Submitted for the SES05 Meeting of The American Physical Society Light Scattering as a Diagnostic... more Submitted for the SES05 Meeting of The American Physical Society Light Scattering as a Diagnostic of Asteroid Structure ASHLEY ESPY, BO GUSTAFSON, Uf Ast — With the identification of the Veritas family as the source of the 9.35 degree dust band of the Zodiacal cloud (Nesvory, et al. 2003), we are presented with a new means to study this family and its precursor asteroid. When an asteroid breaks up, the larger pieces remain together on similar orbits, but the smaller (sub-mm to micron) particles, experience a stronger perturbation from the solar radiation pressure and migrate to the zodiacal cloud. Light scattered by this corresponding dust band can yield information, on the structure of the material in the dust and thus also the precursor. Using the Microwave Scattering Facility (Gustafson 1996), models of these dust particles are created and the scattering intensities and polarizations measured. One hypothesis is that the Veritas precursor was NOT differentiated, but rather an aggr...
In this review of atmospheric investigations from planetary surfaces, a wide variety of measureme... more In this review of atmospheric investigations from planetary surfaces, a wide variety of measurement and instrument techniques relevant to atmospheric studies from future planetary lander missions are discussed. The diversity of planetary surface environments within the solar system precludes complete or highly specific coverage, but lander investigations for Mars and cometary missions are presented as specific cases that represent the broad range of atmospheric-surface boundaries and that also correspond to high priority goals for future national and international lander missions.
La presente invention porte sur un procede de deduction d'une quantite (θ), en deux emplaceme... more La presente invention porte sur un procede de deduction d'une quantite (θ), en deux emplacements distincts, a partir d'autres quantites aptes a etre mesurees distinctes. Le procede comprend les etapes d'observation avec un premier dispositif (CD) de la quantite (θ) d'un signal intercepte, ce par quoi le dispositif est place en un emplacement ayant de premieres coordonnees ((X i , Y i , Z i ); de fourniture d'un deuxieme dispositif (AS) en un emplacement ayant de secondes coordonnees (X s , Y s , Z s ); d'amener le deuxieme dispositif a emettre un signal a intercepter par le premier dispositif (CD), ce par quoi le deuxieme dispositif (AS) a besoin de connaitre les secondes coordonnees et d'etre informe des premieres coordonnees du premier dispositif (CD) pour calculer la quantite (θ) qui peut etre obtenue a partir de mesures par le premier dispositif (CD); la quantite (θ) etant ainsi connue par le deuxieme dispositif (AS) et le premier dispositif (CD) sans...
Asteroids, comets and interstellar dust are possible sources of the particles that constitute the... more Asteroids, comets and interstellar dust are possible sources of the particles that constitute the dust in the inner solar system. Each of these components gives rise to particular, characteristic features, the amplitudes of which can be used to estimate the size of the associated source. The asteroidal component feeds the dust bands and the Earth's resonant ring, while the cometary component may account for the large scale height of the zodiacal cloud observed at 1 AU Previous discussions of the observed strengths of these various features indicated that the source of about one third of the thermal flux observed, for example, in the IRAS 25ÎĽm waveband is asteroidal, while two thirds is cometary. However, a variety of assumptions go into this calculation (the size-frequency distribution of the particles is particularly significant) and we now know that the result is highly dependent on these assumptions. The zodiacal cloud is also the source of the IDPs collected on Earth. Becaus...
Data obtained through microwave analog measurements are used to compare optical polarization char... more Data obtained through microwave analog measurements are used to compare optical polarization characteristics of silicate particles ranging in shape from spheroids and cylinders to chains of spheres. It is confirmed that the dependence of the degree of polarization on scattering angle is a powerful indicator of particle shape. The reversal and steep gradient in the degree of polarization found by Weinberg and Beeson (1976a,b) in the dust tail of comet Ikeya-Seki (1965 VIII) is suggestive of laboratory measurements corresponding to 1.6 ÎĽm long, 0.4 ÎĽm in diameter silicate cylinders.
Dynamical perturbations on ensembles of particles in heliocentric orbits of low eccentricity are ... more Dynamical perturbations on ensembles of particles in heliocentric orbits of low eccentricity are integrated over time. The dust is perturbed by radiation pressure, Poynting-Robertson drag, their corpuscular counterparts, and by gravitation due to any number of planets. A dust cloud is represented by a set of centroids and orbital dispersions (about the centroids). Gravitational perturbations on the centroid are derived from a single matrix, valid for any planet, in the appropriate frame of reference. After transformation of the time derivatives to a common coordinate system, the perturbation rates are summed up and integrated. The time dependence of the planets’ orbital elements are evaluated inside the time integral.
Synthetic infrared pictures are used to illustrate changes in the shape of portions of an interpl... more Synthetic infrared pictures are used to illustrate changes in the shape of portions of an interplanetary dust-cloud. The dust particles, in circular heliocentric orbits, are perturbed by radiation and corpuscular forces combined with gravitational disturbances by the major planets. Dust in the inner solar system and close to the ecliptic or the orbital plane of Venus is brought to a more narrow range of ecliptic latitudes. A dust-band evolves near and inside the orbit of Venus. The cloud’s shape is less affected at high ecliptic latitudes.
The local cloud in which the Sun is embedded participates in a general flow from the direction of... more The local cloud in which the Sun is embedded participates in a general flow from the direction of the Sco-Cen association (Weaver, 1979) while the Sun is moving in the direction of Hercules. The relative motion is well determined by the neutral gas flow (Cox and Reynolds, 1987). A prominent cone of gravitationally focused neutral helium indicates the downwind direction to within ±3°. The average flow speed outside the solar system, 26 km/s, is determined to within ±1 km/s. Measurements from the Ulysses spacecraft (Witte et al., 1993) confirmed this flow. Since interstellar matter contains dust as well as gas, efforts have been made to detect the dust flow through the solar system. However, until recently these efforts have been unsuccessful and modeling of the flow has been controversial.
We have studied several optical systems for dust velocity measurements on a cometary orbiter usin... more We have studied several optical systems for dust velocity measurements on a cometary orbiter using light scattering to detect particles. Two main concepts are considered. The first relies on trajectory imaging, while the second uses time-of-flight measurements between two or more light sheets. Their merits and disadvantages are discussed. The favored system, time-of-flight between two planes with particle localization, is described.
Impact data from the ULYSSES dust detector at 5 AU from the Sun have been interpreted as a flux o... more Impact data from the ULYSSES dust detector at 5 AU from the Sun have been interpreted as a flux of sub-micron interstellar dust particles (Grün et al, 1994) arriving from 252° ecliptic longitude and 2.5° ecliptic latitude. Following the motions of these particles under the influence of solar gravity, radiation pressure and electromagnetic forces, we present results from the modeling of the thermal emission from the resultant particle cloud, and conclude that the chances for the detection of such an interstellar signature in the COBE data are marginal at best.
The conceptual design for an optical instrument capable of characterizing dust particles by in si... more The conceptual design for an optical instrument capable of characterizing dust particles by in situ measurements is described. This instrument, the Integrated Dust Analyzer (IDA), measures the light scattered at several different angles as a particle passes through a pair of polarized light curtains. It is capable of defining or providing an indication of such characteristics as size, index of refraction, absorptivity, and aggregate structure.
For a long time, the dominant scattering theory used in radiative transfer and scattering calcula... more For a long time, the dominant scattering theory used in radiative transfer and scattering calculations has been Mie theory, which is the complete solution to the problems of light scattering by single, isotropic, and homogeneous spheres. However, cosmic dust collections show that most of the largest sized interplanetary dust particles may be porous, inhomogeneous, and aggregated and may have quite different scattering properties. Arbitrary configurations of aggregated spheres may provide a reasonable first approximation to realistic light-scattering models of interplanetary dust particles. In the last few decades, progress has been made in developing light scattering theory for interacting spheres, The development of the addition theorems for scalar and vector spherical wave functions (Friedman & Russek, 1954; Stein, 1961; Cruzan, 1962) opened up a new area in the theoretical study of multisphere scattering problems.
This is a description of the beginning of a systematic investigation into the optical properties ... more This is a description of the beginning of a systematic investigation into the optical properties of dust structures that are likely to be representative of interplanetary dust. I delineate the development of a physical dust model to parameterize the optically important characteristics of the dust. The result is a system with two refractive indexes in an aggregate structure of varying porosity - a challenging model for most current light scattering theories. Experimental data is needed to investigate the scattering by these structures and to test new theoretical solutions (e.g., Xu 1995) as they develop. I give a brief description of the new microwave analog scattering laboratory that has been developed for this purpose at the Laboratory for Astrophysics of the University of Florida's Astronomy Department. Finally, laboratory data is shown in support of dense aggregate models for interplanetary dust.
Submitted for the SES05 Meeting of The American Physical Society Light Scattering as a Diagnostic... more Submitted for the SES05 Meeting of The American Physical Society Light Scattering as a Diagnostic of Asteroid Structure ASHLEY ESPY, BO GUSTAFSON, Uf Ast — With the identification of the Veritas family as the source of the 9.35 degree dust band of the Zodiacal cloud (Nesvory, et al. 2003), we are presented with a new means to study this family and its precursor asteroid. When an asteroid breaks up, the larger pieces remain together on similar orbits, but the smaller (sub-mm to micron) particles, experience a stronger perturbation from the solar radiation pressure and migrate to the zodiacal cloud. Light scattered by this corresponding dust band can yield information, on the structure of the material in the dust and thus also the precursor. Using the Microwave Scattering Facility (Gustafson 1996), models of these dust particles are created and the scattering intensities and polarizations measured. One hypothesis is that the Veritas precursor was NOT differentiated, but rather an aggr...
In this review of atmospheric investigations from planetary surfaces, a wide variety of measureme... more In this review of atmospheric investigations from planetary surfaces, a wide variety of measurement and instrument techniques relevant to atmospheric studies from future planetary lander missions are discussed. The diversity of planetary surface environments within the solar system precludes complete or highly specific coverage, but lander investigations for Mars and cometary missions are presented as specific cases that represent the broad range of atmospheric-surface boundaries and that also correspond to high priority goals for future national and international lander missions.
La presente invention porte sur un procede de deduction d'une quantite (θ), en deux emplaceme... more La presente invention porte sur un procede de deduction d'une quantite (θ), en deux emplacements distincts, a partir d'autres quantites aptes a etre mesurees distinctes. Le procede comprend les etapes d'observation avec un premier dispositif (CD) de la quantite (θ) d'un signal intercepte, ce par quoi le dispositif est place en un emplacement ayant de premieres coordonnees ((X i , Y i , Z i ); de fourniture d'un deuxieme dispositif (AS) en un emplacement ayant de secondes coordonnees (X s , Y s , Z s ); d'amener le deuxieme dispositif a emettre un signal a intercepter par le premier dispositif (CD), ce par quoi le deuxieme dispositif (AS) a besoin de connaitre les secondes coordonnees et d'etre informe des premieres coordonnees du premier dispositif (CD) pour calculer la quantite (θ) qui peut etre obtenue a partir de mesures par le premier dispositif (CD); la quantite (θ) etant ainsi connue par le deuxieme dispositif (AS) et le premier dispositif (CD) sans...
Asteroids, comets and interstellar dust are possible sources of the particles that constitute the... more Asteroids, comets and interstellar dust are possible sources of the particles that constitute the dust in the inner solar system. Each of these components gives rise to particular, characteristic features, the amplitudes of which can be used to estimate the size of the associated source. The asteroidal component feeds the dust bands and the Earth's resonant ring, while the cometary component may account for the large scale height of the zodiacal cloud observed at 1 AU Previous discussions of the observed strengths of these various features indicated that the source of about one third of the thermal flux observed, for example, in the IRAS 25ÎĽm waveband is asteroidal, while two thirds is cometary. However, a variety of assumptions go into this calculation (the size-frequency distribution of the particles is particularly significant) and we now know that the result is highly dependent on these assumptions. The zodiacal cloud is also the source of the IDPs collected on Earth. Becaus...
Data obtained through microwave analog measurements are used to compare optical polarization char... more Data obtained through microwave analog measurements are used to compare optical polarization characteristics of silicate particles ranging in shape from spheroids and cylinders to chains of spheres. It is confirmed that the dependence of the degree of polarization on scattering angle is a powerful indicator of particle shape. The reversal and steep gradient in the degree of polarization found by Weinberg and Beeson (1976a,b) in the dust tail of comet Ikeya-Seki (1965 VIII) is suggestive of laboratory measurements corresponding to 1.6 ÎĽm long, 0.4 ÎĽm in diameter silicate cylinders.
Dynamical perturbations on ensembles of particles in heliocentric orbits of low eccentricity are ... more Dynamical perturbations on ensembles of particles in heliocentric orbits of low eccentricity are integrated over time. The dust is perturbed by radiation pressure, Poynting-Robertson drag, their corpuscular counterparts, and by gravitation due to any number of planets. A dust cloud is represented by a set of centroids and orbital dispersions (about the centroids). Gravitational perturbations on the centroid are derived from a single matrix, valid for any planet, in the appropriate frame of reference. After transformation of the time derivatives to a common coordinate system, the perturbation rates are summed up and integrated. The time dependence of the planets’ orbital elements are evaluated inside the time integral.
Synthetic infrared pictures are used to illustrate changes in the shape of portions of an interpl... more Synthetic infrared pictures are used to illustrate changes in the shape of portions of an interplanetary dust-cloud. The dust particles, in circular heliocentric orbits, are perturbed by radiation and corpuscular forces combined with gravitational disturbances by the major planets. Dust in the inner solar system and close to the ecliptic or the orbital plane of Venus is brought to a more narrow range of ecliptic latitudes. A dust-band evolves near and inside the orbit of Venus. The cloud’s shape is less affected at high ecliptic latitudes.
The local cloud in which the Sun is embedded participates in a general flow from the direction of... more The local cloud in which the Sun is embedded participates in a general flow from the direction of the Sco-Cen association (Weaver, 1979) while the Sun is moving in the direction of Hercules. The relative motion is well determined by the neutral gas flow (Cox and Reynolds, 1987). A prominent cone of gravitationally focused neutral helium indicates the downwind direction to within ±3°. The average flow speed outside the solar system, 26 km/s, is determined to within ±1 km/s. Measurements from the Ulysses spacecraft (Witte et al., 1993) confirmed this flow. Since interstellar matter contains dust as well as gas, efforts have been made to detect the dust flow through the solar system. However, until recently these efforts have been unsuccessful and modeling of the flow has been controversial.
We have studied several optical systems for dust velocity measurements on a cometary orbiter usin... more We have studied several optical systems for dust velocity measurements on a cometary orbiter using light scattering to detect particles. Two main concepts are considered. The first relies on trajectory imaging, while the second uses time-of-flight measurements between two or more light sheets. Their merits and disadvantages are discussed. The favored system, time-of-flight between two planes with particle localization, is described.
Impact data from the ULYSSES dust detector at 5 AU from the Sun have been interpreted as a flux o... more Impact data from the ULYSSES dust detector at 5 AU from the Sun have been interpreted as a flux of sub-micron interstellar dust particles (Grün et al, 1994) arriving from 252° ecliptic longitude and 2.5° ecliptic latitude. Following the motions of these particles under the influence of solar gravity, radiation pressure and electromagnetic forces, we present results from the modeling of the thermal emission from the resultant particle cloud, and conclude that the chances for the detection of such an interstellar signature in the COBE data are marginal at best.
The conceptual design for an optical instrument capable of characterizing dust particles by in si... more The conceptual design for an optical instrument capable of characterizing dust particles by in situ measurements is described. This instrument, the Integrated Dust Analyzer (IDA), measures the light scattered at several different angles as a particle passes through a pair of polarized light curtains. It is capable of defining or providing an indication of such characteristics as size, index of refraction, absorptivity, and aggregate structure.
For a long time, the dominant scattering theory used in radiative transfer and scattering calcula... more For a long time, the dominant scattering theory used in radiative transfer and scattering calculations has been Mie theory, which is the complete solution to the problems of light scattering by single, isotropic, and homogeneous spheres. However, cosmic dust collections show that most of the largest sized interplanetary dust particles may be porous, inhomogeneous, and aggregated and may have quite different scattering properties. Arbitrary configurations of aggregated spheres may provide a reasonable first approximation to realistic light-scattering models of interplanetary dust particles. In the last few decades, progress has been made in developing light scattering theory for interacting spheres, The development of the addition theorems for scalar and vector spherical wave functions (Friedman & Russek, 1954; Stein, 1961; Cruzan, 1962) opened up a new area in the theoretical study of multisphere scattering problems.
This is a description of the beginning of a systematic investigation into the optical properties ... more This is a description of the beginning of a systematic investigation into the optical properties of dust structures that are likely to be representative of interplanetary dust. I delineate the development of a physical dust model to parameterize the optically important characteristics of the dust. The result is a system with two refractive indexes in an aggregate structure of varying porosity - a challenging model for most current light scattering theories. Experimental data is needed to investigate the scattering by these structures and to test new theoretical solutions (e.g., Xu 1995) as they develop. I give a brief description of the new microwave analog scattering laboratory that has been developed for this purpose at the Laboratory for Astrophysics of the University of Florida's Astronomy Department. Finally, laboratory data is shown in support of dense aggregate models for interplanetary dust.
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Papers by Bo Gustafson