Comparison of digital beamforming techniques for enhanced ice sounding radar data processing

Ice sounding radar from high altitudes is compromised by off-nadir ice surface reflections (clutter), which overlays the nadir signal of interest originating from the bedrock and/or internal ice layers. Multi-aperture antenna radar systems were developed to mitigate the impact of surface clutter allowing spatially variant digital beamforming (DBF) processing of the data received from the individual spatially separated apertures. This paper investigates four different beamforming algorithms: conventional beamsteering, nulling of clutter angles, optimum beamformer and the MVDR beamformer. Comparisons are performed based on simulations for an airborne ice sounding scenarios. In addition, real echograms are computed from data acquired by the P-band POLARIS sensor. Relevant conclusions are drawn with respect to the implementation of a future space-based ice sounding mission

Exploiting nonlocal filters for high-resolution InSAR DEM generation

Nonlocal filters show outstanding performance in the field of interferometric phase restoration by providing strong filtering power together with high spatial features preservation. In this work we focus on the generation of Digital Elevation Models (DEM) from a pair of interferometric SAR images. In the specific, we aim at comparing the performance of state-ofthe- art InSAR filtering approaches on the basis of their noise suppression and detail preservation capabilities. We exploit a dataset of TanDEM-X SAR data relative to the volcanic area of the Kamchatka region (Russia)

Heterogeneous retreat and ice melt of Thwaites Glacier, West Antarctica

International audienc

Rapid glacier retreat rates observed in West Antarctica

International audienceThe Pope, Smith and Kohler glaciers, in the Amundsen Sea Embayment of West Antarctica, have experienced enhanced ocean-induced ice-shelf melt, glacier acceleration, ice thinning and grounding-line retreat in the past 30 years. Here we present observations of the grounding-line retreat of these glaciers since 2014 using a constellation of interferometric radar satellites combined with precision surface elevation data. We find that the grounding lines develop spatially variable, kilometre-scale, tidally induced migration zones. After correction for tidal effects, we detect a sustained pattern of retreat coincident with high melt rates of ungrounded ice, marked by episodes of more rapid retreat. In 2017, Pope Glacier retreated 3.5 km in 3.6 months, or 11.7 km yr-1. In 2016-2018, Smith West retreated at 2 km yr-1 and Kohler at 1.3 km yr-1. While the retreat slowed in 2018-2020, these retreat rates are faster than anticipated by numerical models on yearly timescales. We hypothesize that the rapid retreat is caused by unrepresented, vigorous ice-ocean interactions acting within newly formed cavities at the ice-ocean boundary

Grounding Line Retreat of Denman Glacier, East Antarctica, Measured With COSMO‐SkyMed Radar Interferometry Data

International audienceDenman Glacier, East Antarctica, holds an ice volume equivalent to a 1.5 m rise in global sea level. Using satellite radar interferometry from the COSMO‐SkyMed constellation, we detect a 5.4 ± 0.3 km grounding line retreat between 1996 and 2017–2018. A novel reconstruction of the glacier bed topography indicates that the retreat proceeds on the western flank along a previously unknown 5 km wide, 1,800 m deep trough, deepening to 3,400 m below sea level. On the eastern flank, the grounding line is stabilized by a 10 km wide ridge. At tidal frequencies, the grounding line extends over a several kilometer‐wide grounding zone, enabling warm ocean water to melt ice at critical locations for glacier stability. If warm, modified Circumpolar Deep Water reaches the sub‐ice‐shelf cavity and continues to melt ice at a rate exceeding balance conditions, the potential exists for Denman Glacier to retreat irreversibly into the deepest, marine‐based basin in Antarctica

Grenzen der Vermessung der Erde aus dem All mit Synthetischem Apertur Radar

Das Abbildungsprinzip des weltraumgestützten Synthetischen Apertur Radars (SAR) erlaubt grundsätzlich eine Genauigkeit der absoluten Lokalisierung von Objektpunkten auf der Erde im Bereich weniger cm. Darüber hinaus können durch die Nutzung interferometrischer und tomographischer Verfahren Bewegungen von besser als 1 mm/a geschätzt werden, und das für bis zu 1 Million Punkte pro km2. Wir beschreiben, wie diese hohen und geodätisch attraktiven Genauigkeiten erzielt werden können, und welche instrumentellen, signalverarbeitungstechnischen, atmosphärenphysikalischen und geodynamischen Effekte berücksichtigt werden müssen. Die absoluten schätztheoretischen Grenzen der Bestimmung der Position von Objekten bzw. deren Bewegung werden aufgezeigt und diskutiert. Experimentelle Ergebnisse umfassen Messungen zur Geolokalisierung von künstlichen Reflektoren, die eine Geolokalierungsgenauigkeit von ca. 1 cm demonstrieren, einer SAR-tomographischen 3D Rekonstruktion eines Stadtgebiets, sowie der Vermessung der Schrumpfung eines Gebäudes um 0,04 mm/a/m mithilfe der Persistent-Scatterer-Interferometrie. Die Ergebnisse wurden mit Daten der deutschen Satelliten TerraSAR-X und TanDEM-X erzielt