Flavia Giuliani, Fabrizio De Marchi, Daniele Durante
et al.
Measurements of the Doppler shift of a carrier signal have always been the basis of radio science experiments, particularly for planetary gravity field recovery. Doppler observables are affected by correlated (colored) noise; however, standard orbit estimation filters assume that the noise is white and Gaussian. This assumption simplifies the code and reduces the runtime, as the weight matrix is diagonal. In this work, we present a method for incorporating colored noise into least-squares estimation filters by constructing a full noise covariance matrix that reflects the spectral characteristics of all contributing error sources, guaranteeing the proper estimation of parameters and their associated uncertainties. We apply this methodology to the gravity science experiment of NASA’s upcoming Venus Emissivity, Radio Science, InSAR, Topography, And Spectroscopy (VERITAS) mission. Our analysis finds that the white noise assumption is valid for VERITAS—thus supporting the robustness of earlier simulation results. The approach, however, is general and particularly valuable for future missions in which colored noise, such as plasma-induced red noise, dominates the Doppler error budget.
Gauthier Hulot, Louis Chauvet, Robin Deborde
et al.
Abstract The ESA Swarm satellites carry a magnetometry payload consisting of an absolute scalar magnetometer (ASM), a fluxgate vector magnetometer (VFM), and a set of star trackers (STR). The primary role of the ASM is to provide 1 Hz absolute field intensity measurements, while the VFM and STR provide the additional data needed to reconstruct the attitude of the vector field and produce the official nominal Swarm L1b magnetic data. Each ASM instrument, however, can be run in an experimental mode to simultaneously produce its own self-calibrated 1 Hz vector data. Such 1 Hz experimental vector data have been routinely produced ever since launch on Swarm Alpha and Bravo, except during one-week periods every month when the burst mode was activated in yet another experimental mode to produce 250 Hz scalar data. These 1 Hz experimental vector data have been used to produce the only Definitive Geomagnetic Reference Field (DGRF) 2020 candidate model only relying on such data. All other candidate models relied on either nominal Swarm L1b data or data from other satellites and ground observatories. In this paper, we report on the way we built our DGRF candidate model and on the post-calibration strategy that we used to identify and remediate a calibration issue found in both the ASM and VFM vector data. We show that this post-calibration improves the quality of the data and contributes to also improving our DGRF candidate model. Our final candidate model, only based on post-calibrated ASM data, turns out to be one of the DGRF 2020 candidate models closest to the final official DGRF model, a posteriori providing evidence of both the quality of the Swarm ASM experimental vector mode data and the value of our post-calibration strategy. This post-calibration strategy could be used to improve magnetic data from other past, present, or future missions. Graphical abstract
In recent years, a growing number of sensors that provide imagery with constantly increasing spatial resolution are being placed on the orbit. Contemporary Very-High-Resolution Satellites (VHRS) are capable of recording images with a spatial resolution of less than 0.30 m. However, until now, these scenes were acquired in a static way. The new technique of the dynamic acquisition of video satellite imagery has been available only for a few years. It has multiple applications related to remote sensing. However, in spite of the offered possibility to detect dynamic targets, its main limitation is the degradation of the spatial resolution of the image that results from imaging in video mode, along with a significant influence of lossy compression. This article presents a methodology that employs Generative Adversarial Networks (GAN). For this purpose, a modified ESRGAN architecture is used for the spatial resolution enhancement of video satellite images. In this solution, the GAN network generator was extended by the Uformer model, which is responsible for a significant improvement in the quality of the estimated SR images. This enhances the possibilities to recognize and detect objects significantly. The discussed solution was tested on the Jilin-1 dataset and it presents the best results for both the global and local assessment of the image (the mean values of the SSIM and PSNR parameters for the test data were, respectively, 0.98 and 38.32 dB). Additionally, the proposed solution, in spite of the fact that it employs artificial neural networks, does not require a high computational capacity, which means it can be implemented in workstations that are not equipped with graphic processors.
Vahid Isazade, Abdul Baser Qasimi, Abdulla Al Kafy
et al.
Flood events are the most sophisticated and damaging natural hazard compared to other natural catastrophes. Every year, this hazard causes human-financial losses and damage to croplands in different locations worldwide. This research employs a combination of artificial neural networks and geographic information systems (GIS) to simulate flood-vulnerable locations in the Samangan Province of Afghanistan. First, flood-influencing factors, such as soil, slope layer, elevation, flow direction, and land use/cover, were evaluated as influential factors in simulating flood-prone areas. These factors were imported into GIS software. The Fishnet command was used to partition the information layers. Furthermore, each layer was converted into points, and this data was fed into the perceptron neural network along with the educational data obtained from Google Earth. In the perceptron neural network, the input layers have five neurons and 16 nodes, and the outputs showed that elevation had the lowest possible weight (R2 = 0.713) and flow direction had the highest weight (R2 = 0.913). This study demonstrated that combining GIS and artificial neural networks results in acceptable performance for simulating and modeling flood susceptible areas in different geographical locations and significantly helps prevent or reduce flood hazards.
Jeremy Eudaric, Heidi Kreibich, Andrés Camero
et al.
Abstract The impact of climate change and urbanization has increased the risk of flooding. During the UN Climate Change Conference 28 (COP 28), an agreement was reached to establish “The Loss and Damage Fund” to assist low-income countries impacted by climate change. However, allocating the resources required for post-flood reconstruction and reimbursement is challenging due to the limited availability of data and the absence of a comprehensive tool. Here, we propose a novel resource allocation framework based on remote sensing and geospatial data near the flood peak, such as buildings and population. The quantification of resource distribution utilizes an exposure index for each municipality, which interacts with various drivers, including flood hazard drivers, buildings exposure, and population exposure. The proposed framework asses the flood extension using pre- and post-flood Sentinel-1 Synthetic Aperture Radar (SAR) data. To demonstrate the effectiveness of this framework, an analysis was conducted on the flood that occurred in the Thessaly region of Greece in September 2023. The study revealed that the municipality of Palamas has the highest need for resource allocation, with an exposure index rating of 5/8. Any government can use this framework for rapid decision-making and to expedite post-flood recovery.
Mohammad Bagherbandi, Mohammad Bagherbandi, Masoud Shirazian
et al.
Determination of the Earth’s gravity field and geopotential value is one of the fundamental topics in physical geodesy. Traditional terrestrial gravity and precise leveling measurements can be used to determine the geopotential values at a local or regional scale. However, recent developments in optical atomic clocks have not only rapidly improved fundamental science but also contributed to applied research. The latest generation of optical clocks is approaching the accuracy level of 10−18 when facilitating atomic clock networks. These systems allow examining fundamental theories and many research applications, such as atomic clocks applications in relativistic geodesy, to precisely determine the Earth’s gravity field parameters (e.g., geopotential values). According to the theory of relativistic geodesy, the frequency difference measured by an optical clock network is related to the gravity potential anomaly, provided that the effects of disturbing signals (i.e., tidal and non-tidal contributions) are filtered out. The relativistic geodesy principle could be used for a practical realization of global geodetic infrastructure, most importantly, a vertical datum unification or realization of height systems. This paper aims to review the background of relativistic (clock-based) geodesy and study the variations of optical atomic clock measurements (e.g., due to hydrology loading and land motion).
Yoshiaki Tamura, Takahito Kazama, Ryuichi Nishiyama
et al.
Abstract Postseismic gravity changes after the 2011 Tohoku earthquake (Mw9.0) were investigated using the data from superconducting gravimeters (SGs) at Mizusawa, Japan. The data in the period from 2014 to 2021 were used in the analysis. The SG data were first corrected for instrumental drift using the results of absolute gravity measurements. Then, correction for the hydrological effect was applied based on physical modeling of soil moisture. Finally, the effect of vertical displacement of the station (free-air effect) was corrected using GNSS data. After these corrections, residual gravity indicated a long-term increase, with its rate gradually decreasing with time. This fact suggests that viscoelastic relaxation after the earthquake played an important role in producing the long-term gravity changes. Fitting a decaying exponential function of time to the residual series yielded 89.4 ± 4.4 µGal (1 µGal = 10–8 ms–2) as the total gravity change and 635 ± 17 days as the characteristic time scale. In addition to the ground-based observations, the data from satellite gravity missions GRACE/GRACE-FO were analyzed to retrieve gravity changes at Mizusawa. Similar analysis of the satellite-based data yielded 15.2 ± 1.6 µGal as the total gravity change and 3444 ± 599 days as the characteristic time scale. The difference in the estimates of the total gravity change, of a factor of about 6, from the ground-based and the satellite-based observations may be attributed to the limited spatial resolution in the latter method. The difference in the estimates of the time scale, of a factor of about 1/5, may originate from the difference in the depth where the two kinds of gravimetry are mainly sensitive. Referring to recent theoretical studies on postseismic deformations after the 2011 Tohoku earthquake, our results can be interpreted consistently by assuming the existence of a layer of viscoelastic materials with viscosity $$2\times {10}^{18} \text{Pa s}$$ 2 × 10 18 Pa s underneath the Tohoku area of Japan. Graphical Abstract
The satellite gravimetry technology effectively recovers the global Earth’s gravity field. Since 2000s, HL-SST satellite CHAMP, LL-SST satellite GRACE, Gravity Gradient Measurement (GGM) satellite GOCE have been launched successfully, producing some Earth’s gravity models solely from satellites data. However, the space and time resolution of the Earth’s gravity fields do not adequately satisfy scientific objectives. The main reason is that the gravimetry satellites are not enough and observation data insufficient. The paper outlines the current and future status of Chinese gravity satellite missions. The Chinese gravimetry satellite system, named Chinese Gravimetry augment and Mass change exploring mission (ChiGaM), successfully launched in Dec. 2021 after four years of production and over a year of calibration and valiation. The accelerometer, K-band ranging system and the three stellar sensors, among others, were precisely calibrated and trimmed. The satellite mass center was determined and coordinated with the proof center of accelerometer with an accuracy 100μm. The inter-satellite ranging system and BDS/GPS receiver operate together seamlessly. The range and range rate noise is less than 3μm/Hz1/2 and 1μm/s/Hz1/2, respectively, in band of 0.025~0.1Hz. The electrostatic suspension accelerometer is working well. Its high-sensitive axis noise level is 3×10-10 m/s2/Hz1/2 near the frequency 0.1Hz, and 1×10-9 m/s2/Hz1/2 for the less-sensitive axis. Meanwhile the BDS/GPS receiver is used to achieve data for precise orbit determination, yielding an orbit result with accuracy better than 2cm. When compared with KBR observations, the RMS of the bias is less than 1mm. Besides above mission, next gravimetric satellite is being developed now. TQ-2 mission is designed as a totally experimental satellite for gravitational wave detection at low Earth orbit, which can detect the Earth’s gravity field simultaneously. The Bender-type mission is considered the most promising configuration for TQ-2 and consists of two polar satellites and two inclined satellites. Due to the extra observations at the east-west direction derived from the inclined satellite pair, significant improvements has been made in detecting temporal signals with higher accuracy and spatial-temporal resolution. To achieve the scientific goal, the ACC MBW can shift from 0.001~0.1Hz to 0.004~0.1Hz for ACC, and the LRI MBW can shift from 0.01~1Hz to 0.1~1Hz. For future research, a gravimetric potential survey using cold-atomic-clock based on the general relativity theory, cold atom gradiometer should be pursued. Gravimetric technologies should be mined and researched, and the gravimetry satellite constellation should be developed, so as to improve the time resolution and space resolution for meeting the requirements of geophysics, geodesy, earthquake, water resources environment, oceanography, etc.
Hatem M. El-Desoky, Ali Shebl, Ahmed M. Abdel-Rahman
et al.
Through various scales of observation, ranging from remote sensing data, field investigations, hand specimens, microscopic petrographic examinations, XRD, to SEM, indicators of various mineralization types are highlighted in Ras El-kharit-wadi Khashir (Eastern Desert, Egypt). Systematic remote sensing exploration of the mineralized zones is performed through integrating Sentinel 2 and ASTER datasets. False-color combinations, informative band ratios, relative absorption band depth, and CEM techniques were applied to discriminate rock units and various types of hydrothermal alterations. Moreover, ALOS PALSAR DEM was utilized to decipher the structural lineaments. Intensive field investigations confirmed hydrothermally altered zones that were picked out through remote sensing analysis and revealed that the study area is affected by cataclastic metamorphism to some extent. Magmatic and metamorphic rock types are represented by propylitic, phyllic, argillic, and silicification zones. Sericitization, chloritization, epidotization, kaolinitization, carbonatization, and silicification are recorded utilizing petrographic and remote sensing investigations. Moreover, the current study reveals that the detected alteration is the main reason for the apparent wide range of petrographic characteristics of each rock type and bearing several opaque minerals, such as pyrite, magnetite, titanomagnetite, chalcopyrite, arsenopyrite, covellite, galena, goethite, and hematite. Most of these opaques were identified using ore microscopy, XRD, and SEM. The distribution of hydrothermal alterations, representative samples bearing mineralization, structurally dissected zones are integrated to build a mineral potentiality map of the study area. The resultant MPM was confirmed via field survey and emphasized the usefulness of the current integrated approach besides highlighting about 125 km2 as potential mineralized zones.
In low-moisture regimes, strongly-reflecting bedrock underlying soil could provide a dominant return. This offers a novel opportunity to retrieve both the volumetric moisture fraction (mv) and depth (d) of a soil layer using a differential phase. A radar wave traversing the overlying soil slows in response to moisture state; moisture dynamics are thus recorded as variations in travel time—captured back at a radar platform as changes in phase. The Phase Scaled Dielectric (PSD) model introduced here converts phase changes to those in soil dielectric as an intermediate step to estimating mv. Simulations utilizing a real soil moisture timeseries from a site in Sudan were used to demonstrate the linked behaviors of the soil and radar variables, and detail the PSD principle. A laboratory validation used soil with a wet top layer variable in depth 1–2 cm and drying from mv ∼ 0.2 m3m−3, overlying a gravel layer at a depth of 11 cm. The scheme retrieved = 1.49 ± 0.33 cm and a change Δmv = 0.191–0.021 ± 0.009 m3m−3. The PSD scheme outlined here promises a new avenue for the diagnostic measurement of soil parameters which is not currently available to radar remote sensing.
Abstract The parameterization of the magnetospheric field contribution, generated by currents flowing in the magnetosphere is of major importance for the analysis of Mercury’s internal magnetic field. Using a combination of the Gauss and the Mie representation (toroidal–poloidal decomposition) for the parameterization of the magnetic field enables the analysis of magnetic field data measured in current carrying regions in the vicinity of Mercury. In view of the BepiColombo mission, the magnetic field resulting from the plasma interaction of Mercury with the solar wind is simulated with a hybrid simulation code and the internal Gauss coefficients for the dipole, quadrupole and octupole field are reconstructed from the data, evaluated along the prospective trajectories of the Mercury Planetary Orbiter (MPO) using Capon’s method. Especially, it turns out that a high-precision determination of Mercury’s octupole field is expectable from the future analysis of the magnetic field data measured by the magnetometer on board MPO. Furthermore, magnetic field data of the MESSENGER mission are analyzed and the reconstructed internal Gauss coefficients are in reasonable agreement with the results from more conventional methods such as the least-square fit.
This article addresses the global issue of preserving cultural heritage, which is associated, among other things, with the lack of provision for boundaries of protection zones for cultural heritage sites. This paper analyzes the worldwide experience in the field of establishing protection zones for cultural heritage sites, identifies the issues of preserving cultural heritage in Russia, as well as imperfections in the management of lands containing cultural heritage sites. To improve the management of such lands, a method of historical and cultural assessment of territories has been developed, which, on the basis of evaluative factors, makes it possible to characterize the historical and cultural value of a territory. In this article, based on this list of factors, a method for mathematical substantiation of the boundaries of protection zones of cultural heritage sites has been developed; this method includes seven stages. Using mathematical and statistical methods, models were obtained to determine the area of the protection (buffer) zone and the development control zone, the analysis of which revealed differentiation between the factors of historical and cultural assessment that characterize the urban environment, depending on the type of zones. The interpretation of the obtained models and the fields of their use are given.
Mahmoud M. Shokry, Mohamed F. Sadek, Aly F. Osman
et al.
Wadi Khuda-Wadi Shut area in the South Eastern Desert (SED) of Egypt is mainly made up of gneisses, ophiolitic serpentinites and intermediate schistose metavolcanics. These metamorphic rock units are intruded by syn-late-tectonic diorite, granodiorite, ultramafic-mafic, and monzogranite intrusions. The gneisses comprise biotite hornblende gneiss, hornblende gneiss and migmatites. They are of granodiorite and diorite composition. The ophiolitic serpentinite with talc carbonate rocks were thrusted over the metavolcanics with NW-SE thrust contact. The late tectonic ultramafic-mafic rock units are represented in the study area by Dahanib pluton, which is consisted of layered peridotite-dunite associated with olivine gabrro, normal gabbro and gabbro-norite as well as rare hornblende gabbro. These varieties are related to the layered intrusions rather than Alaskan-types, and formed by magmatic differentiation. The granodiorite and monzogranite represent the youngest basement rock units in the study area. The principal components and band ratios of ASTER and Landsat-8 data were successfully used for the first time in lithological discrimination and geological mapping of the study area. This study concluded that, the interpreted data of ASTER and Landsat-8 combined with field study and petrographic investigation clearly discriminated the exposed rock units. Accordingly, a detailed geological map emphasizing the lithological units in Khuda-Shut area has been presented.