Expected Improvements In Modeling Earth S Time Variable Gravity Field Using Multiple Grace Like Satellite Constellations
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Expected Improvements In Modeling Earth S Time Variable Gravity Field Using Multiple Grace Like Satellite Constellations
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Author : Maxon Vaughn Widner (IV)
language : en
Publisher:
Release Date : 2018
Expected Improvements In Modeling Earth S Time Variable Gravity Field Using Multiple Grace Like Satellite Constellations written by Maxon Vaughn Widner (IV) and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.
The Gravity Recovery and Climate Experiment (GRACE) mission has been a principal contributor in the study and quantification of Earth's time-varying gravity field. With continuing missions like GRACE Follow-On and the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) capitalizing on improved technologies such as laser interferometry and drag-free flying systems, respectively, the temporal aliasing of high frequency geophysical processes is anticipated to be the primary source of errors for future missions. Micro-satellite technology has presented the feasibility of improving the architecture of future missions with the implementation of a constellation of satellites having similar characteristics as GRACE. Such a configuration is suggested and analyzed to help address these under-sampling errors. The initial series of simulations is designed to build off the current GRACE mission with a near polar orbit, 450 km altitude, but with each satellite spaced approximately 120 km apart. Because of atmospheric and residual ground interference the reliability of ranging data diminishes at greater distances and therefore scenarios involving distances between satellites greater than 1,100 km are not evaluated. A multi-satellite orbit determination package (MSODP) is used to simulate these configurations and the observations corresponding to their orbits. This data is then processed using the Center for Space Research's Advanced Equation Solver for Parallel Systems (AESoP) linear least squares estimator providing high degree and order gravity field map solutions for each case. A sensitivity analysis is performed by varying certain parameters including: satellite spacing, altitude, and technological improvements. The multiple case results are consolidated to help ascertain the most optimal configuration for error reduction. Another series of data is provided from simulations which represent a constellation of satellites in a similar orbit except for the orbital plane being inclined at 72° with the same methodology implemented. This data is then combined in various configurations with the original data set of measurements and compared with the data from the original polar orbit scenario to determine the impact of a second train of satellites and their mitigation of detrimental effects like longitudinal striping. An analysis is performed to quantify the improvements of these configurations and is then evaluated to find optimal parameters for single and multiplane constellations. These results are extrapolated to show their impact on assessing metrics that would most benefit the water market's interests.
Improving The Observation Of Time Variable Gravity Using Grace Rl04 Data
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Author : Jennifer Anne Bonin
language : en
Publisher:
Release Date : 2010
Improving The Observation Of Time Variable Gravity Using Grace Rl04 Data written by Jennifer Anne Bonin and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
The Gravity Recovery and Climate Experiment (GRACE) project has two primary goals: to determine the Earth's mean gravitational field over the lifetime of the mission and to observe the time-variable nature of the gravitational field. The Center for Space Research's (CSR) Release 4 (RL04) GRACE solutions are currently created via a least-squares process that assimilates data collected over a month using a simple boxcar window and determines a spherical harmonic representation of the monthly gravitational field. The nature of this technique obscures the time-variable gravity field on time scales shorter than one month and spatial scales shorter than a few hundred kilometers. A computational algorithm is developed here that allows increased temporal resolution of the GRACE gravity information, thus allowing the Earth's time-variable gravity to be more clearly observed. The primary technique used is a sliding-window algorithm attached to a weighted version of batch least squares estimation. A number of different temporal windowing functions are evaluated. Their results are investigated via both spectral and spatial analyses, and globally as well as in localized regions. In addition to being compared to each other, the solutions are also compared to external models and data sets, as well as to other high-frequency GRACE solutions made outside CSR. The results demonstrate that a GRACE solution made from at least eight days of data will provide a well-conditioned solution. A series of solutions made with windows of at least that length is capable of observing the expected near-annual signal. The results also indicate that the signals at frequencies greater than 3 cycles/year are often smaller than the GRACE errors, making detection unreliable. Altering the windowing technique does not noticeably improve the resolution, since the spectra of the expected errors and the expected non-annual signals are very similar, leading any window to affect them in the same manner.
An Ensemble Solution For The Earth S Time Varying Gravitational Field From The Nasa Dlr Grace Mission
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Author : Carly Frances Sakumura
language : en
Publisher:
Release Date : 2013
An Ensemble Solution For The Earth S Time Varying Gravitational Field From The Nasa Dlr Grace Mission written by Carly Frances Sakumura and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
Several groups produce estimates of the Earth's time-varying gravitational field with data provided by the NASA/DLR Gravity Recovery and Climate Experiment (GRACE) mission. These unprecedented highly accurate global data sets track the time-variable transport of mass across and underneath the surface of the Earth and give insight into secular, seasonal, and sub seasonal variations in the global water supply. Knowledge gained from these products can inform and be incorporated into ocean and hydrological models and advise environmental policy planning. Therefore, a complete understanding of the accuracy and variations between these different fields is necessary, and the most accurate possible solutions desired. While the various gravity fields are similar, differences in processing strategies and tuning parameters result in solutions with regionally specific variations and error patterns. This study analyzed the spatial, temporal, and spectral variations between four different gravity field products. The knowledge gained in this analysis was used to develop an ensemble solution that harnesses the best characteristics of each individual field to create an optimal model. Multiple methods were used to combine and analyze the individual and ensemble solutions. First a simple mean model was created; then the different solutions were weighted based on the formal error estimates as well as the monthly deviation from the arithmetic mean ensemble. These ensemble models as well as the four individual data center solutions were analyzed for bias, long term trend, and regional variations between the solutions, evaluated statistically to assess the noise and scatter within the solutions, and compared to independent hydrological models. Therefore, the form and cause of the deviations between the models, as well as the impact of these variations, is characterized. The three ensemble solutions constructed in this analysis were all effective at reducing noise in the models and better correlate to hydrological processes than any individual solution. However, the scale of these improvements is constrained by the relative variation between the individual solutions as the deviation of these individual data products from the hydrological model output is much larger than the variations between the individual and ensemble solutions.
Remote Sensing By Satellite Gravimetry
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Author : Thomas Gruber
language : en
Publisher: MDPI
Release Date : 2021-01-19
Remote Sensing By Satellite Gravimetry written by Thomas Gruber and has been published by MDPI this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021-01-19 with Science categories.
Over the last two decades, satellite gravimetry has become a new remote sensing technique that provides a detailed global picture of the physical structure of the Earth. With the CHAMP, GRACE, GOCE and GRACE Follow-On missions, mass distribution and mass transport in the Earth system can be systematically observed and monitored from space. A wide range of Earth science disciplines benefit from these data, enabling improvements in applied models, providing new insights into Earth system processes (e.g., monitoring the global water cycle, ice sheet and glacier melting or sea-level rise) or establishing new operational services. Long time series of mass transport data are needed to disentangle anthropogenic and natural sources of climate change impacts on the Earth system. In order to secure sustained observations on a long-term basis, space agencies and the Earth science community are currently planning future satellite gravimetry mission concepts to enable higher accuracy and better spatial and temporal resolution. This Special Issue provides examples of recent improvements in gravity observation techniques and data processing and analysis, applications in the fields of hydrology, glaciology and solid Earth based on satellite gravimetry data, as well as concepts of future satellite constellations for monitoring mass transport in the Earth system.
Satellite Gravity And The Geosphere
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Author : National Research Council
language : en
Publisher: National Academies Press
Release Date : 1997-09-02
Satellite Gravity And The Geosphere written by National Research Council and has been published by National Academies Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 1997-09-02 with Science categories.
For the past three decades, it has been possible to measure the earth's static gravity from satellites. Such measurements have been used to address many important scientific problems, including the earth's internal structure, and geologically slow processes like mantle convection. In principle, it is possible to resolve the time-varying component of the gravity field by improving the accuracy of satellite gravity measurements. These temporal variations are caused by dynamic processes that change the mass distribution in the earth, oceans, and atmosphere. Acquisition of improved time-varying gravity data would open a new class of important scientific problems to analysis, including crustal motions associated with earthquakes and changes in groundwater levels, ice dynamics, sea-level changes, and atmospheric and oceanic circulation patterns. This book evaluates the potential for using satellite technologies to measure the time-varying component of the gravity field and assess the utility of these data for addressing problems of interest to the earth sciences, natural hazards, and resource communities.
Remote Sensing And Water Resources
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Author : A. Cazenave
language : en
Publisher: Springer
Release Date : 2016-05-04
Remote Sensing And Water Resources written by A. Cazenave and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016-05-04 with Science categories.
This book is a collection of overview articles showing how space-based observations, combined with hydrological modeling, have considerably improved our knowledge of the continental water cycle and its sensitivity to climate change. Two main issues are highlighted: (1) the use in combination of space observations for monitoring water storage changes in river basins worldwide, and (2) the use of space data in hydrological modeling either through data assimilation or as external constraints. The water resources aspect is also addressed, as well as the impacts of direct anthropogenic forcing on land hydrology (e.g. ground water depletion, dam building on rivers, crop irrigation, changes in land use and agricultural practices, etc.). Remote sensing observations offer important new information on this important topic as well, which is highly useful for achieving water management objectives.Over the past 15 years, remote sensing techniques have increasingly demonstrated their capability to monitor components of the water balance of large river basins on time scales ranging from months to decades: satellite altimetry routinely monitors water level changes in large rivers, lakes and floodplains. When combined with satellite imagery, this technique can also measure surface water volume variations. Passive and active microwave sensors offer important information on soil moisture (e.g. the SMOS mission) as well as wetlands and snowpack. The GRACE space gravity mission offers, for the first time, the possibility of directly measuring spatio-temporal variations in the total vertically integrated terrestrial water storage. When combined with other space observations (e.g. from satellite altimetry and SMOS) or model estimates of surface waters and soil moisture, space gravity data can effectively measure groundwater storage variations. New satellite missions, planned for the coming years, will complement the constellation of satellites monitoring waters on land. This is particularly the case for the SWOT mission, which is expected to revolutionize land surface hydrology. Previously published in Surveys in Geophysics, Volume 37, No. 2, 2016
Future Satellite Gravimetry And Earth Dynamics
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Author : Jakob Flury
language : en
Publisher: Springer Science & Business Media
Release Date : 2007-01-25
Future Satellite Gravimetry And Earth Dynamics written by Jakob Flury and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007-01-25 with Science categories.
New and more accurate techniques for satellite gravimetry will be available soon, with promising applications in Earth sciences. With this special issue the authors want to stimulate discussion among Earth scientists on objectives and preferences for future satellite gravimetry missions. This is an urgently needed discussion. Visions for follow-on missions have to be developed today, if they are to be realized within 10 years, given the required preparation time of such satellite missions.
Analysis Of Hybrid Satellite To Satellite Tracking And Quantum Gravity Gradiometry Architecture For Time Variable Gravity Sensing Missions
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Author : Mitchell David Rosen
language : en
Publisher:
Release Date : 2021
Analysis Of Hybrid Satellite To Satellite Tracking And Quantum Gravity Gradiometry Architecture For Time Variable Gravity Sensing Missions written by Mitchell David Rosen and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021 with categories.
The Gravity Recovery and Climate Experiment (GRACE) mission, its follow on (GRACE-FO) and the Gravity-field and steady-state Ocean Circulation Experiment (GOCE) mission have been key contributors to the advancement of the study of Earth's gravity field in the 21st century. The gravity gradiometers on GOCE are limited in their sensitivity and are therefore limited to studying the Earth's static gravity field. However, recent advancements in atomic interferometry have increased the feasibility of implementing this technology to the study of time-variable aspects of the Earth's gravity field, as with the GRACE satellite-to-satellite tracking technology. It is anticipated that these measurement types will provide information about the time-variable gravity field at different wavelengths, and as such a hybrid architecture mission implementing both has been presented. A measurement proof of concept study is performed for this proposed architecture, analyzing the possible improvements over current best time-variable gravity models at mid and small spatial scales and the effects of prominent sources of error. A series of simulations is performed through an orbit that is nearly polar, nearly circular, with an altitude of 450 km and the satellites spaced 220 km apart. The noises present in the gradiometer and pointing knowledge, which serves as a second form of gradiometer error, are tested in combination at varying levels to gain insight into their impact upon the accuracy of the resulting estimated gravity field. The impact of aliasing error upon this hybrid architecture is also tested and analyzed. The results demonstrate clear improvement over the GRACE-FO architecture when the gradiometer noise is sufficiently small. Even at the largest gradiometer noise levels, the inclusion of the gravity gradient data greatly reduces the impact of aliasing error. At varying noise levels, it is shown that either the gradiometer or attitude determination system can become the limiting factor of the architecture. This analysis serves to quantify the improvements in gravity field recovery a hybrid architecture can create with both current and under-development technologies
Space Weather Study Using Multipoint Techniques
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Author : L.-H. Lyu
language : en
Publisher: Elsevier
Release Date : 2002-05-08
Space Weather Study Using Multipoint Techniques written by L.-H. Lyu and has been published by Elsevier this book supported file pdf, txt, epub, kindle and other format this book has been release on 2002-05-08 with Science categories.
Magnetic storms may cause damage to satellites, radiation hazard to astronauts, disruption of radio communications, and interruption of ground electric power lines. Space weather prediction becomes an important issue to be addressed in the twenty-first century. International Solar Terrestrial Program (ISTP) employs five satellites to probe the solar wind and magnetosphere, providing valuable information for space weather prediction. The Asia-Pacific region is becoming one of the economic centers in the world. The continuous drive for scientific and technological progress in parallel is evidenced by the establishment of many space research organizations in many countries of this area. In Taiwan, the National Space Program Office (NSPO) established her third satellite program -- COSMIC (Constellation Obsering Systems for Meteorology, Ionosphere and Climate), which is a science experiment to demonstrate the utility of atmospheric radio limb soundings from a constellation of six low-earth orbiting satellites in operational weather prediction, space weather monitoring, and climate monitoring and research. In order to provide a forum to discuss the many new results in this rapid-moving field and to forge international collaborations, a three-day COSPAR Colloquium on "Space Weather Study Using Multipoint Techniques" was held. This colloquium have provided a forum for experts from the international community to present new results on the timely topic "space weather".
Utilization Of Simulated Grace Inter Satellite Range Accelerations To Estimate Earth S Gravity Field
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Author : Matthew Scott Smith
language : en
Publisher:
Release Date : 2018
Utilization Of Simulated Grace Inter Satellite Range Accelerations To Estimate Earth S Gravity Field written by Matthew Scott Smith and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.
The Gravity Recovery and Climate Experiment (GRACE) provides high-precision K-band Ranging (KBR) data which has been instrumental in improving our understanding of the monthly mass redistribution within the Earth system, and consequently its static and time-varying gravity fields. In practice, estimation of the Earth's gravity field with data from GRACE-like missions is typically done via the range-rate pseudo-observations. This approach is widely used and produces high-quality solutions, however there does exist a well-known North-South striping error in the resulting gravity field. It is thought there may be a potential benefit from utilizing instead the range-acceleration pseudo-observations, which should be sensitive to more spatially-localized mass variations in the signal, thereby reducing the N-S errors in the gravity field and facilitating more precise estimation to higher degrees. Most solutions obtained from range-accelerations to date have been unusable at worst and lesser in quality at best when compared to range-rate derived gravity field solutions. Current understanding is that this is due to the time-differentiation of the KBR signal required to obtain the range-acceleration measurements. The differentiation process acts as a high-pass filter, degrading the signal-to-noise ratio (SNR) at high frequencies, and thus the quality of the solution. The purpose of this work, which explores variational methods solely, is to discover what conditions, if any, make it possible to generate feasible solutions via range-accelerations, and to compare them to one obtained via range-rate. A 180x180 range-rate based gravity field solution produced from simulated August 2008 data was used as a baseline for these comparisons. It is demonstrated that adjusting the parameters of the currently-used filter for obtaining the range-accelerations provides some improvement in the resulting solutions. Conversely, attempts with an alternative approach to filtering the range measurements yielded no benefit over the current method, and only served to degrade the solutions further. However, through an application of filtering the range residuals instead, this research suggests that the culprit is not solely the noise induced by differentiation, but the inclusion of other noisy measurements necessary for the computation of the range-acceleration measurement equation. Through this new method, it is shown that not only are range-accelerations viable for estimating the gravity field, but they can produce solutions more accurate at higher degrees than their range-rate counterparts. While these results are encouraging for processing the range-accelerations, the same technique can be applied to range-rate based solutions, which produces similar improvements and again establishes that quantity as the most suitable for estimating the gravity field, for now.