an up-to-date overview of the German TanDEM-X satellite mission status and its ongoing science activities. The global digital elevation model (DEM) of TanDEM-X became available in 2016 and surpassed all expectations: It has 99.9% coverage, 12-m posting, absolute height accuracy of approximately 1 m and a relative height error (standard deviation) of 0.8 m. This unique data set h...Show More
An overview of the German spaceborne X-Band radar program will be presented in this paper. A view into the wide heritage of the German synthetic aperture radar (SAR) instruments and the paramount results obtained with the German X-band Missions will be provided. This paper will cover the Shuttle Imaging Radar missions (SIR-C/X-SAR) from 1994 and the Shuttle Radar Topography Mission (SRTM) from 200...Show More