Alberto Moreira

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• Prof. Dr.
• Director at German Aerospace Center (DLR)

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 rel...

The main goal of the TerraSAR-X Add-On for Digital Elevation Measurements (TanDEM-X) mission is the generation of a global digital elevation model (DEM) of unprecedented accuracy and coverage. The global TanDEM-X DEM product became available in 2016, surpassed all expectations, and became a reference for a wide range of Earth science, commercial, a...

This paper addresses the critical issue of phase synchronization in multistatic SAR. We present the experimental validation of a GNSS-based synchronization technique planned for use in ESA’s upcoming Earth Explorer mission, Harmony. In this technique, the radar payload and GNSS receiver utilize the same master oscillator, and radar synchronization...

Provides society information that may include news, reviews or technical notes that should be of interest to practitioners and researchers.

Provides society information that may include news, reviews or technical notes that should be of interest to practitioners and researchers.

Provides society information that may include news, reviews or technical notes that should be of interest to practitioners and researchers.

Advanced multichannel spaceborne synthetic aperture radar (SAR) systems with multiple elevation beams allow to obtain 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 paper, the range-ambiguity problem is analytically modeled and solved by employing a ra...

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 b...

The feasibility of single-pass interferometric or multistatic SAR mission concepts largely relies on the ability to achieve the matching of the carrier phase of the different elements of the constellations within a few degrees. We put forward a phase synchronization scheme in which the GNSS receiver and the radar payload share the same oscillator;...

The recently proposed frequency scanning (F-Scan) technique, together with the new International Telecommunication Union (ITU) allocation of 1200MHz 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-sig...

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...

Provides society information that may include news, reviews or technical notes that should be of interest to practitioners and researchers.

Als der Radarsatellit TanDEM-X am 21. Juni 2010 startete, begann eine neue Ära in der Radarfernerkundung. Seit er im engen Formationsflug mit seinem drei Jahre älteren „Zwilling“ TerraSAR-X die Erde umkreist, bilden die beiden Satelliten ein bistatisches Single-Pass-Interferometer im All. Der Abstand zwischen den Zwillingssatelliten variiert je nac...

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 a...

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...

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...

The IEEE Geoscience and Remote Sensing Society’s (GRSS’s) 2022 publications, symposium, and special awards were presented at the IEEE International Geoscience and Remote Sensing Symposium (IGARSS) awards banquet held at the Grand Hyatt, Kuala Lumpur on 21 July 2022. The Grand Hyatt Kuala Lumpur is one of the best hotels in Kuala Lumpur, strategical...

The synthetic aperture radar (SAR) imaging mode described in this paper 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...

EnVision was selected as ESA's 5th Medium-class mission in the Agency's Cosmic Vision plan, targeting a launch in the early 2030s. EnVision's overarching science questions are to explore the full range of geoscientific processes operating on Venus. It will investigate Venus from its inner core to its atmosphere at an unprecedented scale of resoluti...

The field of multicopter unmanned aerial vehicles (UAVs) has seen massive technological advances and decreasing costs over the last decade. Due to the higher prevalence and availability of these multicopter UAVs, there have also been rapid improvements in the software interfaceability, enabling the easy integration of custom software for flight pla...

Presents information on the above named conference.

The SAR imaging mode described in this paper utilizes the available bandwidth to form a narrow frequency-scanning transmit antenna beam illuminating the swath of interest from far to near range. Similarly the frequency-scanning receive antenna beam collects the return echo signal reflected from the ground. The operation parameters of the frequency...

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 (st...

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 signal...

Future spaceborne synthetic aperture radar (SAR) systems are subject to conflicting high-resolution and wideswath imaging requirements. As several studies show, this fundamental conflict can be resolved by advanced instrument modes employing multiple receive channels in elevation and/or azimuth (MAPS). Currently, SAR system concepts include MAPS-Sc...

In March 2021 a field campaign was conducted in the Austrian Alps exploring the application potential and performance of snow mass (snow water equivalent, SWE) retrievals by means of repeat-pass radar interferometry (RP-InSAR). Multiple repeat acquisitions were gained with an airborne polarimetric C-band and L-band SAR, spanning days without snowfa...

On June 10, 2021, the European Space Agency (ESA) announced the selection of EnVision as its newest medium-class science mission. EnVision's overarching science questions are to explore the full range of geoscientific processes operating on Venus [1, 2]. It will investigate Venus from its inner core to its atmosphere at an unprecedented scale of re...

Radio Frequency Interference (RFI) has become a major concern for future Synthetic Aperture Radar (SAR) missions. Each occurence of interference introduces artifacts in the radar imagery, biasing the measurements and leading to erroneous results. In addition to conventional techniques, the use of multichannel SAR for RFI mitigation has been propose...

In the constant strive for improving the capacity of next-generation spaceborne SARs while containing the increase in system complexity, distributed along-track constellations operated below Nyquist appear as one of the most promising solutions for delivering metric resolution imagery over swaths of hundreds of kilometers. In the operation of multi...

In the above article [1] , references [21] and [29] incorrectly provide the publication years. Reference [21] was published in 2020; reference [29] was published in 2021. The references appear in full here:

An intrinsic challenge in the geophysical interpretation of low-frequency SAR imagery of semi-transparent media, such as ice sheets, is the position ambiguity of the scattering structures within the glacial volume. Commonly tackled by applying interferometric and tomographic techniques, their spaceborne implementation exhibits by orders higher comp...

This paper reports the Phase A study results of the interferometric extension of the High-Resolution Wide-Swath (HRWS) mission with three MirrorSAR satellites. According to the MirrorSAR concept, small, low cost, transponder-like receiveonly satellites without radar signal demodulation, digitization, memory storage, downlink, and synchronization ar...

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...

Presents information on the GRSS society IGARSS 2021 Symposium.

The idea of the former Earth Explorer 10 mission Hydroterrais to place a SAR system into a geosynchronous orbit to un-derstand rapid processes of the diurnal water cycle over re-gions of interest in Europe and Africa. The DLR Microwavesand Radar Institute conducted an airborne SAR campaign tosupport the Hydroterra mission. Airborne data were collec...

Hydroterra has been considered as one of three candidates for ESA’s Earth Explorer 10 mission, and consists ofa geosynchronous Synthetic Aperture Radar to measure key processes of the diurnal water cycle. These measurements are expected to improve the prediction of intense rainfall, flooding and landslides. This concept was the subject of Phase 0 s...

The development of synthetic aperture radar (SAR) instruments at higher carrier frequency is motivated, among others, by the relative wavelength scaling, which provides an increased bandwidth and reduced physical dimensions of the RF hardware, for the same coverage. The later causes a reduced area and a high length-to-height aspect ratio of the ant...

The paper provides an up to date overview of the German TanDEM-X satellite mission status and its ongoing science activities. In June 2020 TanDEM-X reached his 10 years of successful operation - a view forward will be presented in the final paper. The global digital elevation model (DEM) of TanDEM-X became available in 2016 and surpassed all expect...

High-resolution and wide swath are known to be inherently incompatible requirements for spaceborne synthetic aperture radar (SAR) imaging systems. Extensive research shows that advanced instrument modes and architectures employing multiple receive channels in elevation and/or azimuth represent a feasible solution for this conflict. Currently, high...

Deployable reflector antennas illuminated by a digital feed array enable spaceborne synthetic aperture radar (SAR) systems to image an ultrawide, continuous swath at a fine azimuth resolution. This is facilitated by the use of dedicated imaging modes and by multidimensional digital beamforming (DBF) techniques. This article is part 1 of a tutorial...

Hydroterra was one of the three mission concepts competing for the Earth Explorer 10. The idea of this concept is to placea SAR system into a geosynchronous orbit to measure key processes of the diurnal water cycle. The DLR Microwavesand Radar Institute conducted an airborne SAR campaign to support the Phase 0 study of Hydroterra and gain knowledge...

Presents information on the IGARSS 2020 Virtual Symposium.

On June 21, 2010 the still unique TanDEM-X mission was launched and opened a new era in spaceborne radar remote sensing. The first formation flying radar system was built by extending the TerraSAR-X Synthetic Aperture Radar (SAR) mission by a second, TerraSAR-X-like satellite TanDEM-X. The resulting large single-pass SAR interferometer features fle...

The paper reports the results from the Phase 0/A study of the High-Resolution Wide-Swath (HRWS) mission with the MirrorSAR concept which is being considered for realization by the German Space Agency of DLR. Besides the generation of high-resolution images for a number of applications, one focus of this mission is on the generation of Digital Eleva...

Modern synthetic aperture radar (SAR) systems for Earth observation from space employ innovative hardware concepts. The key idea is to digitize the output of a multielement antenna almost immediately after the receiver and to dynamically process these data either onboard the radar satellite in real time or on the ground. This article addresses the...

In the context of spaceborne synthetic aperture radar (SAR) imaging, high resolution and wide swath are inherently conflicting requirements. These may however be simultaneously satisfied by advanced imaging modes with multichannel architectures in elevation and/or azimuth. The paper elaborates on a new mode based on multiple elevation beams and a s...

The paper describes the basic components of MirrorSAR and explains how bi- and multistatic SAR acquisitions are achieved by shifting only minimal functionality to the receive satellites. It shows that synchronization is not required or reduced in complexity by a MirrorLink. The MirrorLink forwards the ground reflected radar signal from the receivin...

Synthetic aperture radar (SAR) is a key remote sensing technique for Earth observation. Future SAR missions will deliver weekly high-resolution images of our planet, thereby allowing quantification of several essential climate variables. While this is a huge step forward compared to current systems, some applications require even more frequent temp...

Scan-On-Receive (SCORE) is a promising digital beamforming technique to improve the performance of SAR systems and enable high-resolution wide-swath concepts with multiple elevation beams. The technique is based on a beamsteering law which follows the angle-of-arrival of a pulse’s echo traversing the ground. In practice, SCORE, also known as SweepS...

Synthetic Aperture Radar (SAR) is an established remote sensing technique that can robustly provide high-resolution imagery of the Earth’s surface. However, current space-borne SAR systems are limited, as a matter of principle, in achieving high azimuth resolution and a large swath width at the same time. Digital beamforming (DBF) has been identifi...

The paper reports results of a concrete MirrorSAR mission analysis study with the planned X-band HRWS satellite as transmitter. The driving goal is a next generation global DEM with a much better height performance compared to TanDEM-X. Three small passive receive satellites are spanning differently sized interferometric baselines by flying in-terl...

Deployable reflector antennas illuminated by a digital feed array enable spaceborne synthetic aperture radar (SAR) systems capable to image an ultra-wide continuous swath at fine azimuth resolution. This is facilitated by the use of dedicated operation modes and by multi-dimensional digital beam-forming techniques. This paper is intended as a tutor...

Synthetic aperture radar (SAR) concepts based on digital beamforming (DBF) in elevation and multiple receive beams, for example, staggered SAR, allow high-resolution imaging of wide swaths and are, therefore, well-suited for the systematic observation of dynamic processes on the Earth's surface. While these concepts are compatible with quad-polarim...

Presents the recipients of various GRSS awards at the IGARSS 2019 Banquet. Presents the recipients of GRSS awards that were presented at the 2019 IGARSS conference.

A multistatic synthetic aperture radar (SAR) system offers the potential of exceeding the capabilities of conventional SARs in various ways, one of which is to realize high-resolution imaging over wide swaths when operated under the Nyquist frequency. Due to the decrease of the operational pulse repetition frequency, the Doppler spectrum of the rec...

Existing microwave remote sensing instruments used for Earth observation face a clear tradeoff between spatial resolution and revisit times at global scales. The typical imaging capabilities of current systems range from daily observations at kilometer-scale resolutions provided by scatterometers to meter-scale resolutions at lower temporal rates (...

Twenty-five years ago, the two flights of the SIR-C/X-SAR Synthetic Aperture Radar (SAR) system on the Space Shuttle Endeavour blazed a trail towards the future with a series of radar system innovations —that nearly every spaceborne SAR flown since then has benefited from, and in some cases improved upon. Many of the SAR techniques adopted by SAR s...

Synthetic aperture radar (SAR) is an efficient solution for road traffic monitoring due to its high spatial resolution and independence from daylight and weather conditions. In this sense, a number of ground moving target indication (GMTI) algorithms have been developed, whereas their robustness is often achieved with high costs, increased hardware...

Distributed multichannel synthetic aperture radar (SAR) imaging is a promising concept for future Earth observation missions. The multichannel concept can mitigate the pulse repetition frequency (PRF) or minimum SAR antenna area constraints inherent to single-channel SAR systems. Thus high azimuth resolution can be maintained, while acquiring wide...

Presents information on the IGARSS conference.