scholarly journals Quantifying Horizontal and Vertical Movements in Ho Chi Minh City by Sentinel-1 Radar Interferometry

2020 ◽  
Author(s):  
Dinh Ho Tong Minh ◽  
Yen-Nhi NGO ◽  
Thu Trang Lê ◽  
Trung Chon Le ◽  
Hong Son Bui ◽  
...  
Keyword(s):  
Time Series ◽  
Large Scale ◽  
European Space Agency ◽  
Ground Subsidence ◽  
Ho Chi Minh City ◽  
Vertical Movements ◽  
Space Agency ◽  
Permanent Scatterers ◽  
The City ◽  
East West

Ho Chi Minh City (HCMC), the most populous city and the economic center of Viet Nam, has faced ground subsidence in recent decades. This work aims at providing an unprecedented spatial extent coverage of the subsidence in HCMC in both horizontal and vertical components using Interferometric Synthetic Aperture Radar (InSAR) time series. For this purpose, an advanced InSAR technique PSDS (Permanent Scatterers and Distributed Scatterers) was applied to two big European Space Agency (ESA) Sentinel-1 datasets composed of 96 ascending and 202 descending images, acquired from 2014 to 2020 over HCMC area. A time series of 33 Cosmos SkyMED images was also used for comparison purpose. The combination of ascending and descending satellite passes allows the decomposition of the light of sight velocities into horizontal East-west and vertical components. By taking into account the presence of the horizontal East-west movement, our finding indicates that the precision of the decomposed vertical velocity can be improved up to 3 mm/year for Sentinel-1 data. The obtained results revealed that subsidence is most severe in areas along the Sai Gon river in the northwest-southeast axis and the southwest of the city with the maximum value up to 80 mm/year, consistent with findings in the literature. The magnitude of horizontal East-West velocities is relatively small and a large-scale westward motion can be observed in the northwest of the city at a rate of 2-5 mm/year. Together, these results reinforced the remarkable suitability of ESA's Sentinel-1 SAR for subsidence applications even for non-Europe countries such as Vietnam and Southeast Asia.

scholarly journals Subsidence Monitoring of Fill Area in Yan’an New District Based on Sentinel-1A Time Series Imagery

2021 ◽  
Vol 13 (15) ◽  
pp. 3044
Author(s):  
Mingjie Liao ◽  
Rui Zhang ◽  
Jichao Lv ◽  
Bin Yu ◽  
Jiatai Pang ◽  
...  
Keyword(s):  
Time Series ◽  
Large Scale ◽  
Ground Deformation ◽  
Dynamic Change ◽  
Deformation Monitoring ◽  
Chinese Loess Plateau ◽  
Ground Subsidence ◽  
Shanxi Province ◽  
Environment Change ◽  
Loess Area

In recent years, many cities in the Chinese loess plateau (especially in Shanxi province) have encountered ground subsidence problems due to the construction of underground projects and the exploitation of underground resources. With the completion of the world’s largest geotechnical project, called “mountain excavation and city construction,” in a collapsible loess area, the Yan’an city also appeared to have uneven ground subsidence. To obtain the spatial distribution characteristics and the time-series evolution trend of the subsidence, we selected Yan’an New District (YAND) as the specific study area and presented an improved time-series InSAR (TS-InSAR) method for experimental research. Based on 89 Sentinel-1A images collected between December 2017 to December 2020, we conducted comprehensive research and analysis on the spatial and temporal evolution of surface subsidence in YAND. The monitoring results showed that the YAND is relatively stable in general, with deformation rates mainly in the range of −10 to 10 mm/yr. However, three significant subsidence funnels existed in the fill area, with a maximum subsidence rate of 100 mm/yr. From 2017 to 2020, the subsidence funnels enlarged, and their subsidence rates accelerated. Further analysis proved that the main factors induced the severe ground subsidence in the study area, including the compressibility and collapsibility of loess, rapid urban construction, geological environment change, traffic circulation load, and dynamic change of groundwater. The experimental results indicated that the improved TS-InSAR method is adaptive to monitoring uneven subsidence of deep loess area. Moreover, related data and information would provide reference to the large-scale ground deformation monitoring and in similar loess areas.

scholarly journals Persistent Scatterer Interferometry of Sentinel-1 time series to detect ground subsidence in the city of Recife, Brazil

2020 ◽  
Vol 10 (1) ◽  
pp. 1
Author(s):  
Enton Bedini
Keyword(s):  
Time Series ◽  
Ground Subsidence ◽  
Persistent Scatterer Interferometry ◽  
Persistent Scatterer ◽  
Radar Imagery ◽  
Long Time ◽  
Satellite Radar ◽  
Surrounding Areas ◽  
Satellite Radar Imagery ◽  
The City

Persistent Scatterer Interferometry (PSI) analysis of Sentinel-1 time series was carried out to detect ground subsidence in the city of Recife, Brazil. The dataset consisted of sixty-eight Sentinel-1A Interferometric Wide (IW) Single Look Complex (SLC) images of the time period April 2017 – September 2019. The images were acquired in descending orbit in VV (vertical transmitting, vertical receiving) polarization. The results of the PSI analysis show that in the city of Recife occur several ground subsidence areas. The largest ground subsidence area occurs between the neighborhoods of Afogados, Torrŏes and Cordeiro. The subsidence rates in this area range from few mm/year up to -15 mm/year. This ground subsidence could be a result of groundwater extraction or of subsidence processes in urbanized reclaimed lands. Similar but smaller ground subsidence areas occur in several localities in Recife. In some cases, subsidence with rates of up to -25 mm/year is noted in small zones where new buildings have been constructed in the last decade. This should be due to ground settlement processes, taking a long time due to the particular soils and geology of the locality. This study can serve as a first contribution for further research on the ground subsidence hazard in the city of Recife and the surrounding areas by means of satellite radar imagery.

scholarly journals Extraction of Urban Information for Seismic Hazard and Risk Assessment in Lima, Peru Using Satellite Imagery

2013 ◽  
Vol 8 (2) ◽  
pp. 328-345 ◽  
Author(s):  
Masashi Matsuoka ◽  
◽  
Hiroyuki Miura ◽  
Saburoh Midorikawa ◽  
Miguel Estrada ◽  
...  
Keyword(s):  
Time Series ◽  
Large Scale ◽  
Surface Model ◽  
Building Inventory ◽  
Hazard And Risk ◽  
Hazard And Risk Assessment ◽  
Landsat Satellite ◽  
Time Series Images ◽  
The City ◽  
Area Data

Lima City, Peru, is, like Japan, on the verge of a strike by a massive earthquake. Building inventory data for the city need to be created for earthquake damage estimation, so the city was subjected to the extraction of spatial distribution of building age from Landsat satellite time-series images and an assessing building height from ALOS/PRISM images. Interband calculation of Landsat time-series images gives various indices relevant to land covering. The transition of indices was evaluated to clarify urban sprawl taking place in the northern, southern, and eastern parts of Lima City. Built-up area data were created for buildings by age. The height of large-scale mid-to-highrise buildings was extracted by applying spatial filtering for a DSM (Digital Surface Model) generated from stereovision PRISM images. As a result, buildings with a small square measure, color similar to that of their surroundings, or complicated shapes turned out to be difficult to detect.

scholarly journals Six years of total ozone column measurements from SCIAMACHY nadir observations

2009 ◽  
Vol 2 (1) ◽  
pp. 87-98 ◽  
Author(s):  
C. Lerot ◽  
M. Van Roozendael ◽  
J. van Geffen ◽  
J. van Gent ◽  
C. Fayt ◽  
...  
Keyword(s):  
Cross Sections ◽  
Total Ozone ◽  
Large Scale ◽  
European Space Agency ◽  
Data Sets ◽  
Data Set ◽  
Ozone Data ◽  
Space Agency ◽  
German Aerospace ◽  
The Impact

Abstract. Total O3 columns have been retrieved from six years of SCIAMACHY nadir UV radiance measurements using SDOAS, an adaptation of the GDOAS algorithm previously developed at BIRA-IASB for the GOME instrument. GDOAS and SDOAS have been implemented by the German Aerospace Center (DLR) in the version 4 of the GOME Data Processor (GDP) and in version 3 of the SCIAMACHY Ground Processor (SGP), respectively. The processors are being run at the DLR processing centre on behalf of the European Space Agency (ESA). We first focus on the description of the SDOAS algorithm with particular attention to the impact of uncertainties on the reference O3 absorption cross-sections. Second, the resulting SCIAMACHY total ozone data set is globally evaluated through large-scale comparisons with results from GOME and OMI as well as with ground-based correlative measurements. The various total ozone data sets are found to agree within 2% on average. However, a negative trend of 0.2–0.4%/year has been identified in the SCIAMACHY O3 columns; this probably originates from instrumental degradation effects that have not yet been fully characterized.

Dayside Magnetopause Reconnection and Flux Transfer Events: BepiColombo Earth-Flyby

2021 ◽  
Author(s):  
Wei-Jie Sun ◽  
James Slavin ◽  
Rumi Nakamura ◽  
Daniel Heyner ◽  
Johannes Mieth
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
European Space Agency ◽  
Flux Rope ◽  
Transfer Event ◽  
Flux Transfer Events ◽  
Space Agency ◽  
Flux Ropes ◽  
Flux Transfer ◽  
Magnetospheric Multiscale Mission

<p>BepiColombo is a joint mission of the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) to the planet Mercury. The BepiColombo mission consists of two spacecraft, which are the Mercury Planetary Orbiter (MPO) and Mercury Magnetospheric Orbiter (Mio). The mission made its first planetary flyby, which is the only Earth flyby, on 10 April 2020, during which several instruments collected measurements. In this study, we analyze MPO magnetometer (MAG) observations of Flux Transfer Events (FTEs) in the magnetosheath and the structure of the subsolar magnetopause near the  flow stagnation point. The magnetosheath plasma beta was high with a value of ~ 8 and the interplanetary magnetic field (IMF) was southward with a clock angle that decreased from ~ 100 degrees to ~ 150 degrees.  As the draped IMF became increasingly southward several of the flux transfer event (FTE)-type flux ropes were observed. These FTEs traveled southward indicating that the magnetopause X-line was located northward of the spacecraft, which is consistent with a dawnward tilt of the IMF. Most of the FTE-type flux ropes were in ion-scale, <10 s duration, suggesting that they were newly formed. Only one large-scale FTE-type flux rope, ~ 20 s, was observed. It was made up of two successive bipolar signatures in the normal magnetic field component, which is evidence of coalescence at a secondary reconnection site. Further analysis demonstrated that the dimensionless reconnection rate of the re-reconnection associated with the coalescence site was ~ 0.14. While this investigation was limited to the MPO MAG observations, it strongly supports a key feature of dayside reconnection discovered in the Magnetospheric Multiscale mission, the growth of FTE-type flux ropes through coalescence at secondary reconnection sites.</p>

scholarly journals Unveiling the faint ultraviolet Universe

2021 ◽  
Author(s):  
A. Zanella ◽  
C. Zanoni ◽  
F. Arrigoni-Battaia ◽  
A. Rubin ◽  
A. F. Pala ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Large Scale ◽  
European Space Agency ◽  
Large Scale Structures ◽  
Space Agency ◽  
James Webb Space Telescope ◽  
Ram Pressure ◽  
Infrared Wavelengths ◽  
Scale Structures ◽  
Integral Field Spectrograph

AbstractWith this paper we participate to the call for ideas issued by the European Space Agency to define the Science Program and plan for space missions from 2035 to 2050. In particular we present five science cases where major advancements can be achieved thanks to space-based spectroscopic observations at ultraviolet (UV) wavelengths. We discuss the possibility to (1) unveil the large-scale structures and cosmic web in emission at redshift $\lesssim 1.7$ ≲ 1.7 ; (2) study the exchange of baryons between galaxies and their surroundings to understand the contribution of the circumgalactic gas to the evolution and angular-momentum build-up of galaxies; (3) constrain the efficiency of ram-pressure stripping in removing gas from galaxies and its role in quenching star formation; (4) characterize the progenitor population of core-collapse supernovae to reveal the explosion mechanisms of stars; (5) target accreting white dwarfs in globular clusters to determine their evolution and fate. These science themes can be addressed thanks to UV (wavelength range $\lambda \sim 90 - 350$ λ ∼ 90 − 350 nm) observations carried out with a panoramic integral field spectrograph (field of view $\sim \!1 \times 1$ ∼ 1 × 1 arcmin2), and medium spectral (R = 4000) and spatial ($\sim \!1^{\prime \prime } - 3^{\prime \prime }$ ∼ 1 ′ ′ − 3 ′ ′ ) resolution. Such a UV-optimized instrument will be unique in the coming years, when most of the new large facilities such as the Extremely Large Telescope and the James Webb Space Telescope are optimized for infrared wavelengths.

Combining ExoMars’ Ma_MISS and Drill data

2020 ◽  
Author(s):  
Alessandro Frigeri ◽  
Maria Cristina De Sanctis ◽  
Francesca Altieri ◽  
Simone De Angelis ◽  
Marco Ferrari ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Water Content ◽  
Large Scale ◽  
Mechanical Response ◽  
European Space Agency ◽  
Volcanic Rocks ◽  
Space Agency ◽  
Geophysical Imaging

<p>The ExoMars Rover and Surface Platform planned for launch in 2022 is a large international cooperation between the European Space Agency and Roscosmos with a scientific contribution from NASA.  Thales Alenia Space is the ExoMars mission industrial prime contractor. </p> <p>Besides sensors and instruments characterizing the surface at large scale, the ExoMars’ rover Rosalind Franklin payload features some experiments devoted specifically to the characterization of the first few meters of the Martian subsurface. These experiments are particularly critical for the main ExoMars objective of detecting traces of present or past life forms on Mars, which may have been preserved within the shallow Martian underground [1].</p> <p>Rosalind Franklin will be able to perform both non-invasive geophysical imaging of the underground [2] and subsurface <em>in situ</em> measurements thanks to the Drill unit installed on the rover. The Drill has been developed by Leonardo and its purposes are 1) to collect core samples to be analyzed in the Analytical Laboratory Drawer (ALD) onboard the Rover and 2) to drive the miniaturized spectrometer Ma_MISS within the borehole.   </p> <p>Ma_MISS (Mars Multispectral Imager for Subsurface Studies, [3]) will collect mineralogic measurements from the rocks exposed into the borehole created by the Drill with a spatial resolution of 120 μm down to 2 meters into the Martian subsurface.</p> <p>Rocks are composed of grains of minerals, and their reaction to an applied stress is related to the mechanical behavior of the minerals that compose the rock itself. The mechanical properties of a mineral depend mainly on the strength of the chemical bonds, the orientation of crystals, and the number of impurities in the crystal lattice.</p> <p>In this context, the integration of Ma_MISS measurements and drill telemetry are of great importance.  The mechanical properties of rocks coupled with their mineralogic composition provide a rich source of information to characterize the nature of rocks being explored by ExoMars rover’s drilling activity.</p> <p>Within our study, we are starting to collect telemetry recorded during the Drill unit tests on several samples ranging from sedimentary to volcanic rocks with varying degrees of weathering and water content.  In this first phase of the study, we focused our attention on the variation of torque and penetration speed between different samples, which have been found to be indicative of a particular type of rock or group of rocks and their water content.  </p> <p>We are planning to analyze the same rocks with the Ma_MISS breadboard creating the link between the mineralogy and the mechanical response of the Drill.      </p> <p>This will put the base for a more comprehensive and rich characterization of the <em>in situ</em> subsurface observation by Rosalind Franklin planned at Oxia Planum, Mars in 2023. </p> <p> </p> <p><strong>Acknowledgments: </strong>We thank the European Space Agency (ESA) for developing the ExoMars Project, ROSCOSMOS and Thales Alenia Space for rover development, and Italian Space Agency (ASI) for funding the Ma_MISS experiment (ASI-INAF contract n.2017-48-H.0 for ExoMars MA_MISS phase E/science).</p> <p> </p> <p><strong>References</strong></p> <p>[1] Vago et al., 2017. Astrobiology, 17 6-7. [2] Ciarletti et al., 2017. Astrobiology, 17 6-7. [3] De Sanctis et al., 2017. Astrobiology, 17 6-7.</p>

scholarly journals Gaia Data Release 2

2018 ◽  
Vol 616 ◽  
pp. A16 ◽  
Author(s):  
A. C. Lanzafame ◽  
E. Distefano ◽  
S. Messina ◽  
I. Pagano ◽  
A. F. Lanza ◽  
...  
Keyword(s):  
Time Series ◽  
European Space Agency ◽  
Magnetic Activity ◽  
Variable Stars ◽  
Stellar Rotation ◽  
Dynamo Action ◽  
Space Agency ◽  
Data Release ◽  
Flux Modulation ◽  
Two Populations

Context. Amongst the ≈5 × 105 sources identified as variable stars in Gaia Data Release 2 (DR2), 26% are rotational modulation variable candidates of the BY Dra class. Gaia DR2 provides their multi-band (G, GBP, and GRP) photometric time series collected by the European Space Agency spacecraft Gaia during the first 22 months of operations as well as the essential parameters related to their flux modulation induced by surface inhomogeneities and rotation. Aims. We developed methods to identify the BY Dra variable candidates and to infer their variability parameters. Methods. BY Dra candidates were pre-selected from their position in the Hertzsprung–Russel diagram, built from Gaia parallaxes, G magnitudes, and (GBP − GRP) colours. Since the time evolution of the stellar active region can disrupt the coherence of the signal, segments not much longer than their expected evolution timescale were extracted from the entire photometric time series, and period search algorithms were applied to each segment. For the Gaia DR2, we selected sources with similar periods in at least two segments as candidate BY Dra variables. Results were further filtered considering the time-series phase coverage and the expected approximate light-curve shape. Results. Gaia DR2 includes rotational periods and modulation amplitudes of 147 535 BY Dra candidates. The data unveil the existence of two populations with distinctive period and amplitude distributions. The sample covers 38% of the whole sky when divided into bins (HEALPix) of ≈0.84 square degrees, and we estimate that this represents 0.7–5% of all BY Dra stars potentially detectable with Gaia. Conclusions. The preliminary data contained in Gaia DR2 illustrate the vast and unique information that the mission is going to provide on stellar rotation and magnetic activity. This information, complemented by the exquisite Gaia parallaxes, proper motions, and astrophysical parameters, is opening new and unique perspectives for our understanding of the evolution of stellar angular momentum and dynamo action.

scholarly journals Global maps of Forel-Ule index, hue angle and Secchi disk depth derived from twenty-one years of monthly ESA-OC-CCI data

2020 ◽  
Author(s):  
Jaime Pitarch ◽  
Marco Bellacicco ◽  
Salvatore Marullo ◽  
Hendrik J. van der Woerd
Keyword(s):  
Time Series ◽  
Spatial Resolution ◽  
European Space Agency ◽  
Sensor Data ◽  
Secchi Disk ◽  
Secchi Disk Depth ◽  
The North ◽  
Space Agency ◽  
Free Data ◽  
Hue Angle

Abstract. We document the development and public release of a new dataset (1997–2018), consisting of global maps of the Forel-Ule index, hue angle and Secchi disk depth. Source data comes from the European Space Agency (ESA) Ocean Colour (OC) Climate Change Initiative (CCI), which is providing merged multi-sensor data from the mid-resolution sensors in operation at a specific time from 1997 to the present day. Multi-sensor satellite datasets are advantageous tools for ecological studies because they increase the probabilities of cloud-free data over a given region, as data from multiple satellites whose overpass times differ by a few hours are combined. Moreover, data merging from heritage and present satellites can expand the duration of the time series indefinitely, which allows the calculation of significant trends. Additionally, data are remapped consistently and analysis-ready for scientists. Also, the products described in this article have the exclusive advantage of being linkable to in-situ historic observations and thus enabling the construction of very long time series. Monthly data are presented at a spatial resolution of ~4 km at the equator and are available at PANGAEA, https://doi.org/10.1594/PANGAEA.904266 (Pitarch et al., 2019a). Two smaller and easier to handle test datasets have been produced from the former: a global dataset at 1 degree spatial resolution and another one for the North Atlantic at 0.25 degree resolution.

scholarly journals ASSESSING GROUND SUBSIDENCE PHENOMENA WITH PERSISTENT SCATTERER INTERFEROMETRY DATA IN WESTERN THESSALY, GREECE

2017 ◽  
Vol 50 (3) ◽  
pp. 1693 ◽  
Author(s):  
I. Ilia ◽  
C. Loupasakis ◽  
P. Tsangaratos
Keyword(s):  
European Space Agency ◽  
Research Area ◽  
Sar Interferometry ◽  
Ground Subsidence ◽  
Spatial And Temporal Patterns ◽  
Persistent Scatterer Interferometry ◽  
Subsidence Rate ◽  
Space Agency ◽  
Persistent Scatterer ◽  
The Mean

The main objective of the present study was to investigate ground subsidence in the wider area of Farsala, western Thessaly basin, by means of remote sensing techniques and to identify potential geo environmental mechanisms that contribute to the development of the observed surface fractures affecting the site. In this context, a set of Synthetic Aperture Radar (SAR) images, acquired in 1995-2003 by the European Space Agency (ESA) satellites ERS1 and ERS2 and processed with the Persistent Scatterer Interferometry (PSI) technique by the German Space Agency (DLR) during the Terrafirma project, were evaluated in order to investigate spatial and temporal patterns of deformation. Groundwater table levels of three water boreholes within the research area were processed providing the mean piezometric level drawdown and the mean annual drawdown rate. In addition, a quantitative comparison between the deformation subsidence rate and the thickness of the compressible sediments was also performed. The outcomes of the present study indicated a clear relationship in the subsidence deformation rate and the groundwater fluctuation and also a correlation between the depth of the bedrock and the deformation subsidence rate. Overall, the multitemporal SAR interferometry (DInSAR) data are proved as a valuable and suitable technique for increasing knowledge about the extent and the rate of the deformations in the current study area, proved to be affected with an increasing intensity. 

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