A small fraction of captured meteors shows a peculiar double-peaked light curve. In an attempt to characterise their physical properties, we propose a model of a meteoroid's structure - two concentric layers with their own properties resembling an avocado, hence called 'Avocado model'. Each layer ablates individually and creates its own distinct peak in brightness. We performed atmospheric flight simulations for a small data sample, confronted our approach with models based on differential ablation by other authors. Our findings are in broad agreement with literature, and suggest that solely focusing on changes in ablation is insufficient. Our next step was to include gross-fragmentation into the model. The simulation results show improved accuracy of the fits. One studied case suggests a connection between fragmentation and ablation rate change.

We studied meteors from the eta-Virginid meteor shower that were observed by AMOS all-sky camera network during the increase of activity in the years 2017, 2021 and 2025. Our sample consisted of 28 meteors that could be associated with the eta-Virginid meteoroid stream and their orbital parameters are presented. We describe our modifications to a model of meteoroid erosion previously used by other authors, which was successfully applied to model the luminous trajectory of 19 eta-Virginids. The resulting bulk density was 1672 +/- 587 kg m-3 which clearly indicates that the eta-Virginid stream has asteroidal origin, and the meteoroids possibly have carbonaceous chondritic composition. We also aimed to find members of possible southern branch but we did not conclusively find any even after a broader search.

Recent observations of small bodies of the Solar System showed evidence of the presence of refractory (asteroidal) material in the Oort cloud. Different models of the origin of the Solar System predict different numbers of rocky objects in the Oort cloud, meaning that measurement of this population can be used as an observational constraint for cosmogonic models. The aim of our work is to study how the data obtained from meteor observations can be used as a tool for distinguishing among the existing cosmogonic models. We investigated two meteor databases collected by the cameras of the All-Sky Meteor Orbit System (AMOS) located in the Canary Islands and in Chile. We describe methodology and results of the search for unusually strong rocky meteoroids on cometary orbits with the origin in the Oort cloud. These data will be used to calculate the fluxes of meteors of different compositions in order to constrain the ratio of icy and rocky components of the Oort cloud. For the flux determination, we estimate the observational time and effective area of the AMOS system.

We investigate the dynamical histories of the x-Cygnid and the August Draconid meteoroid streams using numerical N-body simulations. These streams exhibit similar radiants and periods of activity, but possible dynamical connection remains unclear. We map the orbital stability using the MEGNO chaos indicator and perform backward integrations for up to 1000 years, including non-gravitational perturbations. Our results show that the Cygnid-Draconid region contains localized instability islands within the phase space. The August Draconid meteoroids experience a highly chaotic evolution with frequent close encounters with Jupiter, while the x-Cygnids are comparatively less perturbed and concentrate near the 3:2 mean motion resonance with Jupiter. Hypothetical cometary activity simulations reveal that the August Draconids may be observable roughly 88 years after ejection, whereas the x-Cygnids require roughly 174 years. The August Draconids also show a shift in their shower activity to later months. Overall, our results indicate that the x-Cygnids and the August Draconids are unlikely to be dynamically related on the time scales studied.

Systematic and accurate meteor observations allow us to obtain crucial information about the dynamical, physical and compositional properties of small Solar System bodies, which cannot be detected by telescopes. The All-sky Meteor Orbit System (AMOS) global network provides observations of meteors and their spectra, unique both in its global coverage at sites with exceptional sky conditions and its wide scientific scope. Correct reduction of meteor observations from multiple stations is critical for accurate determination of meteor trajectories and heliocentric orbits of meteoroids. We present the procedures used in the AMOS network for meteor detection, astrometry, photometry, trajectory and orbit determination. Using this processing pipeline, we then validate the accuracy of the obtained trajectory and orbital data on a sample of meteor and fireball observations, studied simultaneously by the accurate instruments and procedures of the Czech part of the European Fireball Network. AMOS cover range spans from-12 to +3 magnitude for meteors, best meteor results are obtained in the operation range-4 to +2 magnitude. Special case studies of complex meteor physical and dynamical evaluation are presented.

After their end of operation, the four Cluster-II satellites are re-entering the Earth's atmosphere. The first Cluster-II satellite, named Salsa, re-entered on the 8th of September at 18:46 UTC (2024-09-08T18:46 UTC) over the South Pacific, approximately 2000 km west of Easter Island. An airborne observation team was on station aiming to observe the satellite's break-up. This paper reports the design and execution of the airborne observation under the challenging situation of an entry under plain daylight conditions. The mission planning and preparation in coordination with the observation prediction leads to the flight mission details. Due to the highly eccentric orbit, the entry predictions were particularly challenging and resulted in a wider spread of potential entry corridors. Therefore, based on the very last perigee, only 52 h before the actual entry, and spacecraft data after the maneuver, the team received the last orbit information at 20:30 UTC on the 7th of September (2024-09-07T20:30UTC). Based on this data an appropriate flight path for the aircraft was designed. On board a Falcon 900 business jet, the team deployed six different stations with a total of 26 cameras. All cameras were time-synchronized to the GPS time using a centralized time server. The mission was successful. The infrared cameras detected the entry for approximately 23 s beginning at around 18:47:08 UTC.

Pust & eacute; & Uacute;l'any (PU) is the smallest recovered pedigree fall event meteorite so far and, moreover, was observed during daylight. The results of physical and mineralogical analyses of the new meteorite fall instrumentally observed on June 25, 2022, in the western part of Slovakia are presented. The meteorite fragment of 8.55 g mass was recovered on August 20, 2022, in the strewn field within 100 m of the predicted area of equivalent mass fragments. Mineralogical analyses, computed tomography, physical properties such as bulk and grain densities, as well as magnetic susceptibility were carried out, confirming that PU is an ordinary chondrite of H5 type. Analysis of cosmogenic radionuclides confirmed a fresh fall of the meteorite and helped estimate a pre-atmospheric radius of the meteorite to be 19 +/- 4 cm with a corresponding mass of 98 +/- 24 kg, and a minimum cosmic-ray exposure age of 2-3 Myr.

Meteor spectroscopy presents new opportunities for investigating the diversity of small Solar System bodies and capturing the real distribution of present material types. In this work, we analyzed a sample of 180 higher-resolution meteor spectra from the All-sky Meteor Orbit System (AMOS) network to search for meteoroids with atypical compositions. In addition to several iron bodies, we have identified the first two achondritic meteoroids in our database, both likely meteorite-dropping impactors. We analyzed the two cases in detail using their spectral, dynamical, and physical properties, and compared them with a reference ordinary chondrite meteoroid observed under similar conditions. The spectral analysis revealed atypical features in the two achondrites - strong Mg and Si and low Fe in one case, and strong Ca, Al, and Ti and low Mg in the other. The measured relative elemental abundances imply an aubrite- and a eucrite-like composition. The aubrite-like meteoroid showed an unexpected enhancement in Ca, Mn, and Ti with short-lived intensity spikes not seen in the eucrite-like case, which we interpret as the rapid release of localized inclusions rather than a bulk enrichment. This indicates that transient spectral features can reveal internal heterogeneity in achondritic meteoroids beyond their average composition. The classification of both meteoroids was found to be consistent with the determined dynamical and physical properties. The eucrite meteoroid originated from an orbit affected by the ν6 resonance in the inner main belt, a common delivery mechanism of HowarditeEucrite-Diogenite meteorites, and exhibited ablation behavior corresponding to a compact material with low erosion and an estimated bulk density of ≈3.16 ± 0.10 g cm−3. The aubrite meteoroid originated from a short-period, low-eccentricity orbit similar to some known E-type near-Earth asteroids. Both events also exhibited atypical light curve behavior, but our results indicate that the robust identification of achondritic meteoroids in meteor surveys generally requires emission spectra. This work presents one of the first detailed studies of achondritic meteoroids from meteor observations and aims to provide reference properties of atypical meteors for more efficient identifications of achondrites in future surveys.

To date only very few meteor clusters have been instrumentally recorded. This means that every new detection is an important contribution to the understanding of these phenomena, which are thought to be evidence of the meteoroid fragmentation in the Solar System. On 31 May 2022, at 6:48:55 UT, a cluster consisting of 52 meteors was detected within 8.5 seconds during a predicted outburst of the tau-Herculid meteor shower. The aim of this paper is to reconstruct the atmospheric trajectories of the meteors and use the collected information to deduce the origin of the cluster. The meteors were recorded by two video cameras during an airborne campaign. Due to only the single station observation, their trajectories were estimated under the assumption that they belonged to the meteor shower. The mutual positions of the fragments, together with their photometric masses, was used to model the processes leading to the formation of the cluster. The physical properties of the cluster meteors are very similar to the properties of the tau-Herculids. This finding confirms the assumption of the shower membership used for the computation of atmospheric trajectories. This was the third cluster that we have studied in detail, but the first one where we do not see the mass separation of the particles. The cluster is probably less than 2.5 days old, which is too short for such a complete mass separation. Such an age would imply disintegration due to thermal stress. However, we cannot rule out an age of only a few hours, which would allow for other fragmentation mechanisms.

Increasing space activities, especially in low-Earth orbits (LEO), lead to more orbital debris and night-sky pollution. Spectroscopic analysis of light reflected from artificial space objects can aid to identify dominant surface materials and their reflective properties. Satellites interact with sunlight in diffuse and specular reflections, which can be diffracted, and the visible and near-infrared wavelengths of recorded light analysed. By comparing spectra of aerospace materials measured in a laboratory, material signatures of different material structures can be identified. Hereby presented research will propose methods to identify levels of absorption in different wavelength regions and demonstrate the results on laboratory and observational data. Laboratory measurements were conducted at the Department of Experimental Physics of Comenius University in collaboration with Slovak satellite manufacturer Needronix. Spectra of specular glints of LEO space debris were collected by spectral cameras of All-sky Meteor Orbit System (AMOS), diffuse spectra of various satellites and space debris were observed with 80-cm telescope ZimMain at the Zimmerwald Observatory in Switzerland, and spectrum of 2020SO rocket body observed with 10.4-m Gran Telescopio Canarias (GTC) telescope at Roque de los Muchachos Observatory in La Palma, Spain. Real observational data will be used to assess the reflective properties and correlate them with reflective properties of aerospace materials measured in a laboratory.

We provide an overview of the MetSpec project, which aims to connect meteorite ablation laboratory experiments with meteor spectral observations in the atmosphere aiming at the development of a methodology to identify incoming planetary material distribution into the Earth’s atmosphere. We have selected 28 meteorites of different types to represent known planetary material compositions coming from asteroids, Vesta, Mars and the Moon. Some samples have been tested twice which resulted in overall 31 experiments. Three distinct test campaigns were realized in 2020, 2021 and 2022 with the High Enthalpy Flow Diagnostics Group in the Plasma Wind Tunnel PWK1 where they have developed a unique testing scenario. During the last and most elaborated campaign, 16 cameras observed the artificial meteors in the laboratory. Besides videos and online live streaming, instruments included several spectrometers, and optical and imaging instruments covering UV, visible and IR spectral range. This special collection in Icarus collects the resulting output from the different instruments and results. This overview article provides an introduction and summarizes the main findings of the experimental campaigns.

Emission spectra and diagnostic spectral features of a diverse range of ablated meteorite samples with a known composition are presented. We aim to provide a reference spectral dataset to improve our abilities to classify meteoroid composition types from meteor spectra observations. The data were obtained by ablating meteorite samples in high-enthalpy plasma wind tunnel facilities recreating conditions characteristic of low-speed meteors. Near-UV to visible-range (320-800 nm) emission spectra of 22 diverse meteorites captured by a high-resolution Echelle spectrometer were analyzed to identify the characteristic spectral features of individual meteorite groups. The same dataset captured by a lower-resolution meteor spectrograph was applied to compare the meteorite data with meteor spectra observations. Spectral modeling revealed that the emitting meteorite plasma was characterized by temperatures of 3700-4800 K, similar to the main temperature component of meteors. The studied line intensity variations were found to trace the differences in the original meteorite composition and thus can be used to constrain the individual meteorite classes. We demonstrate that meteorite composition types, including ordinary chondrites, carbonaceous chondrites, various achondrites, stony-iron and iron meteorites, can be spectrally distinguished by measuring relative line intensities of Mg I, Fe I, Na I, Cr I, Mn I, Si I, H I, CN, Ni I, and Li I. Additionally, we confirm the effect of the incomplete evaporation of refractory elements Al, Ti, and Ca, and the presence of minor species Co I, Cu I, and V I.

Optical emission spectra between 522–580 nm of ablating meteorites have been recorded at frame rates as high as 1 kHz for the first time during ground testing with simultaneous spatial and temporal resolution. A novel high frame rate emission spectroscopy arrangement has been developed and employed to diagnose the ablating meteorites in several experimental campaigns. In addition to the identification of species from emission lines detected, the resulting high-speed spectral data were used to study the temporal and spatial evolution of melting droplets and the associated spectral signatures. The time history of radiance from the atomic species emission was used to interpret the fragmentation behavior of various meteorites. Chelyabinsk meteorite exhibit almost constant radiance over time indicating steady droplet detachment whereas Ragland meteorite shows infrequent radiance peaks corresponding to random fragmentation/droplet detachment of varying sizes. A gradual rise in radiance history from iron meteorite Mount Joy shows that it takes finite time for melting and accumulation of droplets.

A set of 28 different meteorites was tested in 32 ablation experiments in the plasma wind tunnel PWK1 at the Institute of Space Systems. All meteorites were exposed to the same flow condition in consecutive experiments. This paper presents the detailed analysis of high-resolution images taken by DSLR cameras during 26 experiments on 22 different meteorites. It is seen that the ablation behavior of the meteorites differs in the way the material melts and flows downstream. While some meteorites appeared more viscous and most material remained connected to the main body, other samples suggest a much lower viscosity as the material was carried downstream and released droplets to the flow. Most droplets of molten material were seen for the two most carbon rich samples from meteorites Murchison and Dhofar 1575. The release of blue colored particles was observed for several meteorites, independent of the viscosity. In contrast to the molten droplets, the blue particles also traveled up to a few millimeters upstream. The abundance of these blue particles is linked to the iron content. Close to no particles or droplets were observed for achondritic samples.

The paper reports the determination of luminous efficiency values from ground testing of a comprehensive set of meteorite samples. The ground testing data is translated with commonly used ground to flight extrapolation analogies from atmospheric entry maneuver's engineering into values of a night observation. This results in a meteor at an altitude of 80 km with a flight speed of 11.7 km/s of a 34.8 mm diameter spherical meteoroid. A method is developed to determine the total luminous efficiency τ in the bands U, B, V, R, and I from the radiance data and the measured mass loss. For the first time, a measurement of luminous efficiency became possible for known materials. The values itself are in the range of 0.01% to ∼ 1%, which is in the range of previous studies from meteor measurements.

We present the orbital evolution of 40 meteorites with known heliocentric orbits, both nominal and their clones as well. The goal of our work was to determine the stability of their orbits and to find possible connections with known near-Earth asteroids. Stability along with a probability of a random association were used to select probable candidates. We have found stable behaviour of orbits for 21 meteorites in the time interval of 100,000 years to the past (e.g. Neuschwanstein, Jesenice). Twelve meteorites displayed different orbital evolution of the nominal orbit and the clones (e.g. Almahata Sitta, Motopi Pan), but in general they were stable. There were seven meteorites on unstable orbits; 3 meteorites exhibited chaotic clone evolutions (Košice, Maribo and Novato) and 4 were on overall unstable orbits (Příbram, Sutter’s Mill, Flensburg and Arpu Kuilpu). This study suggests possible parent bodies from the currently known NEA population for 27 meteorites with very low DSH values and low probabilities of random association.

Spectroscopy of artificial space objects is a method utilised to retrieve the reflectance spectra of satellites, providing valuable information about the surface properties and material composition of objects. However, the reflectance spectrum of an object tends to slightly change over time, in a way that implies the surface shifting to redder colour hues and darkening overall. The causes of this reddening effect are up to this day unknown, although the leading explanation is the deterioration of surface materials due to exposure to the harsh environment of space. Large satellite constellations are ideal for the analysis of this effect. The studied data were obtained by AMOS - All-Sky Meteor Orbit System - developed by the Comenius University in Bratislava, Slovakia. Specular glints of Iridium satellites recorded over the course of six years are analysed to provide further insight into the explanation of the reddening effect.