Simultaneous radar and video meteors

The goal of this thesis is to better understand the physical and chemical properties of meteoroids by using simultaneous radar and video observations of meteors. The Canadian Meteor Orbit Radar (CMOR) and several Gen-III image-intensified CCD cameras were used to measure common meteors and validate metric errors determined through Monte Carlo modelling and to relate radar electron line density (q) to video photon radiant power (I). By adopting an ionisation coefficient from Jones (1997) and using recorded measurements of q/I, a corresponding estimate of the fraction of meteoroid kinetic energy loss converted into light (luminous efficiency) was found. It was found that 7% ± 3% of video meteors were also simultaneously detected as specular echoes by radar, larger than the expected 2% − 5% from modelling. Errors in the fiducial picks for video meteors were found to be anisotropic, with video speeds being higher on average compared to radar speeds, consistent with more deceleration in specular radar measurements. Most radar detections occurred near the end of their meteor trails, suggesting simultaneous observations are biased towards larger, non-fragmenting meteoroids. The peak luminous efficiency was found to be 5.9% at 41 km/s. The magnitude scale and electron line density were found to relate as M = (38.7 ± 1.2) − 2.5 log10 q. These results suggest the masses of higher speed meteoroids are an order of magnitude smaller than previously thought, implying the total meteoroid mass influx for small meteoroids is below earlier estimates. The main uncertainties associated with this analysis are the unknown spectra of individual meteors (which affects estimates of I), and assumptions of the initial meteor trail radius (which affects estimates of q). To improve future simultaneous comparisons, an automated video meteor observatory was constructed. This system, named the Canadian Automated Meteor Observatory (CAMO), features a guided camera which tracks meteors in real-time, giving higher precision video measurements of deceleration and fragmentation for comparison to radar measurements. CAMO can also be used to constrain numerical meteoroid ablation models and to measure the meteoroid mass in-flux at Earth

Meteoroids: The Smallest Solar System Bodies

This volume is a compilation of articles reflecting the current state of knowledge on the physics, chemistry, astronomy, and aeronomy of small bodies in the solar system. The articles included here represent the most recent results in meteor, meteoroid, and related research fields and were presented May 24-28, 2010, in Breckenridge, Colorado, USA at Meteoroids 2010: An International Conference on Minor Bodies in the Solar System

A study of meteor spectroscopy and physics from earth-orbit: A preliminary survey into ultraviolet meteor spectra

Preliminary data required to extrapolate available meteor physics information (obtained in the photographic, visual and near ultraviolet spectral regions) into the middle and far ultraviolet are presented. Wavelength tables, telluric attenuation factors, meteor rates, and telluric airglow data are summarized in the context of near-earth observation vehicle parameters using moderate to low spectral resolution instrumentation. Considerable attenuation is given to the problem of meteor excitation temperatures since these are required to predict the strength of UV features. Relative line intensities are computed for an assumed chondritic composition. Features of greatest predicted intensities, the major problems in meteor physics, detectability of UV meteor events, complications of spacecraft motion, and UV instrumentation options are summarized

Bulk density of small meteoroids

The purpose of our work is to determine the bulk density of meteoroids. Unlike previous works which focused either on the dynamical properties of the meteoroids (deceleration), ignoring fragmentation; or on fitting solely the lightcurves, neglecting the dynamics of the meteoroids, we use both the photometry and astrometry to constrain our model. Our model, based on the dustball model, considers the meteoroid to be a collection of grains held together by a lower boiling point \u27glue\u27. It uses conservation of energy and momentum to model the change in velocity and the light production as a function of time. The free parameters in the model (mass, density, heat of ablation, temperature of fragmentation, boiling temperature, specific heat, molar mass, and thermal conductivity) are varied from values consistent with fragile cometary material, through asteroidal chondritic material, to solid iron, and the entire parameter space is explored, giving all possible solutions which are consistent with the data. An initial study used cameras with small fields of view to achieve high spatial resolution. 42 meteors were detected, but only six meteors were entirely captured in the common observing volume of the cameras, and were therefore suitable for modelling. The modelling revealed that taking fragmentation into account does not necessarily produce high bulk density values, but the fraction of high density (nearly iron composition) meteoroids observed was higher than expected. This study showed that the fraction of small meteoroids with high bulk density (almost iron density) may be underestimated. In order to analyse more data, a model of detector saturation was developed to correct for meteors which were saturated on the 8-bit camera systems. The model was tested on data collected in a special campaign, and found to reproduce the unsaturated lightcurves correctly. This saturation correction was found to be very important in correctly modelling the brighter meteors in the dataset for the final study. Finally, 92 meteors were recorded on wider field systems using higher resolution detectors to measure deceleration precisely. Densities for each meteoroid was calculated, and the meteoroids were grouped by their orbital characteristics for analysis. As expected, meteoroids with asteroidal origins had high densities of 4200 kg m-3 in average, and those with Halley-type cometary orbits had low densities ranging from 380 kg m-3 to 1510 kg m-3. The asteroidal densities are higher than chondritic, suggesting that some have significant iron content. Meteoroids from the Perseid meteoroid stream had densities of 620±200 kg m-3, consistent with the sporadic Halley-type meteoroids. Most surprising result was the high density of Jupiter-family comets (3100±300 kg m-3 for Jupiter-family sporadics, and 3200 kg m-3 in average for the North Iota Aquariids, which are linked to Comet 2P/Encke). This suggests that refractory material may be a major component of Jupiter family comets in agreement with the surprising results of the Stardust mission on comet 81P/Wild 2

Técnicas de detección y caracterización de la materia interplanetaria próxima a la Tierra desde observatorios en tierra

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Astrofísica y Ciencias de la Atmósfera, leída el 05/06/2017Interplanetary matter covers a wide range of mass and size in the Universe, from micrometric dust to multi-kilometre asteroids. This matter plays countless roles in planetary sciences. Dust fills the space in the Solar System, but also in a myriad of exoplanetary systems. Indeed, the interplanetary dust usually outshines the planets in infrared and these hot debris disks have already been observed in several exoplanetary systems. The near-Earth interplanetary matter is also relevant for Earth sciences and space exploration. Extraterrestrial dust plays several roles in the upper atmosphere. Moreover the asteroids are a threat for humankind due to the energy they release in the case of impact against the planet. Asteroids larger than 1 km could produce global devastation and 90% of them are already catalogued. Current efforts are focused on the population larger than 140 m, able to produce an impact of regional proportions. Beyond Earth’s atmosphere, these bodies pose a hazard to spacecraft, especially the small particles that are the most numerous but still carry enough energy to jeopardise their systems. This dissertation undertakes the research of the interplanetary matter near the Earth using two different observational approaches. The first one is based on the detection of the sunlight reflected by the bodies. Individuals bodies can be observed with the use of telescopes, they are the asteroids. For objects close to the Earth the accessible range in size is wider, down to the decametre size and consequently this population are a probe to general population of asteroids in the Solar System. Especially if we consider that recent works suggest that objects larger and smaller than 200 m could be two different populations, being the smaller monolithic bodies while larger ones are more likely rubble piles. And we only have access to the smaller population if they come close enough to the be observable. The detection and characterisation of these nearby population require networks of medium-sized telescopes to survey and track them. We design a robotic system (the TBT telescopes) for the European Space Agency as a prototype for a future network. The first unit is already installed in Spain and we present the results of the commissioning. Additionally we evaluate the expected performance of such an instrument using a simulation with a synthetic population. We consider that the system designed is a powerful instrument for nearby asteroid discovery and tracking. It is based on commercial components, and therefore ready for a scalable implementation in a global network...Bajo el término de materia interplanetaria se engloban objetos en un gran rango de masas y tamaños en el Universo, desde el polvo micrométrico hasta los asteroides de centenares de kilómetros de diámetro. Esta materia toma parte de innumerables procesos en las ciencias planetarias. Además el polvo no sólo está presente en el espacio del Sistema Solar, sino también en una infinidad de sistemas extrasolares. Más aún, el polvo interplanetario es más brillante en el infrarrojo que los propios planetas y ya se han observado muchos de estos discos circunestelares de polvo caliente. La materia interplanetaria en las cercanías de nuestro planeta es también relevante para el estudio de las ciencias de la Tierra y en la exploración espacial. El polvo extraterrestre participa en muchos procesos que tienen lugar en las capas más altas de la atmósfera. Asimismo los asteroides son una amenaza para la humanidad debido a la energía que pueden liberar en caso de impacto contra la Tierra. Se considera que los asteroides mayores de 1 km podrían provocar una catástrofe de proporciones globales y por ello el 90% de ellos ya han sido identificados. Actualmente los esfuerzos se centran en los objetos mayores de 140 m, con consecuencias sólo a nivel regional en caso de colisión. Fuera de la atmósfera terrestre estos cuerpos suponen un peligro para las naves espaciales, especialmente las partículas pequeñas que son las más numerosas y que pese a ello transportan energía suficiente como para comprometer su funcionamiento. Esta tesis estudia la materia interplanetaria desde dos aproximaciones observacionales distintas. Por un lado se observa la luz solar reflejada por estos cuerpos. En este caso encontramos a los asteroides, cuerpos que se pueden observar con telescopios hasta cierto tamaño. Para la población de objetos próximos a la Tierra el rango de tamaños que podemos observar es mayor, hasta tamaños de apenas decenas de metros. Por ello esta población se considera como una muestra relevante a la hora de estudiar la población general de asteroides en el Sistema Solar. Especialmente cuando estudios recientes afirman que puede haber una diferencia estructural entre las poblaciones con diámetro mayor y menor a unos 200 m, donde los pequeños son objetos monolíticos mientras que los grandes son agregados de objetos. Los objetos menores sólo son accesibles a los instrumentos si se aproximan lo suficiente a la Tierra. La detección y caracterización de estos objetos próximos requieren redes de telescopios de tamaño moderado. En este trabajo presentamos el diseño de un sistema robótico (los telescopios TBT) para la Agencia Espacial Europea (ESA), como prototipos de una red futura. El primero de ellos se encuentra ya instalado en España y se incluyen los resultados del comisionado. Por otro lado hemos analizado el rendimiento que se espera de ellos con ayuda de una simulación de las observaciones de una población sintética de objetos. Consideramos que el sistema diseñado es una herramienta potente para el descubrimiento y seguimiento de estos objetos próximos a la Tierra. Es un sistema basado en componentes comerciales y que por tanto se puede replicar para desarrollar una red global...Depto. de Física de la Tierra y AstrofísicaFac. de Ciencias FísicasTRUEunpu

Meteoroids 2013. Proceedings of the International Conference held at the Adam Mickiewicz University in Poznan, Poland August 26-30, 2013

Proceedings of the International Conference held at the Adam Mickiewicz University in Poznan, Poland August 26-30, 201

The Dynamics And Morphology Of Sprites

Thesis (Ph.D.) University of Alaska Fairbanks, 2003In 1999 the University of Alaska Fairbanks fielded a 1000 fields-per-second intensified CCD camera to study sprites and associated upper atmospheric phenomena occurring above active thunderstorms as part of the NASA Sprites99 campaign. The exceptional clarity and definition obtained by this camera the night of August 18, 1999, provides the most detailed image record of these phenomena that has been obtained to date. The result of a frame-by-frame analysis of the data permits an orderly classification of upper atmospheric optical phenomena, and is the subject matter of this thesis. The images show that both elves and halos, which are diffuse emissions preceding sprites, are largely spatially unstructured. Observations of sprites initiating outside of main parts of halos, and without a halo, suggest sprites are initiated primarily from locations of atmospheric composition and density inhomogeneities. All sprites appear to start as tendrils descending from approximately 75 km altitude, and may form other dynamic or stationary features. Dynamic features include downward developing tendrils and upward developing branches. Stationary features include beads, columns, and diffuse "puffs," all of which have durations greater than 1 ms. Stationary sprite features are responsible for a significant fraction of the total optical emissions of sprites. Velocities of sprite tendrils were measured. After initial speeds of 106--107 m/s, sprite tendrils may slow to 105 m/s. Similarly, on some occasions the dim optical emission left behind by the descending tendrils may expand horizontally, with speeds on the order of 105 m/s. The volume excited by the sprite tendrils may rebrighten after 30--100 ms in the form of one of three different sprite after effects collectively termed "crawlers." A "smooth crawler" consists of several beads moving upward (~105 m/s) without a large vertical extent, with "smooth" dynamics at 1 ms timescale. "Embers" are bead-like forms which send a downward-propagating luminous structure towards the cloudtop at speeds of 106 m/s, and have irregular dynamics at 1 ms timescales. In TV-rate observations, the downward-propagating structure of an ember is averaged out and appears as a vertically-extended ribbon above the clouds. The third kind of crawler, so-called "palm tree," appears similar to an ember at TV-rates, but with a wider crown at top

Techniques for near-Earth interplanetary matter detection and characterisation from optical ground-based observatories

Interplanetary matter covers a wide range of mass and size in the Universe, from micrometric dust to multi-kilometre asteroids. This matter plays countless roles in planetary sciences. Dust fills the space in the Solar System, but also in a myriad of exoplanetary systems. Indeed, the interplanetary dust usually outshines the planets in infrared and these hot debris disks have already been observed in several exoplanetary systems. The near-Earth interplanetary matter is also relevant for Earth sciences and space exploration. Extraterrestrial dust plays several roles in the upper atmosphere. Moreover the asteroids are a threat for humankind due to the energy they release in the case of impact against the planet. Asteroids larger than 1 km could produce global devastation and 90% of them are already catalogued. Current efforts are focused on the population larger than 140 m, able to produce an impact of regional proportions. Beyond Earth’s atmosphere, these bodies pose a hazard to spacecraft, especially the small particles that are the most numerous but still carry enough energy to jeopardise their systems. This dissertation undertakes the research of the interplanetary matter near the Earth using two different observational approaches. The first one is based on the detection of the sunlight reflected by the bodies. Individuals bodies can be observed with the use of telescopes, they are the asteroids. For objects close to the Earth the accessible range in size is wider, down to the decametre size and consequently this population are a probe to general population of asteroids in the Solar System. Especially if we consider that recent works suggest that objects larger and smaller than 200 m could be two different populations, being the smaller monolithic bodies while larger ones are more likely rubble piles. And we only have access to the smaller population if they come close enough to the be observable. The detection and characterisation of these nearby population require networks of medium-sized telescopes to survey and track them. We design a robotic system (the TBT telescopes) for the European Space Agency as a prototype for a future network. The first unit is already installed in Spain and we present the results of the commissioning. Additionally we evaluate the expected performance of such an instrument using a simulation with a synthetic population. We consider that the system designed is a powerful instrument for nearby asteroid discovery and tracking. It is based on commercial components, and therefore ready for a scalable implementation in a global network..

Potential for Measurement of Mesospheric Ozone Density from Overdense Meteor Trains with a Monostatic Meteor Radar

Thermally ablating meteoroids, colliding with the Earth’s atmosphere, leave a high temperature trail containing extremely energetic metallic ions and electrons. A well recognized, but unresolved, anomaly associated with ambipolar diffusion of meteor trains, which is more dominant in overdense meteors, takes place in the initial post-adiabatic train expansion. In this work, a newly proposed mechanism explaining this anomaly involves hyperthermal chemical reactions is presented. Data from the SKiYMET meteor radar system, deployed at latitudinally dispersed locations, were used to determine ozone density in the upper atmosphere by analyzing diffusion of overdense meteor trains. The results obtained in this study are in line with satellite measurements of ozone density. Moreover, it was demonstrated that backscatter can detect a direct signature of the newly discovered hyperthermal chemical reactions in overdense meteor trains. The hypothesis proposed in this thesis, suggesting the possibility of measuring the upper atmosphere ozone density using backscatter radar, has been validated