Article
Geochemistry & Geophysics
Hao Ding, ZhiFeng Chen, YuanJin Pan, ChuanYi Zou
Summary: In this study, complex Love numbers of long-period zonal tides were estimated for the first time using the optimal sequence estimation method with GPS displacements. The results allow for the determination of lower mantle anelastic parameters and material-dependent parameters, and can be used to construct attenuation and velocity models of the Earth's interior.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2021)
Article
Geochemistry & Geophysics
A. Michel, J-P Boy
Summary: This paper presents a methodology for computing long term deformations in earth models, particularly focusing on their dependence on rheological parameters. By using the Fourier transform instead of the Laplace transform, the authors take advantage of the fast Fourier transform algorithm to calculate viscoelastic deformation. The study investigates the effects of anelasticity on displacements due to various geophysical signals, such as solid Earth tides, glacial isostatic adjustment, and present-day ice melting.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Geochemistry & Geophysics
A. Michel, J-P Boy
Summary: This study introduces a numerical method for calculating long-term deformations of the Earth, with a focus on the rheological parameters of the Earth model. By using Fourier transform instead of Laplace transform, the study is able to take advantage of fast algorithms and avoid mathematical difficulties. The research highlights the significant impact of mantle anelasticity on long-term deformation and emphasizes the importance of considering it in future models.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
D. Melini, C. Saliby, G. Spada
Summary: This paper revisits the computation of Love numbers for a spherically symmetric viscoelastic Earth, presenting a numerical evaluation method based on Laplace inversion and complex-valued frequency-dependent Love numbers. The implementation is done in the ALMA(3) program, allowing for the computation of Love numbers for planetary bodies with various rheological profiles.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Geochemistry & Geophysics
Fred D. Richards, Mark J. Hoggard, Sia Ghelichkhan, Paula Koelemeijer, Harriet C. P. Lau
Summary: This study addresses the vertical extent and composition of large low-velocity provinces (LLVPs) in the deep mantle using a comprehensive range of geophysical observations. The research suggests that the density anomalies of LLVPs extend vertically to approximately 900 km above the core-mantle boundary (CMB), primarily driven by thermal effects but with a possible dense basal layer containing early-formed chondrite-enriched basalt. These findings have significant implications for understanding mantle plume generation and Earth's supercontinent cycles.
EARTH AND PLANETARY SCIENCE LETTERS
(2023)
Article
Astronomy & Astrophysics
Janosz W. Dewberry, Dong Lai
Summary: Tidal interactions are crucial in astrophysics, but uncertainties remain regarding rapidly rotating, centrifugally distorted stars and gaseous planets. In this study, a precise method for computing the dynamical, nondissipative tidal response of rotating celestial bodies is developed, based on summation over contributions from normal modes driven by tidal potential. The findings highlight the resonance effect between retrograde inertial modes and tesseral components of the tidal potential, which could be relevant to gas giants like Jupiter and Saturn. The study emphasizes the importance of considering centrifugal distortion and high-order corrections in rotational treatments, as well as the role of resonant sectoral f-modes in the tidal response of rapidly rotating, centrifugally distorted planets or stars.
ASTROPHYSICAL JOURNAL
(2022)
Article
Chemistry, Analytical
Jose A. Lopez-Perez, Felix Tercero-Martinez, Jose M. Serna-Puente, Beatriz Vaquero-Jimenez, Maria Patino-Esteban, Pablo Garcia-Carreno, Javier Gonzalez-Garcia, Oscar Garcia-Perez, Francisco J. Beltran-Martinez, Carlos Albo-Castano, Juan D. Gallego-Puyol, Isaac Lopez-Fernandez, Carmen Diez-Gonzalez, Inmaculada Malo-Gomez, Laura Barbas-Calvo, Pablo de Vicente-Abad, Jose A. Lopez-Fernandez
Summary: This paper describes a simultaneous tri-band low-noise cryogenic receiver developed in Spain for geodetic Very Long Baseline Interferometry (geo-VLBI). It is fully coolable to cryogenic temperatures to minimize receiver noise and has been installed in various VGOS stations in Spain, Portugal, and Norway. The receiver demonstrates average noise temperatures and efficiency levels in different frequency bands.
Article
Astronomy & Astrophysics
Ram Brustein, Yotam Sherf
Summary: This study investigates the Love numbers of quantum black holes and finds that they are generally nonvanishing and negative, with magnitude dependent on the energy levels of the black holes. By comparing the Love numbers of exotic ultra compact objects and classical compact stars, it is shown that they have different parametric dependence. The detectability of the quadrupolar quantum Love number in future precision gravitational-wave observations is discussed and it is demonstrated that, under certain conditions, its magnitude is large enough to leave an observable signature on the gravitational waves emitted during the inspiral phase of moderately spinning black holes.
Article
Astronomy & Astrophysics
Ibnu Nurul Huda, Taufiq Hidayat, Budi Dermawan, Sebastien Lambert, Niu Liu, Stephane Leon, Kenta Fujisawa, Yoshinori Yonekura, Koichiro Sugiyama, Tomoya Hirota, Premana W. Premadi, Rene Breton, Young-Chol Minh, Phrudth Jaroenjittichai, Dudy Wijaya, Dhota Pradipta, Nabila S. E. Putri, Sahlan Ramadhan, Lucky Puspitarini, Hesti R. T. Wulandari, Mohammad Hafieduddin
Summary: The addition of Indonesian antennas in the future reduces the estimated repeatability value of dUT1 by about 25%, and decreases the repeatability values of Earth Orientation Parameters and station position by approximately 20% and 12% respectively, even with only one Indonesian antenna included.
EXPERIMENTAL ASTRONOMY
(2021)
Article
Geochemistry & Geophysics
Jungang Wang, Maorong Ge, Susanne Glaser, Kyriakos Balidakis, Robert Heinkelmann, Harald Schuh
Summary: Modeling tropospheric delay is challenging in high-precision VLBI analysis, but applying tropospheric delay observations can improve the observation geometry, solution reliability, and stabilize the VLBI network. It also leads to significant improvements in Earth Orientation Parameters (EOP).
JOURNAL OF GEODESY
(2022)
Article
Physics, Multidisciplinary
Alexandre Le Tiec, Marc Casals
Summary: The study reveals that under certain conditions, black holes can be tidally deformed by external gravitational fields, leading to the existence of Love tensors. However, these Love tensors vanish for non-rotating black holes or axisymmetric tidal perturbations, but are non-zero for spinning black holes.
PHYSICAL REVIEW LETTERS
(2021)
Article
Geochemistry & Geophysics
Matthias Schartner, Christian Ploetz, Benedikt Soja
Summary: This article provides a detailed overview of the VLBI Intensive Observing Programs INT2 and INT3 over the past five years, revealing a strong positive trend in the precision of dUT1 measurements due to changes in the scheduling strategy.
JOURNAL OF GEODESY
(2022)
Article
Physics, Multidisciplinary
Panagiotis Charalambous, Sergei Dubovsky, Mikhail M. Ivanov
Summary: Perturbations of massless fields in a black hole background exhibit a hidden SL(2, R) x U(1) (Love) symmetry in the near zone approximation, allowing for derivation of exact results on static tidal responses. The generators of Love symmetry are globally well-defined for any black hole spin, and regular solutions form infinite-dimensional SL(2, R) representations. Special cases correspond to highest weight representations with vanishing Love numbers, providing an elegant explanation for known static Love numbers.
PHYSICAL REVIEW LETTERS
(2021)
Article
Geochemistry & Geophysics
Victor Puente, Esther Azcue, Yaiza Gomez-Espada, Susana Garcia-Espada
Summary: CONT17 is a 15-day continuous VLBI observation campaign conducted by IVS, providing an opportunity for comparing different geodetic techniques. Analysis of parameters such as EOP, station coordinates, and troposphere delays shows differences between VLBI and GNSS under the same observation conditions. Extensive analysis reveals both consistency and differences between different techniques under the same conditions.
JOURNAL OF GEODESY
(2021)
Article
Astronomy & Astrophysics
C. Gattano, P. Charlot
Summary: The study aims to characterize the astrometric source position variations measured with geodetic VLBI data to determine if they occur along random or preferential directions. It was found that over half of the sources may have at least one preferred direction, with most being characterized by a single direction and the rest showing multiple preferred directions. The identified preferred directions, whether single or multiple, are likely attributed to source-intrinsic physical phenomena.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
J. Gruber, A. Nothnagel, J. Boehm
Summary: The raw telescope data in VLBI observations represents the initial stage of data processing chain, including correlation, fringe-fitting, and parameter estimation. The software package VieRDS can simulate raw telescope data, including delay, delay rate, phase offset, and frequency response for each channel. The simulation concept focuses on digital signal creation, processing algorithms, and software architecture.
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC
(2021)
Article
Geochemistry & Geophysics
Matthias Schartner, Lisa Kern, Axel Nothnagel, Johannes Boehm, Benedikt Soja
Summary: This study demonstrates that the optimal length and orientation of Intensive baselines for Very Long Baseline Interferometry (VLBI) sessions depend on specific factors, with long east-west baselines not always being the best choice and other optimal choices existing in certain cases. North-south baselines are also capable of determining dUT1 with accurate polar motion a priori information.
JOURNAL OF GEODESY
(2021)
Article
Geochemistry & Geophysics
Hana Krasna, Leonid Petrov
Summary: The study revealed that the astronomical 15 GHz VLBA observing program MOJAVE-5 is suitable for estimating geodetic parameters, with systematic errors low enough to be used as a testbed for further investigations. There were minor differences compared to a dedicated geodetic dataset, with the major factor causing discrepancies being the different scheduling approach of the datasets.
JOURNAL OF GEODESY
(2021)
Article
Geochemistry & Geophysics
Hana Krasna, Frederic Jaron, Jakob Gruber, Johannes Bohm, Axel Nothnagel
Summary: The primary goal of geodetic VLBI technique is to provide accurate terrestrial and celestial reference frames, requiring estimation of additional parameters reflecting relative offsets and variations of the atomic clocks of radio telescopes. Significant offsets in observed group delays need to be compensated for by estimating baseline-dependent clock offsets, highlighting their importance for VLBI data analysis.
JOURNAL OF GEODESY
(2021)
Article
Geosciences, Multidisciplinary
Sigrid Boehm, Johannes Boehm, Jakob Gruber, Lisa Kern, Jamie McCallum, Lucia McCallum, Tiege McCarthy, Jonathan Quick, Matthias Schartner
Summary: The deviation of Universal Time from atomic time, known as UT1-UTC, is crucial for precise geodetic applications. Very Long Baseline Interferometry (VLBI) Intensive sessions currently meet the criteria for fast delivery of accurate results. The launch of the SI (Southern Intensive) program in 2020 aims to expand geodetic measurements to the southern hemisphere. Results from the SI sessions demonstrate comparable operations and UT1-UTC accuracy to the conventional Intensive sessions.
EARTH PLANETS AND SPACE
(2022)
Article
Geochemistry & Geophysics
Lucia McCallum, Lim Chin Chuan, Hana Krasna, Jamie McCallum, Johannes Bohm, Tiege McCarthy, Jakob Gruber, Matthias Schartner, Jonathan Quick, Axl Rogers
Summary: This paper describes the upgrading process of global geodetic VLBI to its next-generation observing system VGOS and its impact on Australian stations. It discusses the suitability of mixed-mode observations for geodetic results and suggests their acceptance into standard legacy observations to overcome network gaps caused by VGOS upgrades.
JOURNAL OF GEODESY
(2022)
Article
Geochemistry & Geophysics
Alexander Kehm, Hendrik Hellmers, Mathis Blossfeld, Robert Dill, Detlef Angermann, Florian Seitz, Urs Hugentobler, Henryk Dobslaw, Maik Thomas, Daniela Thaller, Johannes Bohm, Erik Schonemann, Volker Mayer, Tim Springer, Michiel Otten, Sara Bruni, Werner Enderle
Summary: Accurate knowledge of the Earth's orientation and rotation is crucial for scientific and societal applications such as global positioning, navigation, and geodynamic studies. This paper presents an improved strategy for processing and combining various observations to enhance the consistency of Earth rotation parameter (ERP) solutions. By implementing this strategy, the study achieves more accurate and consistent ERP solutions, supporting the goals of the Global Geodetic Observing System (GGOS) in providing precise geodetic parameters for science and applications.
JOURNAL OF GEODESY
(2023)
Article
Geosciences, Multidisciplinary
Pacome Delva, Zuheir Altamimi, Alejandro Blazquez, Mathis Blossfeld, Johannes Boehm, Pascal Bonnefond, Jean-Paul Boy, Sean Bruinsma, Grzegorz Bury, Miltiadis Chatzinikos, Alexandre Couhert, Clement Courde, Rolf Dach, Veronique Dehant, Simone Dell'Agnello, Gunnar Elgered, Werner Enderle, Pierre Exertier, Susanne Glaser, Rudiger Haas, Wen Huang, Urs Hugentobler, Adrian Jaggi, Ozgur Karatekin, Frank G. Lemoine, Christophe Le Poncin-Lafitte, Susanne Lunz, Benjamin Maennel, Flavien Mercier, Laurent Metivier, Benoit Meyssignac, Juergen Mueller, Axel Nothnagel, Felix Perosanz, Roelof Rietbroek, Markus Rothacher, Harald Schuh, Hakan Sert, Krzysztof Sosnica, Paride Testani, Javier Ventura-Traveset, Gilles Wautelet, Radoslaw Zajdel
Summary: Improving time and space reference systems on Earth is critical for scientific and societal endeavors. The Terrestrial Reference Frame (TRF) accuracy of 1 mm and long-term stability of 0.1 mm/year are necessary for various applications in geophysics and navigation sciences. The GENESIS mission aims to achieve these goals by combining and co-locating space geodetic techniques on one satellite platform.
EARTH PLANETS AND SPACE
(2023)
Article
Remote Sensing
Marisa Nickola, Hana Krasna, Aletha de Witt, Ludwig Combrinck, Johannes Boehm
Summary: In the VLBI space geodetic technique, an AO model is used for antennas with non-intersecting rotational axes. The recommended a priori AO values for the HartRAO antennas in geodetic VLBI analysis have been identified as possible sources of error.
SOUTH AFRICAN JOURNAL OF GEOMATICS
(2023)
Article
Astronomy & Astrophysics
H. Krasna, L. Baldreich, J. Bohm, S. Boehm, J. Gruber, A. Hellerschmied, F. Jaron, L. Kern, D. Mayer, A. Nothnagel, O. Panzenbock, H. Wolf
Summary: This article introduces the computation of global reference frames from VLBI observations at the Vienna International VLBI Service for Geodesy and Astrometry (IVS) Analysis Center. The results include high-quality celestial and terrestrial reference frames, with improved positions of radio sources and the inclusion of new sources and newly established VLBI telescopes.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Geochemistry & Geophysics
Lisa Kern, Matthias Schartner, Johannes Boehm, Sigrid Boehm, Axel Nothnagel, Benedikt Soja
Summary: This study systematically investigated the impact of erroneous a priori information on the estimation of UT1-UTC with VLBI Intensive sessions globally. The results showed that errors in station height minimally affect UT1-UTC estimate, while errors in horizontal components of station coordinates significantly impact the results. North-south-oriented baselines are strongly affected by errors in a priori information, while east-west-oriented baselines are more resistant to these errors.
JOURNAL OF GEODESY
(2023)
Article
Geosciences, Multidisciplinary
Helene Wolf, Johannes Boehm
Summary: This study evaluates the accuracy of the frame tie between Galileo satellites and the Earth surface using simulations of VLBI observations to satellites next to quasars. The results suggest that equipping two or three satellites with a VLBI transmitter and allocating 30% to 40% of the observation time for satellite observations would yield the best results.
EARTH PLANETS AND SPACE
(2023)
Article
Geochemistry & Geophysics
Szaboles Rozsa, Markku Poutanen, Bilbil Nurce, Hassen Abdellaoui, Jaime Ricardo Soto, Grigor Avetyan, Shin-Chan Han, Johannes Boehm, Fakhraddin Kadirov, Carine Bruyninx, Medzida Mulic
JOURNAL OF GEODESY
(2020)
