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  • 1
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    Satellite Gravimetry: A Review of Its Realization (2021)
    Springer Netherlands
    Details
    Publication Date: 2023-07-20
    Description: Since Kepler, Newton and Huygens in the seventeenth century, geodesy has been concerned with determining the figure, orientation and gravitational field of the Earth. With the beginning of the space age in 1957, a new branch of geodesy was created, satellite geodesy. Only with satellites did geodesy become truly global. Oceans were no longer obstacles and the Earth as a whole could be observed and measured in consistent series of measurements. Of particular interest is the determination of the spatial structures and finally the temporal changes of the Earth's gravitational field. The knowledge of the gravitational field represents the natural bridge to the study of the physics of the Earth's interior, the circulation of our oceans and, more recently, the climate. Today, key findings on climate change are derived from the temporal changes in the gravitational field: on ice mass loss in Greenland and Antarctica, sea level rise and generally on changes in the global water cycle. This has only become possible with dedicated gravity satellite missions opening a method known as satellite gravimetry. In the first forty years of space age, satellite gravimetry was based on the analysis of the orbital motion of satellites. Due to the uneven distribution of observatories over the globe, the initially inaccurate measuring methods and the inadequacies of the evaluation models, the reconstruction of global models of the Earth's gravitational field was a great challenge. The transition from passive satellites for gravity field determination to satellites equipped with special sensor technology, which was initiated in the last decade of the twentieth century, brought decisive progress. In the chronological sequence of the launch of such new satellites, the history, mission objectives and measuring principles of the missions CHAMP, GRACE and GOCE flown since 2000 are outlined and essential scientific results of the individual missions are highlighted. The special features of the GRACE Follow-On Mission, which was launched in 2018, and the plans for a next generation of gravity field missions are also discussed.
    Description: Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum - GFZ (4217)
    Keywords: ddc:526 ; Gravitational field ; Satellite gravimetry ; Satellite altimetry ; Gravitational field missions ; CHAMP ; GRACE ; GOCE ; GRACE FO ; Satellite orbits ; Satellite design ; Mission objectives ; Gravity field models ; Mass changes ; Satellite gradiometry ; Laser interferometer
    Language: English
    Type: doc-type:article
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    CITATION GEO-LEO
  • 2
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    Forward Gravity Modelling to Augment High-Resolution Combined Gravity Field Models (2020)
    Springer Netherlands
    Details
    Publication Date: 2023-06-09
    Description: During the last few years, the determination of high-resolution global gravity field has gained momentum due to high-accuracy satellite-derived observations and development of forward gravity modelling. Forward modelling computes the global gravitational field from mass distribution sources instead of actual gravity measurements and helps improving and complementing the medium to high-frequency components of the global gravity field models. In this study, we approximate the global gravity potential of the Earth’s upper crust based on ellipsoidal approximation and a mass layer concept. Such an approach has an advantage of spectral methods and also avoids possible instabilities due to the use of a sequence of thin ellipsoidal shells. Lateral density within these volumetric shells bounded by confocal lower and upper shell ellipsoids is used in the computation of the ellipsoidal harmonic coefficients which are then transformed into spherical harmonic coefficients on the Earth’s surface in the final step. The main outcome of this research is a spectral representation of the gravitatioal potential of the Earth’s upper crust, computed up to degree and order 3660 in terms of spherical harmonic coefficients (ROLI_EllApprox_SphN_3660). We evaluate our methodology by comparing this model with other similar forward models in the literature which show sub-cm agreement in terms of geoid undulations. Finally, EIGEN-6C4 is augmented by ROLI_EllApprox_SphN_3660 and the gravity field functionals computed from the expanded model which has about 5 km half-wavelength spatial resolution are compared w.r.t. ground-truth data in different regions worldwide. Our investigations show that the contribution of the topographic model increases the agreement up to ~ 20% in the gravity value comparisons.
    Keywords: ddc:526 ; Gravity forward modelling ; Multi-layer forward modelling ; Ellipsoidal topographic potential ; New-generation gravity field model ; Augmented gravity field models
    Language: English
    Type: doc-type:article
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    CITATION GEO-LEO
  • 3
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    GFZ Precise Science Orbit Products for satellites equipped with DORIS receiver (version 2) (2022)
    GFZ Data Services
    Details
    Publication Date: 2023-01-13
    Description: Abstract
    Description: Orbital products describe positions and velocities of satellites, be it the Global Navigation Satellite System (GNSS) satellites or Low Earth Orbiter (LEO) satellites. These orbital products can be divided into the fastest available ones, the Near Realtime Orbits (NRT, Zitat), which are mostly available within 15 to 60 minutes delay, followed by Rapid Science Orbit (RSO, Zitat) products with a latency of two days and finally the Precise Science Orbit (PSO) which, with a latency of up to a few weeks or longer in the case of reprocessing campaigns, are the most delayed. The absolute positional accuracy increases from NRT to PSO. This dataset compiles the PSO products for various LEO missions and GNSS constellation in sp3 format. GNSS Constellation: - GPS LEO Satellites: -ENVISAT -Jason-1 -Jason-2 -Jason-3 -Sentinel-3A -Sentinel-3B -Sentinel-6A -TOPEX Each solution follows specific requirements and parametrizations which are named in the respective processing metric table.
    Description: TechnicalInfo
    Description: Within the scope of various international working groups and services, and mission involvements, such as Copernicus POD QWG, IDS, ILRS, TanDEM-X, GRACE(-FO), different PSO orbits are generated at GFZ. These orbits ensue to the best of one’s ability the specific requirements and are based either on one individual observation technique or on a combination of several. Adopted processing settings and, in the case of dynamic POD, parameterizations and modeling are listed in a respective processing metric table. The orbits are stored in the GFZ Information System and Data Center (ISDC) and to the extent deemed possible freely available for the scientific community world-wide
    Keywords: Level-3 ; Satellite Geodesy ; Low Earth Orbiter ; Orbit ; TOR ; TSX ; GRACE-FO ; GPS ; RSO ; SAR ; IGOR ; Tracking ; Occultation ; Satellite Laser Ranging ; SLR ; Earth Observation Satellites 〉 ENVISAT ; Earth Observation Satellites 〉 JASON-1 ; Earth Observation Satellites 〉 OSTM/JASON-2 ; Earth Observation Satellites 〉 SATELLITES ; Earth Observation Satellites 〉 Sentinel GMES 〉 SENTINEL-3 ; Earth Observation Satellites 〉 TOPEX/POSEIDON ; Earth Remote Sensing Instruments 〉 Passive Remote Sensing 〉 Positioning/Navigation 〉 DORIS GROUND STATION BEACON ; Earth Remote Sensing Instruments 〉 Passive Remote Sensing 〉 Positioning/Navigation 〉 GNSS ; Earth Remote Sensing Instruments 〉 Passive Remote Sensing 〉 Positioning/Navigation 〉 GPS 〉 GNSS RECEIVER ; Earth Remote Sensing Instruments 〉 Passive Remote Sensing 〉 Positioning/Navigation 〉 GPS 〉 GPS ; Earth Remote Sensing Instruments 〉 Passive Remote Sensing 〉 Positioning/Navigation 〉 GPS 〉 GPS CLOCKS ; Earth Remote Sensing Instruments 〉 Passive Remote Sensing 〉 Positioning/Navigation 〉 GPS 〉 GPS RECEIVERS ; Earth Remote Sensing Instruments 〉 Passive Remote Sensing 〉 Positioning/Navigation 〉 GPS 〉 GPSP ; Earth Remote Sensing Instruments 〉 Passive Remote Sensing 〉 Positioning/Navigation 〉 GYROS ; Earth Remote Sensing Instruments 〉 Passive Remote Sensing 〉 Positioning/Navigation 〉 Laser Ranging ; Earth Remote Sensing Instruments 〉 Passive Remote Sensing 〉 Positioning/Navigation 〉 Laser Ranging 〉 LASER TRACKING REFLECTOR ; Earth Remote Sensing Instruments 〉 Passive Remote Sensing 〉 Positioning/Navigation 〉 Laser Ranging 〉 LRA ; Earth Remote Sensing Instruments 〉 Passive Remote Sensing 〉 Positioning/Navigation 〉 Laser Ranging 〉 SLR ; Earth Remote Sensing Instruments 〉 Passive Remote Sensing 〉 Positioning/Navigation 〉 Radio 〉 DORIS ; Earth Remote Sensing Instruments 〉 Passive Remote Sensing 〉 Positioning/Navigation 〉 Radio 〉 INS ; Earth Remote Sensing Instruments 〉 Passive Remote Sensing 〉 Positioning/Navigation 〉 Radio 〉 USO ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS ; Navigation Platforms 〉 Galileo (Europe's European Satellite Navigation System) ; Navigation Platforms 〉 GPS (Global Positioning System) ; Navigation Platforms 〉 NAVSTAR
    Type: Collection , Collection
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    DATA GFZ
  • 4
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    Gravitationally Consistent Mean Barystatic Sea Level Rise From Leakage‐Corrected Monthly GRACE Data (2020)
    AGU (American Geophysical Union) | Wiley
    Details
    Publication Date: 2023-02-08
    Description: Gravitationally consistent solutions of the Sea Level Equation from leakage‐corrected monthly‐mean GFZ RL06 Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow‐On (GRACE‐FO) Stokes coefficients reveal that barystatic sea level averaged over the whole global ocean was rising by 1.72 mm a−1 during the period April 2002 until August 2016. This rate refers to a truely global ocean averaging domain that includes all polar and semienclosed seas. The result corresponds to 2.02 mm a−1 mean barystatic sea level rise in the open ocean with a 1,000 km coastal buffer zone as obtained from a direct spatial integration of monthly GRACE data. The bias of +0.3 mm a−1 is caused by below‐average barystatic sea level rise in close proximity to coastal mass losses induced by the smaller gravitational attraction of the remaining continental ice and water masses. Alternative spherical harmonics solutions from CSR, JPL, and TU Graz reveal open‐ocean rates between 1.94 and 2.08 mm a−1, thereby demonstrating that systematic differences among the processing centers are much reduced in the latest release. We introduce in this paper a new method to approximate spatial leakage from the differences of two differently filtered global gravity fields. A globally constant and time‐invariant scale factor required to obtain full leakage from those filter differences is found to be 3.9 for GFZ RL06 when filtered with DDK3, and lies between 3.9 and 4.4 for other processing centers. Spatial leakage is estimated for every month in terms of global grids, thereby providing also valuable information of intrabasin leakage that is potentially relevant for hydrologic and hydrometeorological applications.
    Type: Article , PeerReviewed
    Format: text
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    PAPER (OCEANREP)
  • 5
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    Stochastic models for GRACE/GRACE-FO accelerometers and inter-satellite ranging instruments (2023)
    GFZ Data Services
    Details
    Publication Date: 2023-03-01
    Description: Abstract
    Description: This data publication represents the main outcomes of WP4.100 of Individual Project IP4 and of the Deliverable D4.1 of the research unit NEROGRAV summarizing the analyses of the GRACE and GRACE-FO accelerometer (ACC) and satellite-to-satellite tracking data (Microwave instrument (MWI) or Laser Ranging Interferometer (LRI)) in order to derive a characterization of the instrument performance and a stochastic model. A detailed description and discussion focusing on the GRACE data is given in Murböck et al. (submitted to Remote Sensing). This first version of the combined ACC+MWI/LRI noise models is provided with the ASCII-file NEROGRAV_Dataset_GRACE_GRACE-FO_ACC-MWI-LRI_StochasticModel_V01.dat containing header information (17 lines) and the square root power spectral densities (PSDs), i.e. the amplitude spectral densities (ASDs) for the combined accelerometer and ranging observations in terms of range-rates (cf. Fig. 1). It is given for 21600 frequencies from 1/86400 Hz up to 0.25 Hz. Above 0.1 Hz (Nyquist frequency of the 5 s sampled MWI data) the columns for the ACC+MWI models are zero. The five columns consist of the frequency in Hz (col. 1), the combined ACC+MWI models for GRACE 2007 (col. 2), GRACE 2014 (col. 3), GRACE-FO 2019 (col. 4) and the combined GRACE-FO 2019 ACC+LRI model (col. 5) in m/s/√Hz.
    Type: Dataset , Dataset
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    DATA GFZ
  • 6
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    Global Gravity-based Groundwater Product (G3P) (2023)
    GFZ Data Services
    Details
    Publication Date: 2023-03-09
    Description: Abstract
    Description: The Global Gravity-based Groundwater Product (G3P) provides groundwater storage anomalies (GWSA) from a cross-cutting combination of GRACE/GRACE-FO-based terrestrial water storage (TWS) and storage compartments of the water cycle (WSCs) that are part of the Copernicus portfolio. The data set comprises gridded anomalies of groundwater, TWS, and the WSCs glacier, snow, soil moisture and surface water bodies plus layers containing uncertainty information for the individual data products. All WSCs are spatially filtered with a Gaussian filter to be compatible with TWS. Spatial coverage is global, except Greenland and Antarctica, with 0.5-degree resolution. Temporal coverage is from April 2002 to December 2020 with monthly temporal resolution. Gridded data sets are available as NetCDF files containing variables for the parameter value as anomaly in mm equivalent water height and the parameter’s uncertainty as mm equivalent water height. The latest version of the data is visualized at the GravIS portal: http://gravis.gfz-potsdam.de/gws. From GravIS, the data is also available as area averages for several large river basins and aquifers, as well as for climatically similar regions. G3P was funded by the EU Horizon 2020 programme in response to the call LC-SPACE-04-EO-2019-2020 “Copernicus evolution – Research activities in support of cross-cutting applications between Copernicus services” under grant agreement No. 870353. --------------------------------------------------------------------------------------------- Version History: 10 March 2023: Release of Version v1.11. This is the initial release of the data.
    Keywords: Terrestrial Water Storage ; Water Balance ; Satellite Gravimetry ; Copernicus ; Groundwater ; Groundwater Storage Variations ; Mass change ; Gravity Recovery And Climate Experiment ; GRACE ; GRACE Follow-on ; GRACE-FO ; Earth Observation Satellites 〉 NASA Earth System Science Pathfinder 〉 GRACE ; EARTH SCIENCE 〉 TERRESTRIAL HYDROSPHERE 〉 GROUND WATER 〉 WATER TABLE ; environment 〉 natural environment 〉 terrestrial environment ; The Present
    Type: Dataset , Dataset
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    DATA GFZ
  • 7
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    International Combination Service for Time-variable Gravity Fields (COST-G) Monthly GRACE-FO Series (2020)
    GFZ Data Services
    Details
    Publication Date: 2023-12-01
    Description: Abstract
    Description: Operationally combined monthly gravity fields of the GRACE-FO satellite mission in spherical harmonic representation (Level-2 product) generated by the Combination Service for Time-variable Gravity Fields (COST-G; Jäggi et al. (2020):http://dx.doi.org/10.1007/1345_2020_109), a product center for time-variable gravity fields of IAG's International Gravity Field Service (IGFS). COST-G_GRACE-FO_RL01_OP is a combination of AIUB-GRACE-FO_op, GFZ-RL06 (GFO), GRGS-RL05 (unconstrained solution), ITSG-Grace_op, LUH-GRACE-FO, CSR-RL06 (GFO) and JPL-RL06 (GFO). The original time-series were provided by the analysis centers (ACs) and partner analysis centers (PCs) of COST-G.
    Description: Methods
    Description: COST-G performs a harmonization and quality control of the individual input solutions of the COST-G ACs and PCs. The combination of COST-G_GRACE-FO_RL01_OP is then performed applying variance component estimation on the solution level (Jean et al., 2018): https://doi.org/10.1007/s00190-018-1123-5). The resulting COST-G combined gravity fields are validated assessing their signal and noise content in the spectral and spatial domain (Meyer et al., 2019: https://doi.org/10.1007/s00190-019-01274-6) and by the COST-G Product Evaluation Group (PEG).
    Keywords: COST-G ; IGFS Product Center ; Combined solutions ; Time variable gravity ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITATIONAL FIELD ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
    Type: Dataset , Dataset
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    DATA GFZ
  • 8
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    International Combination Service for Time-variable Gravity Fields (COST-G) Monthly GRACE Series (2020)
    GFZ Data Services
    Details
    Publication Date: 2023-12-01
    Description: Abstract
    Description: Combined monthly gravity fields of the GRACE satellite mission in spherical harmonic representation (Level-2 product) generated by the Combination Service for Time-variable Gravity Fields (COST-G; Jäggi et al. (2020):http://dx.doi.org/10.1007/1345_2020_109), a product center for time-variable gravity fields of IAG's International Gravity Field Service (IGFS). COST-G GRACE RL01 is a combination of AIUB-RL02, GFZ-RL06, GRGS-RL04 (unconstrained solution), ITSG-GRACE2018, and CSR-RL06. The original time-series were provided by the analysis centers (ACs) and partner analysis centers (PCs) of COST-G.
    Description: Methods
    Description: COST-G performs a harmonization and quality control of the individual input solutions of the COST-G ACs and PCs. The combination of COST-G GRACE RL01 is then performed applying variance component estimation on the solution level (Jean et al., 2018): https://doi.org/10.1007/s00190-018-1123-5). The resulting COST-G combined gravity fields are validated assessing their signal and noise content in the spectral and spatial domain (Meyer et al., 2019: https://doi.org/10.1007/s00190-019-01274-6) and by the COST-G Product Evaluation Group (PEG).
    Keywords: COST-G ; IGFS Product Center ; Combined solutions ; Time variable gravity ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITATIONAL FIELD ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
    Language: English
    Type: Dataset
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    DATA GFZ
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