Recent observations of small Solar System bodies (comets, meteors) showed unexpected evidence of the presence of refractory objects in the Oort cloud. Models of the origin of the Solar System produce different predictions for their population. Therefore, measurements of the rocky population of the Oort cloud can be used as an observational constraint for different cosmogonic models. The aim of this work is to investigate how data obtained from meteor observations can be used as a tool for distinguishing among the existing cosmogonic models. We analyzed two databases collected by cameras of the All-Sky Meteor Orbit System located on the Canary Islands and in Chile. We searched for unusually strong rocky meteoroids (P_E>-4.6) on cometary orbits (T_J<2) with lower mass limits of 10 g and 1 g originating in the Oort cloud. We then calculated fluxes of meteors of different compositions. Asteroidal and cometary meteor fluxes were used to estimate the ratio of icy and rocky components of the Oort cloud, which we compared with predictions of different cosmogonic models. Our results, combined with the results of other authors, showed that ∼5% of the Oort cloud objects with masses larger than 10 g are rocky. Our estimate is closest to the theoretical prediction of the Grand Tack cosmogonic model. The population of rocky objects in the Oort cloud with masses larger than 1 g is ∼11.7%. The development of more precise orbital and material classifications and the improvement of observational techniques and numerical simulations are needed. The best approach is to combine data from different meteor networks and databases.

Sun Close-Encounter model of Long-Period Comet and Meteoroid Orbit Stochastic Evolution

Improving the precision and accuracy of meteor measurements and reliably determining the uncertainties of meteor parameters are two of the main challenges in meteor astronomy research today. These parameters significantly affect the computation of meteoroid orbits, and using erroneous orbits can distort the analysis of the inferred meteoroid population. We aim to provide a tool to estimate the required accuracy of meteor data in order to unambiguously identify each orbit type and evaluate the reliability of database uncertainties, focusing in particular on hyperbolic orbits. This work assists database authors by improving data-reduction processes and database users by simplifying data selection according to accuracy needs. By simultaneously visualising meteor parameters and meteoroid orbits, we assessed uncertainties and their propagation, starting from measurement errors that are provided in meteor databases. In particular, our analysis scheme suggests whether or not a hyperbolic meteor candidate could be considered, at a given significance level, to be of interstellar nature. In order to do so, and for each candidate, we evaluated the extension of its confidence region beyond the parabolic limit on a plot displaying geocentric speed against radiant elongation. The application of the proposed procedures to several meteor and fireball databases revealed the ineffectiveness of a 3σ filtering process in identifying interstellar meteor candidates among the population of hyperbolic meteors. To test whether or not this evidence can be attributed to an underestimation of measurement errors, we developed an estimator, R, quantifying the slope of the relative decrease of the hyperbolic fraction with increasing confidence levels. According to our model, $ R > 1 $ suggests an underestimation of measurement errors. By referring to two recently established networks, we determined $ R = 1.19 ± 0.05 $ for the Fireball Recovery and InterPlanetary Observation Network (FRIPON) and $ R = 3.10 ± 0.02 $ for the Global Meteor Network (GMN). These results suggest a more reliable uncertainty determination for FRIPON, despite the lower precision of its data compared to that of the GMN data. Our results indicate that when analysing individual meteoroid orbits of a database, it is essential to firstly evaluate the entire database, as this provides an independent assessment of the reported accuracy of the orbits. It is commonly observed that the parameter uncertainties reported in meteor databases reflect the measurement precision within data processing, rather than the actual accuracy limits, thus providing less relevant information for users. The proposed name for the tool introduced for this purpose is the Kresáks' diagram, named in honour of the authors of the original representation.

Abstract Accurate identification of meteoroid streams is central to understanding their origins and evolution. However, overlapping clusters and background noise hinder classification, an issue amplified for missions such as the European Space Agency’s Lunar Meteoroid Impact Observer that rely on meteor shower observations to infer lunar meteoroid impact parameters. This study evaluates the performance of the Hierarchical Density-Based Spatial Clustering of Applications with Noise (HDBSCAN) algorithm for unsupervised meteoroid stream identification, comparing its outcomes with the established Cameras for All-Sky Meteor Surveillance (CAMS) look-up table method. We analyze the CAMS Meteoroid Orbit Database v3.0 using three feature vectors: LUTAB (CAMS geocentric parameters), ORBIT (heliocentric orbital elements), and GEO (adapted geocentric parameters). HDBSCAN is applied with varying minimum cluster sizes and two cluster selection methods (eom and leaf). To align HDBSCAN clusters with CAMS classifications, the Hungarian algorithm determines the optimal mapping. Clustering performance is assessed via the Silhouette score, Normalized Mutual Information, and F1 score, with Principal Component Analysis further supporting the analysis. With the GEO vector, HDBSCAN confirms 39 meteoroid streams, 21 strongly aligning with CAMS. The ORBIT vector identifies 30 streams, 13 with high matching scores. Less active showers pose identification challenges. The eom method consistently yields superior performance and agreement with CAMS. Although HDBSCAN requires careful selection of the minimum cluster size, it delivers robust, internally consistent clusters and outperforms the look-up table method in statistical coherence. These results underscore HDBSCAN’s potential as a mathematically consistent alternative for meteoroid stream identification, although further validation is needed to assess physical validity.

Abstract White-light observations from the Wide-Field Imager for Parker Solar Probe (WISPR) instrument on NASA’s Parker Solar Probe recently revealed the presence of a narrow, dense dust trail close to the orbit of asteroid 3200 Phaethon. Although Geminid related, it aligns imperfectly with Phaethon’s orbit and known Geminid meteoroid orbits. To address the nature of this dust trail, we performed a detailed comparison between the WISPR trail observations and several well-developed Geminid models. Simulating these models in the WISPR field of view visually demonstrates that the WISPR trail almost certainly represents the true “density core” of the Geminid stream. Trends in model trail width and offset from Phaethon’s orbit, both as functions of true anomaly, agree with observations to varying extents. All the models, however, place their apparent core interior to the parent orbit due to Poynting–Robertson forces, contradictory to the WISPR trail, which is exterior to Phaethon’s orbit. Therefore, Phaethon’s current orbit likely does not represent the orbit of the system parent, which most probably had a larger semimajor axis. These findings provide new initial conditions for future Geminid models, with WISPR identifying the Geminid core’s position.

Context. As of today, there is no official definition of a meteor cluster. It is usually identified as a large number of meteors sharing a similar radiant and velocity, all occurring within a few seconds. Only eight clusters have been reported so far, from single-camera or camera network observations. However, a cluster may be observed by several distant networks and remain unnoticed simply because each network is recording a small portion of the cluster. Aims. We aim to provide an overview of meteor clusters to help define what constitutes a cluster by potentially adding more to the already identified ones and determining their common parameters. Methods. A search for new clusters was performed in publicly available International Astronomical Union meteor databases with the DBSCAN algorithm. Then, a statistical significance method was applied to derive the most promising cluster candidates. However, the method still lacks a way to debias the atmospheric area surveyed by the cameras due to a lack of publicly available data. Results. A set of 16 statistically significant potential clusters is identified, involving four to seven fragments. The 90th percentile includes a duration of 8 seconds, a velocity difference of 2.2 km/s, and a radiant spread of nearly 4 degrees. The velocity difference may arise from the method used for orbit computation. Conclusions. Meteor clusters might be more frequent than currently reported. However, we recommend that future meteor orbit databases also include a way to estimate the surveyed area by the cameras involved in the detection. This would strengthen the veracity of the 16 identified cluster candidates and ultimately allow scientists to fully debias the number of clusters, and hence derive the physical lifetime expectancy of meteoroids, which is often overlooked due to the focus on collisional lifetime estimates only. We also recommend that any future cluster observation report include the expected number of random occurrences and consider the event to be real if this value is below 0.1.

ABSTRACT Measurement errors of meteors can substantially affect the accuracy of meteoroid trajectory and orbit determinations, potentially leading to spurious meteoroid orbits. Here, we evaluate the measurement errors associated with the meteor and ionospheric irregularity observation system (MIOS) developed at low-latitude Ledong and Sanya, China, aimed at observing various meteors and their associated plasma density irregularity phenomena, and investigate how these errors affect the determination of meteor trajectories and orbits. The measurement error of meteor position is estimated to be $\sim$2 pixels, corresponding to 0.04$^\circ$, which is sufficient to detect true radiant dispersion and structural characteristics in younger meteor showers. By simulating meteoroids from the Draconid, Geminid, and Perseid meteor showers with the $\sim$2 pixels measurement error and the Monte Carlo trajectory method, the precision of corresponding meteoroid trajectories is derived. The radiant accuracy is 1.09$^\circ$, with right ascension and declination accuracies of 0.78$^\circ$ and 0.77$^\circ$, respectively. The velocity accuracy is 0.64 km/s. The comparison of estimated and true radiant uncertainties shows that the estimated errors of the MIOS are generally consistent with the true meteor trajectory errors. Finally, we estimate the orbital measurement errors, which include an eccentricity of 0.05, a perihelion distance of 0.0086 au, an inclination of 1.4$^\circ$, and an argument of the perihelion of 1.86$^\circ$. Based on observations of eight representative meteor showers during 2019–2023, the accuracy of the MIOS in detecting meteor trajectories and orbits is further validated.

Context. The determination of meteor shower or parent body associations is inherently a statistical problem. Traditional methods, primarily the similarity discriminants, have limitations, particularly in handling the increasing volume and complexity of meteoroid orbit data. Aims. We introduce a new more statistically robust and generalizable method for estimating false positive detections in meteor shower identification, leveraging kernel density estimation (KDE). The method is applied to fireball data from the European Fireball Network, a comprehensive photographic fireball observation network established in 1963 for the detailed monitoring and analysis of fireballs across central Europe Methods. Utilizing a dataset of 824 fireballs observed by the European Fireball Network, we applied a multivariate Gaussian kernel within KDE and Z-score data normalization. Our method analyzes the parameter space of meteoroid orbits and geocentric impact characteristics, focusing on four different similarity discriminants: DSH, D′, DH, and DN. Results. The KDE methodology consistently converges toward a true established shower-associated fireball rate within the EFN dataset of 18–25% for all criteria. This indicates that the approach provides a more statistically robust estimate of the shower-associated component. Conclusions. Our findings highlight the potential of KDE combined with appropriate data normalization in enhancing the accuracy and reliability of meteor shower analysis. This method addresses the existing challenges posed by traditional similarity discriminants and offers a versatile solution adaptable to varying datasets and parameters.

ABSTRACT Statistical analysis of samples of the orbits of celestial bodies is complicated by the fact that the Keplerian orbit is a multidimensional object, the coordinate representation of which non-linearly depends on the choice of orbital elements. In this work, using the construction of the Fréchet mean, concepts of mean orbit and dispersion of the orbit family are introduced, consistent with the distance function on the orbit set. The introduced statistical characteristics serve as analogues of sample mean and variance of a one-dimensional random variable. Exact formulas for calculating the elements of mean orbits and dispersion quantities with respect to two metrics on the orbit space are derived. For a large sample of meteoroid orbits from the Geminid stream, numerical simulations of orbit evolution over 20 000 yr in the past were conducted. By analysing the dependency of statistical characteristics on time, estimates for the age of the stream and the gas outflow velocity are obtained under the assumption of the birth of the Geminids due to the rapid destruction of the cometary nucleus. The estimate of the age of the stream lies in the interval from 1200 to 2400 yr, and the speed of gas outflow at perihelion should have been more than 1.2 km s−1.

A novel methodology to estimate pre-atmospheric dynamical conditions of small meteoroids

On the origin of the Southern Delta Aquariids meteor shower

Abstract The ecological well-being of the Earth is closely connected with the prevention of asteroid-comet-meteoroid hazard. Asteroids and comets are the parent bodies of many meteoroids. Meteoroids, which are observed as meteors in the Earth’s atmosphere, always collide with the Earth. This means that the orbits of such meteoroids can be a signal for the detection of potentially dangerous larger bodies in such orbits. At the same time, the dynamics of the complex of meteoroid orbits has a complex intricate character. Meteor science is also engaged in unraveling the patterns of orbital paths and paths of interplanetary bodies potentially dangerous for life on Earth. A separate section of meteor science is associated with the chemistry of the influx of meteoric matter. The report is devoted to the analysis of the above problems, as well as related issues, using open databases of meteor data and others, with an emphasis on radio data.

An observing campaign to search for meteoroids of Bennu at Earth

Space debris spectroscopy: Specular reflections at LEO regime

We report the start of science operations of a meteor spectroscopic survey in the Nullarbor region, Western Australia. The observation program consists of well-proven observatories developed as part of the All-Sky Meteor Orbit System (AMOS) project. These comprise high-sensitivity all-sky imaging units, as well as spectroscopic instruments observing brighter meteors. They are co-located with Desert Fireball Network (DFN) instruments, which themselves provide high-resolution astrometry for fireballs. There are two goals for this program. One is to keep a constant watch on meteor activity by always having one AMOS sub-network in the dark. The second is to provide spectroscopic coverage for recovered meteorites by the DFN, establishing essential calibration points between meteoritic samples and fireball spectra.

Meteoroid orbit determination from HPLA radar data

ABSTRACT The hydrogen emission from meteors is assumed to originate mainly from the meteoroid composition, making it a potential tracer of H2O molecules and organic compounds. H α line was previously detected in individual fireballs, but its variation in a larger meteor data set and dependence on the dynamical origin and physical properties have not yet been studied. Here, we investigate the relative intensity of H α within 304 meteor spectra observed by the AMOS (All-sky Meteor Orbit System) network. We demonstrate that H α emission is favoured in faster meteors (vi > > 30 km s−1) which form the high-temperature spectral component. H α was found to be a characteristic spectral feature of cometary meteoroids with ∼92 per cent of all meteoroids with detected H α originating from Halley-type and long-period orbits. Our results suggest that hydrogen is being depleted from meteoroids with lower perihelion distances (q < 0.4 au). No asteroidal meteoroids with detected H emission were found. However, using spectral data from simulated ablation of different meteorite types, we show that H emission from asteroidal materials can occur, and apparently correlates with their water and organic matter content. Strongest H emission was detected from carbonaceous chondrites (CM and CV) and achondrites (ureilite and aubrite), while it was lacking in most ordinary chondrites. The detection of H α in asteroidal meteoroids could be used to identify meteoroids of carbonaceous or achondritic composition. Overall, our results suggest that H α emission correlates with the emission of other volatiles (Na and CN) and presents a suitable tracer of water and organic matter in meteoroids.

Abstract The Brazilian Meteor Observation Network (BRAMON) is a TV meteor detection network that has been implemented in Brazil since 2014. The BRAMON data made it possible to determine the high-quality orbits of 630 sporadic meteors observed between 2014 and 2021. Using criteria from Jopek & Williams, we assign each of these meteors an asteroidal or cometary origin. Cometary type orbits correspond to slightly more than 60% of sporadic meteors of our sample, a similar percentage to that obtained from other meteor surveys when considering the same magnitude range.

The mass ranges of meteors, imaged by electro-optical (EO) cameras and backscatter radar receivers, for the most part do not overlap. Typical EO systems detect meteoroid masses down to 10− 5 kg or roughly magnitude + 2 meteors when using moderate field of view optics, un-intensified optical components, and meteor entry velocities around 45 km/sec. This is near the high end of the mass range of typical meteor radar observations. Having the same mass meteor measured by different sensor wavelength bands would be a benefit in terms of calibrating mass estimations for both EO and radar. To that end, the University of Western Ontario (UWO) has acquired and deployed a very low light imaging system based on an electron-multiplying CCD camera technology. This embeds a very low noise, per pixel intensifier chip in a cooled camera setup with various options for frame rate, region of interest and binning. The EO system of optics and sensor was optimally configured to collect 32 frames per second in a square field of view 14.7 degrees on a side, achieving a single-frame stellar limiting magnitude of mG = + 10.5. The system typically observes meteors of + 6.5. Given this hardware configuration, we successfully met the challenges associated with the development of robust image processing algorithms, resulting in a new end-to-end processing pipeline now in operation since 2017. A key development in this pipeline has been the first true application of matched filter processing to process the faintest meteors possible in the EMCCD system while also yielding high quality automated metric measurements of meteor focal plane positions. With pairs of EMCCD systems deployed at two sites, triangulation and high accuracy orbits are one of the many products being generated by this system. These measurements will be coupled to observations from the Canadian Meteor Orbit Radar (CMOR) used for meteor plasma characterization and the Canadian Automated Meteor Observatory (CAMO) high resolution mirror tracking system.

The Database of positional and spectral observations of meteors in 2019–2021 using the automatical video and spectral meteor patrol of the Institute of Astronomy of V. N. Karazin Kharkiv National University has analyzed. The kinematic parameters and elements of the heliocentric orbits of meteoroids were calculated using the methods of meteor astronomy according to the Observation Database. This work describes the methods of processing of spectral video observations. The software “AVSMP_Pro v1” for meteor spectra analysis has been created that allows to generate synthetic spectra and compare them with observed meteor spectra. The data from the NIST ASD electronic database (https://physics.nist.gov/PhysRefData/ASD/lines_form.html) is used for obtaining the composition of chemical elements in the meteoroid. As a result, we obtain an information about the relative quantitative chemical composition of meteoroids and the physical conditions of meteor plasma formation.