G2.3

G2 EDI

The Global Geodetic Observing System (GGOS) provides measurements of the time varying gravity, rotation, and shape of the Earth using space and terrestrial geodetic techniques. These measurements must be accurate to better than a part per billion in order to advance our understanding of the underlying processes responsible for temporal changes in the Earth's
rotation, gravity, and shape. Demanding applications of geodesy include mass transport in the global water cycle, sea level
and climate change, and crustal deformation associated with geohazards. All these measurements require a common reference with the same precision, like the Terrestrial Reference Frame and the Unified Height System. GGOS is designed to unite the individual observations and model into one consistent frame with the highest precision available to be realized as
Global Geodetic Reference Frame (GGRF). This session welcomes contributions on general GGOS topics, particularly those related to scientific and social aspects of GGOS applications.

Convener: Kosuke Heki | Co-conveners: Martin Sehnal, Allison Craddock, Laura Sanchez, David MayerECSECS
Presentations
| Wed, 25 May, 08:30–10:00 (CEST)
 
Room -2.16

Session assets

Session materials

Presentations: Wed, 25 May | Room -2.16

Chairpersons: Martin Sehnal, Allison Craddock
08:30–08:32
GGOS general
08:32–08:38
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EGU22-9106
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Virtual presentation
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Basara Miyahara, Laura Sánchez, Martin Sehnal, and Allison Craddock

The Global Geodetic Observing System (GGOS) is a collaborative contribution of the global Geodesy community to the observation and monitoring of the Earth System. Geodesy is the science of determining the shape of the Earth, its gravity field, and its rotation as functions of time. Essential to reaching this goal are stable and consistent geodetic reference frames, which provide the fundamental layer for the determination of time-dependent coordinates of points or objects, and for describing the motion of the Earth in space. With modern instrumentation and analytical techniques, Geodesy is capable of detecting time variations ranging from large and secular scales to very small and transient deformations – all with increasing spatial and temporal resolution, high accuracy, and decreasing latency. The geodetic observational and analysis infrastructures as well as the high-quality geodetic products provide the foundation upon which advances in Earth and planetary system sciences and applications are built. In this way, GGOS endeavors to facilitate and enable production and sharing of the Earth observations needed to monitor, map, and understand changes in the Earth’s shape, rotation, and mass distribution. GGOS also advocates the global geodetic frame of reference as the fundamental backbone for measuring and consistently interpreting global change processes as well as the essential geospatial infrastructure to ensure a homogeneous and sustainable development worldwide.

GGOS closely works with its parent organization, the International Association of Geodesy (IAG), to keep these fundamental geodetic contributions sustainable. The IAG Services provide the infrastructure and products on which all contributions of GGOS are based, and the IAG Commissions and IAG Inter-Commission Committees provide expertise and support to address key scientific issues within GGOS. Additionally, GGOS supports the IAG by strengthening external and interdisciplinary relations and contributions to the broader geospatial information community, including relevant United Nations groups, in particular, the UN Committee of Experts on Global Geospatial Information Management (GGIM), its Subcommittee on Geodesy, and the new UN Global Geodetic Centre of Excellence (scheduled to commence operations in early 2022). The main contribution of GGOS in this regard is to support actions and initiatives to communicate the value of Geodesy to society as well as to help to understand and solve complex issues facing the global geodesy community. Towards this objective, GGOS is developing a comprehensive Geodesy portal (https://ggos.org/) including detailed descriptions of geodetic observations (https://ggos.org/obs/) and products (https://ggos.org/products/), and various outreach tools such as short videos to explain the roles and importance of Geodesy to non-geodesists.

How to cite: Miyahara, B., Sánchez, L., Sehnal, M., and Craddock, A.: The Global Geodetic Observing System (GGOS) - infrastructure for Science and Society -, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9106, https://doi.org/10.5194/egusphere-egu22-9106, 2022.

08:38–08:44
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EGU22-4537
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On-site presentation
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Detlef Angermann, Thomas Gruber, Michael Gerstl, Robert Heinkelmann, Urs Hugentobler, Laura Sanchez, Peter Steigenberger, Kosuke Heki, Harald Schuh, and Martin Sehnal

The Bureau of Products and Standards (BPS) is a key component of the Global Geodetic Observing System (GGOS) of the International Association of Geodesy (IAG). It supports GGOS in its goal to provide consistent geodetic products needed to monitor, map, and understand changes in the Earth’s shape, rotation, and gravity field. In addition to the operational structure, the Committees “Earth System Modeling” and “Essential Geodetic Variables” as well as the Working Group “Towards a consistent set of parameters for the definition of a new Geodetic Reference System (GRS)” are associated to the BPS. This contribution presents the structure and role of the BPS. It highlights some of the recent activities, which are focused on the classification of geodetic products and on the generation of user-friendly product descriptions to support the establishment of a comprehensive Internet portal for Geodesy under the responsibility of GGOS. The GGOS website www.ggos.org serves as an “entrance door” and information platform to geodetic data and products, and should become an essential tool to make these data and products easier findable and accessible. With this, GGOS is contributing to address different user needs (e.g., geodesists, geophysicists, other geoscientists and further customers) and to make other disciplines and society aware of Geodesy and the importance of its products.

How to cite: Angermann, D., Gruber, T., Gerstl, M., Heinkelmann, R., Hugentobler, U., Sanchez, L., Steigenberger, P., Heki, K., Schuh, H., and Sehnal, M.: GGOS Bureau of Products and Standards: Description and Promotion of Geodetic Products, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4537, https://doi.org/10.5194/egusphere-egu22-4537, 2022.

08:44–08:50
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EGU22-9285
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ECS
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On-site presentation
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Benedikt Soja, Mostafa Kiani Shahvandi, Matthias Schartner, Junyang Gou, Grzegorz Kłopotek, Laura Crocetti, and Mudathir Awadaljeed

Geodetic measurements allow the determination of a wide variety of parameters describing the Earth system, including its shape, gravity field, and orientation in space. The importance of such parameters to science and society is manifested through geodetic contributions to the examination of geodynamic phenomena, climate change monitoring and navigation both on the Earth's surface and in space. In a recent effort led by the Global Geodetic Observing System (GGOS), a set of Essential Geodetic Variables (EGVs) has been defined, which are key quantities characterizing geodetic properties of the Earth. Certain requirements have been assigned to EGVs, including accuracy, spatio-temporal resolution, and latency.

For many real-time applications, the latency of geodetic products has become increasingly critical. Forecasts of certain EGVs at various time horizons are needed to accommodate the user's needs for many applications. In addition, spatial prediction of geodetic quantities on standardized grids on global and regional scales are of great benefit to certain scientific disciplines. The Space Geodesy group at ETH Zurich has thus established a new Geodetic Prediction Center (GPC), which aims to produce spatio-temporal predictions of various EGVs by employing state-of-the-art methods and providing them freely to the scientific community and other interested parties.

In the field of time series forecasting and spatial prediction, machine learning (ML) has become increasingly powerful in recent years due to its high accuracy, efficiency in coping with large amounts of heterogeneous data sets, and capability of capturing complex relationships between various data sources. For instance, ML allows to include auxiliary data in geodetic predictions, also in the cases when no mathematical or physical relation is known. The application of ML has demonstrated promising results in terms of geodetic time series prediction and is thus the tool of choice for many of the parameters provided by the GPC. ML methods applied in this framework include tree-based methods such as random forest as well as variants of convolutional and recurrent neural networks. Such a ML-based approach allows to assimilate geodetic measurements, environmental models, and auxiliary data sets with the aim to provide predictions of utmost accuracy.

Currently, ETH Zurich is invested in the prediction of Earth orientation parameters, Earth angular momentum functions, station coordinates, tropospheric zenith wet delays, ionospheric total electron content, and satellite orbits. In this contribution, an overview of these efforts in the framework of the Geodetic Prediction Center will be provided, highlighting the most recent scientific results.

How to cite: Soja, B., Kiani Shahvandi, M., Schartner, M., Gou, J., Kłopotek, G., Crocetti, L., and Awadaljeed, M.: The New Geodetic Prediction Center at ETH Zurich, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9285, https://doi.org/10.5194/egusphere-egu22-9285, 2022.

08:50–08:56
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EGU22-10982
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Presentation form not yet defined
Kirsten Elger and the GGOS DOI Working Group

The “GGOS Working Group on Digital Object Identifiers (DOIs) for Geodetic Data Sets” is entering its third year of regular meetings and discussions to develop best practices, recommendations and advocate for improved global coordination for using DOI to geodetic data and products. The group was established by the International Association of Geodesy’s (IAG) Global Geodetic Observing System (GGOS) and includes international representatives of IAG Services and geodetic data centres and associated members.

Data publications with digital object identifiers (DOI) are best practice for FAIR sharing data. They are fully citable in scholarly literature and many journals require the data underlying a publication to be available. Initial metrics for data citation allows data providers to demonstrate the value of the data collected by institutes and individual scientists. This possibility to get credit for providing data products and running data services has been identified in the group as key requirement for the motivation to implement DOIs to geodetic data.

Our group activities include the collection of data products and discussions on already existing and planned DOI activities for IAG services and geodetic data centres, including for recent projects, like FAIR GNSS. Whenever possible, we recommend that DOIs shall be included in standard data formats (e.g. Rinex) and cited when using the data. This presentation will give an update of the group activities.

How to cite: Elger, K. and the GGOS DOI Working Group: News from the GGOS DOI Working Group, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10982, https://doi.org/10.5194/egusphere-egu22-10982, 2022.

Height, gravity and clock
08:56–09:02
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EGU22-2523
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Presentation form not yet defined
Laura Sanchez, Jianliang Huang, Riccardo Barzaghi, and Georgios S. Vergos

Measuring, studying, and understanding global change effects demand unified geodetic reference frames with (i) an order of accuracy higher than the magnitude of the effects to be observed, (ii) consistency and reliability worldwide, and (iii) long-term stability. The development of the International Terrestrial Reference System (ITRS) and its realisation, the International Terrestrial Reference Frame (ITRF), enable the precise description of the Earth’s geometry by means of geocentric Cartesian coordinates with an accuracy at the cm-level and with global consistency. An equivalent high-precise global physical reference system that provides the basis for the consistent determination of gravity field-related coordinates worldwide, in particular geopotential differences or physical heights is missing. Without a conventional global height system, most countries are using local height systems, which have been implemented individually, applying in general non-standardised procedures. It is proven that their combination in a global frame presents discrepancies at the metre level. Therefore, a core objective of the international geodetic community is to establish an international standard for the precise determination of physical heights. This standard is known as the International Height Reference System (IHRS). Its realisation has been a main topic of research during the last years. Recent achievements concentrate on (1) compiling detailed standards, conventions, and guidelines for the IHRS realisation, (2) evaluating computational approaches for the consistent determination of potential differences, and (3) designing an operational infrastructure that ensures the maintenance and long-term stability of the IHRS and its realization. This contribution summarises advances and current challenges in the establishment, realization and sustainability of the IHRS.

How to cite: Sanchez, L., Huang, J., Barzaghi, R., and Vergos, G. S.: Towards an international standard for the precise determination of physical heights, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2523, https://doi.org/10.5194/egusphere-egu22-2523, 2022.

09:02–09:08
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EGU22-762
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Virtual presentation
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Vassilios D. Andritsanos, Vassilios N. Grigoriadis, Dimitrios Natsiopoulos, and Georgios S. Vergos

Within the frame of the “Modernization of the Hellenic Gravity Network” project, the homogenization of the Hellenic Vertical Datum is investigated. Two study areas in northern and southern Greece were selected, where the zero-level geopotential value Wo is estimated for each area. Additionally, a combined value is also estimated using a weighted least squares adjustment of Helmert orthometric heights and surface gravity values, that were recently measured, as well as recent global geopotential models. The biases in the vertical datum between northern and southern Greece are investigated through the comparison with a global conventional value. The validation of the results can lead to valuable conclusions on the possibility of a contemporary definition of the Hellenic Vertical Datum.

How to cite: Andritsanos, V. D., Grigoriadis, V. N., Natsiopoulos, D., and Vergos, G. S.: Zero-height geopotential level estimation for the homogenization and modernization of the Vertical Datum of Greece, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-762, https://doi.org/10.5194/egusphere-egu22-762, 2022.

09:08–09:14
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EGU22-2964
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On-site presentation
Axel Rülke, Reinhard Falk, Andreas Engfeldt, Julian Glässel, Andreas Hellerschmied, Domenico Iacovone, Jakub Kostelecký, Vojtech Pálinkáš, Marvin Reich, Ludger Timmen, Christian Ullrich, Alessandro Valluzzi, Hartmut Wziontek, and Barbara Zehetmaier

Geodetic observations on Earth accurate to better than a part per billion require a common reference for the same precision as described in the goals of the Global Geodetic Observing System. The International Gravity Reference System (IGRS) is proposed as a new reference for terrestrial gravity observations (Wziontek et al. 2021).

The International Gravity Reference Frame (IGRF) as the realization of IGRS is represented by absolute gravity measurements traceable to the SI. Due to the lack of a natural reference, absolute gravimeters need to be compared and the gravity reference is realized based on a set of measurements by a group of absolute gravimeters and the functional model for their processing.

We present the international comparison of absolute gravimeters WET-CAG2021 hosted at the Geodetic Observatory Wettzell in autumn 2021. This comparison is classified as an additional comparison following the strategy paper of the Consultative Committee for Mass and related quantities (CCM) and IAG. Seven FG5/X absolute gravimeters and two AQG quantum gravimeters have observed up to four individual piers over a period of twelve weeks. The individual observation epochs are connected by recordings of the continuously operating superconducting gravimeter GWR OSG 030 in the same laboratory.

We show the procedure of data analysis following Pálinkáš et al. (2021) and discuss the results also with respect to the latest regional metrological EURAMET comparison 2018 at the same location.

 

Marti, U., Richard, P., Germak, A., Vitushkin, L., Pálinkáš, V., Wilmes, H.: CCM-IAG Strategy for Metrology in Absolute Gravimetry, 11 March 2014

Pálinkáš, V., Wziontek, H., Vaľko, M. et al.: Evaluation of comparisons of absolute gravimeters using correlated quantities: reprocessing and analyses of recent comparisons. J Geod 95, 21 (2021). https://doi.org/10.1007/s00190-020-01435-y

Wziontek, H., Bonvalot, S., Falk, R. et al.: Status of the International Gravity Reference System and Frame. J Geod 95, 7 (2021). https://doi.org/10.1007/s00190-020-01438-9

How to cite: Rülke, A., Falk, R., Engfeldt, A., Glässel, J., Hellerschmied, A., Iacovone, D., Kostelecký, J., Pálinkáš, V., Reich, M., Timmen, L., Ullrich, C., Valluzzi, A., Wziontek, H., and Zehetmaier, B.: WET-CAG2021: An international comparison of absolute gravimeters for the realization of the International Gravity Reference System, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2964, https://doi.org/10.5194/egusphere-egu22-2964, 2022.

09:14–09:20
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EGU22-10553
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On-site presentation
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Jan Kodet, Ulrich Schreiber, Thomas Klügel, and Johann Eckl

Over the last two decades, the precision of individual measurements of Space Geodesy improved to a millimeter level. However, the overall achieved accuracy remains at a centimeter level due to systematic errors. The fundamental stations operating more than one space geodetic measurement technique present a keystone in systematic error investigation and mitigation. Due to regular surveys, the distances and mutual movements of the reference points are established with millimeter accuracy. The problem arises in the combination at the observation level, where the residuals of the measurements do not match with the established geometrical ties sufficiently well. Internal instrumental signal delays within each technique are causing this detrimental effect.

We have identified time coherence between the individual techniques and fundamental stations as the proper tool to overcome this problem. Within IAG Project QuGe we examine referencing the instrumentations to the optical clocks. In this scenario, the clock parameter in geodesy does not need to be adjusted any more, and all systematic effects would promote. To transfer clock stability within an entire station campus, we use a mode-locked fs-pulse laser, which is distributed using actively delay compensated fiber links, provides the necessary means to identify and remove these systematic errors. This talk illustrates some results and introduces the novel time distribution system of the Geodetic Observatory Wettzell, which realizes an ideal test bench for these clock ties.

How to cite: Kodet, J., Schreiber, U., Klügel, T., and Eckl, J.: Towards Clock Ties for a Global Geodetic Observing System, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10553, https://doi.org/10.5194/egusphere-egu22-10553, 2022.

Network and reference frames
09:20–09:26
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EGU22-2070
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Virtual presentation
Michael Pearlman, Dirk Behrend, Allison Craddock, Erricos Pavlis, Jérôme Saunier, Riccardo Barzaghi, Elizabeth Bradshaw, Claudia Carabajal, Daniela Thaller, Benjamin Maennel, Ryan Hippenstiel, Roland Pail, Ck Shum, Nicholas Brown, Sandra Blevins, and Laura Sanchez

The GGOS Bureau of Networks and Observations works with the IAG Services (IVS, ILRS, IGS, IDS, IGFS, IERS, and PSMSL) to advocate for the expansion and modernization of space geodetic networks for the maintenance and improvement of the reference frame and other applications, as well as for the integration of the techniques.  Of particular interest is the integration of gravimetric and tide gauge networks in view of the forthcoming establishment of a new absolute gravity reference frame and of the International Height Reference System/Frame. New sites are being established following the GGOS concept of “core” and co-location sites, and new technologies are being implemented to enhance performance in data yield as well as accuracy. 

The IAG Committees and Joint Working Groups play an essential role in the Bureau activity. The Standing Committee on Performance Simulations and Architectural Trade-offs (PLATO) uses simulation and analysis techniques to project future network capability and to examine trade-off options. The Committee on Data and Information is working on a strategy for a GGOS metadata system for data products and a more comprehensive long-term plan for an all-inclusive system. The Committee on Satellite Missions is working to enhance communication with the space missions, to advocate for missions that support GGOS goals and to enhance ground systems support. The IERS Working Group on Site Survey and Co-location (also participating in the Bureau) is working to enhance standardization in procedures, outreach and to encourage new survey groups to participate and improve procedures to determine systems’ reference points, a crucial aid in the detection of technique-specific systematic errors.

We will give a brief update on the status and projection of the network infrastructure for the next several years, and the progress and plans of the Committees/Working Groups in their critical role in enhancing data product quality and accessibility to the users, scientists and the general community.   

 

How to cite: Pearlman, M., Behrend, D., Craddock, A., Pavlis, E., Saunier, J., Barzaghi, R., Bradshaw, E., Carabajal, C., Thaller, D., Maennel, B., Hippenstiel, R., Pail, R., Shum, C., Brown, N., Blevins, S., and Sanchez, L.: An Update on the GGOS Bureau of Networks and Observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2070, https://doi.org/10.5194/egusphere-egu22-2070, 2022.

09:26–09:32
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EGU22-10616
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Presentation form not yet defined
Özgür Karatekin, Véronique Dehant, Javier Ventura-Traveset, Markus Rothacher, Pacome Delva, Urs Hugentobler, Zuheir Altamimi, Johannes Boehm, Alexandre Couhert, Frank Flechtner, Susanne Glaser, Rudiger Haas, Adrian Jaeggi, Benjamin Maennel, Felix Perosanz, Harald Schuh, and Hakan Sert

Improving and homogenizing time and space references on Earth and, more directly, realizing the terrestrial reference system with an accuracy of 1 mm and a long-term stability of 0.1 mm/yr are relevant for many scientific and societal endeavours. The knowledge of the terrestrial reference frame (TRF) is fundamental for Earth system monitoring and related applications. For instance, quantifying sea level change strongly depends on an accurate determination of the geocenter motion but also of the position of continental or island reference stations, such as those located at tide gauges, as well as the ground stations of the tracking networks. Also, numerous applications in geophysics require absolute millimetre precision from the reference frame, as for example monitoring tectonic motion or crustal deformation for predicting natural hazards. The TRF accuracy to be achieved (mentioned above) represents the consensus of various authorities, including the International Association of Geodesy, which has enunciated geodesy requirements for Earth science (see GGOS-2020). Moreover, as stated in the A/RES/69/266 United Nations Resolution: “A global geodetic reference frame for sustainable development”, the UN recognizes the importance of “the investments of Member States in developing satellite missions for positioning and remote sensing of the Earth, supporting a range of scientific endeavours that improve our understanding of the Earth system and underpin decision-making, and… that the full societal benefits of these investments are realized only if they are referenced to a common global geodetic reference frame at the national, regional and global levels”. These strong statements by international bodies underline that a dedicated mission is highly needed and timely. Today we are still far away from this ambitious goal. It can be achieved by combining and co-locating, on one satellite platform, the full set of fundamental space-time geodetic systems, namely GNSS and DORIS radio satellite tracking systems, the satellite laser ranging (SLR) technique, and the very long baseline interferometry (VLBI) technique, that currently operates by recording the signals from quasars. This platform can then be considered as a dynamic space geodetic observatory carrying all these geodetic instruments referenced to one another on a unique well-calibrated platform through carefully measured space ties and a very precise atomic clock. It is necessary to set up a co-location of the techniques in space to resolve the inconsistencies and biases between them. Such a mission will be proposed as the first one of a series of missions in the GNSS/NAV Science Programme. The purpose of this abstract/talk is to revive the support of the scientific community for this mission.

How to cite: Karatekin, Ö., Dehant, V., Ventura-Traveset, J., Rothacher, M., Delva, P., Hugentobler, U., Altamimi, Z., Boehm, J., Couhert, A., Flechtner, F., Glaser, S., Haas, R., Jaeggi, A., Maennel, B., Perosanz, F., Schuh, H., and Sert, H.: GENESIS-1 mission for improved reference frames and Earth science applications., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10616, https://doi.org/10.5194/egusphere-egu22-10616, 2022.

09:32–09:38
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EGU22-13321
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ECS
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Virtual presentation
Arnab Laha, Ashutosh Tiwari, Saurabh Srivastava, Shivangi Singh, Bhal Chandra Joshi, Nagarajan Balasubramanian, Ajith Kumar, Yashwant Gupta, and Onkar Dikshit

Very Long Baseline Interferometry (VLBI) technique was developed in the 1960s by astronomers, for high angular resolution observations of celestial radio sources. In the late 1970s, it was adopted for high-precision geodetic applications, in a reverse manner. In this application, VLBI is used to monitor the kinematics of individual points on the Earth, and also of the Earth as a body in the space using the precisely known astronomical positions of radio sources. Despite differences between astronomical and geodetic applications, the instrumentation and analysis techniques employed in VLBI are broadly similar, allowing for antennas designed for VLBI to be usable for either application. In this presentation, we describe a proposal for upgradation of three existing communication antennas with 18-m, 30-m and 32-m diameter, located at Arvi, Pune, India, for astronomical and geodetic VLBI purposes. The main objective is to retrofit the antenna with new gearboxes and modern servo control systems to make them compatible for use in VLBI observations, as well as with suitable L, S, and C band receivers and digital recorders, in a short period of time. Each motor will be driven by a drive with close loop precision pointing system, making it suitable to point to and track celestial sources. The antennas will be fitted with suitable antenna feeds and receiver systems, after the analysis of the dish parameters and its mounting possibilities. A development of cooled S-band feed will also be initiated simultaneously. Further, the three antennas will be fitted with new front-end electronics, baseband converter and digital recorders. The observed bandpass with different feeds (S and C band) will be down converted to L-band. This signal will be transported over optical fibre to the Giant Meterwave Radio Telescope (GMRT) facility, which is located nearby, for data recording and correlation activities. The retrofitted instrument will provide a test bed for instrumentation, tuning analysis pipelines and software, while providing the capability to carry out both astronomical and geodetic VLBI experiments with other international facilities.

How to cite: Laha, A., Tiwari, A., Srivastava, S., Singh, S., Joshi, B. C., Balasubramanian, N., Kumar, A., Gupta, Y., and Dikshit, O.: Retrofitting communication antennas for astronomical and geodetic VLBI applications, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13321, https://doi.org/10.5194/egusphere-egu22-13321, 2022.

09:38–09:44
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EGU22-8593
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On-site presentation
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Mariana Moreira, Esther Azcue, Víctor Puente, Abel García, Diogo Avelar, Elena Martínez, João Ferreira, Javier González-García, José López-Pérez, and Valente Cuambe

RAEGE (Atlantic Network of Geodynamic and Space Stations) is a project resulting from the cooperation between the National Geographic Institute of Spain (IGN) and the Government of Azores. It is a unique project at a geodetic and geodynamic level, in which it is committed to the combination of geodetic techniques in four stations - two in Spain (Yebes and Gran Canaria) and two in Azores (Flores and Santa Maria). Santa Maria and Yebes stations are already fully implemented. The instrumentation foreseen for all four stations and that are currently implemented are radiotelescopes that use the VLBI technique, GNSS receivers, superconductive gravimetries, seismographs, and maser clocks. Furthermore, an SLR system will be shortly installed at Yebes station.

These stations are integrated into the VGOS network and in the Global Geodetic Reference System (GGOS), as multi-technique observatories. These multi-technical observatories are key in the definition of reference systems, as they allow the integration of the individual networks of each technique into a single system. Additionally, they provide an idea of the quality and precision of the systems themselves, thanks to the validation of the results between techniques. Apart from the multi-technique, the uniqueness of the RAEGE project resides in the fact that the four stations will be located on three different tectonic plates, hence their data will be of great importance to understand this triple tectonic junction.

RAEGE not only focuses on providing the necessary infrastructure for observations but also, among its objectives, to promote multi-technical geodetic analysis and obtain studies and results supported by the data collected. The purpose of this contribution is, therefore, to present the current state of the RAEGE project, including the sites and instrumentation, as well as the current analysis activities and prospects, particularly concerning the combination of the techniques present at the stations. 

How to cite: Moreira, M., Azcue, E., Puente, V., García, A., Avelar, D., Martínez, E., Ferreira, J., González-García, J., López-Pérez, J., and Cuambe, V.: RAEGE Project: Status, Analysis Endeavours, and Future Prospects, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8593, https://doi.org/10.5194/egusphere-egu22-8593, 2022.

Troposphere and ionosphere
09:44–09:50
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EGU22-9834
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ECS
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On-site presentation
Dariusz Strugarek, Mateusz Drożdżewski, Krzysztof Sośnica, Radosław Zajdel, and Grzegorz Bury

Satellite Laser Ranging (SLR) is the only one space geodetic technique in which troposphere correction is calculated based on in situ measurements (pressure, temperature, and humidity) and used in the least square adjustment process as a fixed value measured at the epoch of observation.  In the past few years, we observe that the use of malfunctioning barometers for some of the SLR stations significantly affects the SLR-based global geodetic parameter estimates, such as station coordinates, geocenter coordinates, and terrestrial reference frame scale. Thus, we examine different handling of the SLR range tropospheric delay to LAGEOS by analysing the a priori zenith total delay from the standard Mendes and Pavlis (2004) model with a corresponding mapping function, the estimated tropospheric correction, and the range bias parameter. Moreover, we conduct a simulation study of artificial pressure bias, investigating the capability of tested approaches to properly reconstruct the tropospheric error. The new approach based on the estimation of the troposphere delay correction for SLR solutions, which is also widely used in microwave techniques, explicitly demonstrates more suitable handling of errors affecting the SLR station than solutions based on estimation of range biases.

The progress in precise orbit determination of low Earth orbiter (LEO) satellites using GPS demands improvements of the SLR procedures considering their orbit validation, determination of station coordinates, and global geodetic parameters from SLR to LEOs solutions. Within this study, we also consider including the proper handling of range errors in SLR to LEOs. We test solutions incorporating the estimation of tropospheric biases with and without horizontal gradients, range biases, and station coordinate corrections in an example of the SLR observations to LEO Swarm satellites. We discuss the values of estimated corrections and their impact on the solution quality, and dependency of residuals to different measurement conditions, such as elevation angle, azimuth angle, station-satellite distance, or satellite view from a station. Estimating tropospheric biases once-per-day and horizontal gradients, absorbs elevation- and azimuth-dependent errors, provides a reduction of solution statistics, and dependency of SLR residuals for almost all used SLR stations.

How to cite: Strugarek, D., Drożdżewski, M., Sośnica, K., Zajdel, R., and Bury, G.: Estimation of tropospheric biases in SLR to Swarm, and LAGEOS satellites, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9834, https://doi.org/10.5194/egusphere-egu22-9834, 2022.

09:50–09:56
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EGU22-306
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ECS
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Virtual presentation
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Loram Siqueira, Joao Francisco Galera Monico, and Claudinei Rodrigues de Aguiar

Precise point positioning (PPP) is an available solution for one-frequency receivers if the ionosphere delay is informed during the data processing. Such information may be retrieved from the ionospheric maps, which can have a global or regional coverage. IGS has traditionally being providing them globally, throughout different analyses centers. On the other hand, regional products have been increasingly catching the interest of the scientific community.  Regional Ionosphere Maps (RIM) will use local active GNSS networks with multi-frequency receivers to model and represent the ionospheric delays. Because of the larger amount of information from a specific region, which may lack in the global products, the representation can be better and show improvements for areas where the ionosphere is more active. For the South American area, studies have been conducted using active networks. GIB (Brazilian Ionospheric Grid) was developed in 2010 and computes regional maps using GPS data from the Brazilian Continuous Monitoring Stations (RBMC). More recently (2018) the Meteorología espacial, Atmosfera terrestre, Geodesia, Geodinámica, diseño Instrumental y Astrometría (MAGGIA) made available its regional product covering the same area using GNSS data from Brazil, Uruguay and Argentina. Presently we are verging to the beginning of the next solar cycle and understanding the availability of global and regional products for ionosphere correction, and its level of accuracy will be a crucial information to be hold. In this contribution, an evaluation of four products was performed using kinematic PPP for the day 80 of 2021, of course with a reduced amount of data. The global products (CODE and GFZ) used the IGS network on its construction. A reference station from RBMC, with known coordinates was used as the ground truth to determine the accuracy of each product using a simulated PPP kinematics. with residuals and needed system transformation the accuracy and precision for each product was acquired. Overall results show that the MAGGIA product presents the best accuracy, followed by the GFZ, IGS and GIB. For this analysis it was possible to conclude that two elements play an important role when creating ionosphere maps: not only the regional characterization but also using multi constellation GNSS data will play a key role in the products quality. MAGGIA and GIB, both regional products, obtained the best and the worse results, respectively and the major difference being the use of only one GNSS constellation (GIB) and multiple GNSS constellations (MAGGIA) for its calculation.

How to cite: Siqueira, L., Francisco Galera Monico, J., and Rodrigues de Aguiar, C.: Assessment of global and regional ionospheric maps over Brazil using simulated kinematic precise point positioning. , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-306, https://doi.org/10.5194/egusphere-egu22-306, 2022.

09:56–10:00