Hasil untuk "Geodesy"

R. Beyer, O. Alexandrov, S. McMichael

The NASA Ames Stereo Pipeline is a suite of free and open source automated geodesy and stereogrammetry tools designed for processing stereo images captured from satellites (around Earth and other planets), robotic rovers, aerial cameras, and historical images, with and without accurate camera pose information. It produces cartographic products, including digital terrain models, ortho‐projected images, 3‐D models, and bundle‐adjusted networks of cameras. Ames Stereo Pipeline's data products are suitable for science analysis, mission planning, and public outreach.

Himanshu Miriyala, Rishabh Pal, Arijit Sharma

Transportable all-optical atomic clocks represent the next-generation devices for precision time keeping, ushering a new era in encompassing a wide range of PNT (Positioning, Navigation and Timing) applications in the civil and strategic sectors. Their performance relies on ultra-stable, narrow-linewidth lasers, frequency stabilized to a compact portable optical cavity. Among various designs, the cubic spacer-based ultra-stable cavity is particularly well-suited for transportable applications due to its low sensitivity to vibrations, owing to its symmetric geometry and robust mounting structure. While longer cavities offer a lower fundamental thermal noise floor, one needs to strike a balance between transportability and size. In this aspect, the 7.5 cm dual-axis cubic cavity offers a lower fundamental thermal noise floor in comparison to smaller counterparts, while still retaining a reasonable SWaP (Size, Weight and Power) for terrestrial and aerial PNT applications. Its dual-axis design also enables multi-wavelength laser stabilization, making it a promising candidate for future transportable clock applications. This work presents a detailed study of the 7.5 cm dual-axis cubic cavity using FEM (Finite Element Method) to evaluate its mechanical and thermal stability. We analyze the impact of various geometric factors, mounting forces, and machining imperfections, while also modelling thermal effects such as conduction, radiation, and mirror heating within a vacuum chamber and thermally shielded environment. Our findings provide design insights for developing robust dual-axis optical reference cavities, advancing the deployment of portable atomic clocks for next-generation applications in PNT, geodesy, VLBI (Very Long Baseline Interferometry) and deep space missions.

Kenneth Nakasone, Paola Luna, Andrei Zhukov et al.

Quantum inertial sensors test general relativity, measure fundamental constants, and probe dark matter and dark energy in the laboratory with outstanding accuracy. Their precision relies heavily on carefully choreographed quantum control of the atomic states with a collection of lasers, microwaves, electric and magnetic fields. Making this technology available outside of the laboratory would unlock many applications, such as geophysics, geodesy and inertial navigation. However, this requires an apparatus of reduced size, weight, power use and increased robustness, modularity and ease-of-use. Here, we describe the design and implementation of an in-vacuum electromagnet able to create the magnetic fields necessary for various quantum control operations, such as magneto-optical trapping or magnetic levitation to assist evaporative cooling. Placing the electromagnet inside the vacuum chamber has significant advantages, such as fast switching times that are not limited by induced current inside the vacuum chamber metal, reduced size, weight and power usage. However, dissipating the heat produced typically requires complex designs that include bulky metal heatsinks or cooling using water or cryogens. Our design implements heatpipes in a compact, low-vibration and robust apparatus, which use a phase transition in the working fluid to achieve thermal conductivity that is more than one hundred times larger than that of typical bulk metal. We show that the setup can conduct more than 50 W of thermal power in a configuration that provides ample optical access and is compatible with the ultra-high vacuum requirements of atomic and molecular experiments.

Lea Bischof, Melanie Ast, Jiang Ji Ho-Zhang et al.

Designed to detect gravitational waves in the lower-frequency band, the space mission LISA will open a new window to astronomy after its launch in the 2030s. Each LISA spacecraft houses two optical benches that require the exchange of a phase reference between them via an optical connection, called a Backlink. Here we present the construction and commissioning of an ultra-stable quasi-monolithic optical testbed to investigate different Backlink implementations: a direct fiber, a frequency-separated fiber, and a free-beam link, compared in the Three-Backlink Experiment. Dedicated alignment techniques crucial for the construction of these optical benches are presented together with the development of a high-precision beam alignment and measurement tool - a Calibrated Quadrant Photodiode Singleton. An upper limit for the performance of all three investigated Backlink schemes, as determined by initial experiments, can be set at a $15\text{pm}/\sqrt{\text{Hz}}$-equivalent level within the LISA band, spanning 0.1mHz to 1Hz. Our measurements were able to verify the successful construction and commissioning of this very complex interferometer as an interferometric laboratory testbed for LISA. We find no limitations due to the construction on the here reported performance levels. Our results can support the construction of high-precision metrology testbeds for space-based laser interferometry for future gravitational wave or geodesy missions.

Leonid Petrov, Christian Ploetz, Matthias Schartner

We have assessed accuracy of estimates of Earth orientation parameters (EOP) determined from several very long baseline interferometry (VLBI) observing programs that ran concurrently at different networks. We consider that the root mean square of differences in EOP estimates derived from concurrent observations is a reliable measure of accuracy. We confirmed that formal errors based on the assumption that the noise in observables is uncorrelated have a limited use. We found no evidence that advanced scheduling strategies with special considerations regarding the ability to better solve for atmospheric path in zenith direction applied for 1-hr single-baseline sessions have any measurable impact on the accuracy of EOP estimates. From this, we conclude that there is a certain limit in our ability to solve for the atmospheric path delay using microwave observations themselves and a scheduling strategy is not the factor that impairs accuracy of EOP determination. We determined that EOP errors vary with season, being smaller in winter and greater in summer. We got the quantitative estimate of the impact of unmodeled source structure on EOP estimates and we found that the seasonal extra variance is one order of magnitude greater than the impact of source structure. We have established that the EOP errors are scaled with an increase in duration of an observing session as a broken power law with the power of -0.3 at durations longer than 2-4 hours, which we explain as a manifestation of the presence of correlations in the atmospheric noise.

Ming Hui Xu, Patrick Charlot

Active Galactic Nuclei (AGNs) observed with the technique of very long baseline interferometry (VLBI) are used as fiducial references on the sky to precisely measure the shape and orientation of the Earth. Their positions form a celestial reference frame that plays an important role in both astronomy and geodesy. This study investigates the accuracy and stability of the positions of the AGNs that are measured by simultaneous VLBI observations at 3.3, 5.5, 6.6, and 10.5 GHz. Based on position time series from dedicated geodetic solutions, we characterize the observed source position variations and identify the possible factors causing such variations. We find that the primary contributor is source structure for sources above 20-degree declination while the sensitivity of the observations to the declination coordinate predominates for sources below 20-degree declination. The position time series are further explored to derive more realistic uncertainties for the quad-band positions. Significant position offsets with respect to the positions at 2.2/8.6 GHz are found for 15% of the sources. For 6% of the sources, the offsets are larger than 0.8 milli-arcseconds. Source structure may be divided into two parts: the invisible structure (within the beam size) and the visible structure (on larger scales). The latter causes closure delays enlarging post-fit delay residuals in geodetic solutions whereas the former causes source position changes. Such position changes will contribute significantly to the offsets between radio and optical positions. Overall, this work highlights the necessity to have a specific quad-band catalog for processing operational quad-band observations.

Jan Eube, Heiko Röglin

Connected clustering denotes a family of constrained clustering problems in which we are given a distance metric and an undirected connectivity graph $G$ that can be completely unrelated to the metric. The aim is to partition the $n$ vertices into a given number $k$ of clusters such that every cluster forms a connected subgraph of $G$ and a given clustering objective gets minimized. The constraint that the clusters are connected has applications in many different fields, like for example community detection and geodesy. So far, $k$-center and $k$-median have been studied in this setting. It has been shown that connected $k$-median is $Ω(n^{1- ε})$-hard to approximate which also carries over to the connected $k$-means problem, while for connected $k$-center it remained an open question whether one can find a constant approximation in polynomial time. We answer this question by providing an $Ω(\log^*(k))$-hardness result for the problem. Given these hardness results, we study the problems on graphs with bounded treewidth. We provide exact algorithms that run in polynomial time if the treewidth $w$ is a constant. Furthermore, we obtain constant approximation algorithms that run in FPT time with respect to the parameter $\max(w,k)$. Additionally, we consider the min-sum-radii (MSR) and min-sum-diameter (MSD) objective. We prove that on general graphs connected MSR can be approximated with an approximation factor of $(3 + ε)$ and connected MSD with an approximation factor of $(4 + ε)$. The latter also directly improves the best known approximation guarantee for unconstrained MSD from $(6 + ε)$ to $(4 + ε)$.

Slava G. Turyshev

We present a unified post-Newtonian framework for relativistic timing and coordinate transformations covering six time scales (TCB, TCG, TT, TDB, TCL, TL) and three reference systems (BCRS, GCRS, LCRS). Extending the IAU conventions, we define a Lunicentric Celestial Reference System (LCRS) metric that retains all contributions above a fractional threshold of 5 x 10^{-18} and timing terms above 0.1 ps by expanding the lunar gravity field to spherical-harmonic degree l=9 with Love number variations and including external tidal and inertial multipoles to the octupole. We derive closed-form mappings among TCB, TCG, TT, TCL and TL, yielding proper-to-coordinate time transformations and two-way time-transfer corrections at sub-picosecond accuracy. We evaluate secular rate constants and periodic perturbations arising from kinematic dilation, lunar monopole and multipoles, Earth tides and gravitomagnetic effects for clocks on the lunar surface, in very low and low lunar orbits (vLLO/LLO), in elliptical lunar frozen orbits (ELFOs), at the Earth-Moon L1 point, and in near-rectilinear halo orbits (NRHOs). Our analysis demonstrates that harmonics through l=9 and tides through l=8 are sufficient to achieve 5 x 10^{-18} fractional stability for deep cislunar regimes (e.g., NRHO, Earth-Moon L1), supporting sub-picosecond clock synchronization and centimeter-level navigation; near-surface and vLLO realizations generally require a much higher spherical-harmonic degree, l_max >= 300, to meet the same stability goal. This framework underpins high-precision time and frequency transfer, relativistic geodesy, quantum communication links and fundamental physics experiments beyond low Earth orbit.

Marcel Beck, Shreevathsa Chalathadka Subrahmanya, Oliver Gerberding

Space-based gravitational wave detectors, such as the Laser Interferometer Space Antenna (LISA), use picometer-precision laser interferometry to detect gravitational waves at frequencies from 1 Hz down to below 0.1 mHz. Laser interferometers used for on-ground prototyping and testing of such instruments are typically constructed by permanently bonding or gluing optics onto an ultra-stable bench made of low-expansion glass ceramic. This design minimizes temperature coupling to length and tilt, which dominates the noise at low frequencies due to finite temperature stability achievable in laboratories and vacuum environments. Here, we present the study of an alternative opto-mechanical concept where optical components are placed with adjustable and freely positionable mounts on an ultra-stable bench, while maintaining picometer length stability. With this concept, a given interferometer configuration can be realised very quickly due to a simplified and speed-up assembly process, reducing the realisation time from weeks or months to a matter of hours. We built a corresponding test facility and verified the length stability of our concept by measuring the length change in an optical cavity that was probed with two different locking schemes, heterodyne laser frequency stabilisation and Pound-Drever-Hall locking. We studied the limitations of both locking schemes and verified that the cavity length noise is below 1 pm/sqrt(Hz) for frequencies down to 3 mHz. We thereby demonstrate that our concept can simplify the testing of interferometer configurations and opto-mechanical components and is suitable to realise flexible optical ground support equipment for space missions that use laser interferometry, such as future space-based gravitational wave detectors and satellite geodesy missions.

Pangyin Li, Zhe Chen, Chen Long et al.

Semantic segmentation of urban point clouds captured by Airborne Laser Scanning (ALS) is essential for understanding complex 3D environments, serving as a robust underlying data foundation for digital twin applications. The fusion of multimodal data has been proven to significantly improve the performance of ALS semantic segmentation by fully mining rich complementary information in each modality. However, existing fusion-based ALS semantic segmentation methods face critical limitations due to the reliance on multiple sensors, which constrains their applicability. To this end, we propose a novel multimodal framework Elevation Guidance Adaptive Fused Network, termed EGAFNet, that integrates naturally formed top-view projection images from ALS to enhance the information perception of the point cloud. The framework focuses on utilizing projection images, structured around two key components: input representation and feature representation. Specifically, to generate highly discriminative input representation, we propose a novel projection method that accurately preserves the relative height relationships between objects and develop a Height Adaptive Scaling Module (HASM) to adaptively adjust object heights, enhancing the expressive capability of elevation information in the projection images. As for feature representation, we design a dual-branch network that effectively captures local and global context from the projection images within a large receptive field. Meanwhile, we propose an Elevation Guidance Adaptive Fusion Module (EGAFM) that adaptively fuses 2D and 3D features based on occlusion relationships to reduce feature confusion caused by occlusion in elevation projection, ensuring meaningful fusion between multimodal features. Extensive experiments on three public datasets demonstrate that our EGAFNet outperforms current state-of-the-art methods.

Hengyu Gu, Yuhao Lin, Haoyu Hu et al.

Abstract As the COVID-19 pandemic recedes and travel resumes, it is important to understand how the influences on inter-city road travel varied across different stages of the pandemic. However, the underlying spatiotemporal heterogeneity in the relationship between the mobility shifts and its determinants at different pandemic stages is unclear. This research divides the pandemic timeline into four distinct stages based on the data from the Chinese Health Care Commission and Amap platform. By using a multiscale geographically and temporally weighted regression model (MGTWR), this paper analyzes how the pandemic factor, road infrastructure, population mobility motivations, and other external factors impact inter-city road travel at different pandemic stages. Our findings reveal a “falling-rising-stabilizing-falling” pattern in the overall volume of inter-city mobility over time. Despite the pandemic depressed the road travel volumes, it did not significantly alter the overall spatial patterns of inter-city mobility. However, Spatiotemporal heterogeneity is found in many influencing relationships. The impacts of COVID-19 cases and road infrastructure vary across stages and cities, while other factors are relatively temporally stable. These insights inform economic recovery and policy transitions in the post-pandemic era.

Fangchao Yang, Wei Hong, Yujie Zhao

Precision space inertial sensors are imperative for Earth geodesy missions, gravitational wave observations, and fundamental physics experiments in space. In these missions, free-falling test masses(TMs) are susceptible to parasitic electrostatic forces and torques, with significant contributions from the interaction between stray electric fields and TM charge. These effects can make up a sizable fraction of the noise budget. Thus, a charge management system(CMS) is essential in high-precise space-based missions. However, the operating environment for space charge control is full of uncertainties and disturbances. TM charge tracking precision is negatively affected by many physical parameters such as external charging rate, quantum yield, UV light power, etc. Those parameters are rarely measured and supposed to vary because of changes in solar activity, temperature, aging of electronic components and so on. The unpredictability and variability of these parameters affects the CMS performance in long-term space missions and must be evaluated or eliminated. This paper presents a simple physics-based model of the discharging process with high charging/discharging rate based on the geometry of inertial sensors. After that, a disturbance observer sliding mode control (DOSMC) is proposed for the CMS with parametric uncertainties and unknown disturbance to maintain the TM charge below a certain level and improve its robustness. The simulation results show that the DOSMC is able to force the system trajectory coincides with the sliding line, which depends neither on the parameters or disturbances. In this way, the DOSMC can effectively ignore the parameter perturbation and external disturbances. The control precision can reach 0.1 mV, which is superior to that of a classic proportional-integral-derivative controller and conventional sliding mode control.

Yachong An, Hao Ding, Fred D. Richards et al.

Detecting the Earth's inner core motions relative to the mantle presents a considerable challenge due to their indirect accessibility. Seismological observations initially provided evidence for differential/super-rotation of the inner core, but recently demonstrated a possibly about 70-year periodic oscillation. The contrasting results underscore the ongoing enigma surrounding inner core motion, leaving debates unresolved, including the precise oscillate period. In parallel to seismic observations, satellite geodesy has accumulated decades of global high-precision records, providing a novel avenue to probe inner core motions. Here, we detect an about 6-year oscillation from the gravitational field degree-2 order-2 Stokes coefficients derived from satellite observations, and find it has a unique phase correlation with the about 6-year signal in the Earth's length-of-day variations. This correlation is attributed to an inner core oscillation which is controlled by the gravitational coupling between the inner core and lower mantle (mainly due to the density heterogeneity of the two large low-velocity provinces; LLVPs). That is, we independently corroborate the inner core periodic oscillation, albeit with a significantly shorter period than previously suggested. Our findings demonstrate the dense layer of the LLVPs (mean density anomalies of about +0.9 percent at the bottom), consistent with inversions from tidal tomography and Stoneley modes. Furthermore, our research reveals equatorial topographic undulations of about 187 m at the inner core boundary.

Pei Zhang, Xiaodong Song, Jiangtao Li et al.

Lithospheric structure beneath the northeastern Qinghai-Xizang Plateau is of vital significance for studying the geodynamic processes of crustal thickening and expansion of the Qinghai-Xizang Plateau. We conducted a joint inversion of receiver functions and surface wave dispersions with P-wave velocity constraints using data from the ChinArray II temporary stations deployed across the Qinghai-Xizang Plateau. Prior to joint inversion, we applied the H-κ-c method (Li JT et al., 2019) to the receiver function data in order to correct for the back-azimuthal variations in the arrival times of Ps phases and crustal multiples caused by crustal anisotropy and dipping interfaces. High-resolution images of vS, crustal thickness, and vP/vS structures in the Qinghai-Xizang Plateau were simultaneously derived from the joint inversion. The seismic images reveal that crustal thickness decreases outward from the Qinghai-Xizang Plateau. The stable interiors of the Ordos and Alxa blocks exhibited higher velocities and lower crustal vP/vS ratios. While, lower velocities and higher vP/vS ratios were observed beneath the Qilian Orogen and Songpan-Ganzi terrane (SPGZ), which are geologically active and mechanically weak, especially in the mid-lower crust. Delamination or thermal erosion of the lithosphere triggered by hot asthenospheric flow contributes to the observed uppermost mantle low-velocity zones (LVZs) in the SPGZ. The crustal thickness, vS, and vP/vS ratios suggest that whole lithospheric shortening is a plausible mechanism for crustal thickening in the Qinghai-Xizang Plateau, supporting the idea of coupled lithospheric-scale deformation in this region.

Herbert TATA

Gravity anomalies are used for the interpretation of the structures which are beneath the Earth. The availability of gravity anomalies at the early stage of exploration activities makes determining characteristics, forms and location properties beneath the Earth’s crust possible. Different GGMs have different accuracies due to factors such as differences in sources of data and the mode of their formulation. It is essential to know the efficiency of models over an area before being used for serious activity over the area. This research evaluated gravity anomaly derived from Global Gravity Models to determine the best-fit model over Akure City, Nigeria, by accessing ten gravitational models over twenty-three geodetic control points. Free-Air was the Gravity field model, calculated through the ten Global Gravity field Models over the study area. The computations of the anomalies were done at the International Centre for Global Earth Models (ICGEM). Terrestrial gravity anomaly data acquired was the standard against the ten model-based gravity anomalies using a coefficient of correlation and T-test to determine the best models over the area. Based on correlation analysis, SGG_UGM_2 has a value of 0.5995, and EGM2008 was 0.5973, respectively. The two models are the best fit for the study area. Based on the T-test for Free-Air anomaly data, EGM2008 and GECO have no significant difference from the terrestrial gravity models having P-values of 0.0393 mgal and 0.0146 mgal, respectively. This research, therefore, underscores the significance of adopting the best-fit model over the study area.

Wladimir Neumann, Ning Ma, Audrey Bouvier et al.

Abstract The formation of planets in our solar system encompassed various stages of accretion of planetesimals that formed in the protoplanetary disk within the first few million years at different distances to the sun. Their chemical diversity is reflected by compositionally variable meteorite groups from different parent bodies. There is general consensus that their formation location is roughly constrained by a dichotomy of nucleosynthetic isotope anomalies, relating carbonaceous (C) meteorite parent bodies to the outer protoplanetary disk and the non-carbonaceous (NC) parent bodies to an origin closer to the sun. It is a common idea, that in these inner parts of the protoplanetary disks, planetesimal accretion processes were faster. Testing such scenarios requires constraining formation ages of meteorite parent bodies. Although isotopic age dating can yield precise formation ages of individual mineral constituents of meteorites, such ages frequently represent mineral cooling ages that can postdate planetesimal formation by millions or tens of millions of years, depending on the cooling history of individual planetesimals at different depths. Nevertheless, such cooling ages provide a detailed thermal history which can be fitted by thermal evolution models that constrain the formation age of individual parent bodies. Here we apply state-of-the-art thermal evolution models to constrain planetesimal formation times particular in the outer solar system formation region of C meteorites. We infer a temporally distributed accretion of various parent bodies from $$<0.6$$ < 0.6 Ma to $$\approx 4$$ ≈ 4 Ma after solar system formation, with 3.7 Ma and $$2.5-2.75$$ 2.5 - 2.75 Ma for the parent bodies of CR1-3 chondrites and the Flensburg carbonaceous chondrite, and $$<0.6$$ < 0.6 and $$<0.7$$ < 0.7 Ma for the parent bodies of differentiated achondrites NWA 6704 and NWA 011, respectively. This implies that accretion processes in the C reservoir started as early as in the NC reservoir and were operating throughout typical protoplanetary disk lifetimes, thereby producing differentiated parent bodies with carbonaceous compositions in addition to undifferentiated C chondrite parent bodies. The accretion times correlate inversely with the degree of the meteorites’ alteration, metamorphism, or differentiation. The accretion times for the CM, CI, Ryugu, and Tafassite parent bodies of 3.8 Ma, 3.8 Ma, $$1-3$$ 1 - 3 Ma, and 1.1 Ma, respectively, fit well into this correlation in agreement with the thermal and alteration conditions suggested by these meteorites. Our results indicate that individual planetesimals formed rapidly (i.e., within $$<1$$ < 1 Ma), however, distinct planetesimals formed recurrently throughout the total lifetime of the protoplanetary disk. Rapid individual formation is consistent with streaming instabilities assisted by gravitational collapse. However, obviously not the total dust inventory was consumed at early disk evolution stages, so there must have been some delay mechanisms, e.g. collisional destruction of precursor aggregates due to high impact velocities induced by radial drift phenomena. This counterbalance enabled late ( $$>2-3$$ > 2 - 3 Ma) accretion of C planetesimals beyond the snow line which escaped severe planetesimal heating and volatile loss, hence, preserving their volatiles, especially water. Only this delayed formation of water-rich planetesimals allowed Earth to accrete sufficient water to become a habitable planet, preventing it from being a bone dry planet.

Yulei Mu, Jue Huang, Mingxin Song et al.

Study region: Laptev Sea Study focus: The absorption slopes of colored dissolved organic matter (CDOM) in the spectral range of 275–295 nm (S275–295) is a reliable parameter of the source and transformation of CDOM and dissolved organic carbon (DOC) in the estuarine environment. Studying S275–295 in coastal areas can provide important information about CDOM and DOC. This study proposed a new multilayer backpropagation neural network (MBPNN) based on the relationship between S275–295 and aCDOM(443) (absorption of CDOM at 443 nm) as a customization function to invert S275–295. The model accurately estimated S275–295 with a MAPE and RMSE of 6.12 % and 0.0012 nm−1, respectively, and revealed the spatiotemporal distribution of S275–295 in the Laptev Sea between 2002 and 2022 (July to September). The effects of influencing factors on temporal and spatial variations of S275–295 were analyzed. New hydrological insights for the region: The MBPNN model with a customization function has good performance to invert S275–295 in Laptev Sea. The S275–295 in the Laptev Sea ranged from 0.014 to 0.022 nm−1. S275–295 increased gradually from coastal waters to the open sea. Inter-annual S275–295 fluctuated, but no significant trend was observed during the study period (2002–2022). S275–295 was negatively correlated with river discharge (r=-0.41), permafrost thaw depth (r=-0.42), ice extent (r=-0.55) and Normalized Difference Vegetation Index (r=-0.46) but positively correlated with salinity (r=0.86) and wind speed (r=0.46).

Slava G. Turyshev, Viktor T. Toth

We investigate the general relativistic phase of an electromagnetic wave as it propagates in the gravitational field of the Earth, which is modeled as an isolated, weakly aspherical gravitating body. We introduce coordinate systems to describe light propagation in the Earth's vicinity along with the relevant coordinate transformations, and discuss the transformations between proper and coordinate times. We represent the Earth's gravitational field using Cartesian symmetric trace-free (STF) mass multipole moments. The light propagation equation is solvable along the trajectory of a light ray to all STF orders $\ell$. Although we focus primarily on the quadrupole ($\ell=2$), octupole ($\ell=3$), and hexadecapole ($\ell=4$) cases, our approach is valid to all orders. We express the STF moments via spherical harmonic coefficients of various degree and order, $C_{\ell k}, S_{\ell k}$. The result is the gravitational phase shift expressed in terms of the spherical harmonics. These results are new. We also consider contributions due to tides and the Earth's rotation. We estimate the characteristic magnitudes of each term of the resulting overall gravitational phase shift. The terms assessed are either large enough to impact current-generation clocks or will become significant as future-generation clocks offer greater sensitivity. Our formulation is useful for many practical and scientific applications, including space-based time and frequency transfers, relativistic geodesy and navigation, as well as quantum communication links and space-based tests of fundamental physics.

Rodolfo G. Cionco, Sergey M. Kudryavtsev, Willie Soon

The hypothesis that tidal forces on the Sun are related to the modulations of the solar-activity cycle has gained increasing attention. The works proposing physical mechanisms of planetary action via tidal forcing have in common that quasi-alignments between Venus, Earth, and Jupiter (V-E-J configurations) would provide a basic periodicity of $\approx 11.0$ years able to synchronize the operation of solar dynamo with these planetary configurations. Nevertheless, the evidence behind this particular tidal forcing is still controversial. In this context we develop, for the first time, the complete Sun's tide-generating potential (STGP) in terms of a harmonic series, where the effects of different planets on the STGP are clearly separated and identified. We use a modification of the spectral analysis method devised by Kudryavtsev (J. Geodesy. 77, 829, 2004; Astron. Astrophys. 471, 1069, 2007b) that permits to expand any function of planetary coordinates to a harmonic series over long time intervals. We build a catalog of 713 harmonic terms able to represent the STGP with a high degree of precision. We look for tidal forcings related to V-E-J configurations and specifically the existence of periodicities around $11.0$ years. Although the obtained tidal periods range from $\approx$ 1000 years to 1 week, we do not find any $\approx$ 11.0 years period. The V-E-J configurations do not produce any significant tidal term at this or other periods. The Venus tidal interaction is absent in the 11-year spectral band, which is dominated by Jupiter's orbital motion. The planet that contributes the most to the STGP in three planets configurations, along with Venus and Earth, is Saturn. An $\approx 11.0$ years tidal period with a direct physical relevance on the 11-year-like solar-activity cycle is highly improbable.

Robert Oleniacz, Marek Bogacki, Mateusz Rzeszutek et al.

Constantly changing vehicle stock, modification of road infrastructure, and other conditions result in a need to update the knowledge on the effectiveness of individual traffic management strategies, which could form the basis for actions taken by local authorities to improve air quality in crowded city centers, especially in street canyons. The article presents research results that evaluate the theoretical effects of introducing select traffic reorganization scenarios in the example of four street canyons located in Krakow (Poland) that are different in terms of vehicle traffic volume and canyon geometry. These scenarios were based on a reduction in the average traffic speed, road capacity or the admission of cars meeting certain exhaust emission standards. The authors estimated changes in emissions of nitrogen oxides (NO, NO₂ and total NO_x) and particulate matter (PM₁₀ and PM_2.5) as well as investigated the effect of these changes on air quality in the canyons using the Operational Street Pollution Model (OSPM). Significant effects in terms of improving air quality were identified only in scenarios based on a significant reduction in traffic volume and the elimination of passenger cars and light commercial vehicles with internal combustion engines that did not meet the requirements of the Euro 4, Euro 5 or Euro 6 emission standards. For these scenarios, depending on the variant and canyon analyzed, the emission reduction was achieved at a level of approximately 36–66% for NO, 28–77% for NO₂, 35–67% for NO_x and 44–78% for both PM₁₀ and PM_2.5. The expected effect of improving air quality in individual street canyons for these substances was 15–44%, 5–14%, 11–36% and 3–14%, respectively. The differences obtained in the percentage reduction of emissions and pollutant concentrations in the air were the result of a relatively high background of pollutants that suppress the achieved effect of improving air quality to a large extent.