東華大學圖書館 |

Characterization of Meteor Masses by Radar and Optical Remote Sensing Methods.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Characterization of Meteor Masses by Radar and Optical Remote Sensing Methods./
作者:	Tarnecki, L. K.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2023,
面頁冊數:	177 p.
附註:	Source: Dissertations Abstracts International, Volume: 85-03, Section: B.
Contained By:	Dissertations Abstracts International85-03B.
標題:	Remote sensing. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30573479
ISBN:	9798380166782

Characterization of Meteor Masses by Radar and Optical Remote Sensing Methods.
Tarnecki, L. K.

Characterization of Meteor Masses by Radar and Optical Remote Sensing Methods. - Ann Arbor : ProQuest Dissertations & Theses, 2023 - 177 p.

Source: Dissertations Abstracts International, Volume: 85-03, Section: B.

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

Each day billions of small meteoroids enter the Earth's atmosphere, where they burn up completely before reaching the ground. All of their material is deposited in the upper atmosphere, and is the major source of metal input in that region. However, the total mass flux is not well constrained and estimates vary greatly depending on the measurement technique used. Global models, which are used to predict and study atmospheric dynamics, incorporate meteoric input to determine various parameters including composition and density. Error and uncertainty in the mass flux propagate and lead to error in model results. This dissertation aims to address the discrepancy between mass measurements for different observational tools by improving mass estimation methods for the two most common remote sensing techniques for meteors: radar and optical cameras.Radar can not directly measure meteor masses, so various methods have been developed for converting measureable quantities to mass. One technique for doing so utilizes scattering models, which describe how a radar pulse interacts with meteor plasmas. Previous scattering simulations assumed simplified spherically symmetric models of the meteor plasma for simplicity. These models were improved upon by incorporating a physics-based model for the meteor plasma into finite-difference time domain (FDTD) simulations of radar scattering. The FDTD simulations map between observed quantities (velocity, altitude, radar cross section) and physical parameters of the plasma, which are then used to calculate mass. Lookup tables covering a wide range of potential parameter combinations were created by performing thousands of simulations, allowing masses to be easily calculated for a large set of observations. The FDTD method was validated by calculating masses for several hundred meteors observed simultaneously by the MAARSY and EISCAT radars (53.5 and 929 MHz, respectively). The independent mass estimates for the two radars are strongly linearly correlated, indicating that the FDTD method reliably produces consistent mass estimates independent of radar frequency or viewing geometry.The relationship conventionally assumed between optical emissions and mass is more straight-forward than for radar observations, but relevant parameters are poorly characterized. The largest source of uncertainty in photometric masses is associated with the luminous efficiency, a parameter that quantifies the fraction of a meteoroid's kinetic energy that is converted into light output. Calculations of the luminous efficiency using remote sensing observations are sparse and often unreliable, and estimated values cover several orders of magnitude. To address this discrepancy, a laboratory experiment using the CU IMPACT facility was performed to accelerate iron and aluminum dust particles into a pressurized chamber, mimicking the ablation process for meteoroids. Photomultiplier tubes fitted along the chamber recorded any light emitted by the particles along the ablation path. The luminous efficiency was calculated for each dust particle that produced detectable light, and evaluated as a function of mass and velocity. Analysis of the iron and aluminum results show that luminous efficiency does depend on composition as well as velocity, but there is not a significant trend with mass.The results from the modeling and experimental work were validated against each other using a set of 166 meteors observed simultaneously by the MAARSY radar and two wide-field cameras, using the FDTD radar method and applying the experimental luminous efficiency fits to calculate photometric masses. The resulting mass estimates using both methods agree to within a factor of 3 on average. The results show two dominant trends: better agreement as meteoroid velocity increases and underestimation of the radar mass for the largest meteoroids observed (> 10 mg). These trends had not been quantified by previous studies limited by very small sample sizes, and could help to explain the historic discrepancy between mass estimates by different systems. The general agreement between the radar and photometric masses indicates that both methods perform well independently, and can reliably be applied to broader sets of radar or optical observations that do not coincide with observations by another system.

ISBN: 9798380166782Subjects--Topical Terms:

535394
Remote sensing.
Subjects--Index Terms:

Finite-difference time domain

Characterization of Meteor Masses by Radar and Optical Remote Sensing Methods.
LDR:05553nmm a2200409 4500 001 2401383
005 20241022112602.5
006 m o d
007 cr#unu||||||||
008 251215s2023 ||||||||||||||||| ||eng d
020 $a 9798380166782
035 $a (MiAaPQ)AAI30573479
035 $a AAI30573479
035 $a 2401383
040 $a MiAaPQ $c MiAaPQ
100 1 $a Tarnecki, L. K. $0 (orcid)0000-0002-6984-5031 $3 3771476
245 1 0 $a Characterization of Meteor Masses by Radar and Optical Remote Sensing Methods.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2023
300 $a 177 p.
500 $a Source: Dissertations Abstracts International, Volume: 85-03, Section: B.
500 $a Advisor: Marshall, Robert.
502 $a Thesis (Ph.D.)--University of Colorado at Boulder, 2023.
520 $a Each day billions of small meteoroids enter the Earth's atmosphere, where they burn up completely before reaching the ground. All of their material is deposited in the upper atmosphere, and is the major source of metal input in that region. However, the total mass flux is not well constrained and estimates vary greatly depending on the measurement technique used. Global models, which are used to predict and study atmospheric dynamics, incorporate meteoric input to determine various parameters including composition and density. Error and uncertainty in the mass flux propagate and lead to error in model results. This dissertation aims to address the discrepancy between mass measurements for different observational tools by improving mass estimation methods for the two most common remote sensing techniques for meteors: radar and optical cameras.Radar can not directly measure meteor masses, so various methods have been developed for converting measureable quantities to mass. One technique for doing so utilizes scattering models, which describe how a radar pulse interacts with meteor plasmas. Previous scattering simulations assumed simplified spherically symmetric models of the meteor plasma for simplicity. These models were improved upon by incorporating a physics-based model for the meteor plasma into finite-difference time domain (FDTD) simulations of radar scattering. The FDTD simulations map between observed quantities (velocity, altitude, radar cross section) and physical parameters of the plasma, which are then used to calculate mass. Lookup tables covering a wide range of potential parameter combinations were created by performing thousands of simulations, allowing masses to be easily calculated for a large set of observations. The FDTD method was validated by calculating masses for several hundred meteors observed simultaneously by the MAARSY and EISCAT radars (53.5 and 929 MHz, respectively). The independent mass estimates for the two radars are strongly linearly correlated, indicating that the FDTD method reliably produces consistent mass estimates independent of radar frequency or viewing geometry.The relationship conventionally assumed between optical emissions and mass is more straight-forward than for radar observations, but relevant parameters are poorly characterized. The largest source of uncertainty in photometric masses is associated with the luminous efficiency, a parameter that quantifies the fraction of a meteoroid's kinetic energy that is converted into light output. Calculations of the luminous efficiency using remote sensing observations are sparse and often unreliable, and estimated values cover several orders of magnitude. To address this discrepancy, a laboratory experiment using the CU IMPACT facility was performed to accelerate iron and aluminum dust particles into a pressurized chamber, mimicking the ablation process for meteoroids. Photomultiplier tubes fitted along the chamber recorded any light emitted by the particles along the ablation path. The luminous efficiency was calculated for each dust particle that produced detectable light, and evaluated as a function of mass and velocity. Analysis of the iron and aluminum results show that luminous efficiency does depend on composition as well as velocity, but there is not a significant trend with mass.The results from the modeling and experimental work were validated against each other using a set of 166 meteors observed simultaneously by the MAARSY radar and two wide-field cameras, using the FDTD radar method and applying the experimental luminous efficiency fits to calculate photometric masses. The resulting mass estimates using both methods agree to within a factor of 3 on average. The results show two dominant trends: better agreement as meteoroid velocity increases and underestimation of the radar mass for the largest meteoroids observed (> 10 mg). These trends had not been quantified by previous studies limited by very small sample sizes, and could help to explain the historic discrepancy between mass estimates by different systems. The general agreement between the radar and photometric masses indicates that both methods perform well independently, and can reliably be applied to broader sets of radar or optical observations that do not coincide with observations by another system.
590 $a School code: 0051.
650 4 $a Remote sensing. $3 535394
650 4 $a Plasma physics. $3 3175417
650 4 $a Atmospheric sciences. $3 3168354
650 4 $a Aerospace engineering. $3 1002622
653 $a Finite-difference time domain
653 $a Meteor plasmas
653 $a Meteoroid
653 $a Radar
653 $a Optical remote sensing
690 $a 0799
690 $a 0759
690 $a 0725
690 $a 0538
710 2 $a University of Colorado at Boulder. $b Aerospace Engineering. $3 1030473
773 0 $t Dissertations Abstracts International $g 85-03B.
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=30573479