Parent Comets and Asteroids of Meteor Showers

Q.-Z. Ye

The connection between meteor showers and comets (and more recently, asteroids) has been known since 1867. The advance in observational astronomy, as well as planetary exploration in the past several decades, have vastly enriched our knowledge of comets and asteroids, including the ones that manifest meteor showers on Earth. Here I will review the current observational understanding of these parent bodies and discuss how they can be combined with meteor observations to further enhance our understanding of these bodies.

WISE/NEOWISE Thermal Infrared Survey for Asteroidal Stream Parents

T. K. Kasuga, J. R. M. Masiero

We present the space-based infrared study of asteroidal stream parents utilizing the NASA Wide-field Infrared Survey Explorer (WISE; Wright et al. 2010) and the Near-Earth Object WISE (NEOWISE; Mainzer et al. 2011, Masiero et al. 2019). WISE, the full sky survey simultaneously obtained the infrared data at the four infrared wavelength bands 3.4μm (W1), 4.6μm (W2), 12μm (W3), and 22 μm (W4) in 2010. The NEOWISE survey started in December 2013 and is ongoing project taking the shorter two-bands at 3.4μm (W1) and 4.6μm (W2). The each band is specified for investigating physical characters of the asteroids, such as the dust production rate (W1), the gas production rate (W2) and the potentially co-moving objects and dust trails (W3 and W4). Physical disintegration of asteroids result in producing the meteoroid streams. Suggested mechanisms, especially for those of asteroids, include rotational instability, thermal stress, collisions (impacts), and so on (Jewitt & Hsieh 2022). Asteroidal stream parents should be, or used to be, losing mass while among the few mass-loss activities other than activity driven by sublimation of ice are identified (Kasuga & Jewitt 2019). The WISE/NEOWISE multiple observing epochs of the infrared data provide with information about where in the orbit the object is along with the limits, as we might expect a strong variation in production at different points in the orbit. With the scientific view, we investigate asteroidal parent bodies and discuss the results in the conference.

Simulating the Evolution of Large, Near-Earth Meteoroid Streams and Their Properties

A. Humpage, A. A. Christou

One of the main processes involved in the evolution of meteoroids is the breakup and fragmentation of asteroids. Therefore, it is important to understand the timescales and to identify the outcomes of these breakups: asteroid families. This is particularly interesting for asteroids and meteoroids in orbit near the Earth, as the timescales for the dispersion of these families are much shorter, and are the most likely to have encounters with the Earth, becoming meteor streams and fireballs.

In this study, we use an N-body integrator to simulate asteroids in, or near, Earth resonances. Added to the simulation is the velocity dispersion of the asteroid fragments immediately after breakup, and relevant non-gravitational forces, such as Yarkovsky and Poynting-Robertson drag. A large number of families are run, both in and outside of Earth resonances. We present the timescales for the dispersion of asteroids, for a range of parameters and orbital constants. With these timescales, we are able to make suggestions for the most consistent orbital parameters for NEO families. This can be used as a way to identify these families, and to characterise the number which are identifiable and the co-orbital resonances where they are most stable.

The Origin of Large Bolides Recorded from Space: CNEOS Database Evidence for the Disruption of Transitional Objects in Near-Earth Space

E. Peña-Asensio, J. M. Trigo-Rodríguez, A. Rimola

When metric-sized asteroids or comets impact our atmosphere, they produce an exceptional brightness as they undergo the ablation process of most of their masses due to the hypersonic collision with air particles. These spectacular events, called superbolides, are recorded from space by U.S. Government sensors, providing valuable information about the characteristics of the incoming flux of extraterrestrial material to Earth. On numerous occasions, these detections are complemented with ground-based recordings and are especially relevant because of the high probability of becoming meteorite droppers.

These events are published on the CNEOS web portal, sometimes with velocity vector information that allows an orbital reconstruction. Using our 3D-FireTOC software for automatic analysis of fireballs, we estimate the tensile strength, diameter and reconstruct the heliocentric orbit of these potentially hazardous projectiles. This allows us to classify, as a first approach, the origin of these metric projectiles. As of March 15, 2022, the CNEOS public database counted 887 events. However, only 255 contained sufficient data to compute the heliocentric orbit. We find that 11.4% of them have orbits associated with Jupiter-family comets, while 84.3% present a Tisserand parameter typical of asteroid origin. Our results indicate that 68.2% have dynamic strengths of chondritic bodies, while 15.3% exhibit bulk densities typical of cometary meteoroids.

This implies that a significant fraction of meter-sized projectiles producing large bolides may have a cometary origin and points out the relevance of the disruption of comets in near-Earth space in the short timescales.

Chyba, C. F., Thomas, P. J., & Zahnle, K. J. (1993). Nature, 361(6407), 40 Peña-Asensio, E., et al. (2021). MNRAS 504(4), 4829-4840 Trigo-Rodriguez, J. M., & Blum, J. (2009). Planetary and Space Science, 57(2), 243-249 Trigo-Rodríguez, J. M., & Williams, I. P. (2017). In AMAIH (pp. 11-32). Springer, Cham.

Origin of ALTAIR Meteoroids Determined from MODA

J. T. Blanchard, N. Lee, S. Close

The origins of a set of meteors observed by the ALTAIR Radar in 2007–2008 is discussed, including possible interstellar particles. We use the new tool, MODA, to determine orbital elements and uncertainties.

High-Inclination NEAs as Meteor Stream Parent Bodies

A. A. Christou, N. Georgakarakos

Recent meteor radar surveys have uncovered a subpopulation of meteoroids with high orbital inclination and at a=1 au, in the form of a grouping of radiants within the southern toroidal source of sporadic meteors (Brown et al, Icarus, 2010; Pokorny et al, Icarus, 2014). Many of these showers are so far not detected in optical surveys (Jenniskens et al, PSS, 2018; Bruzzone et al, PSS, 2020), implying a meteoroid population deficient in large particles, as might result from the gradual, size-sorting action of P-R drag. Therefore, these meteoroids plausibly represent dynamically old debris from parent bodies at much larger distances from the Sun, such as Halley-type comets (Pokorny et al, 2014 and references therein). Here we consider an alternative source for this subpopulation, namely one or more Near-Earth Asteroids (NEAs) in similar, high inclination orbits as the meteoroids. We test this hypothesis by numerical integration of test particles ejected from a selection of suitable NEAs and evolving under the influence of radiation forces. We pay particular attention to the role of dynamical resonances near the Earth's orbit as well as the Kozai regime in confining the meteoroids, thus countering the dispersive action of drag forces and gravitational scattering.

At the time of submitting this abstract, these simulations were under way and we will report on the outcome at the meeting.

Optical Determination of Meteoroid Physical Properties

V. V. Vojáček

Optical observations are the most common and still most important way of meteor observations in the atmosphere. With nowadays accessible camera equipment meteor observations are easier than ever before. Even data of fireball observations from space satellites are available to the public. We can observe a large size range, from micrometer meteoroids to small asteroids.

Not only for these reasons our methods of determining meteoroid physical properties are crucial in meteor physics. We can use a purely statistical approach to a large number of meteors from automatic surveys and obtain the typical properties of a given sample of sporadic or shower meteoroids. Or we can study smaller samples or individual cases using very precise observations, while the most valuable are combinations of different observation techniques. Dynamics can be determined using direct video or photographic cameras, guided camera systems can significantly improve the study of meteor fragmentation, spectral observations can reveal meteoroids' chemical composition or physical conditions during the flight, fast photometers allow precise photometry, and can observe rapid changes in meteor light curves.

In my talk I will summarize the possibilities that these can offer to determine meteoroid physical properties.

Using Meteoroids to Perform a Survey of the Physical Properties of Cometary Nuclei

N. A. Buccongello, P. G. Brown, D. Vida

In this work we present an optical survey of mm-sized meteoroids using The Canadian Automated Meteor Observatory (CAMO) (Vida et al., 2021). CAMO uses a dual mirror system to track meteors through an image intensified telescopic system with pixel resolutions of order 3” and exposure times of 10ms. This dataset consists of well-tracked events in the period 2016-2021 comprising 18 meteor showers representing 16 unique parent comets. CAMO observations record meteor positions from two stations separated by 50km and permit trajectory solutions with sub-m transverse residuals. CAMO also records wake for each event, providing constraints on meteoroid grain distribution. Here we apply a numerical implementation of the erosion model of Borovicka et al (2007) to these data with the goal of estimating the meteoroid bulk density, minimum and maximum grain size and grain size distribution. By analysing multiple shower events from a particular comet, we provide estimates of the average and range of values of these quantities which can be related to the original parent. Ultimately our goal is to explore variations in these structural features among different cometary populations to explore potential differences which may be correlated to their origin and/or subsequent evolution. References: Borovička J., Spurný P., and Koten P. 2007. Atmospheric deceleration and light curves of Draconid meteors and implications for the structure of cometary dust. Astronomy 672:661–672. Vida D., Brown P. G., Campbell-Brown M. D., Weryk R. J., Stober G., and McCormack J. P. 2021. High precision meteor observations with the Canadian automated meteor observatory: Data reduction pipeline and application to meteoroid mechanical strength measurements. Icarus 354:114097.

The Transition from Photoplate to CMOS Spectra — A Multi-Station Analysis of the Fireball Captured on 14th October 2018

M. Šegon, J. Borovička

With the evolution of technology, CMOS cameras replaced photographic plates previously used for recording meteor spectra. During the transition phase, both recording methods were operative. The fireball, which occurred on 14th October 2018, is one of several which produced a spectrum recorded using both methods. The results of the analysis of three CMOS spectra and one photoplate spectrum of the said fireball will be presented, along with a step-by-step analysis breakdown. Special emphasis will be given to the wavelength calibration and synthetic fit of the spectra. A comparison of spectral line intensities from different stations will be given for two different flares.

Holistic Ablation and Fragmentation Modelling of Orionid Meteoroids

D. Vida, P. G. Brown, M. Campbell-Brown

Understanding the physical properties and structure of meteoroids is critical for understanding comet formation and accurate predictions of future meteor shower activity. Meteoroid physical properties can be constrained through forward modelling of ablation and fragmentation of optical observations of meteors (Vojacek et al., 2019). However, these models have so far been unable to explain directly observed meteor wake at high spatial resolution (Campbell-Brown et al., 2013). In this work, we apply the Borovicka et al. (2007) erosion model to high-resolution meteor observations from the Canadian Automated Meteor Observatory’s (CAMO) mirror tracking system (Vida et al., 2021). Meteor observations are made to +8 mag, with a spatial precision of 1 m, while meteor wake is simultaneously observed with a resolution of 5 m/px. We apply this numerical model to CAMO observations of the Orionids in 2019 and 2020. The model was fit on a total of 18 Orionid meteors for which we were able to simultaneously match the observed light curve, dynamics, and wake. Meteoroid masses ranged between 3-10 x 10^-6 kg using a new empirical luminous efficiency function appropriate to faint meteors. We find the Orionids in our sample have a narrow range of erosion energies from 1-2 MJ m^-2 and wider range of erosion coefficients (0.1 – 1, mean of 0.35). The power law mass distribution index of grains for most fits is s = 2.1 - 2.2, with typical grain sizes being between 20 and 200 um. We find that all Orionids have a bulk density of 300 kg m^-3, in agreement with Vega-2 in-situ measurements of dust of the parent comet 1P/Halley (Krasnopolsky et al., 1988).

Borovicka et al., 2007. Astronomy & Astrophysics, 473(2), pp.661-672. Campbell-Brown et al., 2013. Astronomy & Astrophysics, 557, p.A41. Krasnopolsky et al., 1988. In Exploration of Halley’s Comet (pp. 707-711). Springer, Berlin, Heidelberg. Vida et al., 2021. Icarus, 354, p.114097. Vojacek et al., 2019. Astronomy & Astrophysics, 621, p.A68.

Inverting Physical Properties of Meteoroids Using Machine Learning

J. Kambulow, D. Vida, P. Brown

To reliably extract physical properties of meteoroids requires manual fitting of meteor data through application of a meteor ablation and fragmentation model (e.g. Vojáček et al., 2019). However this process is difficult, subjective, and time consuming. Here we propose a convolutional neural network (CNN) method to make robust automated ablation model fits to optical meteor data. We generate a training dataset of synthetic meteor observations using the Borovička et al. (2007) erosion model covering a wide range of meteoroid physical parameters. This dataset is made more physically realistic by adding noise consistent with observations to simulate real measurements of meteor magnitude, height, and length. The CNN is trained with the synthetic observations as input and the known physical meteoroid properties as output. Our goal is to build a CNN that allows real data to be fed into the CNN and obtain reliable model fits. Our trained model yields promising preliminary results and could provide a faster and more accurate means of extracting physical properties of meteoroids than was previously possible. Addition of Monte Carlo noise to real measurements will allow for multiple CNN fits consistent with measurement uncertainties which in turn can be used to more robustly define allowable ranges in fit parameters.

The Relation Between Physical and Orbital Properties of Meteoroids from the Data of the European Fireball Network

J. Borovicka, P. Spurny, L. Shrbeny

Trajectories, orbits, and light curves of more than 1000 fireballs observed by the digital all-sky cameras of the European Fireball Network between 2017 and present were computed. A new empirical parameter for the classification of physical properties of meteoroids, called Pressure Resistance Factor (Pf) was proposed. It is based on the maximum dynamic pressure suffered by the meteoroid in the atmosphere. We argue it is more robust than the classical PE criterion. The most resistant meteoroids with large Pf are supposed to be of asteroidal origin. Meteoroids of low resistance are mostly cometary, with the exception of irons, which also have low Pf, because they ablate easily. Irons must be recognized from spectra or from their typical light curves. It was found that the aphelion distance (Q) is a better indicator of asteroidal origin than the Tisserand parameter. The approximate limit is Q < 4.9 AU. In addition, another population of asteroidal material was found. Meteoroids of that secondary asteroidal population have even larger aphelia (up to ~ 7 AU) but also either high eccentricities (> 0.88) or high inclinations (> 45 degrees). Of course, there is some diffusion across the limits. A large intrusion of cometary material on asteroidal orbits is connected with comets 2P/Encke (Taurids) and 169P/NEAT (Capricornids). The classification of shower fireballs showed that their parent bodies are not homogeneous objects but contain material of wide range of properties. Still, there are clear differences among various showers, discernible especially when comparing large meteoroids. Geminids and eta Virginids are the most resistant. The next are Southern delta Aquariids. Taurids and Perseids are rather weak and the weakest are Leonids, Capricornids, and Draconids.

Iron Rain: Measuring the Occurrence Rate and Origin of Small Iron Meteoroids at Earth

T. Mills, P. G. Brown, M. J. Mazur, D. Vida, P. S. Gural, A. V. Moorhead

We summarize early results of a comprehensive optical survey of the faint meteor population, with the specific goal of characterizing probable iron meteoroids. During the period of 2016-2020, the survey recorded a total of 34761 two-station meteor events using electron-multiplied charge-coupled devices (EMCCDs), complete to a limiting magnitude of +6. We identify 1068 iron meteors based on their expected ablation characteristics (as summarized in Čapek et al. 2019), including early-peaked light curves, short luminous trajectories, and high energies accumulated per unit cross sectional area at the start of luminous flight. Our iron meteors are most abundant at slow speeds <15 km/s, where they make up ~20% of the de-biased mm-sized meteoroid population. They are overwhelmingly on asteroidal orbits. They have lower orbital eccentricities and smaller semi-major axes as compared to non-irons at the same entry speeds. We suggest this circularization is the result of Poynting-Robertson drag and reflects the older collisional ages of the iron meteoroids relative to the more numerous cometary population. We find that the iron population becomes more abundant at fainter magnitudes, comprising 15% of slow (10-15 km/s) meteors with peak brightness of +3 and rising to 25% at +6 to +7, our survey limit. A few percent of irons are on Halley-type orbits; however, we are unable to determine if these are truly irons or Na-free meteoroids with similar ablation behaviour. We propose a technique using R-band colours to more robustly identify fainter iron meteors and better distinguish them from the Na-free population with very high confidence.

Shapes of Meteoroids

D. Čapek, J. Haloda, J. Kaiser, T. Kohout, P. Koten, R. Macke, J. Pachman, Z. Štubianová, T. Zikmund

The shapes of many asteroids are known due to spacecraft flybys, Earth-based radar observations, or light curve inversions. In the case of meteoroids, their small sizes inhibit the use of these methods and their shapes remain unknown. However, knowledge of meteoroid shapes would allow modelling of many important processes, such as meteoroid rotation in the interplanetary space, the effect of solar radiation pressure, the motion in the atmosphere before the onset of intense ablation and fragmentation, etc. We will present a method that simulates the process of meteoroid formation by hypervelocity destruction of samples of various meteorites and terrestrial rocks. We selected suitable fragments, digitized them and obtained shapes appropriate for meteoroid characterization. These shapes are approximated by polyhedrons with many thousands of triangular surface elements. We will show the parameters describing the properties of the shapes and discuss their statistical distribution as a function of the target material and the way they were disrupted. We will also present an evolving database of digital shapes suitable for the characterization of asteroidal meteoroids.

Resonant Cosmic Dust — How Mean-Motion Orbital Resonances Shape Zodiacal Disks

M. Sommer

Orbital resonances have been known to shape the distribution of small bodies in the solar system since the discovery of the asteroid belt’s Kirkwood gaps, more than a century ago. With decreasing size, meteoroids and ultimately dust grains are increasingly affected by non-gravitational effects (such as Pointing-Robertson drag) giving rise to peculiar dynamics - especially in connection with orbital resonances. Resonant dust has thus been subject of a number of numerical as well as observational studies, in particular concerning the aggregation of particles in certain regions of space: Mean-motion resonances may protect fresh grains in cometary streams from dispersion to form dense swarms, or halt migration of the diffuse micro-meteoroid background to generate broad toroidal structures, the so-called resonant rings. This talk reviews the study of resonant phenomena in cosmic dust, and the features that arise as a consequence in the zodiacal cloud (and in exozodiacal clouds). We focus on the numeric modelling of the resonant rings and analyze how Venus, Earth and Mars interfere with each other’s ability to trap or displace particles near their mean-motion resonances. We look into the disk structure generated by this multi-planet configuration and discuss implications for the survey of exozodiacal disks.

Determining the Relative Contribution of Sources to the Zodiacal Cloud Using High-Resolution Spectroscopic Measurements of the Zodiacal Light

A. J. E. Kehoe, L. M. Haffner, T. J. J. Kehoe, E. J. Mierkiewicz, P. Mann

We know that the dust that comprises the zodiacal cloud comes mainly from cometary and asteroidal source populations, but their relative contributions have proven hard to determine. Asteroidal and cometary particles typically have quite different types of orbits and, accordingly, the relative velocities of these populations with respect to Earth are also quite different. In an ongoing effort to differentiate the sources of dust, we are undertaking a new observational campaign, making spectroscopic measurements of the zodiacal light. This data, when combined with dynamical modeling, will help establish the relative contributions of sources. The zodiacal light is produced by scattering off interplanetary dust particles and the spectrum contains solar absorption lines that are Doppler-shifted by these moving dust particles. The profiles of the shifted absorption lines therefore provide information about the velocities of the dust particles, which are the critical data needed to determine their origin. We have begun measuring these dust particle velocities by observing the zodiacal light, focusing on a pair of scattered solar Mg I Fraunhofer lines, using the Wisconsin H-alpha Mapper (WHAM) — a specialized Fabry-Perot spectrometer used to study wide-scale, diffuse sources. To interpret these observations, we create synthetic Doppler-shifted spectra based upon the results of numerical simulations of the dynamics of the dust composing the cloud. We determine the orbital parameters of dust particles from a range of sources by tracking the dynamical evolution of the particles from their source regions into the inner Solar System. We then use these parameters to produce synthetic observations of how such orbital distributions of dust particles would shift and modify the profiles of the Fraunhofer spectral lines. Comparing these synthetic spectra to the actual observations helps constrain the relative contributions of the sources of dust comprising the zodiacal cloud.

An Analytic Formulation of Ejecta Distributions over Airless Bodies

M. J. Matney

With recent plans to revisit the Moon by robotic and crewed spacecraft, there has been a renewed interest in understanding the ejecta environment on the Moon and other airless bodies. Meteoroid and asteroid impacts can excavate large amounts of material from the surface and, above an airless body, can send this material long distances on (essentially) ballistic orbits. This ejecta, while typically traveling slower than the impactor, can nevertheless achieve high enough speeds to endanger surface operations. Accurate knowledge of this phenomenon is necessary in order to design appropriate shielding for human activities, both for activities on the surface of the Moon and for orbiters in near-lunar space. This phenomenon is also important in the transport of particles above other Solar System objects, such as Jovian satellites, where this ejecta creates a kind of ever-present “halo” of particles around the gravitating body. While Monte Carlo techniques have been successfully used to model this environment, there are useful analytic expressions, developed for use in modeling the meteoroid environment, that can be used to describe this environment as well. Such analytic tools can shed light on the altitude, velocity, and directionality of these ejecta environments.

The Interstellar Dust Size Distribution

V. J. Sterken, S. Hunziker, A. Li, P. Strub, H. Krüger, M. Hajdukova

Interstellar dust from the local interstellar cloud moves through the solar system because of the relative motion of the solar system and its local interstellar environment. The dynamics of micron-sized interstellar dust particles are gravitationally dominated and thus the interstellar dust flow of micron-sized particles is stationary through the solar system. Although often not included in the interstellar dust models constructed from astronomical observations, micron-sized particles have been measured in situ in the solar system with spacecraft impact ionization dust detectors, and by sample return from the Stardust mission. The dynamics of submicron-sized interstellar dust is dominated by solar radiation pressure forces and in addition reacts to the solar cycle through the Lorentz forces on the charged dust particles that move through the plasma of the heliosphere. The resulting size distribution that can be measured in situ thus depends on time and space in the solar cycle and solar system. Interstellar dust of a few nanometers in size cannot enter the solar system as the particles are tightly coupled to the magnetic fields of the heliosphere and move around it. The interstellar dust size distribution outside of the heliosphere can be inferred from in situ data, provided that accurate models of the heliosphere are used and sufficient data from spacecraft are available throughout the solar cycle. This talk reviews the current state of knowledge of the interstellar size distribution from the dust that passes through the solar system, and it addresses several important aspects that are currently being investigated, like the unresolved upper size limit of the dust and heliosphere-dust modelling for the smaller particles.

Micrometeoroid Predictions for MMX and Destiny+ Using the IMEM2 Dust Model

P. Strub, H. Krüger, M. Kobayashi, R. Srama

IMEM2 (Interplanetary Meteoroid Environment Model2) is a new dynamical model of the interplanetary dust cloud originating from Jupiter-family and Halley type comets and main belt asteroids. It takes into account long-term evolution of Interplanetary Dust Particles (IDPs), and simulates the effects of collisions on the dust size distribution. We give an overview of the IMEM2 model, its physical basis, its normalisation based on available data, and discuss its application to determining the dust flux, size-distribution and directionality for space missions. We discuss the predictions of the model for the Martian Moons eXploration (MMX) spacecraft to Phobos and Deimos, and Destiny+ to the active asteroid 3200 Phaethon, both to be launched in 2024.

Hayabusa2 - Sample Return from C-type Near-Earth Asteroid (162173) Ryugu

S. Tachibana

C-type asteroids have been hypothesized as parent bodies of carbonaceous chondrites, of which constituting materials record the early evolution of the solar system and the delivery of volatiles to the inner solar system (e.g., 1). The Hayabusa2 spacecraft explored C-type near-Earth asteroid (162713) Ryugu from June 2018 to November 2019, including two landing operations for sample collection. About one-km-sized asteroid Ryugu is a spinning-top-shaped rubble pile body with a bulk density of 1.19 ± 0.03 g cm–3 [2]. The surface has a low geometric albedo (~0.02) [3], darker than most of meteorites, and shows a weak but ubiquitous 2.72-μm absorption feature of O-H vibration in hydrous minerals [4]. The collected samples at two surface locations were delivered to the Earth in December 2020. The returned 5-g samples well represent the Ryugu surface from spectroscopic and morphological perspectives [5-7]. Ryugu sample (0.3 g in total) has been being investigated by the Hayabusa2 initial analysis team to characterize them chemically, mineralogically, and petrologically and to understand the origin and evolution of Ryugu and the Solar System. The initial analysis team consists of six sub-teams that analyze the samples with different approaches and focuses: Chemistry, Petrology and mineralogy of coarse grains, Petrology and mineralogy of fine grains, Volatiles, Organic macromolecules, and Soluble organic matter. This presentation will give an overview of the initial analysis results of Ryugu sample on behalf of the Hayabusa2 project. [1] Tachibana et al. (2014) Geochem. J. 48, 571. [2] Watanabe et al. (2019) Science 364, 268. [3] Sugita et al. (2019) Science 364, eaaw0422. [4] Kitazato et al. (2019) Science 364, 272. [5] Yada et al. (2021) Nat. Astron. 6, 214. [6] Pilorget et al. (2021) Nat. Astron. 6, 221. [7] Tachibana et al. (2022) Science 375, 1011.

Simulation of Interaction of Cosmic-Ray Particles with 162173 Ryugu Asteroid Using Monte Carlo Simulator GEANT4

P. Č. Čechvala, R. B. Breier, J. M. Masarik

Interaction of cosmic-ray particles with different material can be simulated by different Monte Carlo softwares. Such software is also GEANT4 developed in CERN. GEANT4 enables user to define the geometry and composition of the target together with the applied physics taking place in the interactions. Using GEANT4 we have created simulated asteroid 162173 Ryugu with specific dimension and chemical composition. Asteroid is simulated as the spherical body with concentric shells with defined incress. Asteroid is bombarded by the cosmic-ray particles corresponding to galactic-cosmic-ray spectrum. In concentric shells we study the generation of the secondary protons and neutrons. These cause the generation of radioactive isotopes within the asteroid. GEANT4 itself contains different tables of cross section for reactions with different elements which are stored in the so called Physicslist. In our analysis we focus on the comparision of the generated rates of different radioisotopes for different Physicslists provided by GEANT4.

Cometary Meteoroid Trail Simulations for the DESTINY+ Mission to the Active Asteroid (3200) Phaethon

H. Krüger, R. Srama, P. Strub, M. Sommer, J. Simolka, T. Arai, M. Kobayashi, H. Kimura, S. Sasaki, T. Hirai, DDA Dust Science Team

The DESTINY+ spacecraft (Demonstration and Experiment of Space Technology for INterplanetary voYage with Phaethon fLyby and dUst Science) will be launched to the active asteroid (3200) Phaethon by the Japanese Space Agency JAXA in 2024. The main mission target will be Phaethon with a close flyby in 2028. The Destiny+ Dust Analyzer (DDA) on board will perform in-situ dust analysis measurements during the initial Earth-orbiting phase of DESTINY+ and later during interplanetary cruise including the close flyby at Phaethon. DDA will be able to measure interstellar dust, interplanetary dust including cometary meteoroid trails as well as other potential dust populations. Cometary meteoroid trails consist of the largest cometary particles (with sizes of approximately 0.1 mm to 1 cm) which are ejected at low speeds and remain very close to the comet orbit for several revolutions around the Sun, contrary to comet tails formed by smaller particles which disperse in space much more rapidly. We use the Interplanetary Meteoroid Environment for eXploration (IMEX) dust streams in space model (Soja et al. 2015) to study the detection conditions of cometary dust trail particles and make predictions for particle detections with DDA. The in situ detection and analysis of meteoroid trail particles in space which can be traced back to their source bodies opens a new opportunity for remote compositional analysis of comets and asteroids without the necessity to send a spacecraft to or even land on these celestial bodies.

Comet Interceptor Mission to Long Period Comet and Modular Infrared Molecules and Ices Sensor (MIRMIS) Payload

T. Kohout, N. Bowles, A. Näsilä

The Comet Interceptor mission is an ESA mission to conduct fly-by of a long period comet, preferably, a Dynamically New Comet (DNC). CI will launch to the Earth-Sun L2 point at the end of the decade where it will wait for a suitable target. The CI mission is comprised of three spacecraft. Spacecraft A is the main spacecraft that will pass by the target nucleus at a distance of ~1000 km to mitigate against hazards caused by dust. B1 (supplied by JAXA) and B2 (ESA) sub-spacecrafts will perform closer higher risk/higher return observations of the nucleus. One of the CI payloads is the Modular InfraRed Molecular and Ices Sensor (MIRMIS) instrument that is developed by UK (University of Oxford) and FI (VTT) together with instrument team from the University of Helsinki and NASA’s Goddard Space Flight Centre. MIRMIS will map the spatial distribution of temperatures, ices, minerals and gases in the nucleus and coma of the comet using three sensors covering a spectral range of 0.9 to 25 microns. An imaging Fabry-Perot interferometer will provide hyperspectral maps of the nucleus in near-infrared. A Fabry-Perot point spectrometer will make observations of the coma and nucleus mid-infrared. Thermal imager will map the temperature of the nucleus at thermal infrared wavelengths. The thermal imager will include spectral filters to further constrain nucleus composition. CI will deliver key proximity observations of dust release process from a cometary nucleus as well as map dust, ice, and gas distribution in cometary coma.

Meteoroid Impact Risk Assessments for Interplanetary Spacecraft Mission at European Space Agency

M. Millinger

The European Space Agency (ESA) is planning, designing and operating multiple interplanetary spacecraft missions. In these missions spacecraft are exposed over typically long durations to the varying flux of meteoroids along the spacecraft trajectory. Robustness of the spacecraft design against meteoroid impact induced failures is essential to ensure mission success and in some cases planetary protection. To manage and mitigate the risk posed by meteoroids to spacecraft missions ESA develops engineering models of relevant meteoroid environments and software tools to evaluate the impact risks for specific spacecraft designs. In addition, ground tests and numerical simulations of hypervelocity impacts on spacecraft shielding configurations are performed to ensure adequacy of the risk assessment methods, namely Ballistic Limit Equations, applied in risk assessments. This talk will present the current end-to-end process in performing meteoroid impact risk assessments for spacecraft missions at ESA, ranging from applicable standards and requirements, via software tools, ground tests and numerical simulations of shielding configurations to use-cases of specific ESA missions.

Meteoroids Beyond the Earth's Atmosphere: An Outlook on Future Science Opportunities Enabled by Small Satellites

H. A. R. Devillepoix

What is the meteoroid environment like around Mars? This question has been tackled by various missions at Mars, but so far no meteoroid impact event has conclusively been witnessed. This is because detecting impact events was a stretch goal or side experiment on these missions, hence the instruments were not optimised for such detections. Cubesats open up a new paradigm where it is possible to design a mission around a single science question, with a single payload. Cubesats, particularly within the framework of NASA's Artemis exploration program, have the potential to expand horizons for meteoroid science on planetary bodies other than the Earth (Moon, Mars, etc.). In this talk I want to generate discussions around the community about future meteoroid science opportunities with cubesats.

The Threshold at Which a Meteor Shower Becomes Hazardous to Spacecraft

A. V. Moorhead

Although the risk posed to spacecraft due to meteoroid impacts is dominated by the sporadic complex, meteor showers can raise this risk for short periods of time. NASA's Meteoroid Environment Office issues meteor shower forecasts that describe these periods of elevated risk, primarily for the purpose of helping plan extravehicular activities. These forecasts are constructed using a list of meteor shower parameters that has evolved over time to include newly discovered showers and incorporate improved measurements of their characteristics. However, at this point more than a thousand meteor showers have been reported by researchers, many of which are extremely minor, are unconfirmed, or lack critical pieces of data. Thus, a comprehensive approach to forecasting is no longer feasible. In this report we present a quantitative criterion for a potentially hazardous meteor shower and apply this criterion to the list of established meteor showers in order to determine which showers should be included in our annual forecasts.

Dust Modeling for the Parker Solar Probe

P. Pokorny

The Parker Solar Probe (PSP) is currently exploring the innermost parts of our zodiacal cloud and will shortly reach closer than 0.05 au from the Sun, surpassing the previous record holder Helios-B by 0.25 au. Exploration of these innermost regions presents challenges posed by the energetic dust particles that impact PSP at velocities exceeding 200 km/s. In this talk, we will explore observations of the effects of dust and meteoroid bombardment on the spacecraft and how our dust and meteoroid models are able to predict and reproduce the innermost solar system environment. Despite having no dedicated dust detector, instruments such as FIELDS, ISOIS, snf WISPR provide interesting data sets from direct and indirect dust related phenomena. PSP observations were able to confirm the existence of Venus' circumsolar dust ring, extend our knowledge of the radial shape of the zodiacal cloud, and suggest the existence of the dust free zone. PSP dust impact rates are consistent with at least three dynamically distinctive dust populations: (1) bound dust grains and meteoroids, (2) unbound beta-meteoroids, and (3) meteoroids streams.

All mentioned instruments provide information about dust particles close to the blow-out limit, smaller than a few micrometers. On the other hand, impacts of hyper-velocity particles with radii larger than hundreds of micrometers have the ability to create catastrophic mission ending events. We will explore how the meteoroid models are used to predict the mission threats and why they are an essential component of every mission planning phase.

Revision of Meteor Showers: From D-Criteria to Chaos Map

A. Courtot, J. Vaubaillon, M. Fouchard

Today more than 900 meteor showers are listed by the IAU, implying a similarly large number of parent bodies in the vicinity of the Earth in the near past (1-100 kyrs). This casts a doubt on the methods used to find new meteor showers. We name "meteor group" several meteors sharing a radiant and having the same geocentric speed, while "meteor showers" are a set of meteors coming from the same parent body, through a meteoroid stream. Orbit dissimilarity criteria (D-criteria) are usually used to distinguish meteor groups from actual meteor showers. However, we will recall here how those D-criteria are not as reliable as first hoped. For example, the widely used D_SH criterion (Southworth and Hawkins, 1963) exhibits mathematical, physical and statistical problems, that will be presented. Furthermore, many physically sound criteria would benefit from more thorough robustness tests. Instead of defining a new criterion, a new tool is proposed here to complete information from D-criteria : a chaos map. This tool allows users to quickly establish the chaoticity of any given meteoroid stream, and thus to deduce the evolution of the stream. This will provide some information to help make the distinction between meteor groups and meteor showers. First maps on well-known meteoroid streams, such as e.g. Geminids, will be presented.

Dynamical and Physical Properties of 400 CAMS-Detected Meteor Showers

P. Jenniskens, P. Gural, D. Samuels, J. Albers, S. Rau, J. Baggaley, T. Beck, M. Breukers, W. Cooney, T. Cooper, M. de Cicco, S. Ganju, T. Hanke, S. Heathcote, A. Howell, E. Jehin, C. Johannink, L. Juneau, N. Moskovitz, M. Odeh, M. Towner, O. Unsalan

How do the physical properties of meteoroids, and particle size distributions, depend on the destructive processes in the interplanetary medium and on the intrinsic differences between their parent bodies? Here, we report on an ongoing analysis of the CAMS low-light video survey data. CAMS maps major and minor meteor showers by deploying about 580 low-light video security cameras in 15 networks spread over both the northern and southern hemisphere. Data include the time, trajectory, and orbit of +4 to -5 magnitude meteors and their light curves. The data contain about 400 meteor showers that sample a variety of parent bodies with a range of orbital elements and dynamical histories. We will discuss how orbital element dispersions, light curves and particle size distributions depend on the conditions in the interplanetary medium and on the nature of their parent sources.

On the Origin of Groups of Sungrazing Comets

A. S. Guliyev, R. A. Guliyev

We study statistical dependencies in 4 groups of sungrazers. It is shown that the perihelia of the Kreutz family comets are concentrated near two planes. One of them practically coincides with the plane obtained by averaging the values of the orbital elements Ω and i. The second plane with parameters Ωp=77.7(deg); ip=266.1(deg) has an inclination of about 64(deg) relative to the first one. The distant nodes of the cometary orbits relative to the second plane have a noticeable maximum at a distance of about 2 a.u. A specific example shows that two assumptions about the concentration of perihelia - around one point and nearby two planes - are quite compatible. A new interpretation of the known correlation between the values of Ω and ω for all considered groups is proposed. According to the authors, its origins are associated with the aforementioned concentration of distant nodes of cometary orbits. The distribution of orbital inclinations for the Kreutz family is considered for the first time on a new basis within the framework of the hypothesis of one of the authors. The sharp maximum near values of about 90(deg) probably indicates that the impacts of meteoroid bodies on the protocometary nuclei were of a lateral nature. This could lead to some longitudinal extension in the distribution of perihelion fragments. The already existing hypothesis about the another group of sungrazers has been confirmed. It could have separated from the main Kreutz family in the past. This group is characterized by relatively small inclinations and significant displacement of the apsidal line. The positions of the perihelion concentration planes of the Meyer, Kracht and Marsden comet groups have been calculated. In each of these groups we observe the effect of concentration of distant orbital nodes in specific zones. All of the listed features point to the impact mechanism of disintegration of the protocometary bodies for each group.

Results of the Modeling of Meteoroid Streams Originating in Several Long-Period Comets

L. Neslusan, M. Hajdukova

We present the results of our study of meteoroid streams originating in the nuclei of several long-period comets. We modeled the stream of each studied comet and followed its dynamical evolution performing the numerical integration of the orbits of particles which represented the meteoroids. In this way, we confirmed or found a relationship of the studied comets, as parent bodies, with several known meteor showers. The mean orbit of some of these showers is largely different from the current orbit of their parent comet. In addition, we discovered two new showers: December Iota-Ursae Majorids, January Psi-Scorpiids. Specifically, we dealt with the streams of the following comets (confirmed or found associated showers are given in the parentheses): C/1853 G1 (Schweizer) (Gamma-Aquilids #531 and 52 Herculids #605), C/1992 W1 (Ohshita) (Chi-Andromedids #580 and January Alpha-Ursae Majorids #606), C/1894 G1 (Gale) (December Iota-Ursae Majorids #1049), C/1936 O1 (Kaho-Kozik-Lis) (January Psi-Scorpiids #1048), C/1961 T1 (Seki) (December Rho-Virginids #502 and Gamma-Sagittariids #657), C/1861 G1 (Thatcher) (Lyrids #6), and 109P/Swift-Tuttle (Perseids #7, 49 Andromedids #549, Omicron-Aurigids #696, Omicron-Hydrids #569, January Beta-Craterids #582, Zeta Cassiopeiids #444, u-Andromedids #507, and UY Lyncids #705).

Collisional Grooming of the Zodiacal Cloud: Life and Challenges of Jupiter-Family Comet Meteoroids

P. Pokorny, A. V. Moorhead, M. J. Kuchner

Grain-grain collisions shape the 3-dimensional size and velocity distribution of the inner zodiacal cloud and the impact rates of dust on inner planets, yet they remain the least understood sink of zodiacal dust grains. For the first time, we use the collisional grooming method combined with a dynamical meteoroid model that covers four orders of magnitude in particle diameter to investigate the consequences of grain-grain collisions in the inner zodiacal cloud in 3-dimensions. We particularly focus on Jupiter-family comets that dominate the total mass and cross-section budget in the inner solar system. We compare our model to a suite of observational constraints from meteor radar and optical surveys, space-borne impact records and the Infrared Astronomical Satellite (IRAS) observations and use it to derive collisional strength parameters for zodiacal dust grains. For Jupiter-family comet particles, we derive a specific binding energy that is approximately 1000x higher than those assumed in Grun et al. (1985) making them 1-2 orders of magnitude more resistant to collisions than commonly assumed in various meteoroid modeling studies. We also discuss the significant consequences of this finding for studies of solar and exo-solar dust clouds. Due to higher resistivity to collisions, exo-solar models for dust clouds with optical depths of 100-1000 zodi (2-3 orders of magnitude denser than our Zodiacal Cloud) might need new modeling efforts to capture the Poynting-Robertson drag driven dynamical evolution. Since dust particles can evolve for longer, the resulting dust clouds should extend closer to the host star and the amount of dust created in collisions should be lower. Our models and our code are freely available online.

Probability of Detection of the Meteor Pairs Created in the Vicinity of the Earth

P. Koten, D. Čapek

Recent analyses of the 2006 Geminid meteors observed by the video technique did not find any evidence for the physically connected pairs despite the fact that a number of potential candidates have been observed. The Monte Carlo test showed that all the cases can be results of a random coincidence. This result inspired us to create of the model which follows the evolution of the meteoroid pairs created shortly before the encounter with the Earth. The model assumes different masses of the particles, different ejection angles and velocities as well as the shape of the heliocentric trajectory of a given meteor stream. The influence of the solar radiation pressure is taken into account. Finally, the detectability by the cameras with different field-of-view and sensitivity is estimated. The model is applied on major meteor showers and provides constraints on the time of ejection, ejection velocities and ejection angles, which enable the detection of such pairs in the Earth atmosphere.

Near-Earth Asteroids of Cometary Origin Associated with the Virginid Complex

G. I. Kokhirova, T. Jopek, P. B. Babadzhanov, A. I. Zhonmuhammadi

The Virginid meteoroid streams produce a series of meteor showers active annually during February-May. A certain parent comet is not found but a related association of some showers with near-Earth asteroids was previously established and a cometary origin of these asteroids was suggested. We performed a new search for NEAs belonging to the Virginid asteroid-meteoroid complex. On the base of calculation of orbital evolution of a sample of NEAs and determination of theoretical features of related showers a search for observable active showers close to theoretically predicted ones was carried out. As a result, the predicted showers of 31 NEAs were identified with the observable showers of the Virginid complex. Revealed association points to a cometary nature of NEAs that are moving within the stream and may be considered as extinct fragments of a larger comet-progenitor of the Virginid asteroid-meteoroid complex.

Is 2P/Encke the Main Source of the Taurid Meteoroid Complex?

A. Egal, P. Wiegert, P. G. Brown

The Taurid Meteoroid Complex (TMC) is a broad stream of meteoroids that produces significant meteor activity on Earth. The TMC is associated with at least four annual meteor showers, including the autumn Northern and Southern Taurids (NTA & STA), the Beta Taurids and the Zeta Perseids (BTA & ZPE) in spring. Most models of the TMC were built on the hypothesis that its sole source is the peculiar comet 2P/Encke, and attempted to reproduce the observed Taurid radiants and orbital elements with material ejected by the comet. Problems with this view are the small size of 2P/Encke and its low present activity which suggests 2P is insufficient to explain the large mass of the TMC. An alternative scenario suggests that 2P/Encke is simply the largest member of the Taurid Complex (TC), which was produced by the break-up of larger progenitor comet some 20 ka ago. Here we simulate the formation of the Taurids by ejecting meteoroids from 2P/Encke and several TC NEAs. The modelled streams were numerically integrated and compared with present-day radiant, orbital elements, and shower timing/activity profiles in the visual, optical and radar ranges. We explored more than a hundred stream formation scenarios using clones of comet 2P/Encke. Meteoroids simulated from 2P/Encke's nominal evolution appear to reproduce the radiant structure of the Taurid meteors but do not match the observed time and duration of the showers. The inclusion of material released during a hypothetical fragmentation event 5 to 7 thousand years ago, leading to the creation of 2P/Encke and several NEAs, does not reproduce the showers' activity. Our model shows that the activity and radiant structure of the four Taurid showers can be explained with a particular clone of 2P/Encke, that is consistent with the chaotic evolution of 2P from its current orbit. Our analysis suggests a specific dynamical history for 2P/Encke which is consistent with 2P as the sole parent of the four major TC showers.

On Mean Motion Resonances in the Geminid Meteoroid Stream

G. O. Ryabova

Analysing numerical models of the Geminid meteoroid stream for particle masses 0.00003–0.3 g we found evidence of several mean motion resonances: 1:2, 2:5, 3:7, 3:8 and 4:9 with Venus, 2:3 and 5:7 with the Earth and 7:1 with Jupiter. The resonant meteoroids form dust trails in the stream, but not concentrated swarms. The trails are stable and compact, consist of large (0.003–0.3 g) meteoroids and they are located far from the Earth's orbit. The number of trapped particles is small, not exceeding 0.1%, so they hardly can produce any space density enhancement. The results were obtained for a model, which does not quite match the real Geminids in location and is used as a proxy. These findings suggest repeating the research for the observed Geminids when the precision of orbit determination allows. Currently there is no observational support for resonant effects in the observed Geminid meteor shower. The research was carried out within the state assignment of Ministry of Science and Higher Education of the Russian Federation (theme No. FSWM-2020-0049).

Can Daytime Arietids Fall into the Sun?

A. Sekhar, J. Vaubaillon, D. J. Asher, A. Morbidelli, Q. Ye, G. Li

The Daytime Arietids (IAU #0171 ARI) are one of the strongest known meteor showers (Jenniskens 2006) on Earth in the list of daylight showers. The ARI meteoroid stream is known to show long term General Relativistic (GR) precession (Sekhar 2013) due to its low perihelion distance. In addition, the orbital elements of the ARI stream are such that a large proportion of ARI particles undergo Kozai libration (Sekhar et al. 2017a) during its long term evolution (Sekhar et al. 2016, Vaubaillon et al. 2019). We find that in a purely Newtonian simulation, due to the active Kozai mechanism (Sekhar et al. 2017b), certain sub-structures in the ARI stream can eventually fall into the sun and thereby deplete certain parts of the stream. However when we include the GR precession effect in the simulation, we see that those particles which had sun-colliding trajectories no longer have such paths for an extended time. Switching on the GR precession either delays the sun colliding time frame or changes the long term evolution in such a way that the particles miss the sun. It is therefore shown that GR precession helps in preserving certain sub-structures in the ARI stream from falling into the sun. Calculations to demonstrate this significant change in orbital evolution were done using analytical as well as numerical methods. Analytical calculations were done using a Hamiltonian dynamics formulation (Morbidelli 2011) by employing separate Hamiltonians for both Kozai cases and GR+Kozai cases. Numerical simulations were done using numerical integrations by both excluding and including the GR precession routines. In the future, it would be even more insightful if we could correlate this effect with real observational data (Campbell-Brown 2004). The aim will be to find observational records for certain ARI sub-structures hitting the Earth due to the change in evolution induced by GR precession, thereby demonstrating an exact identification of this phenomenon in real observations.

The Meteor Shower Complex of Comet 109P/Swift-Tuttle

M. Hajduková, L. Neslušan

We investigated all the parts of the theoretical stream of comet 109P/Swift-Tuttle that cross the Earth's orbit, which allowed us to map all possible sibling-showers to the Perseid meteor shower. Our models were derived from both the nominal orbit of the comet and two appropriately chosen cloned orbits. Both approaches confirmed the clear relationship of the comet to the Perseids, #7, and, with regard to the stronger influence of non-gravitational forces, they showed the comets' relationship to the 49 Andromedids, #549. The meteoroids with long evolutionary periods created another substructure of the radiant area corresponding to the Perseids. A clear bimodal character in the distribution of the perihelion distances was predicted. In contrast to the high perihelion sample of the Perseids, the new substructure with low perihelion distances was found to correspond to the omicron-Aurigids, #696. Other possible associated northern showers are zeta-Cassiopeiids, #444, upsilon-Andromedids, #507, and UY Lyncids, #705, depending on which orbit the modeling is based on. A part of the stream of 109P also approached the Earth's orbit from the southern sky. The radiant area of the predicted showers was situated symmetrically to the northern showers in respect to the apex of the Earth's heliocentric motion. An indication of a relationship to the omicron-Hydrids, #569, and January beta-Craterids, #582, was found but only for the particles that were strongly influenced by the non-gravitational forces.

The 2021 Arid Meteor Outburst from Comet 15P/Finlay

Q.-Z. Ye, P. Jenniskens, J. Toth, J. Vaubaillon, J. Marino, J. Albers, D. Samuels, S. Heathcote, T. Abbott, E. Jehin, M. Towner, J. Baggaley, T. Cooper, T. Hanke, D. Lauretta, P. Matlovic, L. Kornos, P. Da Fonseca, F. Bouley, G. Fasola, K. Baillie, J. Desmars, J. P. Amns, P. V. Alfaro, S. Bouquillon, R. Mendez, F. Gutierez, J. L. Nilo, P. Vera, A. Jordan, V. Suc, P. Brown, D. Vida

We rarely have opportunities to study meteor showers at Earth that originated in an outburst of cometary activity just one orbit earlier. However, one of such events was predicted to occur on October 6/7, 2021, when the Earth was calculated to encounter dust ejecta produced by comet 15P/Finlay during two outbursts in 2014 and 2015, in addition to an encounter with normal cometary ejecta from the 2008 return a short time later. Also in late September of 2021, it was calculated that Earth would encounter ejecta from the normal 1988 and 1995 returns of 15P/Finlay. Here we report preliminary results from campaigns organized by several teams to observe the predicted meteor outbursts in optical and radio wavelengths. The predicted encounters were all detected and confirmed by a good agreement between predicted and observed radiant positions. The implications of these detections will be discussed.

Radar Observations of the New Arid Meteor Shower

J. S. Bruzzone, D. Janches, R. Weryk, J. L. Hormaechea, L. Maslov

We present observations of the new Arid meteor shower from comet 15P/Finlay with the Southern Argentina Agile Meteor Radar Orbital System (SAAMER-OS). Radar observations recorded with SAAMER-OS confirm the arrival of debris ejected from comet 15P/Finlay during the outburst episodes in 1995, 2014 and in 2015. SAAMER-OS recorded the crossing of 1995 dust trails centered at Sep 29d03h32m UTC, solar longitude 185.92 degrees, and lasting three hours. The sun-centered ecliptic radiant of the outburst on Sept. 29 is located at (sun-centered) ecliptic longitude 77.658 deg, latitude -34.5 deg (equinox J2000.0), with meteor speeds of 11 km/s (not corrected for meteor deceleration), with a strong 8-sigma detection. Based on a few hundred meteors, the average orbital elements a = 3.551 AU, e = 0.7183, i = 9.273 deg, Peri. = 355.55 deg, Node = 6.285 deg, and M = 0.506 deg (equinox J2000.0) agree with those from optical observers. SAAMER-OS recorded the crossing of the second Arid stream centered at Oct 7d01h UT lasting over 7 hours with a nearly 12-sigma detection. The outburst centered at R.A. = 255.01 deg, Decl. = -48.47 deg with meteor velocities of 10.9 km/s and average orbital elements a = 3.634 AU, e = 0.7276, i = 7.0747 deg, Peri. =347.673 deg, Node = 14.171 deg, q = 0.98974 AU, based on roughly 700 meteors. An initial peak ZHR of 120 is estimated with meteors within 20 deg of the peak radiant location for a fixed mass index value of 2.0.

The Detection of the New Arid Meteor Shower from a Live-Streaming Camera on Maunakea, Hawaii

I. T. Tanaka, M. S. Sato, J. W. Watanabe, T. U. Uda, H. H. Hasegawa, M. H. Higashiyama, Volunteers

We report the detection of the Arid meteor shower, which was forecasted to appear for the first time in history in October 2021, by a high-sensitivity public live-streaming camera installed at the summit of Mauna Kea, Hawaii. The Subaru-Asahi Star Camera, installed at the Subaru Telescope dome last year, is a new public outreach camera. It has been sending the beautiful night sky view to the world since last April using YouTube Live feed. Thanks to the high clear-sky ratio and world-class observation conditions, the camera can capture hundreds of meteors every night, even without major meteor shower events. The extreme sensitivity of our camera (ISO409600) allows us to capture meteors of 6th magnitude or fainter with high S/N across ~2800 deg^2 FOV. Thus, the camera data also has a high potential for regular meteor observations. As a scientific use case of this camera data, we tried to detect the new "Arid" meteor shower, which originated from the ejecta of Comet 15P/Finlay. This meteor shower has been predicted by several researchers, including Mikiya Sato of Japan, to occur in conjunction with the 2021 return of 15P/Finlay. The predicted activity peak (1:00 AM UT on October 7) is at 3:00 PM in Hawaii, but we might detect its ceasing activity in the early evening when the radiant is still above the horizon. We have launched a citizen-science project to evaluate the number of meteors coming from the direction of Arid using the camera data from the evening hours of October 6-8, 2021. Our keen volunteers (viewers) helped identify the faint meteors from the recorded live data, and the gathered data was further checked by IT and MS to make a final determination of the meteor shower members. As a result, we successfully showed a clear increase of potential Arid shower members on the 7th night. Comparing the number with the 6th and 8th data, the increase of the meteors on the 7th reached well above 5 sigma level. As predicted, our Arids candidates are dominated by faint meteors. In the presentation, we will discuss the follow-up results from the subsequent automatic meteor detection and the interpretation of the observation results from our new model.

The 2034 Arids Meteor Shower Outburst

J. J. Vaubaillon, A. Egal, Q. Ye, J. Desmars, M. Sato

The Arids meteor shower comes from comet 15P/Finlay. The first time the associated meteoroid stream encountered the Earth was in 2021. The correct prediction of this event gives us confidence regarding the next encounters in 2027 and especially 2034. The observations also allows us to put boundaries on the expected level of the shower, although the trails are different. Several outburst are expected from different trails. The year 2034 will be exceptional given this Arids outburst will happen a few weeks before the return of the Leonid storm.

Space Debris: The Source of of Small Artificial Meteors and Re-Entry Events

J. Šilha, J. Tóth, P. Matlovič, L. Kornoš, P. Zigo, V. Pazderová, M. Zigo, D. Žilková, P. Vereš

Artificial objects, such as satellites and space debris, are a major population occupying Earth’s surroundings. Due to their orbits, the non-operational objects and fragments tend to be influenced by the environment which affects their dynamical properties. Once the critical altitude is reached, objects enter the atmosphere and go through the ablation process until they disintegrate completely, the larger and more massive fragments or its parts can also reach the ground. In recent years, the space debris population, as well as the space traffic, rapidly increased. This leads to dramatic surge of artificial objects re-entering the atmosphere creating meteor-like effects. These effects can be detected by nominal meteor detection systems such as the All-sky Meteor Orbit System (AMOS) operated by Comenius University in Bratislava, Slovakia. Several cases of confirmed re-entry events, as well as suspicious geocentric meteors, have been detected by AMOS in recent years, providing unique data sets for the dynamical and physical analysis. These data sets help us to understand this population’s dynamical and physical properties and the physics behind the interaction with the atmosphere. In our work, we will present the space debris population, its physical and dynamical properties, and spatial distribution with the focus on low Earth orbits, the region with the primary source of re-entries. The current and future state space debris population will be presented and small particles (sub-centimeter), as well as larger objects such as defunct satellites and upper stages will be discussed. We will present how the surface properties are retrieved from photometry and spectroscopy of objects before the re-entry. In more detail, we will discuss the example case of CZ-3B R/B re-entry event captured by the AMOS systems on the Haleakalā and Maunakea Observatories in Hawaii on October 25th 2020. Preliminary results of the data reduction for the detected fragments will be presented.

Meteors at the Earth from the DART Asteroid Impact

P. Wiegert

The Double Asteroid Redirection Test (DART) spacecraft will impact the secondary of the binary asteroid Didymos in late 2022. The impact will help assess kinetic impact strategies for planetary defense. Ejecta from the craft's impact can escape from the Didymos system and enter solar orbit. The Minimum Orbital Intersection Distance (MOID) of Didymos with the Earth is only 6 million km (about 16 times the Earth-Moon distance), and ejected material can make its way to our planet as meteors. We report here on the delivery of meteoroids from the DART impact to the Earth, both because the observation of ejecta reaching Earth as meteors would increase the scientific payout of the DART mission, and because they may represent the first human-generated meteoroids at Earth, and a test case for human activity on asteroids e.g asteroid mining, and its eventual contribution to the meteoroid environment and spacecraft impact risk. We find that material from the DART impact may reach our planet, but most of it only after thousands of years. Nevertheless it is possible that the smallest particles and/or those ejected at the highest velocities could be delivered to Earth-crossing trajectories almost immediately -though at very low fluxes- and we report the expected radiant and timing. The DART impact will result in a new meteoroid stream within the Solar System, though one which is very minor compared to naturally occurring ones. However, future larger, more capable asteroid impactors of this sort could create meteoroid streams where the particle flux does have implications for spacecraft safety.

Observing the Hayabusa-2 Capsule Re-Entry over Australia

E. K. Sansom, M. -Y. Yamamoto, H. A. R. Devillepoix, S. Abe, S. Nozawa, Y. Hiramatsu, T. Kawamura, K. Fujita, M. Yoshikawa, Y. Ishihara, N. Segawa, Y. Kakinami

Japan Aerospace Exploration Agency’s Hayabusa-2 sample return capsule came back to the Earth on the 5th December 2020 at 17:28 UTC. It was a unique opportunity for a planned, man-made fireball event analogous to the natural phenomena. As such, a scientific campaign was organised to test sensors and record signatures that are hard to collect for sporadic, natural events. We deployed 49 instruments (total of 73 including existing, permanent sensors) to observe the optical, seismo-acoustic, radio and high energy particle phenomena associated with the re-entry. The SRC re-entered the atmosphere over South Australia as a 53 second long fireball, landing in the Woomera military test range. Data collection was successful and we will present the initial results from this campaign.

The Era of Anthropogenic Meteoroids

L. Fladeland, A. C. Boley

The Small-Compact Impactor (SCI) produced a crater on Ryugu as part of the Hayabusa2 mission, ejecting material onto Earth-crossing orbits. The upcoming Double Asteroid Redirection Test (DART), scheduled for impact later in 2022, will also create meteoroids through the associated cratering event. So far, these contributions to the meteoroid population are small, but the actions are part of a new era of space exploration that includes the manipulation of asteroids and with it the possibility of human-generated debris. The extraction of space resources from celestial bodies, including from the Moon and asteroids, could further create non-negligible debris populations in certain cases, whether through the production of new asteroid debris streams or the injection of lunar mining debris into the cis-lunar environment. This work uses high-resolution simulations to model asteroid debris stream formation that might result from the release of asteroid “mining waste”. Even at low relative release speeds, debris can form into streams that regularly encounter Earth for easily accessible asteroid targets. The magnitude of the corresponding meteoroid fluxes relative to natural streams will depend on the extent of mining and should be a consideration for states that authorize mining activities.

Spectroscopy of Laboratory Ablated Meteorites for Improved Meteoroid Composition Diagnostics

P. Matlovič, A. Pisarčíková, J. Tóth, S. Loehle, L. Ferrière, P. Čermák, HEFDiG Team

Our current abilities to study meteoroid composition generally rely on the analysis of meteor emission spectra captured by photographic or video spectrographs. Radiative transfer models applied to high resolution fireball spectra can be used to determine abundances of the main meteoric elements, while larger datasets of lower resolution meteor spectra are usually studied by comparing line intensity ratios of selected species. These spectral methods allow to distinguish rough compositional differences between meteoroids but have not yet been successfully applied to differentiate between specific compositional classes (e.g., between different types of chondrites and achondrites). Laboratory experiments simulating the ablation of meteorites can be used to constrain the behavior and emission of meteoric analogs with known composition. We will provide an overview of the simulated ablation experiments we have performed at the Institute of Space Systems, University of Stuttgart (Germany), and present preliminary results of our efforts to characterize spectral properties of a set of meteorites of various compositions and identify diagnostic spectral features which can be used to constrain meteoroid composition from meteor spectra observations.

Analyzing Persistent Trains and Meteor Radio Afterglows in All Sky Images

L. E. Cordonnier, K. S. Obenberger, G. B. Taylor

This work develops a pipeline for identifying optical persistent trains (PTs) from meteors in images taken by the Widefield Persistent Train (WiPT) camera. Using the correlations between consecutive image frames we can determine whether there are lingering structures indicative of PTs. However, other phenomenon such as clouds and contrails also exhibit similar structures to PTs, so additional filtering is required. Applying this pipeline to the first campaign of the WiPT yielded 22 meteors with PTs, 8 of which were concurrently recorded by the Global Meteor Network (GMN), a database which contains parameters of observed meteors. The current observing campaign which uses an improved camera has found 29 meteors with PTs to date. Additionally, a pipeline to detect meteor radio afterglows (MRAs) using the Long Wavelength Array (LWA) was also implemented. The next step is to use the parameters found in the GMN to statistically analyze the two populations of meteors: those which produce PTs and those that have MRAs. This will enable a better determination of the relationship between these two phenomena.

A Direct Simulation Monte Carlo Approach for Studying High Altitude Meteor Dynamics

D. R. Cecil, M. D. Campbell-Brown

Numerical simulations of meteoroid ablation are a way to investigate poorly constrained parameters such as ionization efficiency and luminous efficiency. Nine preliminary low-density particle-based fluid simulations, using the Direct Simulation Monte Carlo (DSMC) software, SPARTA, have been performed as a first step in this process. The axisymmetric simulations sampled multi-microsecond snapshots of spherical 1 mm diameter carbonaceous chondrite meteors at altitudes of 80, 100, and 120 km, with velocities of 12, 32, and 72 km/s, to characterize the properties of the flow field on a centimeter-scale domain around the meteoroid. In all simulations, Na (around 1% by mass), was found to be responsible for most of the ablated material and the majority of electrons produced in the meteor's wake. Other meteoric and atmospheric species (Mg, K, Fe, Si, O, and N) provided additional ions, at densities 2 to 3 orders of magnitude lower than Na. Expected dependencies of greater ionization rates at faster velocities, and wider envelopes of ablated material at higher altitudes were observed. Flow field temperatures were found to have no physical meaning as thermal equilibrium was never reached, with a steady state of impinging and collisionally disrupted particles existing instead. Most notably, this characterization exposed the current limits of DSMC software in handling the extreme speeds and small sizes of faint meteors. Current work focuses on surpassing these limits with new software, developed to enable fully dynamic meteor evolution, with added fragmentation and spectra, over larger domains. Previously assumed constant values of meteoric composition, ablation rate, surface temperature, mass, diameter, and altitude, will be allowed to vary over the meteor’s full lifetime, enabling precise calculations of both ionization and luminous efficiencies directly from simulated events.

Dynamics of Dust Particles in the Planetary Atmosphere

K. H. Havrila, J. T. Tóth

Particles of cosmic origin interacting with Earth's atmosphere are statistically significant in the form of meteoroids and dust particles. The main component are dust particles whose statistical flux is estimated of 6-270 t/day. The particles pass through the complex dynamics in the atmosphere, which define their next physical state, spatial location over time, concentration, and the probability of impact on the Earth's surface. Our aim is to model the interaction of particles with the planetary atmosphere, estimate the concentration over time and make their localization more effective before and after impact on the surface. In modeling, we focus on the dynamics of dust particles in the Earth's atmosphere, where the input parameters represent the observation data of the meteorite Košice. To define the dynamics of particles we used the µ(m)-Trajectory program with user interface, which modeling the dark phase of flight, draws a shape of the trajectory and impact areas. The program implements the resistance of the atmosphere, local wind field and values of the drag coefficient from several models. Dust particles are generated at altitudes, which are related to the significant increasing in brightness of the light curve of the Košice meteorite. The final output is the relative position of the particles in the atmosphere, the change of the concentration value over time depending on the total input mass of particles and the comparison of the impact areas depending on the size of the dust particles. We study the horizontal shift of dust particles in the atmosphere in connection with the mass and altitude at which they were generated. From the obtained data we can describe the effect of atmospheric flow on particles and their concentrations. The results help us to better locate the particles and create a model for the future fireball cases as meaning that of dust capture in the atmosphere or their collection on the Earth's surface.

Robust Semi-Automatic Fireball Modeling

T. Henych, J. Borovička

Interpretation of fireball observations relies on physical modeling of those events. Modeling of radiometric, photometric and dynamic data is, however, a difficult and time-consuming process. It is therefore desirable to make this process as automatic as possible. Here we introduce a program, called FirMpik, which is dedicated to semi-automatic fireball modeling. The core of this program is the Firmodel program written by Jiří Borovička (Borovička J., Spurný P., Shrbený L.; The Astronomical Journal 160, id. 42, 2020) which is used for manual modeling of atmospheric fragmentation of meteoroids. The outer layer of the FirMpik is a robust parallel optimizer based on genetic algorithms. These global optimization algorithms enable optimizing the above-mentioned data sets altogether and producing plausible physical models describing the meteoroid flight, ablation and fragmentation. We will give examples of successful modeling of fireballs that have been previously modeled manually and we will compare those solutions. We will also present one example fireball for which the optimization did not work correctly with a possible explanation for this failure. In the future, we also want to focus on speeding up the modeling and automate some other parts of the process and further optimize the use of computation resources available. Our long-term goal is to use the FirMpik program for modeling well-observed fireballs for which we have high-quality data from the European Fireball Network and to analyze their physical properties. If successful, this approach should provide a statistically relevant image of mechanical strengths and fragmentation cascades for some of the known meteor showers and exceptional fireballs too.

DSMC Modeling of Meteoroid Heating and Ablation

J. C. Ferguson, N. Lee, S. Close

Direct Simulation Monte Carlo (DSMC) is often utilized to study the aerothermodynamics of meteoroid atmospheric entry. Past DSMC efforts have focused largely on flowfield and surface ablation modeling, with simplifying assumptions for meteoroid geometry, rotation, heat transfer, and fracturing. In this work, we use the SPARTA DSMC solver to relax the assumptions around geometry evolution and heat transfer, to study the effects of these processes on meteoroid ablation. Implicit surfaces, generated by the marching cubes algorithm, are used to track the surface evolution during meteoroid thermal ablation. An immersed boundary finite-volume heat transfer model has been implemented into the SPARTA framework to solve the transient heat transfer within the meteoroid. The immersed boundary and heat transfer methods were developed to allow for heterogeneous composition, with application to differential ablation. Simulations of centimeter-scale meteoroid entry will be presented with transient, spatially resolved, heat transfer and non-uniform shape evolution from ablation. The effect of rotation will be examined, establishing bounds between the extreme cases of a non-rotating meteoroid and a meteoroid with sufficient rotational frequency for self-similarity of the solution to apply. Future work will focus these methods on the prediction of fragmentation, both from thermal/aerodynamic forces and from differential ablation.

Ablation Rates of Organic Compounds in Cosmic Dust and Resulting Changes in Mechanical Properties during Atmospheric Entry

J. M. C. Plane, D. L. Bones, J. D. Carrillo-Sanchez, S. D. A. Connell, A. N. Kulak, G. W. Mann, M. D. Campbell-Brown

Cosmic dust consists of mineral grains that are held together by a refractory organic "glue". It has been proposed that loss of the organics leads to fragmentation of dust particles into micron-sized fragments. If this happens, there are several important implications in the Earth’s atmosphere: 1) slow-moving particles may be undetectable by radar, so that the total dust input could be considerably larger than current estimates of 20 – 50 tonnes per day; 2) meteoritic fragments may freeze stratospheric droplets in the polar lower stratosphere, producing polar stratospheric clouds that cause ozone depletion; and 3) the measured accumulation rates of meteoric smoke particles and micrometeorites in the polar regions may be better explained. At Leeds we have developed a new experimental system for studying the pyrolysis of the refractory organic constituents in cosmic dust during atmospheric entry. The pyrolysis kinetics of meteoritic fragments was measured by mass spectrometric detection of CO2 at temperatures between 625 and 1300 K. The complex time-resolved kinetic behaviour is consistent with two organic components – one significantly more refractory than the other, probably corresponding to the insoluble and soluble organic fractions, respectively. The measured temperature-dependent pyrolysis rates were then incorporated into the Leeds Chemical Ablation Model (CABMOD), which demonstrates that organic pyrolysis should be detectable using a high performance radar. Atomic force microscopy was used to show that although the residual meteoritic particles became more brittle after organic pyrolysis, they will nevertheless withstand stresses that are at least 3 orders of magnitude higher than would be encountered during atmospheric entry. This suggests that most small cosmic dust particles (radius < 100 μm) will not fragment during entry into the atmosphere as a result of organic pyrolysis, although a subset of slow-moving, low density particles could fragment.

Can Laser-Induced Plasma be Useful for Laboratory Modeling of Meteor Spectra?

T. A. Labutin, A. S. Zakuskin, A. A. Berzhnoy, A. M. Popov, A. V. Stolyarov

Here we can try to outline possible application of laser plasma to overcome challenges in the interpretation of meteor spectra. The first “direct” application of laser plasma is the studying of emission of iron oxides (FeO/FeO2) observed during meteor events. Since theoretical simulation of the FeO spectra is not feasible the spectra of laser plasma was used to mimic the FeO pseudo-continuum spectrum. The laboratory spectra of the orange bands are found to be closest to their astronomical counterparts registered during meteor events than previously used chemiluminescence spectra. The next interesting task to register spectra of FeO and CaO bands in laser plasma and vary conditions to make spectra profiles as close as possible to the ones observed during the Benešov bolide event to attempt reconstruction of a behavior of meteor wake. We showed that the similar profile is formed under 7–10 times higher pressure than the one at the corresponding altitude of bolide event. Furthermore, study of the relative intensities of molecular bands at different pressures allows us to claim that the intensity of the FeO band is almost independent of pressure, while the intensity of the CaO band has strong dependency. This lead us to suggestion that the formation of CaO in plasma occurred primarily using oxygen from atmosphere. Therefore, abundance of CaO should have a strong dependency on the pressure of the surrounding media. Thus, we can conclude that laser plasma is versatile and promising plasma source for interpreting emission of meteor events. This work was supported by the RSF (grant 18-13-00269-П).

Recent Results from Rebuilding of Meteors in Ground Testing Experiments

S. Loehle, J. Vaubaillon, P. Matlovic, J. Toth, S. Romuleure, M. Eberhart, R. Ravichandran, D. Leiser, F. Grigat, C. Dürnhofer, E. Poloni, F. Hufgard, I. Hörner

It has been shown (see presentation Meteoroids 2019, Loehle et al. ApJ 2017) that by using the high enthalpy air flows of a so-called Plasma Wind Tunnel together with Meteoritic samples, a meteor situation can be experimentally simulated in a ground testing environment. This offers the fundamentally new feature to be able to investigate meteors using known materials. Meanwhile, a total of four different experimental campaigns have been completed with 30 artificial meteor experiments. A wide variety of meteoritc material samples were used to analyse their associated meteor in the wind tunnel. The data acquired consist in spectroscopic data sets from the UV to the IR, Video and Photo in high resolution as well as Lightfield imaging and thermographic measurements of the surface temperatures of the samples during the experiment. In the present paper, a comprehensive description of the experimental approach will be given. The facility setup will be described with a focus on the definition of the flow condition. The diagnostics used will be detailed. The surface temperature data and the emission spectroscopic data are the principal outcome of these measurements. The experiments were designed to simulate a meteoroid entry into the Earth atmosphere at a velocity of ~11km/s at an altitude of 80km. The size of the object corresponds to a ~4cm spherical object. Although these parameters are on the lower end of typical meteor shower events, this simulation is (at the operational limits of the facility) a unique opportunity to study meteor radiation. The shape change during the experiment and the surface spallation are currently investigated. Furthermore, the spectral data sets acquired throughout the different campaigns have been evaluated with respect to luminous efficiency. These results will be presented as well.

Hydrogen Emission from Meteors and Meteorites: Mapping Traces of H₂O Molecules and Organic Compounds in Small Solar System Bodies

A. Pisarčíková, P. Matlovič, J. Tóth, S. Loehle

Detection of the H emission in meteor spectra indicates the presence of organic matter and water in the population of small bodies in the solar system. Hα 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. In this talk, we will present the results of our analysis of the H emission in a dataset of 304 meteor spectra from mm to dm-sized meteoroids captured by the AMOS (All-sky Meteor Orbit System) network. We examined the variations of Hα line intensity and its dependency on orbital and physical properties of meteoroids. Our results show that stronger Hα emission is characteristic for cometary bodies and likely indicates increased presence of volatiles and hydrated minerals. We also performed the study of the H emission in spectra of ablated meteorite samples of different meteorite types in the plasma wind tunnel facility. We have shown that H emission from asteroidal materials can also occur and apparently correlates with their water and organic matter content. This laboratory experiment was performed in cooperation between the Comenius University and the High Enthalpy Flow Diagnostics Group at the Institute of Space Systems, University of Stuttgart.

Luminous Efficiencies from Simultaneous Radar and High-Resolution Optical Observations

R. L. Dewsnap, M. D. Campbell-Brown

The luminous efficiency of meteors (fraction of kinetic energy which produces light) is an important parameter for determining properties of meteoroids from optical observations, particularly their mass. However, the value of the luminous efficiency remains a perennial problem and estimates cover orders of magnitude. On the other hand, the ionization coefficient necessary for analyzing radar meteors has seen comparatively better agreement between experimental measurements (e.g. DeLuca et al., 2018) and theoretical approaches (Jones, 1997). By examining meteors observed simultaneously through optical and radar instruments, we can constrain the luminous efficiency of the meteor to values compatible with the ionization coefficient. We consider events observed by both the multi-frequency Canadian Meteor Orbit Radar (CMOR) and optically by the Canadian Automated Meteor Observatory (CAMO). We estimate electron line densities from the radar echo based on a three-frequency full wave scattering model, and relate this to the optical light curve to obtain an estimate of luminous efficiency. Previous studies have assumed values for the initial radius of the scattering meteor train, but observing the same echo simultaneously with three frequencies provides a strong constraint to this parameter. In addition, we use the luminous efficiency estimates in a dynamical model of each meteor’s ablation based on CAMO’s narrow-field tracking cameras, in order to determine physical properties of the meteoroids, taking into account the observed high-resolution fragmentation of the meteoroids.

Estimating Fireball Luminous Efficiency from Near-Field Infrasonic Detections

L. McFadden, P. Brown, D. Vida

Meteor fragmentation points produce spherical shockwaves. The associated direct infrasound arrivals at the ground produce overpressures which correspond to individual fireball fragmentation energy deposition (Kinney and Graham 1985). The regular (cylindrical or ballistic) shock also produces direct signals at the ground which relate to energy deposition per unit path length (ReVelle, 1976). Here we identify fragmentation and ballistic infrasound signals in the near field (<200 km range) for fireballs with well measured light curves. We independently estimate luminous efficiency along the fireball track for each acoustic source height. Using the Bolide Acoustic Modelling (BAM) software, we isolate fragmentation and ballistic infrasound arrivals at multiple infrasound stations. From these we have determined fragmentation and ballistic energy yields (McFadden et al., 2021), for several well observed fireballs. We compare our estimates of luminous efficiency to model estimates produced by the semi-empirical fireball fragmentation model of Borovicka et al (2013) at multiple source points along several fireball tracks. We present results based on an analysis of a subset of well observed fireballs which happen to have near field infrasound data including the Romania superbolide of Jan 7, 2015 (Borovicka et al., 2017).

Photometric Meteor Masses Derived from Experimentally Determined Luminous Efficiencies

L. K. Tarnecki, R. A. Marshall, Z. Sternovsky, P. Brown, T. Munsat

The total mass flux into the Earth’s atmosphere due to input from meteoroids and dust is poorly constrained. Historically, mass flux estimates calculated using different techniques vary widely. Many methods of measuring this parameter exist, each with associated biases and errors. These include velocity biases, restrictions to limited mass ranges, and poor estimates of physical properties which lead to a discrepancy of several orders of magnitude in determinations of the total meteor mass flux. This work focuses on an effort to make improved measurements of one such physical property, the luminous efficiency, using laboratory experiments, and to apply the results to observed meteors. To improve luminous efficiency estimates, we use the dust accelerator at the Institute for Modeling Plasma, Atmospheres and Cosmic Dust (IMPACT) at the University of Colorado. We have modified a gas ablation target (used previously by Thomas et al. 2016 to measure the ionization coefficient) to include a more advanced optical system and a high-speed data acquisition system, which measures the light output of a dust particle as it ablates with high spatial and temporal resolution. We have conducted two data collection campaigns to study iron and aluminum dust particles, and have observed more than 1,300 ablation events. By combining this data with the measured masses and velocities of the original particles, we can determine the luminous efficiency for a wide range of speeds and particle masses. The experimental results can then be applied to optical observations. We calculate photometric masses for a set of 150 meteors observed by a camera network in Norway. These meteors were observed simultaneously by the MAARSY radar, allowing us to calculate independent radar masses. We present masses determined from both systems and compare the results to make an overall mass estimate, constrain the error in the mass, and provide insight into the discrepancy between radar and photometric masses.

Study of Organic Species in Meteoroids Using Laboratory Experiments

A. Uda, S. Abe, R. Fuse, M. Orita, J. Okuyama, S. Hasegawa

When a meteoroid enters the atmosphere from interplanetary space, that separates by several fragments by heating. That forms a meteor wake, the luminous intensity of the meteor is equal to total of that of the main meteoroid body and separated fragments. However, it is difficult to obtain data with high temporal and spatial resolution because it is impossible to predict the time and location of meteor appearances and they are short time phenomena of less than 1 second. In addition, direct detection of emission in visible light from organic species contained in meteoroids has not been done. Therefore, we performed laboratory experiments to simulate meteor emissions in a chamber using projectiles made by carbon-rich polycarbonate spheres. In order to investigate the physical processes of the meteoroids’ fragmentation, the artificial meteors were generated by using a two-stage light gas gun, and measured by high-speed imaging and spectroscopic camera in this experiment. It was carried out in the between 400-800nm wavelength range. The laboratory experiments showed that the emission intensity enhanced with increasing the fragmentation of the projectile. And, we were able to prove that C2 can emit light in the visible light range.

Can We Detect Very-Low-Frequency Radio Emissions from Meteors?

P. Vankawala, R. Marshall, D. Vida, P. Brown

Meteors are generally observed through visual detections from their optical emissions, however they can also be detected through scattering of radar waves transmitted from the ground, typically in high frequency (HF, 3–30 MHz) through ultra-high-frequency (UHF, 0.3–3 GHz) bands. It has been confirmed that meteors do radiate in the HF/VHF range naturally (Obenberger et al 2020). These detections raise interest in the physical interactions behind these phenomena and provide insight into the development and evolution of meteor plasma. For decades, it has been suspected that meteors are radiating frequencies in the very-low-frequency range (3-30 kHz). This has been theorized as a possible explanation for the simultaneous audio signatures and optical detections on the ground by means of electrophonics in a conductor (Astapovich 1958). However, there remains uncertainty about the origin of these VLF detections and whether they truly are from meteors (Sung et al 2020). In this paper, we discuss the early results from our new VLF and meteor camera network in search of these elusive emissions. For the past two years, four all-sky cameras and three VLF receivers have been operating in Colorado and Utah. The cameras operate under the University of Western Ontario’s automated meteor detection software and detect meteors from sunset to sunrise every night. The VLF receivers record broadband 0.3-50 kHz VLF data continuously at each site. A variety of signal processing techniques have been applied to the data to separate possible meteor signatures from other natural and anthropogenic signals. Most notably, a “Sparse Separation” technique (Strauss 2013) is used to extract Fourier components (e.g. powerline harmonics and Navy VLF transmitter signals) as well as Wavelet components (e.g. lightning-generate sferics) to isolate possible meteor emissions. Despite this analysis, no clear evidence has been found to indicate that meteors are emitting VLF radio emissions.

The Oxygen Line in Fireball Spectra and Implications to Satellite Observations of Fireballs

V. V. Vojáček, J. B. Borovička, P. S. Spurný

We examined the spectral region at 777 nm, where the oxygen triplet dominates, in spectra of 43 fireballs with magnitudes from -8 to -15 obtained within the European Fireball Network. The radiant intensity was compared with other selected spectral regions and also with the energy radiated in the whole spectrum. It was found that meteor properties, especially the velocity, strongly affect the intensity of the oxygen triplet. In slow meteors, the excitation of atmospheric elements, including oxygen, is low and the relative brightness of atmospheric lines is lower than it is in the case of fast meteors. Only a continuum was detected at 777 nm in some slow meteors. On the other hand, the oxygen triplet belongs to the brightest lines in the spectra of fast meteors. This behavior must be taken into account when estimating total fireball magnitude from narrowband observations at 777 nm, as is the case with the Geostationary Lightning Mapper (GLM) onboard the GEOS satellites. We derived an empirical relation between meteor speed, radiation at 777 nm, and the absolute visual magnitude of the meteor. We have successfully applied this relation to real GLM data and are able to estimate the magnitude of the fireballs observed from these weather satellites.

Molecular Barcode of Extraterrestrial Iron Cyano Complexes: A Computational Vibrational Spectroscopic Approach

B. Yilmaz, O. Ünsalan

Iron cyano carbonyl (ICC) complexes are thought to be important for prebiotic chemistry on early Earth. The source of exogenous cyanide by meteorites may have boosted the amount of cyanide produced on early Earth. Hydrogen cyanide (HCN) detected in the Murchison meteorite (Pizzarello, 2012) has shown that its origin is extraterrestrial. It has been revealed that the source of the cyanide released in the Murchison meteorite is different from the cyanide responsible for the synthesis of some extraterrestrial amino acids and other organic compounds (Pizzarello, 2014). In addition, two iron cyanocarbonyl complexes, [FeII(CN)5(CO)]3− and [FeII(CN)4(CO)2]2−, were identified in the Lewis Cliff 85311 meteorite. These extraterrestrial organometallic compounds are possible sources of free cyanide (HCN/CN−) (Smith et al., 2019). Here, we investigated computational Infrared (IR) and Raman spectra for ICC cis-trans structures via Gaussian 09 software by DFT/B3LYP theory level with the 6-311++G(d,p) basis set. We evaluated thermodynamic parameters for ICC cis-trans isomers in Mars, Mercury, and Venus conditions in various pressure and temperature settings. This study contributes vibrational spectra of organometallic compounds which might be detected in various planetary environments. This work was supported by Ege University Scientific Research Projects Coordination Unit. Project Number: FYL-2020-22523. (Part of a M.Sc. thesis project of Berguzar Yilmaz).

Santa Catharina Meteorite: From Micro to Nanostructure

F. Danoix, F. Cuvilly, J. Gattacecca, C. Maurel, R. Danoix

Santa Catharina meteorite has motivated a number of microstructural and magnetic investigations. This is in particular because of its uncommon high Ni content, and resulting magnetic properties. Using scanning electron microscopy and Energy Dispersive X-Ray spectroscopy, we confirm previously published results, including the average composition and microstructural features, such as large sub-millimiter size sulphides. In addition, the presence of micrometer scale lath shaped phosphides was also observed. Down to the nanometer scale, Kikuchi Transmission Diffraction and Atom Probe Tomography reveal the existence of a cloudy zone like region, a 3D fully interconnected network of taenite and tetrataenite, with a typical wavelength of about 10nm, and composition respectively 85±5at%Fe-15±5at%Ni and 50±5at%Fe-50±5at%Ni. The volume fraction of each phase is about 50%. On the basis of the observed nanostructure, it is likely that it was formed by spinodal decomposition, although this hypothesis is impossible to prove due to the absence of any kinetic data. Because only two phases have been observed in the FCC matrix, taenite and tetrataenite, this study rules out the existence of an intermediate-Ni-content phase, sometimes referred to as anti taenite. We suggest to reinterpret the Mössbauer Spectroscopy data on which this conclusion is based.

Continuing the Hunt for Elusive Extraterrestrial Liquid Water in Astromaterials

P. A. B. Krizan, Q. H. S. Chan, A. Gough, D. Papineau

Ever since the discovery of the first true extraterrestrial liquid water within the Zag and Monahans (1998) ordinary chondrites [1], there has been great speculation as to whether any additional direct water samples exist in other astromaterials. Our understanding of transient water and its significant abundance throughout the Solar System has greatly improved within the last decade. Its presence is predominantly detected in the form of solid ice – an observation that is consistent with the observed evidence of aqueous alteration in primitive meteorites [2]. Until now, it has remained unknown if any additional extraterrestrial liquid water samples do exist, and why they have continued to evade our detection, despite the apparent widespread influence of hydrothermal alteration throughout the solar system. Here, we present our findings from our assessment of previous unsubstantiated claims of fluid inclusions, using a wide range of meteorite samples, and their likelihood of containing true liquid water. We analysed one achondrite meteorite (Allan Hills A77256) and fourteen chondrite meteorites (Allan Hills 84029, Bells, Bjurböle, Cochabamba, Holbrook, Ivuna, Jilin, Lonewolf Nunataks 94101 & 94102, Mighei, Orgueil, Santa Cruz, Sutter’s Mill, and Sayama) from a set of both freshly and previously produced thin sections. Our fresh thin sections were prepared using a specially designed anhydrous technique, specifically for the study of fluid inclusions. We show that both petrographically primary and secondary fluid inclusions are observed and hosted in a range of minerals. We also show the compositional analyses from some of the trapped fluids within suitable inclusions (diameter >1μm), using a combination of Raman spectroscopy and SEM-EDS. References: [1] Zolensky et al. (2017). Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 375(2094). [2] Tsuchiyama et al. (2021). Science Advances, 7(17).

The Fall, Recovery, and Initial Analysis of the Winchcombe Meteorite

H. C. Bates, Winchcombe Consortium

At 21:54 (UT) on the 28th February 2021 a bright fireball was observed travelling approximately West to East over the UK. The fireball lasted ~7 seconds and was recorded by 16 stations operated by the six meteor camera networks of the UK Fireball Alliance (UKFAll); it was also caught on numerous dashboard and doorbell cameras and there were >1000 eyewitness accounts, including reports of a sonic boom. Following an appeal in the national media, the main mass (~320 g) of the meteorite was discovered by a family in Winchcombe, Gloucestershire. The stone landed on the family’s driveway, shattering into a pile of dark mm- to cm-sized fragments and powder, most of which they collected wearing gloves and sealed within plastic bags ~12 hours after the fall. Further meteorites were recovered in the local area over the following week by members of the public and during an organised search by the UK planetary science community, with the largest piece being a 152 g fusion-crusted stone found on the 6th March 2021 on farmland. In total, >500 g of the Winchcombe meteorite was recovered less than seven days after the fall, with no significant rainfall having occurred during that time. Initial analysis, some of which was carried out less than a week after the fall, shows that Winchcombe is a CM (“Mighei-type”) carbonaceous chondrite. The CM chondrites are rich in water-bearing phyllosilicate minerals and organic matter and come from asteroids that have remained largely unchanged since the formation of the solar system. Winchcombe is the first meteorite fall to be recovered in the UK for 30 years, only the fifth carbonaceous chondrite fall with a known pre-atmospheric orbit, and due to its rapid recovery is among the most pristine members of the CM group. The mineralogical, elemental and organic properties of Winchcombe therefore provide a snapshot of conditions in the protoplanetary disk and insights into the chemical and dynamic evolution of volatiles in the early solar system.

PRISMA: An Italian Fireball Network for the Recovery of Freshly Fallen Meteorites

D. Barghini, A. Carbognani, A. Cozzumbo, M. Di Carlo, M. Di Martino, D. Gardiol, G. Pratesi, W. Riva, G. M. Stirpe, A. Volpicelli

PRISMA is the Italian fireball network dedicated to the systematic observation of bright meteors and fireballs. It started in 2016 and nowadays involves more than 60 institutes, coordinated by INAF, the Italian National Institute for Astrophysics. To date, the network counts more than 60 all-sky cameras deployed over the Italian territory. PRISMA is also a member of the European FRIPON collaboration. Since the beginning of its activities, PRISMA has observed more than 2000 bright meteors. The analysis of these observations unveiled that at least six of them were meteorite-dropping fireballs, with a predicted strewn-field over the Italian territory. On 4th January 2020, two meteorite fragments were recovered near Cavezzo (MO) in the area predicted thanks to PRISMA observations and just three days after the fall. This was the first recovery of this type in Italy. More recently, on the evening of the 5th March 2022, ten PRISMA cameras observed an outstanding event over central Italy, that reached -11m peak brightness and lasted almost 15 seconds, collecting hundreds of eyewitness reports from all over the country. For this recent event, searches for meteorites on the ground are still ongoing. In addition, four more meteorite-dropping fireballs were observed in 2017, 2018 and 2021, for which a reliable strewn-field is available. In this contribution, we will report on the current status of the project and network operations.

Trajectory and Orbit of the Golden, BC, Meteorite Fall

P. G. Brown, A. R. Hildebrand, D. Vida, P. J. A. McCausland, L. Hanton, C. D. K. Herd, P. Hill, H. Devillepoix, M. Mazur, D. E. Moser, W. J. Cooke, D. Hladiuk

A bright fireball with peak absolute magnitude near -13 was widely observed at 05:33:43 UTC on Oct 4, 2021 near the Alberta/British Columbia (BC), Canada border. The fireball produced a 1.3 kg meteorite which penetrated the roof and landed on the bed of Ruth Hamilton of Golden, BC. Subsequent searches in Golden yielded one additional fragment of 0.9 kg mass. The meteorite fall, an L5 chondrite, was documented by more than half a dozen casual video recordings and two large format all sky fireball cameras of the MORP2.0 project. From calibration of five cameras a trajectory and speed was measured. The apparent ground-fixed radiant azimuth was found to be 308 and the entry angle 54 degrees. The initial entry speed was 18 km/s with significant luminosity beginning at 84 km and luminous flight ending at 18 km altitude. The pre-impact orbit is evolved with semi-major axis of 1.6 AU and a high inclination of 23 degrees. Infrasound from the fireball recorded at two stations provides an energy estimate, using standard explosive period-yield relations, of 0.002-0.003 kT TNT. This corresponds to a pre-impact meteoroid mass of 50-80 kg and diameter of 0.3-0.4m. Here we describe the circumstances of the fall and observed behaviour of the fireball producing the Golden meteorite.

Analysis of the Daylight Fireball of July 15, 2021, Leading to Meteorite Fall and Find Near Antonin, Poland, and Description of the Recovered Meteorite

L. Shrbeny, J. Borovicka, P. Spurny, A. M. Krzesinska, Z. Tyminski, K. Kmieciak

Three video cameras of the Czech part of the European Fireball Network recorded a daylight fireball on July 15, 2021. The whole fireball flew over the territory of Poland. We were able to describe all its basic parameters. Even though the final part of the bolide was not recorded by the cameras, as the bolide flew behind the clouds or it was out of the field of view, the meteorite fall was very probable, since the last detection was at an altitude of 25 km and the fireball still had a velocity of about 13 km/s and the dynamic mass of the order of few tens of kilograms. Few days after the fall we published the basic information and the impact area on our website and informed our colleagues and searchers in Poland. So far, one piece of meteorite, weighing almost 352 grams, has been recovered during a dedicated recovery expedition exactly in the predicted impact area. The specimen is almost fully fusion crusted and with only minor brown staining due to Fe oxidation seen in its interior, close to fusion crust. Soon after the recovery in August 2021, the meteorite was analysed for presence of short-lived cosmogenic radionuclides. The analytical results corroborate that it is fresh. Petrographic investigation by optical and scanning electron microscopy and electron probe microanalysis indicates it is L5 chondrite. The minerals are homogeneous and chemically equilibrated: olivine contains 24.4 mol% Fa, pyroxene has 20.9 mol% Fs, and kamacite comprises 6.6 wt% Ni and 0.72 wt% Co. Plagioclase crystals are rare, and instead feldspathic glass is commonly retained. Meteorite is moderately shocked. Silicates reveal weak intracrystalline deformation, but shock melt pockets at contacts of plagioclase and metal and plessitic metal grains are widespread.

Orbital Elements and Dynamical History of the 07.11.2020 Iron Meteoroid

I. Slyusarev, I. Kyrylenko, O. Golubov, J. Visuri, M. Gritsevich, Yu. Krugly, I. Belskaya, V. Shevchenko

A bright fireball was observed and instrumentally recorded over Scandinavia on November 7, 2020, at 21h 27min UTC. First records of the fireball gave a preliminary fall position on the ground, and a month later, a 13.8 kg iron meteorite was recovered in a vicinity of the predicted area. This makes it the first instrumentally documented fall of an iron meteorite. Analysis of the images obtained by the Finnish Fireball Network and the Norwegian meteor camera network allowed us to obtain more accurate values of the meteoroid orbital elements. The orbital evolution in the past of the meteoroid was analyzed using the GENGA package. We found no close affinity of the meteoroid's orbit with any known near-Earth asteroid. Our estimation of the probability of source regions of the meteoroid using NEOPOP software shows that the meteoroid entered its near-Earth orbit via the ν6 secular resonance. From the pre-atmospheric size of the meteoroid and the tensile strength of iron meteorites, we estimate the YORP-disaggregation time of the meteoroid to be at most 20 Myr, which is enough for the meteoroid to reach its orbit from the main belt as a separate body. The meteoroid's orbital inclination is two to three times larger than the typical values for the most prominent families in the inner part of the main belt (Flora, Vesta, Nysa-Polana), which parent bodies probably were differentiated and for which the presence of iron-rich asteroids is possible. The forthcoming laboratory analysis of isotopic abundances will estimate its CRE age and can verify our predictions about the origin of the meteoroid.

Update on Weather Radar Detection of Meteorite Falls in the United States

M. Fries, M. Broussard

Weather radar is a proven technique for detecting meteorite falls and aiding in their rapid recovery. We will present an overview of the technique, describe some example meteorite falls, and present statistics for detections and recoveries in the United States to date. We will discuss work on quantifying meteorite fall mass from radar data as well as development of mathematical means for automated fall detection. We will also describe the Jörmungandr dark flight model which was developed specifically for radar-based strewn field modeling. Future improvements to the U.S. weather radar system and their impacts on meteorite fall detection will also be discussed. Finally, we will present the case for a dedicated meteorite fall recovery team utilizing weather radar and other data for rapid recovery of fresh falls, and options for how such a team might be organized.

Using Machine Learning for Bolide and Meteor Detection in Doppler Radar Data

B. Smeresky, P. Abell, M. Fries, M. Hankey

One of NASA’s goals is to better characterize the asteroid/meteoroid population through the expeditious recovery and analysis of surviving fragments. Unsupervised machine learning techniques provide a promising method to detect meteor and bolide fragments as distinct signatures within weather data from the national WSR-88D Doppler radar network. Unsupervised learning methods are used to characterize and classify potential meteorites by identifying the relationships among individual data points from four weather radar sites during two known bolide events: the KFWS radar for the Ash Creek bolide and the KDAX, KRGX, and KBBX radars for the Sutter’s Mill bolide. A combination of algorithms is presented: Principal Component Analysis to increase dataset variance, t-Distributed Stochastic Neighbor Embedding to reduce dataset dimensionality, and Nearest Neighbors Density Pruning to reduce dataset size while identifying meteorite signatures. The algorithms execute in less than 8 minutes for a 121,000-return sized dataset and classifies the data with a 99.7% accuracy rate. Accuracy and specificity are high due to the large number of non-meteorites within the dataset; conversely, the classifier’s recall and precision rates remain low due to difficulties in correctly classifying true positive meteorite fall events. Increasing the number of true positives and decreasing the number of false negatives would enable higher levels of confidence in the performance of the algorithm. The output of this research presents an algorithm combination that yields a refined list of probable returns for human review and confirmation. This leads to the faster confirmation of meteorite fall events and subsequent dispatch of recovery teams to fall locations. Ref: Smeresky, B., Abell, P., Fries, M. and Hankey, M. (2021), Bolide fragment detection in Doppler weather radar data using artificial intelligence/machine learning. Meteorit Planet Sci, 56: 1585-1596. https://doi.org/10.1111/maps.13718.

Fireball Network BOCOSUR

G. Tancredi, M. Caldas, A. Guaimare, V. Abraham, L. Barrios, M. Hernández, L. Velasco

The current status of the Fireball/Bolides Network BOCOSUR (Bólidos del Cono Sur), which is being deployed in different locations in Uruguay, is presented, as well as some preliminary results and developed products. The network consists of a set of stations designed and build by us. Each contains a high sensitivity CMOS camera (ASI178MM), fisheye lens (FOV 180 deg), dew prevention systems and PC, all housed within a watertight cabinet. The stations run an application of their developed by us, which detects, stores, and sends the videos of one night via FTP to a central server. The bolides detected are subsequently processed with another application, also developed locally, which allows astrometry and photometry of the event to be performed. The stations have been installed in various public secondary schools in the country. The network currently has 7 operational stations, and 13 more are in the process of being installed. During all stages of deployment (assembly of equipment, installation, operation, and maintenance) the active participation of local educational agents (teachers and high school students) is sought, as well as of undergraduate students of the Bachelor of Astronomy who, together with researchers make up the stable staff of the project. The general objective of the project is to consolidate a research group, strongly committed to university outreach, which contributes to the characterization of meteor activity at the regional level. Likewise, it seeks to involve local educational communities, with a citizen science approach. Several tens of fireball has been detected in over a year of operation. Many of them were detected simultaneously from 2-3 stations, which allowed us to compute the pre-atmospheric orbit. A brief description of the network, of the detection and post-processing applications developed, as well as some primary data based on detections made to date, will be presented.

Parametric Study for Shape Estimation of Beni M'hira Meteorite

V. V. Vinnikov, M. I. Gritsevich, E. A. Pshehotskaya

The paper is concerned with the study of estimated shapes of meteorites depending on the sub-sampling of the recovered fragments mass distribution. Since the empirical histogram suffers from the incomplete fragment recovery on both ends of the distribution, we consider the respective impact on the shape estimation, and the robustness of shape estimation technique. The parametric study is carried out numerically using the least squares method. Each sample of fragments from the overall recovered distribution is formed by selecting the initial lower and upper fragment masses, that are a sought for. Next, for each fragment mass taken as a lower cutoff limit we solve the system of nonlinear equations by a dichotomy method for an upper fragment mass wrapped over a scalar Newton method for a histogram-fitting parameter. Then, we obtain the set of shape estimations, and carry out the respective statistical analysis. The necessity of relying on dichotomy method originates from non-smooth mass distributions that prevent more advanced methods from converging.

FRIPON Meteor Cameras in Austria and the Recovery of Meteorites

L. Ferrière, C. Koeberl

Only eight meteorites (5 observed falls and 3 finds), all ordinary chondrites, have been recovered over the last 250 years in Austria. The first observed fall in Austria, the Mauerkirchen (L6) meteorite, occurred in the year 1768. Then, Minnichhof in 1905, Lanzenkirchen (L4) in 1925, Prambachkirchen (L6) in 1932, and, finally, Kindberg (L6) in 2020. In term of meteorite finds, Mühlau was recovered in 1877, Ischgl (LL6) was picked up in 1976 but only recognized as a meteorite in 2008, and, finally, Ybbsitz (H4) was found in 1977. The Neuschwanstein (EL6) meteorite, a fall from 2002, is not listed here, as it is recognized as a German meteorite – even though the main mass was recovered in Austria. Based on the rather limited number of meteorites recovered in Austria, in 2015 we decided to join the Fireball Recovery and InterPlanetary Observation Network (FRIPON), and to extend the network over the entire Austrian territory. A “test” camera and a radio receiver station were then installed on the roof of the main building of the Natural History Museum Vienna. More recently, eleven additional FRIPON cameras were acquired and will be installed at different locations in Austria, as part of the FRIPON-Austria network. Involving experts in meteoritics and astronomers, we hope that this interdisciplinary project will create new synergies between different institutions in Austria. It will also provide a chance to involve the general public in the meteorite search campaigns – a perfect case of “citizen science”. In this respect, two large fireballs were seen over Austria in the year 2020, one on April 6th, witnessed by several hundred people (https://fireball.amsmeteors.org/members/imo_view/event/2020/1591) and one on November 19th, for which one stone, the Kindberg meteorite, was recovered after an intense meteorite search campaign organized by one of us (LF), involving media and local residents. Acknowledgements: Thanks to the Austrian Academy of Sciences for partial funding.

A Modelling Study of the Seasonal, Latitudinal, and Temporal Distribution of the Meteoroid Mass Input at Mars: Constraining the Deposition of Meteoric Ablated Metals in the Upper Atmosphere

J. D. Carrillo Sánchez, D. Janches, J. M. C. Plane, P. Pokorny, M. Sarantos, M. Crismani, W. Feng, D. Marsh

This study provides a complete description of the deposition of meteor-ablated metals in the upper atmosphere of Mars, accounting for the temporal, vertical, latitudinal, and seasonal distribution. For this purpose, the Leeds Chemical Ablation MODel (CABMOD) is combined with the Meteoroid Input Function (MIF) to characterize spatially and temporally the size and velocity distributions of three distinctive meteoroid populations around Mars – The Jupiter-Family Comets (JFCs), the main-belt asteroid (ASTs), and the Halley-Type Comets (HTCs). The modelling results show a significant midnight-to-noon enhancement of the total mass influx because of the axial tilt. The maximum total mass input occurs between the northern winter (Ls = 270 degrees) and the FCEP with 2.30 tons sol-1, with the JFCs being the main contributor to the overall influx with up to 56% around the Mars equator. Similarly, total ablated atoms mainly arise from the HTCs with maximum rates between the perihelion and the northern winter with 0.71 tons sol-1. In contrast, the minimum mass and ablated inputs occur between the maximum vertical distance above the ecliptic plane (Ls = 56 degrees) and the aphelion with 1.50 tons sol-1 and 0.42 tons sol-1, respectively. Meteoric ablation occurs approximately between 100 and 60 km in the Mars’ upper atmosphere with a strong midnight-to-noon enhancement at equatorial latitudes. Nevertheless, refractory metals – such as Ca and Al – are released more efficiently during the dawn terminator where small and fast particles dominate. Additionally, the axial tilt of Mars leads to a shift of the ablation peak into lower altitudes at mid- and high-latitudes, especially during the winter season. The eccentricity and the inclination of the Mars’ orbit produces a significant shift of the altitude of the ablation peak at high latitudes as Mars moves towards, or away, from the northern/southern solstices.

The Study of Mass Distributions of Meteoroid Streams Provides Information About Comet Inner Structure

J. M. Trigo-Rodriguez, J. Blum

Comets are fragile objects formed in the protoplanetary disk from the accretion of primordial materials made of grains consisting of minerals, organics and ices. When a comet approaches the Sun, its surface is heated and the ices sublimate into space, dragging particles away from the comet nucleus. While the smallest produce the well-known dust tail, the larger form the dust trail, evolving and redistributing along the entire orbit. When the Earth crosses it, a meteor shower is observed. The study of meteor showers provides clues on the sizes of the particles and can be used to compute the flux of cometary materials reaching the Earth. Meteor physics provides clues about the size, structure, and density of cometary disintegration products, establishing a bridge between research fields. We computed the mass distributions and compared them with observations of dust particles released from several comets measured by spacecraft. From these mass distributions, we integrated the incoming mass for the most significant meteor showers. In addition, we compared them with the mass of the IDPs collected in the stratosphere, finding a gap of several orders of magnitude. The largest examples of fluffy particles are clusters of IDPs no larger than 100 µm in size (or 5×10^-7 g in mass), whereas the largest cometary meteoroids are centimeter-sized particles (termed pebbles). Large particles are present because they are associated with the building blocks of comets in the current comet-formation scenario in which a cloud of pebbles in the solar nebula was concentrated by the streaming instability and then collapsed due to a gravitational instability. These pebbles are products of collisional growth processes of dust/ice grains in the solar nebula and their size depends on a variety of parameters related with the formation location as the size of the constituent dust/ice grains, the dust-to-ice ratio, and the particular chemistry in the region where they formed.

Summation of the Results on the Dynamics of the Meteoroid Environment Based on the Data of Radar Observations in Kharkiv and Others

S. V. Kolomiyets, I. Yu. Kyrychenko, M. M. Kaliuzhnyi, S. G. Kundyukov, Yu. V. Cherkas, V. I. Chumakov, K. A. Kolomiiets, V. V. Mitrokhina

Models of the meteoroid environment near the Earth's orbit and in the Solar system are built on the basis of data from ground-based radar observations and others. Radar observations have a very strong selectivity to the conditions of observation and other factors. The results of radar observations of meteors (of a significant volume) are known both in the past (eg in Ukraine or New Zealand) and modern (eg in Canada or Argentina/USA). Some generalization of information about the dynamics of meteoroids will be presented, using the experience of Kharkiv radio meteor studies and other data. We will discuss the results and prospects of using information radio technologies and other approaches to analyze the distributions of meteoroid orbital elements, as well as data on the number of meteors and their velocities.

Using Space-Based Meteor Observations to Determine an Upper Mass Limit for Major Meteor Showers

K. Wisniewski, P. Brown

The population of larger sized meteoroids contained in different meteor showers is not well constrained. As most showers have a shallow mass index, the upper-mass population cutoff is critical for determining the total mass in a meteoroid stream. The challenge in estimating the maximum size of meteoroid in a stream is the large atmospheric time-area collecting area required to make a statistically useful measurement. It has been shown recently (Jenniskens et al., 2018) that the Geostationary Lightning Mapper (GLM) onboard the GOES-16 and GOES-17 satellites are able to detect bolides. At low speeds, the threshold magnitude for fireball detection is of order -14 (Jenniskens et al 2018), but this is certainly lower at higher speeds where the 777 nm Oxygen line is more prominent. In this work we examine the GLM dataset and attempt to isolate bolides which are likely linked to specific meteor showers. We have filtered GLM detection to identify bolides detected during the activity period of major meteor showers and where the local radiant is above the horizon. Compared to the background level of bolide activity, this simple level of spatial/temporal filtering reveals strong signals from both the Leonids and Perseids. We plan to also apply a velocity filter whereby we compare the expected on-plane velocity component of possible shower bolides with the expected values. As well, a subset of detections made by both satellites are examined for height information as a final filter. Our ultimate goal is to measure the flux to the GLM limiting threshold brightness per shower based on the satellite look geometry and known shower radiant. We will present our initial results of this GLM meteor shower survey in this talk. References Jenniskens P. et al. 2018. Detection of meteoroid impacts by the Geostationary Lightning Mapper on the GOES-16 satellite. Meteoritics & Planetary Science 25.

Radar Flux Measurements of the Geminid Meteor Shower

M. D. Campbell-Brown, P. G. Brown

The Geminid meteor shower is particularly interesting both because of its strong, consistent activity and because its parent, 3200 Phaethon, is an apparently asteroidal object. Stream modelling suggests that the flux of Geminid meteors is currently increasing, and an analysis of visual observations show an increasing trend from 1985 to 2016, and an increase in video fluxes observed from 2011 to 2016 (Ryabova & Rendtel, 2018). The Canadian Meteor Orbit Radar (CMOR) has been running at three frequencies (17.45, 29.85 and 38.15 MHz) with good calibration since 2002. Fluxes have been calculated for each frequency over all active years. The fluxes take into account changes in the transmitter power and antenna calibrations, solar activity, and local radio noise on each system. The population of meteoroids observed by CMOR is lower mass than optical observations, with a radar limiting magnitude of approximately +8. Ryabova, G. O. and Rendtel, J. (2018) MNRAS: Letters 475, L77-L80.

Characterizing the Daytime Sextantids Meteor Shower and Unveiling the Nature of the Phaethon-Geminids Stream Complex

Y. Kipreos, P. Brown, M. Campbell-Brown, D. Vida

The Geminid (GEM) meteor shower is the strongest meteor shower on Earth. However, questions about the cometary or asteroidal nature of its parent body, 3200 Phaethon, and the origin of the Phaethon-Geminids Stream Complex (PGC) remain. An avenue for further exploration is the study of the Daytime Sextantids (DSX) meteor shower. The Daytime Sextantid stream is a member of the PGC and is considered to be closely related to the Geminids. While the Daytime Sextantids have long been recognized as being related to the Geminids, the shower is poorly studied. Here we characterize the flux, mass distribution, and orbital element variations with time of the Daytime Sextantids meteor shower as observed by the Canadian Meteor Orbit Radar (CMOR) and the Global Meteor Network (GMN). We aim to explore further the relationship between the DSX parent body, 2005 UD, and the GEM parent body, 3200 Phaethon. The connection between the DSX and the PGC is a timely topic as in 2024, JAXA will launch the DESTINY+ mission, which will fly-by 3200 Phaethon and 2005 UD. To characterize the DSX, we have developed two new analysis techniques which can be used in large meteor datasets to improve the way contamination is removed during analysis. The first method statistically defines the radiant space of a meteor shower relative to the sporadic background in such a way that individual shower members can be isolated with a confidence level of 95%. The second method we developed uses a mixing model to remove the effect of sporadic contamination from mass index calculations of a shower. We will present our results related to the duration, radiant drift, orbital elements, mass index, relative meteoroid strength compared to the Geminids, and flux of the Daytime Sextantids meteor shower. In doing so, we lay the framework for the data received by the DESTINY+ mission.

IAU Meteor Data Center Database of Meteor Orbits – Data Update

M. Jakubik, J. Svoren, L. Neslusan

The IAU Meteor Data Center presents an update in the database of meteor orbits. The database has expanded significantly since the previous Meteoroids conference in 2019. Including the SonotaCo video-meteor database and replacing the version 2 of the CAMS video-meteor data with version 3, the number of the video meteors in the IAU MDC has grown to 824813. Next, a sample of 8916 radio-meteors was added, and finally original data-records of 4873 meteors detected by the photographic technique are also the part of presented version of the database. In addition to the increase of the number of meteor orbits, the functionality of the MDC web pages was improved. The database is stored in MySQL and this made it more flexible to work with. User can download or view data in several formats specifying catalogs, parameters and period of meteor detection. In this contribution, we present a more detailed information about the data update and web-portal development within the IAU MDC orbital database.

The Status of the IAU Meteor Data Center – Shower Database 2022

R. Rudawska, M. Hajdukova, T. Jopek, M. Koseki

We present the steps taken to reorganize the MDC Database, improve its functioning and the quality of the data contained therein. To keep the literature on meteor showers transparent, the MDC assigns a unique name, number and 3-letter code to each newly reported shower. Due to significant increase of discoveries, applying the current meteor shower nomenclature rules has been proven problematic. The obtained names are getting longer and longer, but worse still, finding unique stream names according to these rules is quite often troublesome or impossible. The reason lies in the imprecision of these rules. We propose to remedy this situation by introducing a new, two-stage, procedure for naming meteoroid streams. The MDC collects submitted shower data, validates them with respect to the nomenclature rules and provides a central list of all meteor showers. However, the content of the MDC has not yet been checked for the correctness of the shower parameters and their bibliographic records contained there-in. Hence, we verified the data stored in the MDC by comparing their values with those given in the source publications. As a result, ~1500 corrections have been made. Moreover, we supplemented the database with a few additional parameters (e.g. activity intervals or missing orbital elements), and re-stored some data as given in the original papers. The second problem relates to the issue of the official approval of names of meteoroid streams by the IAU. This task should be carried out by the Working Group on Meteor Shower Nomenclature on the basis of the relevant criteria. We propose such criteria that must be met if the stream is to be officially named by the IAU. We present the conditions for shifting showers to the List of Removed Showers due to: their low reliability, the incompleteness of the bibliographic references or being duplicates. Finally, we present the new MDC website, its structure and a few tools in preparation to facilitate the use of the database.

Meteor Shower Activity in 2017–2021 from Kazan Meteor Radar (Russia)

S. A. Kalabanov, D. V. Korotishkin, O. N. Sherstykov, R. A. Ishmuratov, F. S. Valiullin

Kazan Meteor Radar is a new system installed on the area of Kazan Federal University, Tatarstan, Russia (55 N, 48 E) in the beginning of 2015. It has 15kW power in pulse and uses single transmitting antenna of all sky configuration and receiving eleven-antennas for meteor trail detection. The new software designed in Kazan University increases the sensitivity of the radar enabling the detection of about 6000-8000 of meteors per day. Annual surveys for 5 full consecutive years show that Kazan Meteor Radar observes a strong contribution of the Northern Celestial Hemisphere sources. The radar uses on-line analysis software of meteor detection to get position determination parameters such as the time of the detection, the height of the detection, the zenith and the azimuth angles of the detection, the entrance speed of the meteors. The off-line analysis software developed in Kazan University is able to determine the radiant coordinates of meteor showers and their orbits. Finally, results from radar meteor observations for five consecutive years will be presented in this contribution. It will be shown an unknown meteor shower at the end of 2021.

Low-Light Video Meteor Surveillance Systems in Turkey

O. Ünsalan, P. Jenniskens, D. Samuels, M. Boyukata, O. Arslan, I. Kucuk

Since the Earth is being bombarded with occasional brief episodic meteor showers, constructing, and developing meteor surveillance systems over the whole globe is important to not miss these events. Such meteor showers are analyzed to get more knowledge on meteoroids and their trajectories/orbits, which is important to both planetary defense and making robust links to their parent bodies. CAMS Turkey systems were setup at three locations at Yozgat Bozok University, Akdagmadeni Vocational High School, and Kayseri Erciyes University in Turkey. This network consists of six, five and five WATEC 902H2 Ultimate cameras, respectively at these locations, equipped with 8mm and f/1.0 lenses. It was observed that these lenses show rich star fields. System resources of each network includes Windows 10 PC (x64 architecture) with Intel(R) Xeon(R) CPU E3-1220v3@3.10 GHz processor with four pieces of 3 TB hard disk drives per each station. Systems in the network use the CAMS software to look for signs of meteors in the video frames. The detected astrometric tracks are triangulated by a central coordinator to determine speed, angle of attack, altitude, and finally the orbital elements of the meteors. Results are posted at http://cams.seti.org/FDL/index-TK.html in near-real time. The first light was achieved on the night of 3 August 2021, when two Perseids and one sporadic meteor were captured from Kayseri and Yozgat. Acknowledgements: Ozan Unsalan acknowledges Yozgat Bozok University Akdagmadeni Vocational High School Department of Travel Tourism and Entertainment Service (Dr. Ilker Kilic), UZAYBİMER at Astronomy and Space Sciences Department at Kayseri Erciyes University, Yozgat Bozok University Faculty of Arts and Sciences Department of Physics for hosting CAMS systems in Turkey. This work was supported by the Scientific and Technological Research Council of Turkey (TUBITAK) (project number MFAG/113F035).

On Radio Meteor Processing

I. Kyrychenko, S. Kolomiyets

The NURE meteor database contains large data (in particular, about 250,000 meteor orbits obtained by the radar method during 1972-1978). For a long time, it was the largest in the world in the number of orbits of radio meteors, and today it ranks fourth after the Canadian (more than 5 million orbits of CMOR), Argentinean (multiple radar orbits of SAAMER, USA) and New Zealand (about 500 thousand orbits of AMOR). Modern computer data processing programs for their visualization allow you to easily compare the resulting distributions of radio meteors over different periods of time. In particular, the visualization of meteor data distributions for the period 1972-1978 according to certain parameters and under certain conditions is presented. Visualization was performed using modern computer programs Aladin and TOPCAT. It was found that both programs are suitable for meteor processing data and constructions of meteor radiants on celestial spheres in the second equatorial and ecliptic coordinate systems. As a result of studying the distributions of meteor substance for radar data of back reflection by means of Aladin and TOPCAT were installed: that the distribution from year to year is approximately the same. Detected differences can be attributed to insufficient statistical completeness. Distributions were constructed in the coordinate system (β', λ' - λa) for meteors, the parent bodies of which are presumably comets or asteroids. The distributions built according to the Kharkiv database are visually compared with similar distributions of other researchers in order to clarify general patterns, for example, such as the Helion source and others.

The Coming Era of Global Meteor Camera Networks

D. Vida

Currently, several meteor and fireball network are operating on the global scale. This talk will review their current status, identify the scientific contributions they can make, and explore the challenges such networks will encounter. The experiences from the Global Meteor Network will be presented.

Sub-Milligram Meteor Detection Instrumentation and Software for Simultaneous Optical and Backscatter Radar Observations

P. S. Gural, M. J. Mazur, P. G. Brown

Having the same meteor simultaneously measured by multiple sensors covering different wavelength bands, improves the calibration of masses for both optical and radar systems. With this goal in mind, a set of fully automated, four very low light, imaging electron-multiplying CCD cameras (EMCCD), were deployed at two dark sky sites near the University of Western Ontario, one of which is co-located with the Canadian Meteor Orbit Radar (CMOR). A key aspect of this system was development of a software processing pipeline designed to push the optical detection limits as faint as possible while also maintaining high measurement accuracy. The EMCCD sensor hardware was optimally configured to achieve a single-frame stellar limiting G-magnitude of +10.5, and typically observes meteors with peak brightness of +6.5, with some as faint as +8.0 while running at 32 frames per second. This is in the mass range of 10 to 100 micrograms typically seen by CMOR and below the underdense radar limit. The EMCCD processing software development involved innovations in new and robust image pre-processing and detection algorithms, whose key implementation was the first true application of matched filter processing to meteor imagery. The EMCCD processing pipeline pushes the detection limiting magnitudes down to nearly the noise floor of the optical system, while also yielding high quality automated metric measurements of meteor focal plane positions. A summary of the software pipeline and examples of results obtained since the beginning of operations in 2017 will be presented.

BRAMS: An Update on the Network and Data Processing

H. Lamy, M. Anciaux, J. Balis, S. Calders, A. Calegaro

BRAMS (Belgian RAdio Meteor Stations) is a network using forward scatter of radio waves on ionized meteor trails to study meteoroids. It is made of a dedicated transmitter and of 42 receiving stations located in or near Belgium. The network started in 2010 but has recently been extended and upgraded. The transmitter emits a CW radio wave with no modulation at a frequency of 49.97 MHz and with a power of 130 W. The antenna was designed with the aim of emitting a circularly polarized wave. Unfortunately, the radiation pattern was very different and in-situ measurements using a dedicated payload and a captive weather balloon were necessary to determine the exact amount of power transmitted in a specific direction. The experiment and results will be presented. Since 2019, the design has been improved to properly transmit a circularly polarized radio wave. Each receiving station uses a 3-element zenith pointing Yagi antenna. The first stations used analog ICOM-R75 receivers and a PC. Since 2018, new improved stations have been installed using digital RSP2 receivers and a RPi. The new stations will be presented as well as a comparison between old and new ones. BRAMS data files will be presented. Since the stations are relatively close to the transmitter, most of them detect a direct signal from the transmitter, which often superimposes with meteor echoes. To remove it properly, it must be reconstructed by accurately computing its amplitude, frequency and phase, and then subtracted from the raw data. Examples will be presented. Two algorithms for automatic detection of meteor echoes in BRAMS data will be introduced : one using a moving median along the columns of the spectrograms and a second one using convolutional neural networks. Examples and statistics will be shown for the two methods. Finally, possible upgrades of the BRAMS network are considered: (a)add a second transmitter, (b)add a backscatter meteor radar, (c)add a phase coding to the CW transmitted signal.

Synthetic Modeling for Debiasing an EMCCD Meteor Camera System

M. J. Mazur, P. Brown, P. Gural, D. Vida

As part of the dual station Canadian Automated Meteor Observatory (CAMO) a set of four fully automated Electron-Multiplied Charge Couple Device (EMCCDs) cameras have been in operation since 2016. These cameras are capable of imaging to limiting peak meteor magnitudes of +7 and operate in conjunction with the Canadian Meteor Orbit Radar (CMOR). Between 2016 and 2022, more than 91,000 orbits have been measured and fully 11,000 of these orbits are correlated with CMOR radar meteor echoes. A purpose-built detection algorithm was developed for this system (Gural et al., 2021) called “DetectionApp”. It regularly detects and measures astrometry and photometry for hundreds of dual station faint meteors each night. We find that there are a number of different factors that influence the efficiency of our detection software. These include frame-to-frame rate of motion (segment length), total number of segments, position angle of the meteor track in the image, x/y location in the image, shape of light curve, noise characteristics and peak magnitude. To test the performance of DetectionApp, in this talk we present the results of a set of realistic meteor simulations which inject meteors through the entire DetectionApp pipeline. By modeling meteors originating from an all-sky grid of radiants, we select only those meteors which simultaneously pass through the fields of view of the two cameras located at our Elginfield and Tavistock CAMO field locations. More than 10,000 synthetic meteors are injected into both real and simulated star fields. To constrain peak magnitude biases, the injections are run in constant magnitude sets ranging from peak magnitudes of +3 to +9. Time-of-day biases are considered and we test light curve shape biases and the effects of system noise. In total, more than 500,000 meteors were generated to test DetectionApp efficiency; preliminary results of this system-level debiasing investigation will be described.

A Statistical Analysis of Bolides Detected with the GOES Geostationary Lightning Mapper

J. C. Smith, R. Morris, R. Longenbaugh, N. McCurdy, J. Dotson, C. Henze

The Geostationary Lightning Mapper (GLM) instrument onboard the GOES 16 and 17 satellites has been shown to be capable of detecting bolides in the atmosphere. Due to its large, continuous field of view and immediate public data availability, GLM provides a unique opportunity to detect a large variety of bolides, including those in the 0.1 to 3 m diameter range that complements current ground-based bolide detection systems, which are typically sensitive to smaller objects. We have deployed a machine learning based bolide detection and light curve generation pipeline with detections being promptly published on a NASA hosted publicly available website, https://neo-bolide.ndc.nasa.gov. The goal is to generate a large catalog of calibrated bolide light curves to provide an unprecedented data set for three purposes: 1) to inform meteor entry models on how incoming bodies interact with the atmosphere, 2) to infer the pre-entry properties of the impacting bodies and 3) to statistically analyse bolide impact populations across the globe. The pipeline has now been operational for almost 3 years and we have amassed a catalogue of over 3300 bolides. We present a statistical analysis of the bolides detected and how our bolide database can be used to study bolide impacts and how it can aid the planetary defense community.

Reconstructing Meteoroid Trajectories Using Forward Scatter Radio Observations from the BRAMS Network

J. Balis, H. Lamy, M. Anciaux

When meteoroids hit Earth’s atmosphere molecules, a trail of plasma located downstream of the meteoroid is created. This region, composed of free electrons and positively charged ions, is capable of reflecting radio signals. The reflection on the plasma trails is usually assumed to be specular, which means that the radio wave is reflected only at a given point along the meteoroid trajectory. For forward scatter systems, the position of this specular point depends on the trajectory on the one hand, and on the position of both the emitter and the receiver on the other hand. Using non-collocated receivers, one obtains several specular points along the trajectory. The receivers will thus detect the reflected signal at different time instants on a given trajectory. In this work, we introduce a method that aims at reconstructing meteoroid trajectories using only the time differences of the meteor echoes measured at the receivers of a forward scatter radio system. Assuming a constant speed motion, the position (three degrees of freedom) and the three velocity components have to be determined. Two alternative formulations to solve this complex problem through non-linear optimization are compared. The first one is based on the minimization of the bistatic range, while the second looks for the tangent line to several ellipsoids. A Monte-Carlo analysis is performed to highlight the sensitivity of the output trajectory parameters to the input time differences. The application of this method to actual radio observations from the BRAMS (Belgian RAdio Meteor Stations) network is also presented. The post-processing steps allowing to extract meteor echoes from the raw radio signals are described. For comparison about the quality of trajectory reconstruction, data from the optical CAMS-BeNeLux network are used. Promising results showing the reconstructed position, velocity and inclination of several meteoroid trajectories are discussed.

A Comparison of Cloud Coverage Determinations for Fireball Networks

M. Frühauf, D. Koschny, D. Deivasihamani, A. Soneji, Y. Heidegger, T. Huber, J. Vallejo Ortiz

Our team is working on the development of a fireball flux density model by using recordings of the AllSky7 fireball camera network. For achieving this goal, the spatial coverage, the time coverage and percentage of cloud coverage of the system have to be known. In this presentation, we focus on the cloud coverage. We have compared four different techniques, based on external or internal data sources, to determine if a period can be used for data generation or not. The different methods each have advantages and disadvantages. Since the AllSky7 system deletes old recordings, the cloud coverage can not be retrospectively determined by image analysis. External cloud coverage sources often offer historic data, which means fireball observations recorded in the past can be exploited, too. However, time and spatial resolution of external sources can be large, why interpolation is needed. This issue does not appear, if a station produces the cloud coverage by its own recordings. We present the preliminary results of our cloud coverage determination analysis, based on: 1. EUMETSAT Cloud Mask by Meteosat Second Generation (MSG); 2. Hourly weather records of the German Weather Service (DWD); 3. Histogram data generated from AllSky7 camera images; 4. Star detection from AllSky7 camera images.

Order-of-Magnitude Measurement Accuracy Improvement of Meteor Head Echo Range Rate and Deceleration from High-Power Radar Data

T. Hedges, N. Lee, S. Close

On October 10th and 11th, 2019, concurrent high-power large-aperture (HPLA) meteor radar observations were performed at varying latitudes and similar longitudes at Resolute Bay Incoherent Scatter Radar (RISR-N), Jicamarca Radio Observatory (JRO), and MIT Haystack Observatory (MHO), with the goal to study latitudinal variation of properties of the upper atmosphere, and understand how this influences meteoroid entry dynamics. The concurrent observations spanned 8 hours, in addition to 8 hours of non-concurrent observations at RISR-N and JRO separately, with thousands of meteor head echoes observed at each facility. In this work, an inter-pulse phase matching technique for phase-coded pulses is proven to consistently reduce uncertainty in the head echo range rate (velocity component along radar beam) by an order of magnitude versus range rates obtained via a bank of Doppler shifted matched filters. For many meteors, this brings uncertainty down to the order of 10 m/s, but it ultimately depends on the head echo signal strength, consistency and duration. The algorithm depends on removing the 2 pi modulo in the phase change of the matched-filter signal peak between pulses, which can be done very reliably by inspection, and somewhat reliably via an automated procedure. At RISR-N, of a population of 1099 meteors, an automated first-pass algorithm accurately determines the range rate of 72% of the observed meteors, and another 25% are determined via manual adjustment. The resulting range rates are smooth enough that linear or quadratic regressions yield reasonably accurate range decelerations. Future work will utilize decelerations at all three facilities to quantify meteoroid mass and density.

Meteoroid Distribution Model Based on Kernel Density Estimation

M. Baláž, J. Tóth

We present a method for estimating the probability distribution function (PDF) for meteors or meteoroids in an arbitrary parameter space. In the first step a parameter space is devised, for instance the tuple (velocity, absolute magnitude, time) for meteor observations, or the standard set of orbital parameters plus mass for meteoroids. Second, a proper metric (a distance function for any pair of points within the parameter space) is found, a measure of correlations between individual parameters as a function of location is designed and correct bandwidth for every observed data point is determined. Finally we describe and implement a suitable data structure for querying the observation database efficiently. The PDF can be then estimated by the adaptive multivariate kernel density estimation method at any point of the parameter space. Optionally we may reduce the result to a lower number of dimensions. The computed PDF can be sampled to obtain a synthetic meteor data set which approaches the actual distribution of meteors observable in the atmosphere. Other uses include determination of spatial density and flux of meteoroids; predictions of future activity of meteor showers, especially in absence of a known parent body where direct simulation is not applicable; and determination of adherence of meteoroids to particular meteoroid streams.

Bolides, Fireballs and Airbursts: A Multi-Disciplinary Approach

E. A. Silber

Our planet is constantly bombarded with extraterrestrial material, from dust particles to cm-sized meteoroids. While more sizeable objects (meters to tens of meters in diameter), or asteroids, impact less frequently, they can pose a serious hazard. Two aspects are of paramount importance to improve risk assessment: (1) identify and characterize all Near-Earth Objects (NEO) that could pose a threat; and (2) use ground truth and multi-instrumental observations of known (albeit small) events to develop tools necessary to characterize and localize any bolide, and rapidly infer its parameters (e.g., size, velocity, composition). One of technologies utilized to detect bolides and estimate their energy deposition is infrasound monitoring using a global network of sensing stations. Infrasound, or low frequency sound (f<20 Hz), is a resultant of a decayed shockwave generated by a bolide. One of the best-known and well-documented examples is the spectacular superbolide and the subsequent airburst over Chelyabinsk that occurred nearly a decade ago. It provided a sobering realization of destructive potential of such events and highlighted the importance of multifaceted studies aimed at detecting and characterizing NEOs. Because of the shallow entry angle, the shockwave sweeping over the region resulted in significant damage on the ground and caused injuries to local residents. Infrasound records place the energy estimate at ~500 kt of TNT equivalent. Multi-instrument observations coupled with post-impact investigation of the affected area provided a plethora of data that is still garnering interest of the scientific community. The importance of infrasound in bolide detections through representative examples will be discussed. SNL is a multimission laboratory operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration.

The Frequency of Interstellar Bolides

A. P. Jackson, S. J. Desch

The Earth is probably struck regularly by macroscopic (metre-sized) objects from outside the solar system, but the frequency and size distributions of such objects are unknown. Dust detectors on spacecraft, as well as radar and optical detections of micrometeoroids entering Earth’s atmosphere, have demonstrated a flux of small (~10^-6 – 10^-5 m) interstellar particles with mass distribution N(>M) ~ M^-5/6, consistent with a collisional cascade, as well as a distribution N(>M) ~ M^-6/5, for interstellar particles ~10^-5 – 10^-2 m in size. It is difficult to assess whether these represent distinct populations, because of the relatively small range of sizes. The recent discoveries of the interstellar objects (ISOs) 1I/'Oumuamua in 2017 and 2I/Borisov in 2019 permit an examination of whether these trends extend to large (~10^2 m) objects. Constraining their sizes and occurrence rates, we show that these ISOs probably are part of the same population as the ~10^-5 – 10^-2 m interstellar particles. Assuming this trend holds for intermediate sizes, we predict roughly one metre-sized interstellar bolide should strike the Earth every 10-20 years. This would be consistent with the claim by Siraj & Loeb (2019) of one interstellar fireball in the CNEOS database, although that claim cannot be confirmed using CNEOS data. Nevertheless, searches for interstellar fireballs in the size range ~10^-2 – 1 m would be a useful complement to the searches for ISOs by the Vera Rubin Observatory, to further test whether objects from ~10^-5 to 10^2 m in size form a single mass distribution distinct from that of smaller, micron-sized objects.

A Preliminary Comparison of Bolide Measurements by the Geostationary Lightning Mapper (GLM) and US Government Sensors

R. Longenbaugh, P. Brown

Measurements of fireballs produced by meter-sized impactors from ground-based instruments are rare due to the large time-area products required; the global impact rate of such NEOs is only of order once per 10 days (Brown et al., 2002). Detection of large numbers of such impactors thus requires global coverage. Historically, data from US Government sensors (Brown et al., 2016) has provided impact time, location, height of peak brightness and total energy as well as velocities in some cases. However, the accuracy of some of these measurements is uncertain as evidenced by differences in specific cases where ground-based data are also available (Devillepoix et al., 2019). Recently, it has been shown that the GLM sensors onboard GOES-16 and 17 satellites are able to geolocate, provide lightcurves (albeit in a narrow bandpass near 777nm) and, for stereo detections, heights for bolides, (Jenniskens et al, 2018). An outstanding question remains how representative is the narrow bandpass GLM lightcurves to the overall radiation budget of a bolide? Here we make use of the recent release of detailed optical lightcurves from US Government sensors to compare GLM events with USG sensor data. We find that GLM lightcurves generally show the same qualitative global features as USG broadband data, consistent with the conclusion of Jenniskens et al (2018) that most large bolides detected by GLM (which have comparatively low entry speeds) are dominated by continuum emission. We also find good agreement between the peak heights detected by both systems, re-enforcing the conclusions of Brown et al (2016) and Devillepoix et al., (2019) that USG heights are accurate to of order several km or better.

NELIOTA: The Long Term Monitoring Campaign for Lunar Impact Flashes

A. L. Liakos, A. B. Bonanos, E. M. X. Xilouris, D. V. K. Koschny, P. B. Boumis, I. B.-V. Bellas-Velidis, R. M. Moissl, A. M. Maroussis

We present scientific results from the systematic observations of lunar impact flashes of the ESA-funded NELIOTA program. Using the 1.2 m Kryoneri telescope and the fast frame-rate cameras of the system, NELIOTA has recorded over 130 validated lunar impact flashes since the beginning of its operation in early 2017, while other ~55 have been characterized as suspected. We will present results concerning the dimensions, the masses and the appearance frequency of the meteoroids in the vicinity of the Earth. Moreover, statistics for the temperatures of the collisions and the calculation of the meteoroid frequency on various distances from the Earth and the Moon provide for the first time quantitative results for the risk assessment for space and satellite missions as well as for future establishment of lunar bases.

Impact Cratering as a Viable Mechanism for Creating Habitable Environments on Titan

A. P. Crósta, E. A. Silber, R. M. C. Lopes, M. J. Malaska

Among potentially habitable worlds Titan stands out due, being an ocean world, an icy world, an organic world, and with a dense atmosphere. However, habitable environments can only exist under certain specific conditions, as surface temperatures on Titan are too low for allowing habitability. Pre-biotic and biotic lifeforms may have developed in its deep ice and water ocean underneath the ice shell, provided pathways connecting surface materials and subsurface water ocean existed. We examine the role of large impacts on Titan in creating such conditions, as hypervelocity collisions of large bodies may have allowed exchange of materials (organic compounds, water, etc.) between the surface, the near subsurface and the ocean, creating niches for the development of primitive lifeforms. To investigate impact-induced potential exchange pathways we modeled the formation of the largest crater on Titan, Menrva, with a diameter of ca. 425 km, using numerical simulations performed in iSALE-2D shock physics code. The parameters employed included current estimates of Titan’s ice shell’s thickness based on geophysical data. Results indicate that significant deformation and mass movements occur in the center of the crater, before the complete breach of the ice shell, at ca. 6100 s from the moment of impact. This promoted local melting of the ice shell, mixing the organic layer, ice shell and underlying ocean. In such scenario, optimal conditions are met for materials from the ice shell+organics and the water ocean to mix. We conclude that large hypervelocity impacts can have a key role in creating habitable environments or niches on Titan. We argue that a combination of these processes, in an environment containing organic compounds and water, heated to ca. 280 K by the transfer of thermal energy from the impact to the crust, would result in a near-optimal habitable ecosystem. Thus, Menrva crater and its immediate surrounds offer a potentially favorable location for future exploratory missions in search for biosignatures.

Assessing the Consequences of Asteroid and Comet Impacts on the Earth

D. O. Glazachev, O. P. Popova, E. D. Podobnaya, V. V. Shuvalov, N. A. Artemieva, V. V. Svetsov, V. M. Khazins

Impacts of large cosmic bodies on the Earth lead to hazardous effects that can have a harmful effect on humans, animals and plants, and on economic objects. Damage on the ground produced by the shock waves and radiation fluxes are most important dangerous effects. For example, even enough small Chelyabinsk airburst resulted in numerous broken windows, window frames and doors. The thermal radiation can be strong enough to be dangerous to people, to ignite fires and even to melt rocks. The Chixculub crater-forming impact of an asteroid 10–15 km in size generated global wildfires, and the Tunguska event, caused by the entry of an object about 50 m in diameter, generated a forest fire within a radius of 10–15 km. The shock wave is also the cause of seismic effects. The Richter scale magnitude and Mercally scale intensity are used for determination of the instrumental characteristics of a seismic disturbance in the observational point. Atmospheric plume resulting from impact rises to high altitudes (100-300 km) and generate atmospheric disturbances expanding to distances up to thousands of kilometres. For crater-forming impacts, important characteristics are the size of the crater and the parameters of the layer of ejecta from. A serial numerical modeling of the interaction of cosmic objects with the atmosphere has previously been performed for a large number of different scenarios under the hydrodynamic model. Based on these simulation results scaling relations for the most important parameters of the shock wave, radiation, seismic effects and atmospheric disturbances are constructed. Suggested scaling relations are dependent only on the properties of the entering object. Precise impact risk assessment is a significant computational challenge. This motivates the usage of simplified approaches and fast assessment of effects, which can be based on suggested scaling relations. Such calculator have been developed and it is available via internet: http://AsteroidHazard.pro.

The Relevance of Fireball Networks for Planetary Defence

D. Koschny, M. Frühauf

'Planetary Defense' is a term used for the topic of dealing with the possible impact threat of near-Earth asteroids or comets (NEOs). In Europe, the European Space Agency (ESA) is a very active player in this field. It operates their so-called Planetary Defence Office. The European Commission is also funding NEO-related activities, with new activities being managed via ESA's Planetary Defence Office. Both ESA and EC are and will be funding observational activities, which include the observations of fireballs and lunar impact flashes. Here we will address the rationale behind this. Most of the fireballs recorded by existing networks are caused by objects in the cm- to meter-size. Only occasionally, larger objects are observed. This is mainly because of the fact that larger objects occur less frequent. But even some of the objects too small to cause damage on the ground are bright enough to raise the public's awareness. If they trigger fear, or occur over sensitive locations, planetary defence officials should be aware of these events. A second point relates to the flux density of objects in the size range of meters to several tens of meters. The flux density is not very well constrained for two reasons: Telescopic observations can only discover objects in that size range when they are very close to the Earth. Ground-based fireball cameras, on the other hand, only cover a small area in the Earth's atmosphere and therefore don't observe many events in this size range. As a conclusion, fireball networks should expand even more, and data from different networks should be combined to increase number statistics. More work is needed to ensure proper de-biasing of the different systems. This presentation will summarise the current status of flux density measurements in the size range of decimeters to tens of meters, and expand on the points mentioned above.

Impact Plasmas: Probing the Heliosphere Through the Dust that Bombards Spacecraft

A. C. Fletcher, S. Close, C. Crabtree

Cosmic dust grains are pervasive in the solar system and affect both the dynamics of space plasmas and the survivability of human-made spacecraft. Instruments on many scientific missions (such as Voyager, Cassini, and Parker Solar Probe) detect the aftermath of impacts through electromagnetic field measurements. The impact speed is so large (up to 72 km/s near Earth) that spacecraft material is ionized, creating a rapidly expanding plasma. Plasma and other ejecta from impacts alter the surrounding space environment and interact with the spacecraft itself through electrostatic and electromagnetic fluctuations. Impact plasmas offer an opportunity to learn about the tiny building blocks of our solar system and their role in the heliosphere. In this talk, I discuss the physical mechanisms that govern impact plasmas from the theoretical, computational, and experimental perspectives. A complete description requires the solid mechanics of the surface and dust particle, the phase change and ionization in a high-energy density state, the transition between a highly collisional plasma to a collisionless plasma, the interaction with ambient electric and magnetic fields, and the mode conversion from waves within the plasma to free-space electromagnetic waves that propagate to a nearby sensor. The analysis, in combination with ground-based impact experiments, has driven the design of an in situ experiment. Furthermore, Parker Solar Probe has seen an unprecedented amount of peculiar field measurements associated with impacts. One ultimate objective is to use this combination of in situ impact measurements, theory, and simulations to solve the inverse problem: i.e., use field measurements from impacts to determine the mass, velocity, source, and composition of cosmic dust.

Lunar Impact Flashes: Physical Properties of the Impactor and Link to Craters

C. Avdellidou, D. Sheward, E. Munaibari, R. Larson, M. Delbo, A. Cook, J. Vaubaillon, P. Hayne, M. Wieczorek

Observing live the light from the meteoroid impacts on the Moon we are now able to infer the physical properties of the small impactors. Furthermore, by identifying and measuring the respective crater we can inform impact scaling laws as well as we can constrain better the luminous efficiency, which is the fraction of the meteoroids kinetic energy that converts to light upon impact. Lunar surface provides an excellent opportunity to study meteoroid impacts, due to the proximity to Earth and to the lack of atmosphere. In a broader picture, we can consider those impacts are an extension in size and energy scales of the current laboratory impact experiments using light-gas guns, where masses are up to a few grams and velocities limited to around 8 km/s. Our team developed methods to detect in real time the lunar impact flashes in telescope images, to derive the selenographic coordinates of the events and to identify the origin of each meteoroid impactor. Moreover, we have developed through the years methods to measure the temperatures of lunar impact flashes as well as the mass of the meteoroid. We retrieved from the literature the lunar impact flash observations of the last 20 years, and we constructed the peak temperature distribution of those events, when possible, which is in great agreement with the theoretical estimations by previous studies. We also constructed the size distribution of the cm-dm meteoroid impactors and we found that it is very similar to the one derived from the fireball data of the Canadian camera network. In addition, our team developed the PYNAPLE algorithm to identify the fresh craters on the lunar surface using the LRO data and searching around the coordinates of the reported lunar impact flashes. Here we report the first crater detection following this method. PYNAPLE will become a publicly available tool for all the lunar observers.

New Systems for the Observation of Lunar Impact Flashes and the IAA Participation in the ESA CARMEN Project

J. M. Madiedo, J. L. Ortiz, N. Morales, P. Santos-Sanz, F. Organero, L. Ana-Hernández, F. Fonseca

In this work we present the contribution of our team to ESA's CARMEN project, where we focus on the detection and analysis of lunar impact flashes. Our team at the Institute of Astrophysics of Andalusia (IAA-CSIC) has been involved in the observation and analysis of these events since 1997. These impact flashes provide key information about the impact processes taking place when meteoroids hit the Moon, allow us to estimate the flux of interplanetary matter that impacts our planet, and also allow quantifying the impact hazard of asteroids and comets for Earth and the future outposts on the moon. In the framework of CARMEN we employ several telescopes located at two observatories in Spain: La Sagra, and Sevilla. These employ high-sensitivity video cameras to record these events, including CMOS cameras with a maximum frame rate of 168 fps at full resolution (1920x1200 pixels). We also focus here on the development of two new systems that will be used for several goals including the study of lunar impact flashes, which are being deployed at the Calar Alto Observatory (Spain). One of these systems can observe these events simultaneously in three different wavelengths by means of high-frame-rate and high-resolution CMOS cameras. The system is attached to the 1.25 m telescope located at that observatory. The other system is based on a 60-cm light-weight telescope that has been located under a 4-m dome.

Trajectory Estimation for Fresh Impacts on Mars

E. D. Podobnaya, O. P. Popova, D. O. Glazachev

In recent years, more than 700 fresh dated meteoroid impact sites were discovered on Mars, which formed single craters and crater fields with crater sizes up to 50 m. Due to more rarefied Mars atmosphere (in comparison with Earth) falling meteoroids are less destroyed, nevertheless near 50% of meteoroids are fragmented in the Martian atmosphere and are forming crater clusters. The study of craters on Mars allows us to study the fragmentation details that cannot be detected in terrestrial conditions. The scattering ellipses constructed by various methods for crater clusters on Mars are considered. According to them, the azimuth of the meteoroid trajectory and the entry angle are estimated, ellipse size contains information about fragmentation. Our results are in good agreement with previously published results. In the case of oblique impacts, the crater ejecta are distributed asymmetrically and permits to determine the direction of flight. Ejecta distribution and corresponding azimuth are found based on Mars images made by HiRISE cameras for crater clusters. Ejecta-based estimates of azimuth for 42 clusters are compared with azimuths obtained by constructing the scattering ellipses. For azimuths calculated by craters ejecta inclination of meteoroid trajectory projection fits previous results for about 70% of clusters, direction of meteoroid flight fits in about 30% of clusters. Discrepancy between azimuth estimations based on ejecta pattern and on scattering ellipses requires other approaches. Preliminary results of mathematical modeling show that the developing fragmentation model will make it possible to describe clusters and to suggest better methods for estimation of flight direction and impactor properties.

Scaling Relations for Transient Impact Scenario

O. Popova, D. Glazachev, V. Shuvalov, V. Svetsov, E. Podobnaya

The impact of large cosmic objects into the atmosphere is typically considered within one of two scenarios, i.e. airburst or crater-forming. Chelyabinsk/Tunguska and Chicxulub are bright examples of these limiting cases. Hazardous effects of these impact types are often considered separately, the boundary between these two limits is connected with effective airburst altitude, which corresponds to the main energy release. When the estimated effective altitude is approaching the ground, the considerable part of energy still is releasing in the atmosphere thus decreasing the cratering/ejecta effects. Impacts in this impactor size range may be called transient ones. This presentation will suggest an approach to hazardous effects estimates for transient cases of impacts.