In recent years, small Synthetic Aperture Radar (SAR) satellite constellations have emerged as a viable solution due to their ease of design and relatively low launch costs. These next generation systems aim to meet the growing needs of the Differential Interferometric SAR (DInSAR) community, including high spatial resolution and temporal acquisition frequency. Nevertheless, despite their benefits, small satellites face drawbacks such as low power budgets and limited imaging capabilities, needing the exploration of new orbital configurations to meet specific mission objectives. Among these, mid-inclination orbits (MIOs) offer the unique advantage of enabling the retrieval of North-South surface displacements, overcoming a key limitation of conventional sun-synchronous orbits (SSOs). In this study, we analyze three SAR datasets acquired by Capella Space over the Campi Flegrei (CF) caldera (Italy), exploiting a 45° MIO. The presented results, validated against GNSS measurements, show a mean standard deviation of 3-4 mm between DInSAR and GNSS LOS-projected time series, while the uncertainty for the North South component is estimated to be less than 5 mm. Furthermore, we retrieve, for the first time, comprehensive North-South deformation products of the CF caldera, including both a high resolution map and displacement time series. These outcomes represent a precursor for the upcoming Italian SAR constellation NIMBUS, part of the IRIDE program, which will be launched in a similar MIO configuration and become operational during 2027.

We present an innovative Phase Unwrapping (PhU) method for multi-temporal, small baseline differential interferogram sequences that benefits from the Minimum Cost Flow (MCF) algorithm and the Compressive Sensing (CS) theory. The developed algorithm advances the Extended MCF (EMCF) method by (1) introducing a new approach for the temporal PhU operation and (2) enhancing the retrieval capability of the existing spatial PhU procedure. In particular, the temporal PhU exploits the sparsity of the phase gradient signal and efficiently searches for a minimum L1-norm solution in the temporal/perpendicular baseline plane with no need, unlike the EMCF method, of any Delaunay triangulation in this domain. Furthermore, the spatial PhU capitalizes on the obtained temporal solution and performs a multi-trial PhU operation of each interferogram by exploiting different cost functions; the final unwrapped interferograms are then obtained through a pixel-by-pixel weighted average of the unwrapped solutions retrieved in each trial. To evaluate the performance of the proposed algorithm, which is tailored to multi-look interferograms, we carry out a comparative analysis with the results of the original EMCF technique by using simulated and real SAR data. In particular, we process a SAOCOM-1 (L-band) SAR dataset acquired over the Stromboli Island, characterized by intense and fast deformation signals, to assess the algorithm effectiveness when dealing with challenging DInSAR interferogram sequences obtained from a limited number of SAR acquisitions. Subsequently, the performance of the proposed PhU approach is further investigated by processing two large Sentinel-1 (C-band) datasets acquired over the Stromboli Island and the Etna Volcano, both sites located in southern Italy. The obtained results clearly show the robustness and effectiveness of the developed technique in retrieving the detected displacement signals, even when characterized by fast and highly nonlinear behaviors.

We examine the 6 February 2023 Türkiye–Syria earthquakes using an extensive SAR dataset, addressing some limitations of previous studies. Large surface displacements caused significant loss of coherence in the Sentinel-1 Differential SAR Interferometry (DInSAR) results and prior analyses using Pixel Offset Tracking (POT) were limited by the poor azimuthal resolution of the available Sentinel-1 and ALOS-2 SAR images. For the first time, we present high-azimuth-resolution displacement measurements obtained thanks to the SAOCOM-1 sensors. Azimuth information is important considering that the main movements occurred were horizontal and, in some areas, with an important N-S component. By exploiting multi-frequency Sentinel-1, ALOS-2, and SAOCOM-1 SAR data and applying the DInSAR and POT techniques, where appropriate, we derived a detailed displacement field and retrieved an elaborated fault model comprising 22 segments; this model accurately characterizes the geometry and kinematics of the two main faults. Maximum slip reaches ∼15 m for both faults, and the total seismic moment corresponds to Mw 7.9. A finite-fault ShakeMap generated from this source model shows improved agreement with near-field ground motions relative to point-source formulations, while on-fault static stress changes identify low-slip areas that remained unbroken during rupture. The three-dimensional displacement field reveals a broad uplifted region and opposing horizontal motions between the two main ruptures, indicating distributed deformation within an interfault block that accommodates part of the Arabia–Anatolia convergence. This off-fault deformation has not been documented previously for the 2023 sequence and provides new constraints on strain partitioning and future seismic hazard along the East Anatolian Fault Zone.

On 1 September 2025, an Md 4.0 earthquake occurred within a seismic swarm at the Campi Flegrei caldera (Italy) and produced an unprecedented coseismic displacement. The resulting ground deformation, reaching approximately up to 4 cm, clearly outlined the directions of motion of a distinct crustal block and revealed an extensional displacement pattern. This deformation developed in an area where a geodetic anomaly (an uplift deficit, in particular), superimposed on the long-term background deformation field, was identified in previous studies. The spatial distribution and geometry of the deformation, retrieved through GNSS and DInSAR measurements, closely replicate those of the previously recognized anomaly in the Mt. Olibano–Accademia sector, thereby confirming the active involvement of this structural domain in the ongoing caldera dynamics. The sharp and well-defined displacement associated with the Md 4.0 earthquake allowed us to retrospectively identify smaller, analogous deformation episodes that occurred earlier in the unrest sequence but remained less distinct due to their limited amplitude. Altogether, these observations place new constraints on the mechanical behavior of the central–eastern sector of the Campi Flegrei caldera. They improve our understanding of how localized fracturing and faulting processes, within the shallow crust, interact with the broader deformation field driven by the current unrest phase.

Highlights What are the main findings? A novel and general method to optimize satellite formations for interferometry applications in a long-baseline scenario like the one foreseen by Harmony mission. Optimal configurations for both low- and high-latitude regions. What are the implications of the main findings? Mission Feasibility. The findings ensure that the Harmony mission can achieve its scientific objectives globally while maintaining safe and fuel-efficient satellite formations. Conceptual Design. The findings contribute to a multistatic SAR mission design, offering insights into the trade-offs between interferometric performance and formation stability.Highlights What are the main findings? A novel and general method to optimize satellite formations for interferometry applications in a long-baseline scenario like the one foreseen by Harmony mission. Optimal configurations for both low- and high-latitude regions. What are the implications of the main findings? Mission Feasibility. The findings ensure that the Harmony mission can achieve its scientific objectives globally while maintaining safe and fuel-efficient satellite formations. Conceptual Design. The findings contribute to a multistatic SAR mission design, offering insights into the trade-offs between interferometric performance and formation stability.Abstract In the framework of Harmony, the 10th ESA Earth Explorer mission, this paper presents a general methodology to optimize the formation parameters relevant to the single-pass, cross-track interferometry (XTI) configuration. The proposed method considers the requested height sensitivity and the maximum allowable temporal lag and derives the formation parameters for an optimal coverage over different ranges of latitudes by leveraging the relative eccentricity and inclination vector formalism. Our approach addresses the problem of interferometric coherence through the wavenumber support alignment method which is able to take into account the specific geometry of XTI in Harmony, which is a long-baseline multistatic configuration with large squint angles. The analysis is completed by an estimate of the propellant budget, required to maintain the optimized formation, which can be used as a further trade-off parameter within the mission design process. The results indicate that the passively stable helix configuration (with relative eccentricity and inclination phase angles set to 90 degrees) provides a robust solution at equatorial and mid-latitude regions with perpendicular baselines up to the order of 1 km and temporal lag below 10 ms. Conversely, for high-latitude and polar regions, two alternative strategies are identified, revealing a trade-off between enhanced interferometric performance and increased formation maintenance requirements. For polar regions, a first strategy adopts relative eccentric and phase angles of 10 degrees, achieving satisfactory performance across most latitudes, whereas an alternative approach retains the value of 90 degrees and optimizes the formation specifically for high latitudes. These two options result in distinct station-keeping demands since the former strategy requires a Delta V budget about two orders of magnitude higher, while the latter remains within a Delta V range that is typical for missions of the considered class.

In recent years, small synthetic aperture radar (SAR) satellite constellations have emerged as a viable solution due to their ease of design and relatively low launch costs. These next-generation systems aim to meet the growing needs of the differential interferometric SAR (DInSAR) community, including high spatial resolution and temporal acquisition frequency. Nevertheless, despite their benefits, small satellites face drawbacks such as low power budgets and limited imaging capabilities, needing the exploration of new orbital configurations to meet specific mission objectives. Among these, mid-inclination orbits (MIOs) offer the unique advantage of enabling the retrieval of North-South surface displacements, overcoming a key limitation of conventional sun-synchronous orbits. In this study, we analyze three SAR datasets acquired by Capella Space over the Campi Flegrei (CF) Caldera (Italy), exploiting a 45 degrees MIO. The presented results, validated against GNSS measurements, show a mean standard deviation of 3-4 mm between DInSAR and GNSS LOS-projected time series, while the uncertainty for the North-South component is estimated to be less than 5 mm. Furthermore, we retrieve, for the first time, comprehensive North-South deformation products of the CF caldera, including both a high-resolution map and displacement time series. These outcomes represent a precursor for the upcoming Italian SAR constellation NIMBUS, part of the IRIDE program, which will be launched in a similar MIO configuration and become operational during 2027.

In this work, we present an overview of the state-of-the-art of operational Differential SAR Interferometry (DInSAR) services aimed at detecting ground displacements caused by worldwide earthquakes and Italian volcanoes. In particular, the developed automated services systematically process Sentinel-1 data through the Parallel Small BAseline Subset (P-SBAS) DInSAR algorithm, to finally retrieve coseismic displacement maps of the main earthquakes on Earth and ground displacement time series of the Italian active volcanoes. Furthermore, we show how the so generated DInSAR measurements can be integrated into civil protection frameworks for hazard evaluation and risk management and mitigation. We finally, highlight the initiatives, primarily the European Plate Observing System (EPOS), that allow the sharing of DInSAR measurements with the wide Solid Earth scientific community, ensuring data reproducibility and knowledge exchange.

This study investigates the SAOCOM-1 L-band DInSAR time series accuracy across Italian volcanic and tectonic sites, through cross-validation with radar line of sight projected GNSS measurements. In particular, the displacements retrieved through Parallel Small BAseline Subset (P-SBAS) processing are compared with those of the GNSS networks at Campi Flegrei Caldera, Mount Etna, and Northern Apennines, achieving sub-cm average standard deviation values for the displacement measurements and subcm/yr mean velocity accuracy. Our results represent a step toward operational L-band DInSAR monitoring, providing performance metrics for the generated time series.

Advanced DInSAR techniques are used to investigate the temporal evolution of the deformations through the retrieval of the displacement time series, achieved through the inversion of an appropriate set of multi-temporal interferograms. Among them, the Small BAseline Subset (SBAS) is a well-established approach which has been widely used for the analysis of several deformation phenomena.In this context, an effective and robust Phase Unwrapping (PhU) algorithm must be typically implemented and exploited in order to accurately retrieve the ground deformation signals. This operation represents a critical step because of the intrinsically ill-posed nature of the problem which may lead to solutions that, despite being mathematically correct, do not reproduce the actual unwrapped phase profile.A common indicator for the quality of the PhU solution within advanced DInSAR methods like SBAS is the temporal coherence. This is a point-like parameter available for methods where the displacement time-series are retrieved through the inversion of an overdetermined linear equation system [M, N], with M>N, where M is the number of the generated (redundant) interferograms and N represents the exploited SAR images, whose solution can be obtained in the LS sense.We present in the following a simple solution to identify and correct possible PhU errors, based on a different and innovative use of the temporal coherence parameter.In principle, the higher the value of the temporal coherence, the better the quality of the PhU solution; however, unfortunately, the temporal coherence sensitivity decreases when the number of interferograms increases. To overcome this issue we propose to compute for each point a time series of local temporal coherences, computed by exploiting a limited number of interferograms. To do this, starting from the first acquisition date of the analysed dataset, we define a time window range, say Δw, and a time sampling, say ti , where the step size Δt= ti+1 -ti is selected in agreement with the satellite revisiting time. Accordingly, for the generic i-th step, we consider the time window centred around the ti value and we calculate the temporal coherence by on a limited subset of interferograms whose master and/or slave images are included in the selected time window [ti-Δw/2 , ti+Δw/2]This solution is computationally efficient and allows us to regain sensitivity on possible PhU errors. Indeed, by doing so, the number of interferograms to be analysed in order to identify those characterized by PhU errors has been drastically reduced, making the local temporal coherence more sensitive to small variations in a single interferogram. A subsequent algorithm of PhU errors correction can be then applied only to the involved interferograms, reducing the time computing and increasing the ability to spot and correct the wrong interferogram.

Spaceborne Differential Synthetic Aperture Radar Interferometry (DInSAR) represents a well-established technique to accurately retrieving ground surface displacements over large areas of the Earth, in both natural and anthropogenic hazard scenarios, with limited costs and with a centimeter to millimeter accuracy. However, the DInSAR technique retrieval capability may be affected by the so-called “temporal decorrelation phenomena” due to possible temporal changes of the imaged scene electromagnetic response. In this regard, the low-frequency SAR sensors, as those operating at the L-band, characterized by a significantly larger wavelength (~23 cm) with respect to the X-band (~3 cm wavelength) and C-band (~5.6 cm wavelength) ones, are particularly suited to mitigate the above-mentioned decorrelation effects, thanks to their capacity of maintaining the interferometric coherence for a long period. Moreover, these L-band SAR systems also imply considerable robustness with respect to the possible occurrence of phase unwrapping errors. These peculiarities have pushed the worldwide space agencies to invest in the development of L-band spaceborne SAR sensors as, for instance, the NISAR mission, jointly developed by NASA and ISRO, the PALSAR-3 mission of JAXA and the ROSE-L mission developed by ESA, as well as the already operative SAOCOM-1 sensors of CONAE. In this work, we focus on the Argentinean SAOCOM-1 constellation which is composed of two twins, full-polarimetric L-band SAR sensors. This system guarantees, over a large part of Europe (with a priority given to the Italian territory coverage), a systematic, DInSAR-oriented acquisition plan of SAR images in the StripMap mode, with a revisit time varying among 16, 24 and 48 days, in order to avoid coverage gaps. Moreover, we largely exploit the Parallel Small BAseline Subset (P-SBAS) approach, which is an advanced DInSAR method that allows us to effectively and efficiently generate displacement time-series with sub-centimeter accuracy. The capability of the P-SBAS algorithm to retrieve C- and X-band DInSAR time-series, relevant to both natural and anthropogenic hazard scenarios has already been widely demonstrated, as well as its capacity to perform analyses at different spatial resolution scales. Accordingly, we present here the results of the L-band SAOCOM-1 P-SBAS analysis carried out at medium spatial resolution (about 30 m) in different ground deformation scenarios affecting the Italian territory. In particular, the presented results are relevant to a portion of the Tuscany region (central Italy), which is affected by significant landslide phenomena. Moreover, we also consider the volcanic contexts of the Campi Flegrei caldera, Mount Etna and Stromboli island, all located in southern Italy. In this case, we fully benefit from the availability of GNSS measurements to provide a quantitative assessment of the retrieved L-band deformation time-series.Finally, some SAOCOM-1 results, achieved by applying the full resolution P-SBAS approach over the urban areas of Rome and Naples municipalities, are also presented. Such a full spatial resolution (about 5 m of pixel size) analysis allows us to investigate the potentialities of the L-band data to overcome some of the limitations of the current high resolution X-band SAR systems in urbanized scenarios.

This article presents an innovative, parallel implementation of the Small BAseline Subset (SBAS) approach to automatically and efficiently process large volumes of multitemporal differential synthetic aperture radar (SAR) interferometry (DInSAR) interferograms generated at the native full spatial resolution of the SAR images. The starting point of the developed full-resolution parallel-SBAS (FR P-SBAS) technique involves some algorithmic extensions for improving the quality of the DInSAR time series to effectively analyze extended deformations and localized displacement phenomena, such as those affecting single buildings and infrastructures. The main focus of the work is on the efficient and scalable FR P-SBAS processing chain implementation, extensively exploiting graphical processing unit (GPU) architectures. Moreover, the presented scalability analysis demonstrates the GPU capability of efficiently generating full-resolution displacement time series starting from large DInSAR datasets. Furthermore, it is also shown that the implemented processing solution easily allows us to deal with SAR data acquired through the Stripmap and TOPS modes. To assess the quality of the generated DInSAR products, an extensive experimental analysis is also shown, based on long sequences of X-Band COSMO-SkyMed Stripmap and C-Band Sentinel-1 TOPS acquisitions relevant to the Campi Flegrei Caldera (Southern Italy), which is monitored through a dense GNSS network. The presented results demonstrate the effectiveness of the FR P-SBAS processing chain in retrieving multifrequency and multiplatform displacement time series at the full spatial resolution with subcentimetric accuracy and in very short time frames, from a few hours for the COSMO-SkyMed datasets up to some tens of hours for the Sentinel-1 case.

We present an innovative solution to identify and correct possible phase unwrapping (PhU) errors, to improve the results obtained from a redundant sequence of multitemporal, small baseline differential SAR interferometry (DInSAR) interferograms. In particular, the proposed algorithm is based on the cascade of three main steps: the first one consists in reducing the amount of pixels and interferograms to be analyzed for the errors identification by generating a novel parameter for the evaluation of the best possible corrections. To do this, we extend the temporal coherence parameter, originally defined as a single value point-like quality factor of the PhU operation, by sampling it into a series of values, which we refer to as local temporal coherence (LTC) time series. This allows us to effectively select, for each identified pixel, a subset of interferograms to be evaluated as possible PhU errors candidates. The second step benefits from the compressive sensing theory and is based on a L1-norm inversion, to sharply identify the interferograms of the pixels selected through the previous step, which are more likely affected by the PhU errors. Once identified them, the third step consists in a guided search of the possible PhU corrections, for the examined pixels, by means of a genetic algorithm, which maximizes the LTC time series. To evaluate the performance of the proposed algorithm, we carry out a comparative analysis between the corrected and uncorrected results, obtained from simulated data relevant to different deformation regimes and a Sentinel-1 SAR dataset relevant to descending orbits over the Mt. Etna volcano (Sicily, southern Italy). The obtained results clearly demonstrate the effectiveness of the presented approach.

The IRIDE constellation is an ambitious Italian space program that will support the national authorities in their analyses and monitoring activities, with a focus on Italian territory mapping. It will comprise a series of small satellite subconstellations exploiting a wide range of remote sensing technologies. This article analyses the NIMBUS X-Band synthetic aperture radar (SAR) IRIDE subconstellation, exploring potential orbital configurations beyond the more conventional and widespread dawn-dusk sun-synchronous orbit (SSO) one. In particular, starting from the mission target, we show that a 49 degrees mid-inclination orbit (MIO) in a right-looking StripMap acquisition mode represents a highly effective choice for NIMBUS. We demonstrate that this configuration enhances the systematic coverage of the Italian territory with six nodal days of interferometric revisit time and high spatial resolution, thereby facilitating detailed observations of both natural phenomena and anthropic activities. In terms of differential SAR interferometry (DInSAR) performance, we prove that MIOs do not show significant limitations for what attains the critical baseline and geometric distortions. In addition, MIOs may lead to future advances in creating 3-D displacement maps because they allow for the recovery of the North-South deformation component that, conversely, cannot be precisely measured with DInSAR systems operating in SSO.

We present in this work the new advances of the differential synthetic aperture radar (SAR) interferometry (DInSAR) technique referred to as the parallel Small BAseline Subset (P-SBAS) approach for the generation of displacement time series from the recently available L-band SAR image sequences acquired by the Argentinian SAOCOM-1 constellation. In particular, we first discuss the algorithmic extensions allowing us to retrieve SAOCOM-1 DInSAR products, with a main focus on the exploitation of Stripmap SAR images and multilook interferograms. These algorithmic improvements are relevant to the adjacent single look complex (SLC) image slices merging to the multitemporal residual orbital artifacts mitigation and to the phase unwrapping procedure enhancement. Subsequently, the effectiveness of the extended P-SBAS processing chain is shown through a comparative analysis between the achieved SAOCOM-1 DInSAR results and the corresponding ones relevant to Sentinel-1 and COSMO-SkyMed acquisitions. Moreover, a comparison between the SAOCOM-1 displacement time series and the GNSS measurements, relevant to the Campi Flegrei Caldera (Italy), is presented. This shows that the mean standard deviation value of the differences between the DInSAR and the GNSS time series, the latter projected in the radar line of sight, is about 1 cm, further confirming the effectiveness of the P-SBAS processing chain extension.

We present a quantitative assessment of the SAOCOM-1 L-band Differential SAR Interferometry (DInSAR) time-series accuracy. To do this a comparative analysis between the DInSAR displacements, retrieved by applying the Parallel Small BAseline Subset (P-SBAS) approach, and the corresponding GNSS measurements, is presented. The focus of the work is on the Italian territory and, in particular, the study zones are relevant to the Campi Flegrei and Etna volcanos (located in southern Italy) and to a northern Italy Apennines zone, where large SAOCOM-1 dataset are available as well as GNSS measurements of dense networks. The presented results are very relevant for the ongoing development of an L-band DInSAR deformation national retrieval service and they may also have a significant impact as a precursor of the availability of the new ALOS-4, NISAR, and ROSE-L L-band missions.

This contribution is aimed at drawing the professional and human profile of our colleague and friend Mariarosaria, based on the memories and materials that we have collected during her 20 years’ activity at the Institute for Electromagnetic Sensing of the Environment (IREA) of the National Research Council (CNR), Naples, Italy. Beside a short overview of her professional contribution at IREA-CNR, we intend to provide also our personal memories picked up from 20 years of co-workership and friendship. Anecdotes, stories and facts will be also provided, with the objective to transmit Mariarosaria’s intelligence, competence, passion, courage, poise, firmness, gentleness, determination and sweetness, all enclosed in her wonderful smile and amazing blue eyes. All this represents her legacy that we want to pass on.

Differential Synthetic Aperture Radar (SAR) Interferometry (DInSAR) plays nowadays a crucial role in studying ground deformations with centimeter-to-millimeter accuracy. Initially exploited to investigate individual deformation events, such as earthquakes and volcanic unrests, DInSAR has evolved in the last two decades thanks to the accessibility to large multi-temporal SAR data archives. This evolution has led to the development of advanced (also referred to as multi-temporal) DInSAR techniques, enabling to follow the temporal evolution of the detected surface displacements through the retrieval of deformation time series. Despite the wide availability of spaceborne SAR systems with different characteristics (i.e., spatial coverage, spatial resolution, revisit time, orbital tube, etc.), the DInSAR community increasingly demands better coverage performance and improved imaging capabilities to address the latest emerging needs. For instance, short revisit time and high spatial coverage and resolution are usually needed to study fast deformation phenomena. Moreover, most SAR constellations exploit single plane, dawn-dusk, sun-synchronous orbits because this simplifies the satellite design across all subsystems, resulting in cost savings. However, in this traditional orbital design, the interferometric revisit time becomes considerable, thus representing a limiting factor. Furthermore, the poor sensitivity to the North-South deformation component that characterizes the sun-synchronous DInSAR systems represents a fundamental limitation in investigating the deformation phenomena. In this scenario, the use of small SAR satellites is gaining traction, thanks to the simplified design and manufacturing processes. Additionally, the ability to launch multiple satellites, by using the same vehicle, enables the deployment of an entire constellation in a single mission. However, these systems, being smaller and lighter, have constraints on their imaging performance, potentially compromising coverage capabilities. Consequently, innovative mission configurations are necessary for their effective use. This work focuses on a SAR component of the Italian IRIDE program, which will be implemented for the Italian government and completed by 2026 under the management of the European Space Agency, with the support of the Italian Space Agency. This SAR component, called NIMBUS, is expected to include, in its first batch and its preliminary design, 6 high-resolution X-band small satellites operating at altitudes between 490-550 km and in various operating modes including a StripMap one with a swath extension that is not designed to be extremely wide (25-30 km). To cover the Italian territory with high spatial resolution and the shortest interferometric revisit time, we investigate a Mid Inclination Orbit solution that, through the DInSAR exploitation, can effectively measure the North-South deformation component, thus permitting us to investigate the three-dimensional behavior of the retrieved displacements. Our simulations show that the analyzed IRIDE SAR component, through the preliminary setup in a 49° inclination orbit, permits covering nearly all the Italian territory with a 6-day revisit time in a right-looking acquisition mode. Moreover, we show that the simulated configuration would provide an excellent DInSAR retrieval capability for the North-South deformation component. Indeed, with such an orbital configuration, more than 40% of this component contributes to the SAR Line of sight projection, significantly better than what is typically achievable with sun-synchronous systems.

Differential Interferometric Synthetic Aperture Radar (DInSAR) techniques have emerged as powerful tools for monitoring and surveillance at both single-building and territorial levels, offering sub-centimetric accuracy with manageable costs. Among these techniques, the DInSAR method known as Small BAseline Subset (SBAS) and its parallel algorithmic implementation, referred to as the Parallel SBAS (P-SBAS) approach, stand out for their ability to provide systematic displacement measurements at both regional, national and continental scales through the generation of spatially and temporally dense deformation time series, contributing to investigate various hazard scenarios related to the natural and the built-up environments. Moreover, by exploiting the full-resolution extension of the P-SBAS approach, it is also possible to generate long-term deformation time series at different spatial resolution scales for regional and local displacement investigations. This work focuses on the extensive use of the full-resolution P-SBAS approach for local-scale DInSAR analyses aimed at detecting localized deformation phenomena in wide urban areas, with a particular interest in infrastructure and individual building displacements. To this aim, we can profitably capitalize on the highest spatial resolution of the SAR images collected by the currently available and future advanced satellite SAR systems characterized by different operational modes (Stripmap, TOPSAR, ScanSAR) and frequency bandwidths (L-, C-, and X-band). Among these, we leverage the extensive archives of X-band (about 3 cm wavelength) SAR data acquired since 2009 along the overall Italian territory by the sensors of the Italian COSMO-SkyMed constellation of the first (CSK) and second (CSG) generation, operated through the Stripmap mode (about 3 m x 3 m spatial resolution) within the so-called Map Italy program. This huge SAR dataset makes it possible to monitor the surface deformations affecting the built-up environment with a very high spatial and temporal measurement density. In this work, we perform a full-resolution P-SBAS analysis over some Italian cities (e.g., Roma, Napoli, Bologna, Catania), where large sequences of ascending and descending CSK/CSG SAR data are available, in order to assess the health conditions of critical infrastructures and buildings related to extended built-up environments. Moreover, we also present the preliminary full-resolution P-SBAS results achieved by processing the available L-band SAR data acquired by the new twin sensors of the Argentinian SAOCOM-1 constellation of CONAE (spatial resolution about 5x5 m). Thanks to the longer wavelength characterizing the L-Band data, we can investigate the possibilities of overcoming some of the typical limitations of X-band SAR systems (e.g., the occurrence of phase unwrapping problems). Our approach involves the use of parallel hardware and software solutions, including GPU parallel programming techniques, which prove to be highly effective in rapidly generating full-resolution P-SBAS deformation time series over large urbanized areas. These measurements can help to define a roadmap for identifying and preventing critical conditions in buildings and infrastructures.

In 2023, seismic activity of considerable magnitude occurred along the Türkiye-Syria border, characterised by an Mw 7.8 earthquake on the 6th of February and was followed by an Mw 7.5 event, nine hours later. These earthquakes, which are the strongest recorded in recent years, resulted in over 50,000 casualties and are related with the activity of the East Anatolian Fault Zone —a 600 km-long plate boundary where the Arabian and Anatolian plates meet. To analyse these seismic events, we leveraged data from diverse satellites, including SAOCOM-1, Sentinel-1, and ALOS-2. Employing InSAR techniques, such as conventional interferometry and Pixel Offset tracking, we assessed surface deformations caused by the events. The high-resolution Synthetic Aperture Radar displacement results underwent non-linear and linear inversions, enabling the creation of detailed variable slip fault models. A meticulous multiscale sampling approach was applied, that facilitated a comprehensive examination of the tectonic structures triggering these events. The fault zone exhibited a pronounced left-lateral strike-slip character, with components of dip-slip movements observed in specific segments. Additionally, we capitalised the detailed slip models, to estimate the distribution of the intensity of ground motions in the affected region.

The Campi Flegrei caldera is an active volcano located in southern Italy that, over the last two decades, was affected by a phase of progressively rising uplift accompanied by increasing seismicity and geochemical anomalies. The ground displacement pattern, which is monitored through GNSS and Differential SAR Interferometry (DInSAR), is mainly radial with a maximum uplift in the area corresponding to Rione Terra (Pozzuoli). Recently, we have identified a geodetic anomaly in the uplift displacement pattern, near the Mt. Olibano-Accademia area, where most of the recent seismicity of the caldera is concentrated. In particular, the area affected by the detected anomaly experiences a reduced uplift with respect to the surrounding region. This anomaly, which is analyzed by exploiting the DInSAR measurements of several spaceborne SAR systems operating at different frequencies, becomes clearly recognizable starting from 2021 and represents a potentially critical area for the caldera dynamics and related hazard understanding.