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  • 1
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    First In-Orbit Experience of TerraSAR-X Flight Dynamics Operations (2007)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: TerraSAR-X is an advanced synthetic aperture radar satellite system for scientific and commercial applications that is realized in a public-private partnership between the German Aerospace Center (DLR) and the Astrium GmbH. TerraSAR-X was launched at June 15, 2007 on top of a Russian DNEPR-1 rocket into a 514 km sun-synchronous dusk-dawn orbit with an 11-day repeat cycle and will be operated for a period of at least 5 years during which it will provide high resolution SAR-data in the X-band. Due to the objectives of the interferometric campaigns the satellite has to comply to tight orbit control requirements, which are formulated in the form of a 250 m toroidal tube around a pre-flight determined reference trajectory (see [1] for details). The acquisition of the reference orbit was one of the main and key activities during the Launch and Early Orbit Phase (LEOP) and had to compensate for both injection errors and spacecraft safe mode attitude control thruster activities. The paper summarizes the activities of GSOC flight dynamics team during both LEOP and early Commissioning Phase, where the main tasks have been 1) the first-acquisition support via angle-tracking and GPS-based orbit determination, 2) maneuver planning for target orbit acquisition and maintenance, and 3) precise orbit and attitude determination for SAR processing support. Furthermore, a presentation on the achieved results and encountered problems will be addressed.
    Keywords: Spacecraft Design, Testing and Performance
    Type: Proceedings of the 20th International Symposium on Space Flight Dynamics; NASA/CP-2007-214158
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    NASA TECHNICAL REPORTS
  • 2
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    Spaceborne Autonomous and Ground Based Relative Orbit Control for the TerraSAR-X/TanDEM-X Formation (2007)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: TerraSAR-X (TSX) and TanDEM-X (TDX) are two advanced synthetic aperture radar (SAR) satellites flying in formation. SAR interferometry allows a high resolution imaging of the Earth by processing SAR images obtained from two slightly different orbits. TSX operates as a repeat-pass interferometer in the first phase of its lifetime and will be supplemented after two years by TDX in order to produce digital elevation models (DEM) with unprecedented accuracy. Such a flying formation makes indeed possible a simultaneous interferometric data acquisition characterized by highly flexible baselines with range of variations between a few hundreds meters and several kilometers [1]. TSX has been successfully launched on the 15th of June, 2007. TDX is expected to be launched on the 31st of May, 2009. A safe and robust maintenance of the formation is based on the concept of relative eccentricity/inclination (e/i) vector separation whose efficiency has already been demonstrated during the Gravity Recovery and Climate Experiment (GRACE) [2]. Here, the satellite relative motion is parameterized by mean of relative orbit elements and the key idea is to align the relative eccentricity and inclination vectors to minimize the hazard of a collision. Previous studies have already shown the pertinence of this concept and have described the way of controlling the formation using an impulsive deterministic control law [3]. Despite the completely different relative orbit control requirements, the same approach can be applied to the TSX/TDX formation. The task of TDX is to maintain the close formation configuration by actively controlling its relative motion with respect to TSX, the leader of the formation. TDX must replicate the absolute orbit keeping maneuvers executed by TSX and also compensate the natural deviation of the relative e/i vectors. In fact the relative orbital elements of the formation tend to drift because of the secular non-keplerian perturbations acting on both satellites. The goal of the ground segment is thus to regularly correct this configuration by performing small orbit correction maneuvers on TDX. The ground station contacts are limited due to the geographic position of the station and the costs for contact time. Only with a polar ground station a contact visibility is possible every orbit for LEO satellites. TSX and TDX use only the Weilheim ground station (in the southern part of Germany) during routine operations. This station allows two scheduled contact per day for the nominal orbit configuration, meaning that the satellite conditions can be checked with an interval of 12 hours. While this limitation is usually not critical for single satellite operations, the visibility constraints drive the achievable orbit control accuracy for a LEO formation if a ground based approach is chosen. Along-track position uncertainties and maneuver execution errors affect the relative motion and can be compensated only after a ground station contact.
    Keywords: Spacecraft Design, Testing and Performance
    Type: Proceedings of the 20th International Symposium on Space Flight Dynamics; NASA/CP-2007-214158
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    NASA TECHNICAL REPORTS
  • 3
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    Safe Switching of the GRACE Formation Using an Eccentricity/Inclination Vector Separation (2004)
    In:  Proceedings of the 18th International Symposium on Space Flight Dynamics : 11-15 October 2004, Munich, Germany
    Details
    Publication Date: 2020-02-12
    Type: info:eu-repo/semantics/conferenceObject
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  • 4
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    Lusi hydrothermal structure inferred through ambient vibration measurements (2018)
    In:  Marine and Petroleum Geology
    Details
    Publication Date: 2020-11-24
    Description: The spectacular Lusi mud eruption started in northeast Java, Indonesia, the 29th of May 2006 following a M6.3 strike slip seismic event. After the earthquake several mud pools aligned along a NE-SW direction appeared in the Sidoarjo district. The most prominent eruption site was named Lusi. Lusi is located ∼10 km to the NE of the northernmost cone of the Arjuno-Welirang volcanic complex with which it is connected by the Watukosek Fault System. In this study, we applied the HVSR method, which is a common tool used for site effect investigations as well as to infer buried structures and reconstruct sub-surface geology. The method is based on the ratio of the horizontal to vertical components of ground motion and it generally exhibits a peak corresponding to the fundamental frequency of the site. Spectral ratio results highlight a fundamental frequency band between 0.4 and 1.0 Hz in the Lusi neighborhood. We interpret these peaks as related to the velocity lithological contrast at depth between alluvial deposits and bluish grey clay. Our analysis also highlights the presence of a “depocenter”, characterized by fundamental frequency up to 0.3 Hz, which is interpreted as the subsidence caused by withdrawal of mud and fluids from depth (as also shown by the comparison of the HVSR results with gravimetry data). Moreover, in the area of the Lusi vent a broad-band frequency range is related to the Lusi conduit. In this paper, we show that detailed microtremor surveys could be used as a preliminary and fast approach to locate mud conduits with sufficient precision.
    Language: English
    Type: info:eu-repo/semantics/article
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  • 5
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    Temporal variations of seismic velocities from ambient noise: monitoring groundwater in the Maltese islands (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-09-18
    Description: The Maltese islands, approximately 314 km2 in area with a high population density, face high levels of water stress due to low amounts of rainfall and a dependence on groundwater abstraction. Until now, in-situ borehole readings have been the only method utilised to monitor the quantitative status of groundwater in the Maltese islands. This study investigates an innovative, cost-effective approach to groundwater monitoring in a small island environment by computing cross-correlations and autocorrelations of ambient seismic noise recorded on seismic networks of broadband and short-period stations in the Maltese islands. We compare the borehole readings of groundwater levels ranging from 0.28-3.39 m above mean sea level with the variations in seismic velocity (δv/v). We apply appropriate filters for the broadband and short-period stations of 0.1-1 Hz and 0.3-3 Hz, respectively. The results demonstrate clear seasonal changes in the seismic velocities, which can be correlated with changes in groundwater levels in nearby boreholes. We find that variations of the δv/v from autocorrelations are more pronounced than the cross-correlation, with maximum seismic velocity changes of ~2% and ~0.3% respectively. The quality of the δv/v deteriorates at longer interstation distances where seasonal variations are less noticeable. Presumably, this is because longer interstation paths tend to traverse more complex geology, different types of aquifers, or even the sea.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 6
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    Overview of ORFEUS Data Services and Activities to Integrate Access to Seismic Waveform Data in the Euro-Mediterranean Region (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-12-11
    Description: ORFEUS (Observatories and Research Facilities for European Seismology, orfeus-eu.org) coordinates and promotes seismology in the Euro-Mediterranean region through harmonized collection, archival and distribution of seismic waveform data & metadata, based on services and products managed at national level by more than 60 participating seismological Institutions. ORFEUS is one of the founding members of EPOS Seismology (www.epos-eu.org/tcs/seismology) and its services are largely integrated in the EPOS Data Access Portal (www.ics-c.epos-eu.org). ORFEUS comprises: (i) the European Integrated waveform Data Archive (EIDA; orfeus-eu.org/data/eida); (ii) the European Strong-Motion databases (orfeus-eu.org/data/strong); and iii) the recently established group representing the community of European mobile pools, including amphibian instrumentation (orfeus-eu.org/data/mobile). Currently, ORFEUS facilitates access to the waveforms acquired by more than 18,000 stations including dense temporary experiments (e.g., AlpArray, AdriaArray), with strong emphasis on open, high-quality data. Access to data and products is ensured through state-of-the-art technologies - with strong emphasis on web services - clear policies and licenses, and acknowledging the crucial role played by data providers. Significant efforts are underway to enhance the existing services to tackle the challenges posed by the Big Data Era and the needs of computational seismology, and to actively encourage interoperability and integration of multidisciplinary datasets in geoscience workflows. ORFEUS also implements community services that include software and travel grants, webinars, workshops, editorial initiatives and discussion forums. ORFEUS activities are assessed and improved through the interaction with a User Advisory Group, which comprises European Earth scientists with expertise on a broad range of disciplines.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 7
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    Status and Outlook of ORFEUS Data Services, Products and Activities to Coordinate Access to Seismic Waveform Data in the Euro-Mediterranean Region and Beyond (2024)
    In:  Abstracts
    Details
    Publication Date: 2024-05-03
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 8
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    Catalogo Macrosismico dei Terremoti Etnei dal 1832 al 2005 (2008)
    Details
    Publication Date: 2021-03-01
    Description: La necessità di un catalogo di terremoti specifico per l'Etna deriva dal fatto che il Catalogo Parametrico dei Terremoti Italiani CPTI non consente una caratterizzazione di dettaglio della sismicità a scala del vulcano in quanto riporta solo gli eventi principali selezionati in base a soglie energetiche e finestre spazio-temporali. La frequente sismicità dell'area è eccezionalmente documentata da un'ampia base di dati storici che a partire dal 1800 "rendicontano" con continuità e dovizia di particolari i fenomeni sismici e vulcanici all'Etna. La compilazione del Catalogo Parametrico dei Terremoti Etnei passa attraverso l'utilizzo di questo patrimonio informativo - circa 200 fonti "primarie" analizzate tra studi, relazioni e bollettini - e giunge a definire un quadro completo ed omogeneo sulla sismicità locale negli ultimi 170 anni. È a partire da questo set di dati che si rende possibile lo studio delle sequenze sismiche anche in relazione alle diverse fasi di attività vulcanica, dei meccanismi di rilascio sismico delle faglie attive che attraversano le aree urbanizzate, cioè in definitiva delle relazioni tra processi geodinamici locali e meccanismi eruttivi. Il catalogo, nella versione aggiornata dal 1832 al 2005, riporta 1783 terremoti suddivisi in eventi principali e repliche, dei quali 177 al di sopra della soglia del danno. Per tutti gli eventi è disponibile la base dati di intensità espressa secondo la Scala Macrosismica Europea 1998; complessivamente l'archivio macrosismico contiene 8422 osservazioni al sito. Ogni terremoto è riportato con i seguenti parametri: localizzazione ed intensità epicentrale, magnitudo macrosismica, classe di qualità del dato macrosismico e, ove possibile, struttura sismogenetica cui è associato. Dagli anni '70 in poi sono disponibili anche magnitudo e profondità strumentali. Il catalogo ed il relativo database delle osservazioni macrosismiche è disponibile in rete in formato semplificato. La versione completa, che consente interrogazioni complesse e supporta mappe interattive, è scaricabile dal sito e installabile su PC (solo per Windows).
    Description: Published
    Description: 5.1. TTC - Banche dati e metodi macrosismici
    Description: open
    Keywords: osservazioni Macrosismiche, Terremoti etnei ; 04. Solid Earth::04.06. Seismology::04.06.05. Historical seismology ; 05. General::05.02. Data dissemination::05.02.02. Seismological data
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: web product
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  • 9
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    Il terremoto di Palermo del 6 settembre 2002: effetti macrosismici (2012)
    Istituto Nazionale di Geofisica e Vulcanologia
    Details
    Publication Date: 2021-03-01
    Description: On September 6, 2002, at 01:21 GMT, the western part of the Tyrrhenian coast of Sicily was hit by an earthquake of magnitude ML = 5.6, representing the mainshock of a seismic sequence of roughly 500 earthquakes recorded in about one month. The event, although characterized by a moderate magnitude and located some forty kilometres offshore, produced relevant macroseismic effects in the Palermo area. A macroseismic survey was carried out soon after the earthquake with the aim of defining, for Civil Protection purposes, the damage scenario over a territory which is densely urbanised. In all, 134 localities were investigated. Damage generally depended on the high vulnerability of the buildings both for problems related to the old age - as is the case of the Palermo historical centre - and for peculiar unfavourable conditions due to site effects, particularly in some quarters of the city and in the nearby locality of Ficarazzi. Damage to masonry consisted of falling plaster, failure of corner walls, diagonal cracks in walls and widening of previous fissures. Some degraded buildings, almost abandoned and with evident lack of maintenance, suffered partial structural failure of roofs and floors. As regards reinforced concrete (RC) frame buildings, several edifices with 5-10 storeys suffered cracks in partitions and infill walls, sometimes with failure of these elements, and falling plaster. Fine cracks in beams of frames have also been observed, but without determining significant structural problems. In general, damage affects the lowest storeys of the RC frame buildings. According to the European Macroseismic Scale 1998, the maximum value of intensity, 6, was assigned to Palermo and Ficarazzi. The earthquake has also provoked effects on natural surroundings. Two types of phenomena have been detected: (i) hydrological effects and (ii) slope instability processes. The most relevant was the landslide which occurred near the village of Cerda, 60 km from the epicentre.
    Description: Published
    Description: 1-15
    Description: 1.11. TTC - Osservazioni e monitoraggio macrosismico del territorio nazionale
    Description: N/A or not JCR
    Description: open
    Keywords: Palermo ; terremoto 2002 ; macrosismica ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 10
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    Forecasting macroseismic scenarios through anisotropic attenuation: a Bayesian approach (2011)
    Details
    Publication Date: 2021-03-01
    Description: In this work we aim at two objects: quantifying, by a binomial-beta probabilistic model, the uncertainty involved in the assessment of the intensity decay, an ordinal quantity often incorrectly treated as real variable, and, given the finite dimension of the fault, modelling non-symmetric decays but exploiting information collected from previous studies on symmetric cases. To this end we transform the plane so that the ellipse having the fault length as maximum axis is changed into a circle with fixed diameter. We start from an explorative analysis of a set of macroseismic fields representative of the Italian seismicity among which we identify three different decay trends by applying a hierarchical clustering method. Then we focus on the exam of the seismogenic area of Etna volcano where some fault structures are well recognizable as well as the anisotropic trend of the attenuation. As in volcanic zones the seismic attenuation is much quicker than in other zones, we first shrink and then transform the plane so that the decay becomes again symmetric. Following the Bayesian paradigm we update the model parameters and associate the estimated values of the intensity at site with the corresponding locations in the original plane. Backward validation and comparison with the deterministic law are also presented.
    Description: This work was funded by the Italian Dipartimento della Protezione Civile in the frame of the 2007-2009 Agreement with Istituto Nazionale di Geofisica e Vulcanologia (INGV) - Project V4 FLANK Volcanology.
    Description: Published
    Description: Universidad Carlos III de Madrid, Colmenarejo Campus, on July 5th-8th, 2010
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: open
    Keywords: anisotropy ; Bayesian inference ; seismic attenuation ; Etna volcano ; Italy ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Extended abstract
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