High precision meteor observations with the Canadian Automated Meteor Observatory -- Data reduction pipeline and application to meteoroid mechanical strength measurements
Denis Vida, Peter G. Brown, Margaret Campbell-Brown, Robert J. Weryk, Gunter Stober, John P. McCormack
Context. The mirror tracking system of the Canadian Automated Meteor Observatory (CAMO) can track meteors in real time, providing an effective angular resolution of 1 arc second and a temporal resolution of 100 frames per second.
Aims. We describe the upgraded hardware and give details of the data calibration and reduction pipeline. We investigate the influence of meteor morphology on radiant and velocity measurement precision, and use direct observations of meteoroid fragmentation to constrain their compressive strengths.
Methods. On July 21, 2017, CAMO observed a ~4 second meteor on a JFC orbit. It had a shallow entry angle ~8 deg and 12 fragments were visible in the narrow-field video. The event was manually reduced and the exact moment of fragmentation was determined. The aerodynamic ram pressure at the moment of fragmentation was used as a proxy for compressive strength, and strengths of an additional 19 fragmenting meteoroids were measured in the same way. The uncertainty in the atmosphere mass density was estimated to be +/-25% using NAVGEM-HA data.
Results. We find that meteor trajectory accuracy significantly depends on meteor morphology. The CAMO radiant and initial velocity precision for non-fragmenting meteors with short wakes is ~0.5' and 1 m/s, while that for meteors with fragments or long wakes is similar to non-tracking, moderate field of view optical systems (5', ~50 m/s). Measured compressive strengths of 20 fragmenting meteoroids (with less precise radiants due to their morphology) was in the range of 1-4 kPa, which is in excellent accord with Rosetta in-situ measurements of 67P. Fragmentation type and strength do not appear to be dependent on orbit. The mass index of the 12 fragments in the July 21 meteoroid was very high (s = 2.8), indicating possible progressive fragmentation.
Meteoroids are pieces of asteroids and comets. They serve as unique probes to the physical and chemical properties of their parent bodies. We can derive some of these properties when meteoroids collide with the atmosphere of Earth and become a meteor or a bolide. Even more information can be obtained when meteoroids are mechanically strong and slow enough to drop meteorites. Through physical modeling of bright meteors, we describe their fragmentation in the atmosphere. We also derive their mechanical strength and the mass distribution of the fragments, some of which may hit the ground as meteo…
Luminous efficiency is a necessary parameter for determining meteoroid mass from optical emission. Despite this importance, it is very poorly known, with previous results varying by up to two orders of magnitude for a given speed. We present the most recent study of luminous efficiency values determined with modern high-resolution instruments, by directly comparing dynamic and photometric meteoroid masses. Fifteen non-fragmenting meteoroids were used, with a further five clearly fragmenting events for comparison. Twelve of the fifteen non-fragmenting meteoroids had luminous efficiencies less t…
We examine meteoroid orbits recorded by the Canadian Meteor Orbit Radar (CMOR) from 2012-2019, consisting of just over 11 million orbits in a search for potential interstellar meteoroids. Our 7.5 year survey consists of an integrated time-area product of $\sim$ 7$\times$ 10$^6$ km$^2$ hours. Selecting just over 160000 six station meteor echoes having the highest measured velocity accuracy from within our sample, we found five candidate interstellar events. These five potential interstellar meteoroids were found to be hyperbolic at the 2$σ$-level using only their raw measured speed. Applying a …
Many existing optical meteor trajectory estimation methods use the approximation that the velocity of the meteor at the beginning of its luminous phase is equivalent to its velocity before atmospheric entry. Meteoroid kinetic energy loss prior to the luminous phase cannot be measured, but for some masses and entry geometries neglecting this loss may lead to non-negligible deceleration prior to thermal ablation. Using a numerical meteoroid ablation model, we simulate the kinematics of meteoroids beginning at 180 km with initial velocities ranging from 11 km/s to 71 km/s, and compare model veloc…
We investigate the spectra, material properties, and orbital distribution of millimeter- to decimeter-sized meteoroids. Our study aims to distinguish the characteristics of populations of differently sized meteoroids and reveal the heterogeneity of identified meteoroid streams. We verify the surprisingly large ratio of pure iron meteoroids on asteroidal orbits detected among mm-sized bodies. Emission spectra and multi-station meteor trajectories were collected within the AMOS network observations. The sample is based on 202 meteors of -1 to -14 magnitude, corresponding to meteoroids of mm to d…
Meteoroids impacting the Earth on a daily basis are fragments of asteroids and comets. By studying fireballs produced during their disintegration in the atmosphere, we can gain information about their source regions and the properties of their parent bodies. In this work, data on 824 fireballs presented in an accompanying paper and catalog are used. We propose a new empirical parameter for the classification of the physical properties of meteoroids, based on the maximum dynamic pressure suffered by the meteoroid in the atmosphere. We then compare the physical and orbital properties of meteoroi…
We describe how meteors recorded at the Earth can be used to partly reconstruct the meteoroid environments of the planets if a large sample (i.e. millions of orbits at a minimum) is available. The process involves selecting from the Earth-based sample those meteors which passed near a planet's orbit prior to arriving at the Earth, and so carry information about the planetary meteoroid environment. Indeed this process can be extended to any location in the Solar System, though some regions of space are better sampled than others. From such a reconstruction performed with data from the Canadian …
The number density and flux of a meteoroid stream is enhanced near a massive body due to the phenomenon known as gravitational focusing. The greatest enhancement occurs directly opposite the massive body from the stream radiant: as an observer approaches this location, the degree of focusing is unbound for a perfectly collimated stream. However, real meteoroid streams exhibit some dispersion in radiant and speed that will act to eliminate this singularity. In this paper, we derive an analytic approximation for this smoothing that can be used in meteoroid environment models and is based on real…
The internal structure and strength of small asteroids and large meteoroids is poorly known. Observation of bright fireballs in the Earth's atmosphere can prospect meteoroid structure by studying meteoroid fragmentation during the flight. Earlier evaluations showed that meteoroid strength is significantly lower than that of the recovered meteorites. We present detailed study of atmospheric fragmentation of seven meteorite falls, all ordinary chondrites, and 14 other fireballs, where meteorite fall was predicted but the meteorites, probably also ordinary chondrites, were not recovered. All obse…
The detected Na/Mg ratio in a sample of 17 Na-enhanced and Na-rich meteors is investigated based on obtained spectral, orbital and structural data. We utilize the meteor observations of the AMOS network obtained within a survey of medium-sized meteoroids supplemented by higher-resolution spectra observed on the Canary Islands. Ground-based meteor observations are then compared with high-resolution Echelle spectra of simulated ablation of known meteorite samples in a high-enthalpy plasma wind tunnel. It was found that most Na-enhanced and Na-rich spectra can be explained by the effect of low me…
Context. Generating a synthetic dataset of meteoroid orbits is a crucial step in analysing the probabilities of random grouping of meteoroid orbits in automated meteor shower surveys. Recent works have shown the importance of choosing a low similarity threshold value of meteoroid orbits, some pointing out that the recent meteor shower surveys produced false positives due to similarity thresholds which were too high. On the other hand, the methods of synthetic meteoroid orbit generation introduce additional biases into the data, thus making the final decision on an appropriate threshold value u…
By using an array of high-sensitivity CCD video devices and spectrographs, the activity of meteor events from the poorly-known $ρ$-Geminid meteoroid stream has been monitored during January 2012 and 2013. As a result of this research, the atmospheric trajectory and radiant position of 10 of these events has been obtained, but also the orbital parameters of the progenitor meteoroids and the tensile strength of these particles. The data reveal that the progenitor of this stream must be a comet. In addition, the emission spectra produced by three $ρ$-Geminid meteors were also recorded. These are …
We analyze the activity of the Northern ω-Scorpiid meteor shower between 2010 and 2012. For this purpose we have employed an array of low-lux CCD video cameras and spectrographs deployed at different astronomical observatories in Spain. As a result of our survey, the atmospheric trajectory and radiant position of 11 of these meteor events were obtained. The tensile strength and orbital parameters of the progenitor meteoroids have been also calculated. The calculated orbital data and the behaviour of these meteoroids in the atmosphere are compatible with an asteroidal origin of this stream. In …
The physical composition and structure of meteoroids gives us insight into the formation processes of their parent asteroids and comets. The strength of and fundamental grain sizes in meteoroids tell us about the environment in which small solar system bodies formed, and the processes which built up these basic planetary building blocks. The structure of meteorites can be studied directly, but the set of objects which survive entry through the atmosphere is biased toward large, strong objects with slow encounter speeds. Fragile objects, small objects and objects with high relative speeds are v…
This article describes our approach to quantifying the characteristics of meteors such as temperature, chemical composition, and others. We are using a new approach based on colourimetry. We analyze an image of Leonid meteor-6230 obtained by Mike Hankey in 2012. Analysis of the temporal features of the meteoroid trail is performed. For determining the meteor characteristics we use the "tuning technique" in combination with a simulation model of intrusion. The progenitor of the meteor was found as an object weighing 900 kg at a speed of 36.5 km/s. The meteoroid reached a critical value of the p…
The origin of the Taurid complex is still debated. In addition to comet 2P/Encke, various asteroids were proposed to be members of the complex and thus possible parent bodies of Taurid meteoroids. Studies of physical properties of Taurid meteoroids can provide constrains on their source. We used a well defined orbital sample of 16 Taurid fireballs with detailed radiometric light curves. The sample represented meteoroids of initial masses from 8 grams to 650 kg (diameters 1 - 70 cm). The semi-empirical fragmentation model was used to study their atmospheric fragmentation and derive strength dis…
Context. The determination of meteoroid mass indices is central to flux measurements and evolutionary studies of meteoroid populations. However, different authors use different approaches to fit observed data, making results difficult to reproduce and the resulting uncertainties difficult to justify. The real, physical, uncertainties are usually an order of magnitude higher than the reported values. Aims. We aim to develop a fully automated method that will measure meteoroid mass indices and associated uncertainty. We validate our method on large radar and optical datasets and compare results …
A Machine Learning Approach to Meteor Classification
Northern Arizona University（北亚利桑那大学）；Lowell Observatory（洛厄尔天文台）；The University of Western Ontario（韦仕敦大学）；Institute for Earth and Space Exploration, The University of Western Ontario（韦仕敦大学地球与太空探索研究所）
Eta-Virginids: another asteroidal meteoroid stream
Astronomical Institute of the Czech Academy of Sciences（捷克科学院天文研究所）；Astronomical Institute of the Slovak Academy of Sciences（斯洛伐克科学院天文研究所）；Österreichischer Astronomischer Verein（奥地利天文协会）
This is an overview of recent research on meteors and the parent bodies from which they are produced. While many meteor showers result from material ejected by comets, two out of the three strongest annual showers (the Geminids and the Quadrantids) are associated with objects whose physical properties are apparently those of asteroids. In the last decades dynamical and observational studies have confirmed the existence of a number of Asteroid-Meteoroid Complexes, comprising streams and several macroscopic, split fragments. Spectroscopy of meteor showers has been utilized to investigate the per…
Various meteor and fireball networks exist worldwide. Most data sets which include ground-based observational data of meteors are affected by biases. The larger and faster the entering meteoroid, the brighter is the produced meteor. Hence, small and slow objects often stay undetected. This bias of meteor observations towards faster meteoroids is a challenge if quantitative population and flux models are derived. In this work the velocity distribution of objects in space is analysed by using different data sets that are not affected by this velocity bias since they include only large objects, l…
Infrasound monitoring has proved to be effective in detection of the meteor generated shock waves. When combined with optical observations of meteors, this technique is also reliable for detecting centimeter-sized meteoroids that usually ablate at high altitudes, thus offering relevant clues that open the exploration of the meteoroid flight regimes. Since a shock wave is formed as a result of a passage of the meteoroid through the atmosphere, the knowledge of the physical parameters of the surrounding gas around the meteoroid surface can be used to determine the meteor flow regime. This study …
Taurids are an extensive stream of particles produced by comet 2P/Encke, which can be observed mainly in October and November as a series of meteor showers rich in bright fireballs. Several near-Earth asteroids have also been linked with the meteoroid complex, and recently the orbits of two carbonaceous meteorites were proposed to be related to the stream, raising interesting questions about the origin of the complex and the composition of 2P/Encke. Our aim is to investigate the nature and diversity of Taurid meteoroids by studying their spectral, orbital, and physical properties determined fr…
The hydrogen emission from meteors is assumed to originate mainly from the meteoroid composition, making it a potential tracer of H$_{2}$O molecules and organic compounds. H$α$ line was previously detected in individual fireballs, but its variation in a larger meteor dataset and dependency on the dynamical origin and physical properties have not yet been studied. Here we investigate the relative intensity of H$α$ within 304 meteor spectra observed by the AMOS network. We demonstrate that H$α$ emission is favored in faster meteors ($v_i >>$ 30 km s$^{-1}$) which form the high-temperature spectr…
Meteorites with known orbital origins are key to our understanding of Solar System formation and the source of life on Earth. However, these pristine samples of space material are incredibly rare. Less than 40 of the 60,000 meteorites held in collections around the world have known dynamical origins. Fireball networks have been developed globally in a unified effort to increase this number by using multiple observatories to record, triangulate, and dynamically analyse ablating meteoroids as they enter our atmosphere. The accuracy of the chosen meteoroid triangulation method directly influences…
Achondrites in meteor data: Spectra, dynamics, and physical properties of candidate aubrite and eucrite impactors
Faculty of Mathematics, Physics and Informatics, Comenius University Bratislava（布拉迪斯拉发康斯坦丁神学家大学数学、物理与信息学院）；Astronomical Institute of the Czech Academy of Sciences（捷克科学院天文研究所）；Space Science and Technology Centre, School of Earth and Planetary Sciences, Curtin University（科廷大学地球与行星科学学院空间科学与技术中心）；International Centre for Radio Astronomy Research, Curtin University（科廷大学国际射电天文学研究中心）
We use the Slovak and Czech video meteor observations, as well as video meteoroid orbits collected in the CAMS, SonotaCo, EDMOND and DMS catalogues, for an analysis of the distribution of meteoroid orbits within the stream of the Geminids and of the dispersion of their radiants. We concentrate on the influence of the measurement errors on the precision of the orbits obtained from the video networks that are based on various meteor-detection software packages and various meteor orbital element softwares. The observed orbital dispersions in the Geminid stream described by the median absolute dev…
Meteor physics can provide new clues about the size, structure, and density of cometary disintegration products, establishing a bridge between different research fields. From meteor magnitude data we have estimated the mass distribution of meteoroids from different cometary streams by using the relation between the luminosity and the mass obtained by Verniani (1973). These mass distributions are in the range observed for dust particles released from comets 1P/Halley and 81P/Wild 2 as measured from spacecraft. From the derived mass distributions, we have integrated the incoming mass for the mos…
Burns et al. (1979) use the parameter beta to describe the ratio of radiation pressure to gravity experienced by a small particle in the solar system. The central potential that these particles experience is effectively reduced by a factor of (1 - beta), lowering the escape velocity. Burns et al. (1979) also provide a simple expression for the value of beta at which particles ejected from a comet follow parabolic orbits and thus leave the solar system; this paper expands on this to calculate critical beta values that take ejection velocity into account. We first derive an expression for the sp…
We report results of a four-year survey using Electron Multiplied Charged Coupled Device (EMCCD) cameras recording 34761 two-station video meteor events complete to a limiting magnitude of +6. The survey goal was to characterize probable iron meteoroids. Using only physical properties of the meteor trajectories including early peaking light curves, short luminous trajectories, and high energies accumulated per area at beginning, we identified 1068 iron meteors. Our iron candidates are most abundant at slow speeds < 15 km/s, where they make up approximately 20% of the mm-sized meteoroid populat…
The orbital distributions of dust particles in interplanetary space are inferred from several meteoroid data sets under the constraints imposed by the orbital evolution of the particles due to the planetary gravity and Poynting-Robertson effect. Infrared observations of the zodiacal cloud by the COBE DIRBE instrument, flux measurements by the dust detectors on board Galileo and Ulysses spacecraft, and the crater size distributions on lunar rock samples retrieved by the Apollo missions are fused into a single model. Within the model, the orbital distributions are expanded into a sum of contribu…
In studies of the oldest solar system bodies - comets and asteroids - it is their fragments - meteoroids - that provide the most accessible planetary material for detailed laboratory analysis in the form of dust particles or meteorites. Some asteroids and comets were visited by spacecrafts and returned interplanetary samples to Earth, while missions Hayabusa 2 and OSIRIX-REx visiting asteroids Ryugu and Bennu are ongoing. However, the lack of representative samples of comets and asteroids opens the space to gain more knowledge from direct observations of meteoroids. At collision with the Earth…
We present an algorithm developed to measure the fluxes of major meteor showers as observed in NASA's All-Sky Fireball Network cameras. Measurements of fluxes from the All-Sky cameras not only improve the Meteoroid Environment Office's (MEO's) ability to provide accurate risk assessments from major showers, but also allows the mass distribution of meteoroids within the shower to be constrained. This algorithm accounts for the shower-specific and event-specific exposure time and collecting area of the sky for nights where sufficiently large samples of shower meteors ($\sim 30$ or more from the …
The existence of a hypothetical Planet 9 lurkng in the outer solar system has been invoked as a plausible explanation for the anomalous clustering in the orbits of trans-Neptunian objects. Here we propose that some meteoroids arriving at Earth could serve as messengers with the potential of revealing the presence of a hitherto undiscovered massive object. The peculiar meteor CNEOS 2014-01-08, recently put forward as the first interstellar meteor, might be one such messenger. The meteor radiant is in the maximum probability region calculated for the Planet 9 location in previous works. The odds…
NASA's Meteoroid Environment Office (MEO) produces an annual meteor shower forecast in order to help spacecraft operators assess the risk posed by meteoroid streams. Previously, this forecast focused on the International Space Station and therefore reported meteoroid fluxes and enhancement factors at an orbital altitude of 400 km. This paper presents an updated forecast algorithm that has an improved calculation of the flux enhancement produced by showers and can calculate fluxes at any selected Earth or lunar orbital altitude. Finally, we discuss and generate forecasted fluxes for the 2018 Dr…
Since 2007, the Meteor Data Center (MDC) has had two components: the Orbital database (OD) and the Shower database (SD). The orbital part is in charge of the efficient collection, checking, and dissemination of geocentric parameters and orbits of individual orbits. Is also acts as a central depository for meteoroid orbits obtained by different techniques: photographic, television, video, CCD and radar. The shower database collects the geocentric and orbital parameters of the meteor showers and meteoroids streams. It is not an archive of all information related to meteor showers, its primary ta…
Everyday thousands of meteoroids enter the Earth's atmosphere. The vast majority burn up harmlessly during the descent, but the larger objects survive, occasionally experiencing intense fragmentation events, and reach the ground. These events can pose a threat for a village or a small city; therefore, models of asteroid fragmentation, along with accurate post-breakup trajectory and strewn field estimation, are needed to enable a reliable risk assessment. In this work, a methodology to describe meteoroids entry, fragmentation, descent, and strewn field is presented by means of a continuum appro…
Context. The existence of meteor clusters has long since been a subject of speculation and so far only seven events have been reported, among which two involve less than five meteors, and three were seen during the Leonid storms. Aims. The 1995 outburst of Comet 73P/Schwassmann-Wachmann was predicted to result in a meteor shower in May 2022. We detected the shower, proved this to be the result of this outburst, and detected another meteor cluster during the same observation mission. Methods. The τ-Herculids meteor shower outburst on 31 May 2022 was continuously monitored for 4 hours during an …
Shock waves and the associated phenomena generated by strongly ablating meteoroids with sizes greater than a few millimeters in the lower transitional flow regime of the Earth's atmosphere are the least explored aspect of meteor science. In this paper, we present a comprehensive review of literature covering meteor generated shock wave phenomena, from the aspect of both meteor science and hypersonic gas dynamics. The primary emphasis of this review is placed on the mechanisms and dynamics of the meteor shock waves. We discuss key aspects of both shock generation and propagation, including the …
The Quadrantid meteor shower is among the strongest annual meteor showers, and has drawn the attention of scientists for several decades. The stream is unusual, among others, for several reasons: its very short duration around maximum activity (~12 - 14 hours) as detected by visual, photographic and radar observations, its recent onset (around 1835 AD) and because it had been the only major stream without an obvious parent body until 2003. Ever since, there have been debates as to the age of the stream and the nature of its proposed parent body, asteroid 2003 EH1. In this work, we present resu…
