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Improving Low-Degree Gravity Estimat...

Tucker, Evan S.

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Improving Low-Degree Gravity Estimates Through New Laser Ranging Satellites, Ground Stations, and Combination Solutions.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Improving Low-Degree Gravity Estimates Through New Laser Ranging Satellites, Ground Stations, and Combination Solutions./
Author:	Tucker, Evan S.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2023,
Description:	142 p.
Notes:	Source: Dissertations Abstracts International, Volume: 85-06, Section: B.
Contained By:	Dissertations Abstracts International85-06B.
Subject:	Aerospace engineering. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30692057
ISBN:	9798381165616

Improving Low-Degree Gravity Estimates Through New Laser Ranging Satellites, Ground Stations, and Combination Solutions.
Tucker, Evan S.

Improving Low-Degree Gravity Estimates Through New Laser Ranging Satellites, Ground Stations, and Combination Solutions. - Ann Arbor : ProQuest Dissertations & Theses, 2023 - 142 p.

Source: Dissertations Abstracts International, Volume: 85-06, Section: B.

Thesis (Ph.D.)--University of Colorado at Boulder, 2023.

Earth's mass is constantly redistributing due to climatic and geophysical dynamics. Although changes in the deep solid Earth tend to occur over geologic timescales, near-surface processes take place over hours to years. These mass changes, which include earthquakes as well as movement of the atmosphere, hydrosphere, and ice sheets, constitute Earth's time-variable gravity (TVG) field. The observation of TVG is critical to understanding sea-level rise, terrestrial water storage, ice sheet melting, and other climatic processes. Of particular importance are certain components of low-degree, large-scale TVG signals to which dedicated gravity missions, such as the Gravity Recovery and Climate Experiment (GRACE), lack sensitivity. Alternative methods are therefore favored for estimating these parameters. Satellite Laser Ranging (SLR) is a proven technique with applications to many areas of fundamental geodesy. Through a constellation of passive satellites and network of ground tracking stations, SLR delivers more accurate estimates of low-degree gravity coefficients, which allows for validation and enhancement of the GRACE data.This work uses high-fidelity numerical simulations to investigate potential improvements to SLR-derived gravity estimates. First, existing simulation techniques are further developed for application to SLR. A combination of real data and geophysical models ensures realistic tracking statistics in the simulation. Potential new SLR satellites are investigated at various altitudes and inclinations, with a particular focus on the inclination after it is determined to be more impactful. It is found that the addition of a low-inclination satellite significantly improves the SLR gravity solution by introducing a unique sensitivity to the gravity field that decorrelates key coefficients. Several cases involving the addition of new ground stations are then investigated. In general, the filling of geographic gaps at the poles and in the Southern hemisphere reduces errors in the recovered gravity field by improving the observing geometry. However, a hypothetical case involving a uniformly distributed ground network reveals that stations lack the ability to systematically improve SLR gravity estimates in the way that a new satellite can. Finally, the simulated SLR data are combined with simulated GRACE data to investigate a jointly inverted solution. The results show that this method fully leverages the information in the SLR data, which enhances the GRACE data more than a simple substitution of coefficients. The simulation environment provides a novel way to quantify the improvements from these rigorous combination solutions. A variety of global and regional techniques are applied to analyze these solutions.

ISBN: 9798381165616Subjects--Topical Terms:

1002622
Aerospace engineering.
Subjects--Index Terms:

Low-degree gravity

Improving Low-Degree Gravity Estimates Through New Laser Ranging Satellites, Ground Stations, and Combination Solutions.
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300 $a 142 p.
500 $a Source: Dissertations Abstracts International, Volume: 85-06, Section: B.
500 $a Advisor: Nerem, R. Steven.
502 $a Thesis (Ph.D.)--University of Colorado at Boulder, 2023.
520 $a Earth's mass is constantly redistributing due to climatic and geophysical dynamics. Although changes in the deep solid Earth tend to occur over geologic timescales, near-surface processes take place over hours to years. These mass changes, which include earthquakes as well as movement of the atmosphere, hydrosphere, and ice sheets, constitute Earth's time-variable gravity (TVG) field. The observation of TVG is critical to understanding sea-level rise, terrestrial water storage, ice sheet melting, and other climatic processes. Of particular importance are certain components of low-degree, large-scale TVG signals to which dedicated gravity missions, such as the Gravity Recovery and Climate Experiment (GRACE), lack sensitivity. Alternative methods are therefore favored for estimating these parameters. Satellite Laser Ranging (SLR) is a proven technique with applications to many areas of fundamental geodesy. Through a constellation of passive satellites and network of ground tracking stations, SLR delivers more accurate estimates of low-degree gravity coefficients, which allows for validation and enhancement of the GRACE data.This work uses high-fidelity numerical simulations to investigate potential improvements to SLR-derived gravity estimates. First, existing simulation techniques are further developed for application to SLR. A combination of real data and geophysical models ensures realistic tracking statistics in the simulation. Potential new SLR satellites are investigated at various altitudes and inclinations, with a particular focus on the inclination after it is determined to be more impactful. It is found that the addition of a low-inclination satellite significantly improves the SLR gravity solution by introducing a unique sensitivity to the gravity field that decorrelates key coefficients. Several cases involving the addition of new ground stations are then investigated. In general, the filling of geographic gaps at the poles and in the Southern hemisphere reduces errors in the recovered gravity field by improving the observing geometry. However, a hypothetical case involving a uniformly distributed ground network reveals that stations lack the ability to systematically improve SLR gravity estimates in the way that a new satellite can. Finally, the simulated SLR data are combined with simulated GRACE data to investigate a jointly inverted solution. The results show that this method fully leverages the information in the SLR data, which enhances the GRACE data more than a simple substitution of coefficients. The simulation environment provides a novel way to quantify the improvements from these rigorous combination solutions. A variety of global and regional techniques are applied to analyze these solutions.
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650 4 $a Aerospace engineering. $3 1002622
650 4 $a Remote sensing. $3 535394
653 $a Low-degree gravity
653 $a Mass changes
653 $a Geographic gaps
653 $a Satellite Laser Ranging
653 $a Numerical simulations
653 $a Time-variable gravity
690 $a 0538
690 $a 0799
690 $a 0800
710 2 $a University of Colorado at Boulder. $b Aerospace Engineering. $3 1030473
773 0 $t Dissertations Abstracts International $g 85-06B.
790 $a 0051
791 $a Ph.D.
792 $a 2023
793 $a English
856 4 0 $u https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30692057