Georg Fischer

German Aerospace Center (DLR) | DLR · Department of Radar Concepts

The amount of water in a snow pack can be described by the Snow Water Equivalent (SWE). SWE is a crucial parameter for hydrological models, for example for flood predictions. Previous studies have shown that the interferometric phase between two repeat-pass SAR measurements can be used to determine the change in SWE. However, a limitation of this m...

Spaceborne differential SAR interferometry (D-InSAR) has been demonstrated to potentially allow snow water equivalent (SWE) change measurements for dry snow on a spatial scale, resolution, and accuracy unprecedented by other sensor concepts. However, its operational use is hindered mainly because of i) low coherence areas resulting from temporal de...

This paper presents the latest results obtained during the Phase A study of the Harmony mission for land applications. The contribution will focus on the performance of the 3-D deformation vectors (TDV) and topography change (TOC) products, for both solid Earth and land ice products, by using semi-analytical models and end-to-end simulations. Both...

The Snow Water Equivalent (SWE) is the amount of water contained in a snow pack and is therefore an important variable for hydrological and climate models . Differential Interferometric Synthetic Aperture Radar (DInSAR) techniques can relate the interferometric phase of two repeat pass SAR acquisitions to the SWE change between them. However, only...

Single-pass InSAR elevation measurements of dry snow, firn, and ice are known to be substantially biased downward due to a partial penetration of the radar signals into the medium, resulting in a phase center location within the volume. The so-called penetration bias, i.e., the elevation difference between surface and InSAR phase center, can be est...

Snow Water Equivalent (SWE) is important for hydrological models. It has been shown that the interferometric phase between two repeat-pass SAR measurements can be related to SWE change, but this method is limited due to phase wrapping. It is possible to relate the Co-polar Phase Difference (CPD) between two channels to the fresh snow depth. This st...

Information about ice sheet subsurface properties is crucial for understanding and reducing related uncertainties in mass balance estimations. Key parameters like the firn density, stratigraphy, and the amount of refrozen melt water are conventionally derived from in situ measurements or airborne radar sounders. Both types of measurements provide a...

Artificial Intelligence for Cold Regions (AI-CORE) is a collaborative approach for applying Artificial Intelligence (AI) methods in the field of remote sensing of the cryosphere. Several research institutes (German Aerospace Center, Alfred-Wegener-Institute, Technical University Dresden) bundled their expertise to jointly develop AI-based solutions...

SKADI[1] is a mission proposal submitted to the Earth Explorer 11 call that aims to address and quantify dynamic processes in cold environments by measuring the static and dynamic topography. This information is essential for understanding, modelling and forecasting the dynamics and interactions within the different elements of the cryosphere and w...

Single-pass interferometric synthetic aperture radar (InSAR) enables the possibility for sea ice topographic retrieval despite the inherent dynamics of sea ice. InSAR digital elevation models (DEMs) are measuring the radar scattering center height. The height bias induced by the penetration of electromagnetic waves into snow and ice leads to inaccu...

Single-pass interferometric synthetic aperture radar (InSAR) enables the possibility for sea ice topographic retrieval despite the inherent dynamics of sea ice. InSAR digital elevation models (DEM) are measuring the radar scattering centre height. The height bias induced by the penetration of electromagnetic waves into snow and ice leads to inaccur...

Polarimetric and (multi-baseline) interferometric techniques are promising tools to investigate the subsurface properties of glaciers and ice sheets, due to the signal penetration of up to several tens of meters into dry snow, firn, and ice. Two different lines of research were addressed in recent years. The first is based on PolSAR, which provides...

The influence of the subsurface properties of ice sheets on polarimetric synthetic aperture radar interferometry (Pol-InSAR) measurements is well known. In order to invert this relationship for the extraction of geophysical parameters from Pol-InSAR data, models of the subsurface scattering structure are required. One potential application is the e...

Synthetic Aperture Radar Interferometry (InSAR) is able to provide important information for the characterization of the surface topography of glaciers and ice sheets. However, due to the inherent penetration of microwaves into dry snow, firn, and ice, InSAR elevation models are affected by a penetration bias. The fact that this bias depends on the...

The penetration of microwave signals into snow and ice, especially in dry conditions, introduces a bias in digital elevation models generated by means of synthetic aperture radar (SAR) interferometry. This bias depends directly on the vertical backscattering distribution in the subsurface. At the same time, the sensitivity of interferometric SAR me...

Remote sensing is a fundamental tool to measure the dynamics of ice sheets and provides valuable information for ice sheet projections under a changing climate. There is, however, the potential to further reduce the uncertainties in these projections by developing innovative remote sensing methods. One of these remote sensing techniques, the polari...

Digital elevation models generated with SAR interferometry (InSAR) are an important information source for glacier and ice sheet mass balance. However, the measured elevations suffer from a penetration bias due to the interferometric phase center being up to several tens of meters below the surface. The penetration of the microwave signals depends...

The need of large scale observations with high temporal frequency has promoted airborne and satellite remote sensing techniques for glaciological applications. In particular, active microwave sensors, such as synthetic aperture radars (SARs), offer all-weather and daylight independent operability which is of great advantage at high latitudes, where...

The analysis of data from an airborne synthetic aperture radar (SAR) campaign in the percolation zone of Greenland revealed an interferometric coherence undulation behavior with respect to vertical wavenumber, which cannot be explained with existing models. We propose a model extension that accounts for scattering from distinct layers below the sur...

Estimation of ice zones' extent and their temporal variations is fundamental for the retrieval of surface mass balance of glaciers and ice sheets. Several approaches have been proposed to map ice zones by means of Synthetic Aperture Radars (SARs), most of which are based on intensity measurements and their seasonal variations. Here, an alternative...

The vertical structure of firn below the surface of the Greenland ice sheet is driven by meteorological conditions like the intensity and duration of melting periods. The formation of ice inclusions through melt-refreeze processes leads to strong scatterers whose vertical distribution influences interferometric coherences. Interferometric coherence...

To study how the water cycle changes over time, satellite and airborne remote sensing missions are typically employed. Over the last 40 years of satellite missions, the measurement of true water inventories stored in sea and land ice within the cryosphere have been significantly hindered by uncertainties introduced by snow cover. Being able to dete...

Since the very first studies, polarimetric synthetic aperture radars (Pol-SARs) revealed a great potential for the study of glaciers and ice sheets. Besides the high spatial resolution and all-weather all-season operability inherited from conventional SAR systems, they can provide information about the dielectric and geometric properties of surface...

This paper reports on the on-going activities at DLR for the definition of a verification/validation strategy for the operational higher level products and offers a first overview of the developing validation concept. Moreover, it will represent a spring board for establishing new synergies with international parters, aiming at improving knowledge...

The application of SAR Tomography (TomoSAR) to ice bodies is in a rather early stage, essentially due to the limited amount of experimental and validation data. In order to contribute to fill this gap, the objective of this paper is to present first results in the characterization of the 3-D backscattered signal of ice volumes at different frequenc...

Based on the advances of recent Pol-InSAR studies for glaciological research, their limitations and the latest progress in understanding of polarimetric backscatter from snow and firn, the relationship between glacier subsurface structure and Pol-InSAR measurements at different frequencies is revisited. The investigations are supported by a new air...

The Helheim glacier in south-east Greenland faces a retreat and thinning like many other Greenland outlet glaciers, but showed two particular huge and fast retreats between 2000 and 2005, coinciding with an acceleration of glacier flow [1]. The estimation of glacier retreat and thinning are established procedures based on a variety of remote sensin...

Directional microwave scattering, as investigated in this study, is characterized by a strong and narrow scattering pattern that varies strongly for only minor aspect angle changes. As was noted already in the past directional scattering is relevant for applications and cannot just be ignored. The overall objective of our work was to better underst...