ALBERT

Beschreibung: This paper investigates the potential of performing orbit determination directly in the Earth-fixed frame based on Inter-Satellite Ranging (ISR) measurements as primary observables, combined with Ground-to-Satellite Ranging (GSR) measurements from a small regional ground network. Current Global Navigation Satellite Systems (GNSSs) use L-band pseudo-range and carrier phase measurements from global or regional ground station networks to perform dynamic Orbit Determination and Time Synchronization (ODTS), whereas sparse Satellite Laser Ranging measurements are mainly used for validation. Future GNSSs may be equipped with inter-satellite links (ISLs) to enable inter-satellite clock offset estimation, ranging and data relay. These capabilities carry the potential to significantly improve ODTS procedures. In this work, we assume a fully connected constellation via pair-wise ISLs, with measurement topology assigned by appropriate link schedulers. The satellite orbits are parametrized with the standard 15 Galileo broadcast perturbed Keplerian elements, estimated by using ISR and GSR measurements. This processing strategy eliminates the complex modeling of gravitational and non-gravitational forces, making it particularly suitable for on-board applications and offering an alternative to classical GNSS orbit determination processing architectures. The proposed orbit determination scheme can be used in case of a ground segment failure as a back-up procedure to estimate the orbits of the GNSS satellites onboard of each satellite and guaranteeing a continuous navigation message generation for the system users. The performance of the proposed method depends on a number of factors, such as the length of the data fitting interval, the measurement quality (precision and accuracy), the scheduling and geometry of ISR and GSR measurements, the number and distribution of ground stations, and the accuracy of the ground station coordinates. Preliminary results show that an orbit-only Signal-in-Space Range Error (SiSRE) in the order of 7–9 cm can be obtained by processing 2 to 3 h data with a limited set of supporting ground stations. In this study, the orbit determination scheme proposed is tested on different scenarios, providing a first assessment of attainable performance.

Beschreibung: In streams, short‐term element‐specific solute fluxes are often not balanced with long‐term chemical weathering fluxes determined in the residual solids from fractional element loss and denudation rate. The ratio of both estimates—the “Dissolved Export Efficiency” (DEE)—is frequently 〈1, indicating deficits in the stream dissolved load. To explore the cause of the stream deficits, we performed a daily water sampling campaign for one year in a forested headwater watershed in Southern Germany. We sampled surface runoff, above‐canopy and below‐canopy precipitation, subsurface flow from the organic soil layer, upper, and deep mineral soil, and groundwater. Regolith samples were obtained from a drill core and revealed the weathering front to lie between 7 and 15 m depth. We found a DEE 〈 1 for K, Si, Al, Fe. These elements are characterized by shallow slopes in C‐Q relationships, and the imbalances were found to originate in the deep saprolite. Their export pathway potentially includes “hidden” Critical Zone compartments or fluxes, presumably unsampled colloids that are exported preferentially during rare flushing events with stochastic temporal distribution. The DEE of nutritive elements like Ca, Mg, and P is also 〈1. These elements are characterized by steeper C‐Q slopes, and their imbalance can be explained by deep nutrient uptake followed by nutrient retainment in re-growing forest biomass or export in plant debris. The collective evidence for these imbalances, including previous evidence from metal stable isotopes, suggests that the deep Critical Zone represents the location for chemical or biogenic retention and release of solutes.

Beschreibung: The BASE (Barberton Archean Surface Environments) scientific drilling project aimed at recovering an unweathered continuous core from the Paleoarchean Moodies Group (ca. 3.2 Ga), central Barberton Greenstone Belt (BGB), South Africa. These strata comprise some of the oldest well-preserved sedimentary strata on Earth, deposited within only a few million years in alluvial, fluvial, coastal-deltaic, tidal, and prodeltaic settings. They represent a very-high-resolution record of Paleoarchean surface conditions and processes. Moodies Group strata consist of polymict conglomerates, widespread quartzose, lithic and arkosic sandstones, siltstones, shales, and rare banded-iron formations (BIFs) and jaspilites, interbedded with tuffs and several thin lavas. This report describes objectives, drilling, and data sets; it supplements the operational report. Eight inclined boreholes between 280 and 495 m length, drilled from November 2021 through July 2022, obtained a total of 2903 m of curated core of variable quality through steeply to subvertically dipping, in part overturned stratigraphic sections. All drilling objectives were reached. Boreholes encountered a variety of conglomerates, diverse and abundant, mostly tuffaceous sandstones, rhythmically laminated shale-siltstone and banded-iron formations, and several horizons of early-diagenetic silicified sulfate concretions. Oxidative weathering reached far deeper than expected. Fracturing was more intense, and BIFs and jaspilites were thicker than anticipated. Two ca. 1 km long mine adits and a water tunnel, traversing four thick stratigraphic sections within the upper Moodies Group in the central BGB, were also sampled. All boreholes were logged by downhole wireline geophysical instruments. The core was processed (oriented, slabbed, photographed, described, and archived) in a large, publicly accessible hall in downtown Barberton. A geological exhibition provided background explanations for visitors and related the drilling objectives to the recently established Barberton Makhonjwa Mountains World Heritage Site. A substantial education, outreach, and publicity program addressed the information needs of the local population and of local and regional stakeholders.

Beschreibung: The increasing importance of Earth observation information for society and environment, particularly in the expanding domain of hyperspectral remote sensing, along with the significantly increasing data availability, emphasizes the demand for online education to address the growing need for expertise in this domain. We present a comprehensive review of existing online education programs on Earth observation that underline the limited availability of online resources for hyperspectral remote sensing. To respond to this demand, we introduce HYPERedu, an online education program on hyperspectral remote sensing that has been developed as part of the EnMAP satellite mission since 2019. The program’s core components, content, and participation statistics, along with insights from participant feedback, are presented. HYPERedu offers a wide range of resources, including slide collections, tutorials, video screencasts, and online courses, making them accessible to a broad audience for university teaching, training schools and individual learning. The program’s effectiveness as well as challenges and insights encountered during program development are discussed. We emphasize the importance of collaborative learning, sustainability efforts for long-term material accessibility and quality assurance, and the need to bridge the digital divide with offline options, opensource tools, and multilingual content. Effective content presentation is vital, focusing on consistent branding, concise modules, interactive features, and narrative-style videos. Additionally, we explore the future of online Earth observation learning, considering enhanced participant interaction and the integration of new learning concepts. Finally, we underscore the significance of outreach and training for satellite mission utilization and advocate for open education to promote open science, data, software, and accessibility for inclusive education.

Beschreibung: Central Afar is shaped by the interaction between the Red Sea (RS) and Gulf of Aden (GoA) rifts. While there have been several studies conducted in the region, we know surprisingly little about the mechanism of connection between these two rift branches. Here we use high-resolution 3D lithospheric scale geodynamic modeling to capture the evolution of linkage between the RS and GoA rifts in central Afar. Our results demonstrate that the two rifts initially overlap and interact across a broad zone of faulting and vertical axis block rotation. However, through time, rift overlap is abandoned in favor of direct linkage which generates a series of localized en-echelon basins. The present-day direct linkage between the two rifts is supported by geodetic observations. Our study reconciles previously proposed models for the RS and GoA rift connection by considering spatial and temporal evolution of the rifts.

Beschreibung: Enhanced geothermal systems (EGSs) developed by hydraulic stimulation are promising for exploiting petrothermal heat by improving fluid pathways in low-permeable geothermal reservoir rocks. However, fluid injection into the subsurface can potentially cause large seismic events by reactivating pre-existing faults, which is a significant barrier to EGSs. The management of injection-induced seismicity is, therefore, essential for the success of EGSs. During the hydraulic stimulation of an EGS, fluid can be injected into a fault zone or into the rock matrix containing pre-existing faults adjacent to the injection well. The differences in hydromechanical responses between fluid injection into and adjacent to a fault have not been investigated in detail. Here, we performed triaxial fluid injection experiments involving injecting fluid directly and indirectly into a fault in granite rock samples to analyse the distinct hydromechanical responses and estimate the injection-induced seismicity in both cases. Our results suggest that in addition to directly injecting fluid into a critically stressed fault, injecting into nearly intact granite adjacent to the fault could also cause injection-induced seismic hazards owing to the high fluid pressure required to create new fractures in the granite matrix. It is, therefore, important to carefully identify pre-existing faults within tight reservoirs to avoid injecting fluid adjacent to them. Additionally, once prior unknown faults are delineated during hydraulic stimulation, appropriate shut-in strategies should be implemented immediately to mitigate seismic risks.

Beschreibung: Fault slip is a complex natural phenomenon involving multiple spatiotemporal scales from seconds to days to weeks. To understand the physical and chemical processes responsible for the full fault slip spectrum, a multidisciplinary approach is highly recommended. The Near Fault Observatories (NFOs) aim at providing high-precision and spatiotemporally dense multidisciplinary near-fault data, enabling the generation of new original observations and innovative scientific products. The Alto Tiberina Near Fault Observatory is a permanent monitoring infrastructure established around the Alto Tiberina fault (ATF), a 60 km long low-angle normal fault (mean dip 20°), located along a sector of the Northern Apennines (central Italy) undergoing an extension at a rate of about 3 mm yr−1. The presence of repeating earthquakes on the ATF and a steep gradient in crustal velocities measured across the ATF by GNSS stations suggest large and deep (5–12 km) portions of the ATF undergoing aseismic creep. Both laboratory and theoretical studies indicate that any given patch of a fault can creep, nucleate slow earthquakes, and host large earthquakes, as also documented in nature for certain ruptures (e.g., Iquique in 2014, Tōhoku in 2011, and Parkfield in 2004). Nonetheless, how a fault patch switches from one mode of slip to another, as well as the interaction between creep, slow slip, and regular earthquakes, is still poorly documented by near-field observation. With the strainmeter array along the Alto Tiberina fault system (STAR) project, we build a series of six geophysical observatory sites consisting of 80–160 m deep vertical boreholes instrumented with strainmeters and seismometers as well as meteorological and GNSS antennas and additional seismometers at the surface. By covering the portions of the ATF that exhibits repeated earthquakes at shallow depth (above 4 km) with these new observatory sites, we aim to collect unique open-access data to answer fundamental questions about the relationship between creep, slow slip, dynamic earthquake rupture, and tectonic faulting.

Beschreibung: Dynamic failure in the laboratory is commonly preceded by many foreshocks which accompany premonitory aseismic slip. Aseismic slip is also thought to govern earthquake nucleation in nature, yet, foreshocks are rare. Here, we examine how heterogeneity due to different roughness, damage and pore pressures affects premonitory slip and acoustic emission characteristics. High fluid pressures increase stiffness and reduce heterogeneity which promotes more rapid slip acceleration and shorter precursory periods, similar to the effect of low geometric heterogeneity on smooth faults. The associated acoustic emission activity in low-heterogeneity samples becomes increasingly dominated by earthquake-like double-couple focal mechanisms. The similarity of fluid pressure increase and roughness reduction suggests that increased stress and geometric homogeneity may substantially shorten the duration of foreshock activity. Gradual fault activation and extended foreshock activity is more likely observable on immature faults at shallow depth.

Beschreibung: Cosmic radiation near the Earth's surface is influenced by solar activity, atmospheric conditions, and changes of nearby soil moisture or snow. To better understand how cosmic‐ray neutron measurements should be corrected for meteorological effects, we operated a detector for low‐energy neutrons in a buoy on a lake in Germany for 5 months in 2014. Since the water content in the surroundings is constant, we were able to isolate the signal from almost any ground‐related disturbances. With this instrument, we challenged traditional and recent theories on the neutron response to water, air humidity, and to reference data from high‐energy neutron monitors around the world. We found that in some cases, recent theories showed superior performance over traditional approaches. We also found a stronger response of the neutrons detected by the buoy to a major solar event than was observed by traditional neutron monitors. The concept of a neutron detector on a lake could be useful as a reference station for similar land‐side detectors and help provide more reliable soil moisture products.