Análise do eixo de rotação da terra no Japão considerando a ocorrência de terremoto ocorrido em março de 2011

Objetivou-se analisar o eixo de rotação da terra no período superior a um ano, considerando a ocorrência de um fenômeno natural, como o terremoto do Japão ocorrido em março de 2011, para saber se o mesmo contribuiu para alterar o eixo de rotação da Terra e quais as variações sofridas durante o período de estudo. Foram coletados os dados na página oficial do IERS (International Earth Rotation and Reference Systems Service) os dados de orientação da Terra, que são encontrados nos Boletins B, enumerados e coletados no intervalo do boletim B 278 até boletim B 285, que representam o período de setembro de 2010 a setembro de 2011. Com o uso do Excel 2016, tabelou-se e organizaram-se os dados, os quais se referem ao movimento do polo de x e y na unidade de milésimo de segundo (mas). Feito a organização, houve a criação do gráfico no próprio software. As figuras expostas demonstram que as oscilações obedeceram ao padrão cíclico do Movimento de Chandler, de modo que é possível inferir que, apesar da magnitude do evento, não houve interferência sobre o movimento analisado.

Observing UT1-UTC with VGOS

We present first results for the determination of UT1-UTC using the VLBI Global Observing System (VGOS). During December 2019 through February 2020, a series of 1 h long observing sessions were performed using the VGOS stations at Ishioka in Japan and the Onsala twin telescopes in Sweden. These VGOS-B sessions were observed simultaneously to standard legacy S/X-band Intensive sessions. The VGOS-B data were correlated, post-correlation processed, and analysed at the Onsala Space Observatory. The derived UT1-UTC results were compared to corresponding results from standard legacy S/X-band Intensive sessions (INT1/INT2), as well as to the final values of the International Earth Rotation and Reference Frame Service (IERS), provided in IERS Bulletin B. The VGOS-B series achieves 3–4 times lower formal uncertainties for the UT1-UTC results than standard legacy S/X-band INT series. The RMS agreement w.r.t. to IERS Bulletin B is slightly better for the VGOS-B results than for the simultaneously observed legacy S/X-band INT1 results, and the VGOS-B results have a small bias only with the smallest remaining standard deviation.

Trends and variations in the irregularities of the Earth’s rotation

The paper presents results of modeling various variations of the Universal Time (UT1). To develop a variation models, UT1 observations from 1901 to 2020 published by the International Earth Rotation and Reference Systems Service (IERS) were used. Using the developed method, the main variations are identified from the diverse spectrum of irregularities in the Earth’s rotation, the models of which are presented as a superposition of a limited number of harmonic components. The results obtained in this paper are important for improving the accuracy of predictions of Universal Time.

Observing UT1-UTC with VGOS

We present rst results of UT1-UTC determinations using the VLBI Global Observing System (VGOS). During December 2019 through February 2020 a series of 1 hour long observing sessions were performed using the VGOS stations at Ishioka in Japan and the Onsala twin telescopes in Sweden. The data of this VGOS-B series were correlated, post-correlation processed, and analysed at the Onsala Space Observatory. The derived UT1-UTC results were compared to corresponding results from standard legacy S/X Intensive sessions (INT1/INT2), as well to the nal values of the International Earth Rotation and Reference Frame Service (IERS), provided in IERS Bulletin B. The VGOS-B series achieve 3-4 times lower formal uncertainties for the UT1-UTC results than standard legacy S/X INT series. Furthermore, the root mean square (RMS) agreement with respect to the IERS Bulletin B is 30-40 % better for the VGOS-B results than for the INT1/INT2 results.

Status of ESA’s independent Earth Orientation Parameter products

<p>The availability of highly accurate, up-to-date Earth Orientation Parameters is of major importance for all positioning and navigation applications on Earth, Sea, Air and also in Space. This is equally true for ESA missions and the EU space programs, e.g. Galileo, EGNOS and Copernicus.</p><p>In the frame of its responsibility to provide the Geodetic reference for ESA missions, ESA’s Navigation Support Office at ESOC is already contributing to the realisation of the International Terrestrial Reference Frame (ITRF) and the combined Earth Orientation Parameters provided by the International Earth Rotation Service (IERS). The contribution is realised through individual contributions to international services such as the International GNSS Service (IGS), the International Laser Ranging Services (ILRS), the International DORIS Service (IDS), the International Earth Rotation Service (IERS) and in the future also to the International VLBI Service (IVS).</p><p>For the combination and the long-term predictions of the Earth orientation products ESA is still relying on the International Earth Rotation Service (IERS). Over the past years, ESA repeatedly experienced problems with outdated or missing predictions of the Earth orientation parameters (Bulletin A). Considering the importance of up-to-date Earth orientation parameters, the dependence on a single source outside Europe is considered a risk for European industry, for ESA missions and for EU programmes. For this reason, ESA initiated in 2017 a study with the target to develop independent ESA Earth Orientation parameter products. This study, executed by a consortium led by the Deutsches Geodätisches Forschungsinstitut (DGFI-TUM), is expected to finish in the course of this year.</p><p>In this presentation we will give an overview of ESAs up-to-date reference products and discuss their quality. It will outline the combination approach and discuss the way forward to an fully operational provision of the ESA Earth Orientation Parameter products.</p>

Tidal Parameters as a Tool for the Determination of the Coordinates of the SLR Stations

One of the primary objectives of satellite geodesy is the determination of coordinates of the satellite laser ranging (SLR) stations. This task is conducted by using laser ranging techniques. The main goal of the current study was to assess the influence of using varied values of the tidal parameters (Love h2 and Shida l2 numbers) on the determination of the positions of chosen SLR stations. The obtained results are presented for coordinates determination conducted for six SLR stations: Mt Stromlo (no. 7825, Australia), Matera (no. 7941, Italy), Grasse (no. 7845, France), McDonald (no. 7080, USA), Arequipa (no. 7403, Peru) and Beijing (no. 7249, China). The analysis covers SLR data for 2 satellites (LAGEOS1 and LAGEOS2), which were observed for 10 consecutive years (from 2008 to 2018). The analysis was performed using the ITRF2014 reference frame in two scenarios of calculations. In scenario 1, the SLR stations coordinates were calculated using the nominal values as per the International Earth Rotation and Reference System Service (IERS) standards recommendation of the Love/Shida numbers: h2 = 0.6078, l2 = 0.0847. In scenario 2, the coordinates were estimated using the harnessing values of the Love/Shida numbers (h2 = 0.6140 and l2 = 0.0876), which were proposed by authors in a previous publication. The effect of the application of different values of the Love/Shida numbers for the determination of SLR stations coordinates was scrutinized.

COMPATIBILIZAÇÃO DE REFERENCIAIS DE COORDENADAS E VELOCIDADES COM ESTIMATIVA DE PRECISÃO

Resumo:As transformações de coordenadas e velocidades entre as realizações do ITRS (International Terrestrial Reference System), bem como a atualização de coordenadas, tornar-se-ão tarefas rotineiras em levantamentos geodésicos devido ao emprego de sistemas de referência dinâmicos e ao movimento das placas tectônicas. Neste estudo foram realizadas compatibilizações de sistemas de referência (ITRF2000, ITRF2005 e ITRF2008) das coordenadas e velocidades com suas respectivas estimativas de precisão, via propagação de variância, de 11 estações distribuídas nas placas tectônicas Norte e Sul Americanas e da Eurásia. Foi verificado com base nas coordenadas nos ITRF2008, época 2005 e ITRF2005, época 2000, obtidas pelo IERS (International Earth Rotation and Reference System Service), que 54,55% das discrepâncias planimétricas são centimétricas e 45,45% decimétricas. Comparando as coordenadas no ITRF2008, época 2005,0 e no ITRF2000, época 1997,0 verificou-se discrepâncias planimétricas da ordem do decímetro para todas as estações. Confrontando as coordenadas ITRF2000, época 1997,0 obtidas pelo IERS com as calculadas com base nas transformações entre sistemas de referência e atualizações verifica-se discrepâncias planimétricas da ordem do milímetro em 72,73% dos casos e da ordem do centímetro em 27,27%. As análises realizadas confirmam a necessidade de atualizar e compatibilizar o referencial das coordenadas e velocidades para aumentar a acurácia do posicionamento

Relativity in the IERS Conventions

In the last years, a fully general relativistic definition of reference systems and of their application to astronomy and geodesy has been passed into Resolutions of the scientific unions, following work of several working groups and of the community at large. In this community, the role of the International Earth Rotation and Reference systems Service (IERS) is to generate the terrestrial and celestial reference systems and the transformation between them, and the IERS Conventions provide the set of models and procedures used in the generation of IERS products. It is therefore essential that the IAU framework for relativity is introduced in the IERS Conventions, and that this is done consistently and completely throughout the document. The paper reviews relativistic aspects in the IERS Conventions and presents recent and on-going work aiming at providing a complete and consistent presentation for a new reference edition of the IERS Conventions, expected to appear in the next year.