COST-G gravity field models for precise orbit determination of Low Earth Orbiting Satellites

Peter, Heike; Meyer, Ulrich; Lasser, Martin; Jäggi, Adrian

doi:10.1016/j.asr.2022.04.005

Cited by 15 publications

(4 citation statements)

References 32 publications

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“…A typical example is the surface mass balance estimates at polar regions, e.g., Greenland and Antarctica (see The IMBIE team 27 , 28 ) exhibit relatively lower mass change rates until late 1990s followed with an onset of dramatic increase in mass loss after 2000 due to the accelerated ocean-driven melting of the ice sheets. Similar extrapolation errors are also reported 29 for the long-term static gravity field solutions with co-estimated (TVC) time-variable coefficients (secular and seasonal periodic components), e.g. GOCO06S 30 , by evaluating the differences of mass anomaly from the monthly GRACE-FO solutions and those extrapolated from the static field with TVC computed from the data solely within the GRACE era, suggesting that the static gravity models with TVC cannot be used for long-term (>2-3 years) extrapolation and at least should be frequently updated with the newly available GRACE-FO data, e.g.…”

Section: Methodssupporting

confidence: 88%

High-resolution temporal gravity field data products: Monthly mass grids and spherical harmonics from 1994 to 2021

Uz,

Akyılmaz,

Shum

et al. 2024

Sci Data

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Since April 2002, Gravity Recovery and Climate Experiment (GRACE) and GRACE-FO (FollowOn) satellite gravimetry missions have provided precious data for monitoring mass variations within the hydrosphere, cryosphere, and oceans with unprecedented accuracy and resolution. However, the long-term products of mass variations prior to GRACE-era may allow for a better understanding of spatio-temporal changes in climate-induced geophysical phenomena, e.g., terrestrial water cycle, ice sheet and glacier mass balance, sea level change and ocean bottom pressure (OBP). Here, climate-driven mass anomalies are simulated globally at 1.0° × 1.0° spatial and monthly temporal resolutions from January 1994 to January 2021 using an in-house developed hybrid Deep Learning architecture considering GRACE/-FO mascon and SLR-inferred gravimetry, ECMWF Reanalysis-5 data, and normalized time tag information as training datasets. Internally, we consider mathematical metrics such as RMSE, NSE and comparisons to previous studies, and externally, we compare our simulations to GRACE-independent datasets such as El-Nino and La-Nina indexes, Global Mean Sea Level, Earth Orientation Parameters-derived low-degree spherical harmonic coefficients, and in-situ OBP measurements for validation.

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Section: Methodssupporting

confidence: 88%

High-resolution temporal gravity field data products: Monthly mass grids and spherical harmonics from 1994 to 2021

Uz,

Akyılmaz,

Shum

et al. 2024

Sci Data

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“…The International Association of Geodesy established the International Combination Service for Time-variable Gravity Fields (COST-G) dedicated to the combination of monthly global gravity field models generated by individual GRACE analysis centers. Based on the combined GRACE and GRACE Follow-On solutions provided by the COST-G (Meyer et al 2020a;Meyer et al 2020;Peter et al 2022) up to degree and order 60, we determined the trend and amplitude of ice mass changes in Greenland and the Eastern and Western Antarctic regions. The COST-G solution is a combination of monthly global gravity field models provided by the NASA Jet Propulsion Laboratory (JPL 2019), University Of Texas Center For Space Research (UTCSR 2018), the German Research Centre for Geosciences (GFZ, (Dahle et al 2018)), and by several other analysis centers, e.g., the Astronomical Institute of the University of Bern (AIUB, (Lasser et al 2020)), the Centre National d'Etudes Spatiales/Groupe de Recherche de Géodésie Spatiale (GRGS, (Lemoine 2023)), the Institute of Geodesy at Graz University of Technology (IfG, (Mayer-Gürr et al 2018)), the Leibniz Universitxiät Hannover (LUH, (Koch et al 2023)), the Chinese Academy of Sciences (IGG, (Wang et al 2015)), Huazhong University of Science and Technology (HUST, (Zhou et al 2016)), Tongji University Shanghai (Chen et al 2018), and Wuhan University (WHU, (Guo et al 2017)).…”

Section: Methodsmentioning

confidence: 99%

Impact of the combination and replacement of SLR-based low-degree gravity field coefficients in GRACE solutions

Gałdyn,

Sośnica

2024

Prog Earth Planet Sci

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GRACE and GRACE Follow-On (FO) missions provide time-variable gravity field models of unprecedented quality that allow for the hydrological, oceanic, and ice mass change studies on a global scale. However, the very low-degree coefficients derived from GRACE and GRACE-FO are of inferior quality due to thermal effects acting on satellites and malfunctioning of the onboard accelerometers. Therefore, C20 and C30 coefficients describing the Earth’s oblateness and the pear shape of the Earth, respectively, are being replaced by values derived from satellite laser ranging (SLR) in the standard GRACE solutions. This study assesses the impact of the replacement of low-degree gravity field coefficients in GRACE/GRACE-FO solutions by SLR data on the trend and seasonal signals of ice mass changes in Greenland and Antarctica. We found that the replacement of the low-degree gravity field coefficients changes the estimates of trends by 4, 8, and 22 Gt/year in Greenland, West, and East Antarctica, respectively, depending on the source of SLR coefficients and period for which the coefficients are replaced. In SLR and GRACE solutions, all coefficients of the same order and the same parity of degrees are strongly correlated. Therefore, replacing only two selected coefficients may lead to a biased solution. Thus, we propose to combine GRACE with SLR solutions up to a degree and order 10 × 10 to properly consider the sensitivity of each of the techniques to gravity field coefficients, instead of replacing two coefficients from SLR in GRACE solutions. The combined solution reduces the residual trend of post-glacial rebound from 1.2 to 0.9 Gt/year and from − 57.8 to − 57.0 Gt/year in Scandinavia and South Canada, respectively, when compared to GRACE/GRACE-FO solutions with the replacement of coefficients. The SLR-GRACE combination reduces the noise in the GRACE/GRACE-FO solutions by 8%, from 38 to 35 Gt, in the Fennoscandia region. In the periods when GRACE is at the end of its mission and observations are disrupted, the weights adjust the contribution from SLR and GRACE based on relative ratio of variances from each techniques. Thus, the combined solutions are more consistent with independent geophysical models of glacial isostatic adjustment, and the combinations are affected by smaller noise than the standard GRACE solutions and properly account for different sensitivities of SLR and GRACE techniques to low-degree time-variable gravity field coefficients.

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“…For missions providing long-term climatological data records, it is therefore essential to perform the most accurate POD in a reference frame which is consistent across many years for the data analysis of many different spacecraft. In addition to a stable reference frame, which is crucial to not contaminate sea level rise measurements with reference frame drifts (Altamimi and Collilieux 2013), the highly accurate modeling of non-gravitational (e.g., Flohrer et al 2011;Mao et al 2021) and gravitational forces, e.g., the proper modeling of temporal gravity variations across many years (Couhert et al 2015;Peter et al 2022), as well as a full exploitation of multiple tracking techniques (Luthcke et al 2003;Choi et al 2004) is mandatory for the most accurate POD.…”

Section: Positioning Of Satellites and Space Probesmentioning

confidence: 99%

GENESIS: co-location of geodetic techniques in space

Delva

Altamimi

Blazquez

et al. 2023

Earth Planets Space

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Improving and homogenizing time and space reference systems on Earth and, more specifically, realizing the Terrestrial Reference Frame (TRF) with an accuracy of 1 mm and a long-term stability of 0.1 mm/year are relevant for many scientific and societal endeavors. The knowledge of the TRF is fundamental for Earth and navigation sciences. For instance, quantifying sea level change strongly depends on an accurate determination of the geocenter motion but also of the positions of continental and island reference stations, such as those located at tide gauges, as well as the ground stations of tracking networks. Also, numerous applications in geophysics require absolute millimeter precision from the reference frame, as for example monitoring tectonic motion or crustal deformation, contributing to a better understanding of natural hazards. The TRF accuracy to be achieved represents the consensus of various authorities, including the International Association of Geodesy (IAG), which has enunciated geodesy requirements for Earth sciences. Moreover, the United Nations Resolution 69/266 states that the full societal benefits in developing satellite missions for positioning and Remote Sensing of the Earth are realized only if they are referenced to a common global geodetic reference frame at the national, regional and global levels. Today we are still far from these ambitious accuracy and stability goals for the realization of the TRF. However, a combination and co-location of all four space geodetic techniques on one satellite platform can significantly contribute to achieving these goals. This is the purpose of the GENESIS mission, a component of the FutureNAV program of the European Space Agency. The GENESIS platform will be a dynamic space geodetic observatory carrying all the geodetic instruments referenced to one another through carefully calibrated space ties. The co-location of the techniques in space will solve the inconsistencies and biases between the different geodetic techniques in order to reach the TRF accuracy and stability goals endorsed by the various international authorities and the scientific community. The purpose of this paper is to review the state-of-the-art and explain the benefits of the GENESIS mission in Earth sciences, navigation sciences and metrology. This paper has been written and supported by a large community of scientists from many countries and working in several different fields of science, ranging from geophysics and geodesy to time and frequency metrology, navigation and positioning. As it is explained throughout this paper, there is a very high scientific consensus that the GENESIS mission would deliver exemplary science and societal benefits across a multidisciplinary range of Navigation and Earth sciences applications, constituting a global infrastructure that is internationally agreed to be strongly desirable. Graphical Abstract

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COST-G gravity field models for precise orbit determination of Low Earth Orbiting Satellites

Cited by 15 publications

References 32 publications

High-resolution temporal gravity field data products: Monthly mass grids and spherical harmonics from 1994 to 2021

High-resolution temporal gravity field data products: Monthly mass grids and spherical harmonics from 1994 to 2021

Impact of the combination and replacement of SLR-based low-degree gravity field coefficients in GRACE solutions

GENESIS: co-location of geodetic techniques in space

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