Sentinel-1 instruments status and product performance update for 2023

The Copernicus program, and particularly Sentinel-1, are among the largest Earth Observation SAR data providers, serving an ever-increasing number of services, users, and applications. A key aspect of the program is the constant provision of quality data, which requires long term engagement to carefully monitor, preserve, and even improve the system performances. These tasks are mainly carried out within the SAR Mission Performance Cluster (SAR-MPC), an international consortium of SAR experts in charge of the continuous monitoring of the Sentinel-1 instruments status and of the L1 and L2 products quality. This paper provides an update on the monitoring and the actions implemented by the SAR-MPC during 2022 and 2023. The analysis regards the monitoring of the instrument status, the evaluation of the instrument radiometric and geometric accuracy, and the updates of the S-1 Instrument Processing Facility

Uncertainties and Perspectives on Forest Height Estimates by Sentinel-1 Interferometry

Forest height is a key parameter in forestry. SAR interferometry (InSAR) techniques have been extensively adopted to retrieve digital elevation models (DEM) to give a representation of the continuous variation of the Earth’s topography, including forests. Unfortunately, InSAR has been proven to fail over vegetation due to low coherence values; therefore, all phase unwrapping algorithms tend to avoid these areas, making InSAR-derived DEM over vegetation unreliable. In this work, a sensitivity analysis was performed with the aim of properly initializing the relevant operational parameters (baseline and multilooking factor) to maximize the theoretical accuracy of the height difference between the forest and reference point. Some scenarios were proposed to test the resulting “optimal values”, as estimated at the previous step. A simple model was additionally proposed and calibrated, aimed at predicting the optimal baseline value (and therefore image pair selection) for height uncertainty minimization. All our analyses were conducted using free available data from the Copernicus Sentinel-1 mission to support the operational transfer into the forest sector. Finally, the potential uncertainty affecting resulting height measures was quantified, showing that a value lower than 5 m can be expected once all user-dependent parameters (i.e., baseline, multilooking factor, temporal baseline) are properly tuned

Automated global water mapping based on wide-swath orbital synthetic-aperture radar

This paper presents an automated technique which ingests orbital synthetic-aperture radar (SAR) imagery and outputs surface water maps in near real time and on a global scale. The service anticipates future open data dissemination of water extent information using the European Space Agency's Sentinel-1 data. The classification methods used are innovative and practical and automatically calibrated to local conditions per 1 × 1° tile. For each tile, a probability distribution function in the range between being covered with water or being dry is established based on a long-term SAR training dataset. These probability distributions are conditional on the backscatter and the incidence angle. In classification mode, the probability of water coverage per pixel of 1 km × 1 km is calculated with the input of the current backscatter – incidence angle combination. The overlap between the probability distributions of a pixel being wet or dry is used as a proxy for the quality of our classification. The service has multiple uses, e.g. for water body dynamics in times of drought or for urgent inundation extent determination during floods. The service generates data systematically: it is not an on-demand service activated only for emergency response, but instead is always up-to-date and available. We validate its use in flood situations using Envisat ASAR information during the 2011 Thailand floods and the Pakistan 2010 floods and perform a first merge with a NASA near real time water product based on MODIS optical satellite imagery. This merge shows good agreement between these independent satellite-based water products

Разработка программного приложения для расчета технических характеристик бортового радиолокационного комплекса для мониторинга земной поверхности и океанов

Целью работы является разработка web-приложения под рабочим названием "Расчет характеристик БРЛК" для расчета основных характеристик бортового радиолокатора с синтезированной апертурой, позволяющего быстро производить множественные, трудоемкие расчеты характеристик радиолокатора и представлять их в удобном графическом виде. Перспективным направлением дальнейшей исследовательской работы является доработка созданного web-приложения так, чтобы оно выводило графическое отображение полета спутника по орбите. Также представляется возможным сделать "привязку" приложения к корпоративной электронной почте сотрудника, для возможности получения по требованию сотрудника расчетных данных.The aim of the work is to develop a web application under the working title "Calculation of the characteristics of the BRLC" for calculating the main characteristics of the onboard radar with a synthesized aperture, which allows you to quickly make multiple, time-consuming calculations of the characteristics of the radar and present them in a convenient graphical form. A promising direction for further research work is to refine the created web application so that it displays a graphical display of the satellite's flight in orbit. It is also possible to make a" binding " of the application to the employee's corporate e-mail, to be able to receive the calculated data at the request of the employee

Monitoring von Hangbewegungen mit InSAR Techniken im Gebiet Ciloto, Indonesien

In this doctoral thesis, the InSAR techniques are applied to detect the ground movement phenomenon and to assess the InSAR result geometrically in the Ciloto area, Indonesia. Mainly, one of those techniques, the SB-SDFP algorithm, overcomes the limitations of conventional InSAR in monitoring rural and agricultural areas and can observe extremely slow landslides. The InSAR strategy is positively known as a promising option to detect and quantify the kinematics of active landslides on a large areal scale. To minimize the bias of the InSAR displacement result, the correction of the tropospheric phase delay was carried out in a first step. This procedure is demonstrated in experiments both in the small study area in Ciloto and in a larger area. The latter is an area located in Northern Baja California, Mexico and is dominated by tectonic activity as well as groundwater-induced subsidence. A detailed investigation of the slope movement's behavior in the Ciloto district was conducted utilizing multi-temporal and multi-band SAR data from ERS1/2 (1996-1999), ALOS PALSAR (2007-2009) and Sentinel-1 (2014-2018) satellites. The region was successfully identified as a permanent active landslide prone area, especially in the vicinity of the Puncak Pass and Puncak Highway. The full 3D velocity field and the displacement time series were estimated using the inversion model. The velocity rate was classified from extremely slow to slow movement. To comprehend the landslide's behavior, a further examination of the relationship between InSAR results and physical characteristics of the area was carried out. For the long period of a slow-moving landslide, the relationship between precipitation and displacement trend shows a weak correlation. It is concluded that the extremely slow to slow deformation is not directly influenced by the rainfall intensity, yet it effectuates the subsurface and the groundwater flow. The run-off process with rainfall exceeding a soil's infiltration capacity was suspected as the main driver of the slow ground movement phenomenon. However, when analyzing rapid and extremely rapid landslide events at Puncak Pass, a significant increase in the correlation coefficient between precipitation and displacement rate could be observed.In dieser Doktorarbeit wird die Anwendung von erweiterten Verarbeitungsstrategien von InSAR Daten zur Erkennung und geometrischen Bewertung der Bodenbewegungen im Ciloto - Indonesien dargestellt. Dieser Ansatz überwindet die Beschränkungen konventioneller SAR-Interferometrie und ermöglicht sowohl ein kontinuierliches Monitoring dieses landwirtschaftich geprägten Gebietes als auch die Erfassung extrem langsamer Hangrutschungen. Um eine Verzerrung der InSAR Deformationsergebnisse zu minimieren, wurde zunächst eine Korrektur der troposphärischen Phase durchgeführt. Diese neuartige Strategie wird sowohl im Forschungsgebiet Ciloto als auch an einem größeren Gebiet demonstriert. Bei letzterem handelt es sich um einen Küstenstreifen im nördlichen Niederkalifornien, Mexiko, welcher durch hohe tektonische Aktivität und grundwasserinduzierte Landsetzungen charakterisiert ist. Die detaillierte Untersuchung des Verhaltens von Hangrutschungen im Ciloto erfolgte durch die Verarbeitung multi-temporaler SAR-Daten unter Nutzung verschiedener Frequenzbänder, darunter ESR1/2 (1996-1999), ALOS PALSAR (2007-2009) und Sentinel-1 (2014-2018) Daten. Die Region konnte erfolgreich als permanent aktives Hangrutschungsgebiet identifiziert werden, wobei der Puncak Pass und der Puncak Highway ein erhöhtes Gefahrenpotential aufweisen. Ein 3D- Geschwindig-keitsfeld der Deformation und die zugehörigen Zeitreihen wurden mit dem Inversionsmodell berechnet. Die Geschwindigkeitsrate wurde als langsam bis extrem langsam klassifiziert. Um das dynamische Verhalten der Hangrutschung zu verstehen wurde, in einer weiteren Untersuchung die Beziehung zwischen dem InSAR-Ergebnis und den physikalischen Begebenheiten im Forschungsgebiet analysiert. Es wird der Schluss gezogen, dass die langsame bis extrem langsame Verformung nicht direkt von der Niederschlagsintensität beeinflusst wird, diese sich aber auf den Untergrund und die Grundwasserströmung auswirkt. Es wird vermutet, dass der Oberflächenablauf, welcher die Infiltrationskapazität des Bodens übersteigt, ausschlaggebend für das Phänomen der langsamen Bodenbewegung ist. Für die schnellen und extrem schnellen Hangrutschungen jedoch konnte eine signifikante Erhöhung des Korrelationskoeffizienten zwischen Niederschlag und Verschiebungsrate bei Untersuchungen der Hangrutschung am Puncak-Pass nachgewiesen werden

Soil Moisture Estimation for landslide monitoring: A new approach using multi-temporal Synthetic Aperture RADAR data

This study explores the utility of the Spotlight2 X-band Synthetic Aperture Radar product developed by the Italian Space Agency for use in multi-temporal estimation of soil moisture in a landslide monitoring context, using a time series of monthly images of the Hollin Hill Landslide Observatory – North Yorkshire, UK. The study shows the complexity of surface soil moisture at an active landslide, using high resolution in situ soil moisture data. This in situ data is also used for ground truthing the soil moisture estimations from the SAR data. The study shows the limitations of inter-and intra-sensor calibration within the Cosmo-SkyMed array and contextualises this problem within the current research climate where SAR imagery is increasingly being created using multi-satellite constellation, while being used, increasingly, by environmental scientists rather than remote sensing specialists

A Fusion of Remotely Sensed Data to Map the Impervious Surfaces of Growing Cities of Punjab, Pakistan

Urban population is expected to exceed 70% of the world’s total by the middle of the 21st century. Thus, growth in number as well as the sizes of the cities are certain in the near future. The urbanization rates will be much higher in the developing countries than the developed. Such phenomena are accompanied by conversion of land cover from its natural use to built up environment to accommodation growing population. Built up surfaces include road networks, buildings, parking lots and pathways. They are permanently impervious and hydrologically active surfaces. Large volume and discharges of runoff characterize impervious surfaces with frequently occurring flash floods in cities. Besides, proliferating impervious surface is responsible for increasing surface temperature due to Urban Heat Island effect and are the major Nonpoint Source pollutants in the receiving water bodies. At the face of climate change, the consequence of urbanization and increasing impervious surface is exacerbating. Therefore, for sustainable development, spatial and temporal expansion information of impervious surfaces is essential to the planners. Thus, the overall objective of this thesis is to map the impervious surfaces and estimate the expansion rates in the growing cities of Punjab, Pakistan in the last four years. In this thesis, combined and individual datasets from Sentinel-1 and Sentinel-2 satellites were used to extract the amounts of impervious surfaces at city scale and to estimate the expansion rates of various cities of Punjab, Pakistan. The study period for the change analysis is from 2015-2021 based on the availability of satellite imagery. The satellite imageries were obtained from the Copernicus Services Data Hub. Information on different land covers in the form of reflectance, backscattering signal, and texture from a wide range of electromagnetic spectrum of light derived from Sentinels were used to map impervious surfaces. The following land covers were defined: barren soil, vegetation, water, and built-up surface. Four classification models were created from Random Forest algorithms and trained with land covers samples from Google Earth high resolution imagery. The 10 cities considered in this study were among the 50 cities extensively studied by the Urban Unit Pakistan covering the dynamics of Punjab in terms of urban extent, population distribution, area, and expansion. They make up the 21st largest cities in the province as well as represent spatial distribution from north to south. They include various climatic conditions ranging from arid in Multan to humid subtropical in Rawalpindi. They also represent different topographies of the cities such as plain and hilly. Validation samples for each land cover were also obtained from high resolution images to assess the classified land cover maps. Apart from validation of classified maps, quantitative comparison of resultant impervious surfaces was also conducted. For the purpose, the study used published datasets from Atlas of Urban Expansion and the Copernicus Land Service. If available, administrative boundaries of the cities were also used to define the urban extent. For other cities, coordinates were manually defined. The combined Sentinel datasets were able to improve the overall accuracy and kappa coefficient of the classified maps by up to 11% and 7% respectively. McNemar test revealed that the models trained with fused data performed better than the models trained with optical alone data for land cover classification. The cities were expanding at rates ranging from 0.5% to 2.5% annually. The highest rate was encountered in Rawalpindi-Islamabad which is also the capital city of Pakistan. At least for one of the study years (2015/6 or 2020/21) the area was being overestimated by the single optical data. For instance, the optical data overestimated the impervious area of Lahore by a factor of 1.12 times while that of Bahawalpur by a factor of 1.2 times. The incorrect original results attributed to misclassification of barren soil as built up. This conclusion emphasized that additional information on backscattering signal and texture derived from radar image aided to reduce the misclassified bare soil pixels into built up. Spectrum plots also showed that sigma db and variance bands from radar image added a distinct feature to the classifier to distinguish built-up surfaces from other non built-up surfaces. The built-up surface had the highest value in backscatter signals and variance texture bands. This study emphasized the usefulness of combining freely available remote sensing datasets for updating the city scale impervious surfaces cover information in developing countries. The contribution includes the assessment of suitability of combined Sentinel datasets to map the impervious surface at city scale. It also evaluates the rate of expansion of the cities. In conclusion, the combined radar and optical data can enhance the accuracy of classified maps for impervious cover mapping with benefits in complex topographies to update impervious surface information in developing countries. The results from this study could be used as inputs in hydrological and runoff models for urban studies. Other useful applications could be service allocation, drainage improvement, location determination for low impact development (LID) structures, stormwater utility fee determinations, flood control, and pollutants removal from runoff