Meteor Orbits Research Articles

A generalizable method for estimating meteor shower false positives

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.

Age of Geminids derived from the statistics of meteoroid orbits

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

Recent observations using the Wind and Ulysses spacecrafts and the Solar Occultation For Ice Experiment (SOFIE) during the period between 2007 and 2020 indicate a total cosmic dust influx at Earth ranging from 22 to 32 tonnes per day. Much is still unclear about the formation, evolution, and propagation of this cosmic dust throughout our Solar System, as well as the transport and chemical interaction of such particles within our own atmosphere. Studying meteoroids, which are particles small and fast enough to ablate in the Earth’s upper atmosphere producing meteor plasma detectable by meteor radars, offers an opportunity to better understand these processes. While meteor radars provide a powerful tool to detect meteoroids, they are limited to detecting particles that produce a sufficient amount of plasma within the instrument’s field-of-view, and thus most of their trajectory remains undetected. In this work, we report a novel methodology, using new polarization measurements as well as two state-of-the art models, to determine the pre-atmosphere dynamical characteristics of the detected particles, before they suffer any significant ablation or deceleration. We present the results for 20 meteor detection case studies, and find that for the majority of particles, at least 80% (typically 95%) of the particle mass has already been lost at the time of detection. In addition, while all particles experienced deceleration by the time of detection, this was typically small (≤4% of their initial velocity). Future work will implement this new methodology to automatically determine the initial mass and velocities of individual meteors. This will help provide more precise meteor orbits and characterization of parent source populations, as well as the identification of potential interstellar particles.

On the origin of the Southern Delta Aquariids meteor shower

We determine the begin and end heights of meteors to calculate and compare the median kB parameter (Ceplecha, 1967) of several meteor showers observed throughout 2013. This parameter gives an indication on the type of parent body from which meteor showers originate. We propose that the meteoroids giving rise to the Southern Delta Aquariids consist of high strength material, likely asteroidal, unlike most meteor showers. In particular their parent body could be a C-type asteroid. We discuss the potential candidates in the light of existing literature and conclude that it could be a combination of comet 96P and asteroid 2003 EH1, with a higher relative abundance of the asteroid. The following results are obtained using observations from CILBO, a double station meteor camera set-up in the Canary Islands. Meteors are detected with MetRec, a meteor detection software (Molau, 1999) and the characteristics of their trajectories are computed using the Meteor Orbit and Trajectory Software (Koschny and Rio, 2002).

An observing campaign to search for meteoroids of Bennu at Earth

An observing campaign was conducted in the Southern Hemisphere using low-light video camera triangulation to measure the trajectories and orbits of meteoroids with a possible origin at asteroid Bennu. New CAMS (Camera for Allsky Meteor Surveillance) video camera networks were established in Australia, Chile, and Namibia, and networks in New Zealand and South Africa were expanded. During observing periods in September 2019, 2020, and 2021, we measured 7672, 4936, and 5890 orbits, respectively. Based on the non-detection of predicted meteoroid trail encounters, Bennu's meteoroid production rate was <1.5 kg/s during 1500–1800 CE. Indeed, the current production rate is many orders of magnitude lower. Bennu may have an associated annual meteoroid stream of much older ejecta at a particle flux density of ≤1.3 × 10−6 km−2 h−1, based on seven Bennu-like orbits detected during the first three years of observations.

Space debris spectroscopy: Specular reflections at LEO regime

Space debris, the dysfunctional human-made objects on Low Earth Orbits (LEO), occasionally irradiate bright specular flares or glints which can be detected by a ground-observer. These events are reflections of sunlight from flat, highly reflective surface elements and their spectra represent the ability of the material to reflect sunlight in specific regions of wavelengths. Spectral features then define satellite’s exterior properties, mainly the colour of the surface material. Presented here are the reduction techniques and reflectance spectra of LEO space debris acquired by slit-less spectral cameras AMOS-Spec–HR. Cameras are a part of world-wide distributed network All-sky Meteor Orbit System(AMOS), designed for meteor observation, and operated by the Comenius University in Bratislava. During spectroscopic observations from 2016 to 2021, AMOS-Spec–HR harnessed numerous debris recordings and by data mining of its archives, dozens of spectra of flares and glints were retrieved. According to their properties, reflectance spectra can be organized into distinct categories: Category I – Convex Spectra (includes spectra of solar panels), Category II – Spectra Increasing towards Red Wavelength Region (common for spectra of golden polyimide Kapton foil, the surface material of Multi-Layer Insulation), and Category III – Flat, Straight-lined Spectra (typically includes spectra of aluminium, or other silvery alloys and metals). Defined spectral types were confronted and correlated with laboratory spectra of reflective aerospace materials obtained from literature.

A Meteor Spectroscopic Survey in the Nullarbor

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

High-power large-aperture radars have revolutionized meteor science by allowing highly accurate position and velocity estimates to be made from meteor head echoes. This paper describes a new open-source software, MODA, for determining the heliocentric orbital parameters of these meteoroids. We compare MODA with other current methods, both analytical and numerical. We describe our modeling of third-body perturbations and atmospheric drag, as well as solar radiation pressure, which is not taken into account in other works. We verify MODA against results from the literature and use it to compute the orbits for two small particles observed by ALTAIR in 2008.

Hydrogen emission from meteors and meteorites: mapping traces of H2O molecules and organic compounds in small Solar system bodies

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 &amp;gt; &amp;gt; 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 &amp;lt; 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.

Comet-Asteroid Classification Among Orbits of Sporadic Meteoroids Observed by BRAMON Between 2014 and 2021

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 &amp; 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.

Development of a very faint meteor detection system based on an EMCCD sensor and matched filter processing

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.

МЕТЕОРНА БАЗА ДАНИХ ЗА СПОСТЕРЕЖЕННЯМИ У 2019–2021 роках ІЗ ВИКОРИСТАННЯМ АВТОМАТИЗОВАНОГО ВІДЕОСПЕКТРАЛЬНОГО МЕТЕОРНОГО ПАТРУЛЯ ХАРКІВСЬКОГО НАЦІОНАЛЬНОГО УНІВЕРСИТЕТУ ІМЕНІ В. Н. КАРАЗІНА

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.

Search for possible connections of the h-Virginids meteor shower with near-Earth asteroids

Asteroids and comets are the oldest objects in the Solar System and contain the initial matter that existed at the moment of its formation. By studying those small celestial bodies one may describe the processes taking place at the early stages and conditions of the formation of the Solar System. The study of the genetic relationships (using metrics based on orbital elements) of meteor showers with parent bodies (asteroids and comets) can be used to develop the theory of evolutionary processes that took place at the time of the formation of the solar system. In this work, we have studied the genetic relationships of the small meteor shower of the h-Virginids (HVI) with the near-Earth asteroids of the Apollo group. An author’s multi-factor method is applied, which implies the use of D-criterion by Drummond, metric by Kholshevnikov, Tisserand’s parameter, μ and ν quasi-stationary parameters of the restricted three-body problem, and the analysis of the orbit’s perihelion longitude π. The observational base includes television catalogues meteor orbits that are in the public domain: Meteoroid Orbit Database v2.0 (2010–2012) (CAMS) and the European meteor network EDMOND (2001–2016) catalogues. As a result of this study, the orbit of the h-Virginids (HVI), according to the values of Tisserand’s parameter, was found to be transitional, and thus, it was impossible to identify whether it was of cometary or of asteroid type. Using the author’s method, the asteroids 2001SZ269 and 2014HD19 were distinguished. The 2001SZ269 asteroid was distinguished as a candidate having a possible connection with the h-Virginids’ parent body.

Triple-frequency meteor radar full wave scattering

Context. Radar scattering from meteor trails depends on several poorly constrained quantities, such as electron line density, q, initial trail radius, r0, and ambipolar diffusion coefficient, D. Aims. The goal is to apply a numerical model of full wave backscatter to triple frequency echo measurements to validate theory and constrain estimates of electron radial distribution, initial trail radius, and the ambipolar diffusion coefficient. Methods. A selection of 50 transversely polarized and 50 parallel polarized echoes with complete trajectory information were identified from simultaneous tri-frequency echoes recorded by the Canadian Meteor Orbit Radar. The amplitude-time profile of each echo was fit to our model using three different choices for the radial electron distribution assuming a Gaussian, parabolic-exponential, and 1-by-r2 electron line density model. The observations were manually fit by varying, q, r0, and D per model until all three synthetic echo-amplitude profiles at each frequency matched observation. Results. The Gaussian radial electron distribution was the most successful at fitting echo power profiles, followed by the 1∕r2. We were unable to fit any echoes using a profile where electron density varied from the trail axis as an exponential-parabolic distribution. While fewer than 5% of all examined echoes had self-consistent fits, the estimates of r0 and D as a function of height obtained were broadly similar to earlier studies, though with considerable scatter. Most meteor echoes are found to not be described well by the idealized full wave scattering model.

MALBEC: fine-tuning of the pointing direction of cameras for stratospheric double-station observation of meteor showers

ABSTRACT To guarantee the successful observation of a meteor shower, the ‘Meteor Automated Light Balloon Experimental Camera’ will put two meteor cameras aboard stratospheric nacelles, at altitudes where clouds can no longer hinder the observation. After simulating the 3D trajectory of each nacelle and checking the overall feasibility of double-station meteor observation, the attitude of each camera is set and different configurations are explored. It often happens in meteor sciences that the two cameras are pointing towards each other. However, we show that an azimuth offset sometimes better suits the observation constraints and yields a high number of observed double-station meteors. A roll offset of the camera might be applied in order to maximize the atmosphere area overlap by the two cameras. Similarly, to increase the size of the field of view or to decrease the elevation of the camera, both result in a higher number of detected meteors, as expected. However, this comes with a loss of spatial resolution, which decreases the number of accurate measurements of meteoroid orbits. A satisfactory compromise is to increase the time of flight thanks to ceiling-balloon capabilities. In addition, we find that the current method used to compute the expected number of meteors from a stratospheric platform underestimates this number. More work is needed to understand the link between visual ground-based observations and stratospheric video records.

An Improved Method to Measure Head Echoes Using a Meteor Radar

Abstract We present an improved methodology to obtain absolute position and velocity of meteor head echoes, which can yield orbital information, generally limited to the use of High-Power, Large-Aperture radars, using an advanced-designed specular meteor radar. The observations, which were performed during a period when an outburst of the β-Taurid meteor shower was expected, were performed with the Southern Argentine Agile MEteor Radar. Three different methodologies are utilized to confirm our results: an improved interferometric solver building on previous work, and two different target localization techniques using remote receiving stations. In addition, we performed simultaneous optical observations during the meteor shower period. Overall, 71 radar head echo events were detected and analyzed using interferometry, while 12 of those events have detected signals strong enough to be analyzed using localization methods at the remote sites. Due to poor weather, however, the optical cameras only observed two events simultaneously with the radar. Results from these events are in agreement with the radar results. We find that interferometry methods from both radar and optical data resulted in the most accurate estimation of meteor properties, while target localization techniques derived similar results, albeit with larger uncertainty. We also computed heliocentric meteoroid orbits, and while a fraction was hyperbolic, we believe these to be due to uncertainty. Two events are suspected to be β-Taurid shower members.

Radar observations of the daytime β-Taurids and ζ-Perseids

ABSTRACT We measure the activity, orbital characteristics, and mass index of the strongest daytime Taurid meteor showers (ζ-Perseids and β-Taurids) as observed by the Canadian Meteor Orbit Radar during 2002–2020. This survey recorded ∼2 × 104 stream orbits and more than 4 × 104 single-station events with speed measurements, for meteoroids with masses ${\sim }1 \times 10^{-7}{\, \mathrm{kg}}$ and sizes ${\sim }5 \times 10^{-4}\, \mathrm{m}$. ζ-Perseid activity occurred during the interval 56○ ≤ λ⊙ ≤ 92○ and peaked at λ⊙ = 77.0○, while the β-Taurids were active during the overlapping period 85○ ≤ λ⊙ ≤ 103○ and peaked at λ⊙ = 95.0○. The corrected out-of-atmosphere velocities at these activity peaks were 26.4 and 26.3 km s−1, respectively. The showers display a broad period of activity with an asymmetric profile, with a gradual increase at the beginning and a sharper decrease after the peak. The mass indices of the ζ-Perseids and β-Taurids during their periods of activity were found to be 1.81 ± 0.05 and 1.87 ± 0.05, with the ζ-Perseids reaching a minimum of 1.71 ± 0.05 around the peak of activity.

The Global Meteor Network – Methodology and first results

ABSTRACT The Global Meteor Network (GMN) utilizes highly sensitive low-cost CMOS video cameras which run open-source meteor detection software on Raspberry Pi computers. Currently, over 450 GMN cameras in 30 countries are deployed. The main goal of the network is to provide long-term characterization of the radiants, flux, and size distribution of annual meteor showers and outbursts in the optical meteor mass range. The rapid 24-h publication cycle the orbital data will enhance the public situational awareness of the near-Earth meteoroid environment. The GMN also aims to increase the number of instrumentally observed meteorite falls and the transparency of data reduction methods. A novel astrometry calibration method is presented which allows decoupling of the camera pointing from the distortion, and is used for frequent pointing calibrations through the night. Using wide-field cameras (88° × 48°) with a limiting stellar magnitude of +6.0 ± 0.5 at 25 frames per second, over 220 000 precise meteoroid orbits were collected since 2018 December until 2021 June. The median radiant precision of all computed trajectories is 0.47°, 0.32° for $\sim 20{{\ \rm per\ cent}}$ of meteors which were observed from 4 + stations, a precision sufficient to measure physical dispersions of meteor showers. All non-daytime annual established meteor showers were observed during that time, including five outbursts. An analysis of a meteorite-dropping fireball is presented which showed visible wake, fragmentation details, and several discernible fragments. It had spatial trajectory fit errors of only ∼40 m, which translated into the estimated radiant and velocity errors of 3 arcmin and tens of meters per second.

Meteor showers from known long-period comets

What long-period comets with orbital periods >250 years cause detectable meteor showers on Earth? Low-light video cameras are used to track the motion of +4 to −5 magnitude meteors in our atmosphere by triangulation and calculate the meteoroid orbit in space. In recent years, the CAMS (Cameras for Allsky Meteor Surveillance) low-light video camera network was greatly expanded and, together with other video networks, now has increased the total video meteoroid orbit database to over 2.2 million orbits. Here, we searched this database for meteor showers associated with known long-period comets. Previously, five associations were known. Now, we find 14, as well as six uncertain but likely associations. These showers show a change of longitude of perihelion with node that is a strong function of inclination. Showers of longer duration show a steeper magnitude distribution index, presumably due to aging of the meteoroid population. Showers are generally detected only if the orbital period of the comet is less than 4000 years and the Earth-Comet orbital miss distance is ≤0.10 AU. The lack of an associated meteor shower sets lower limits on the orbital period of poorly observed comets.

Galactic Cosmic Rays, Cosmic-Ray Variations, and Cosmogenic Nuclides in Meteorites

Abstract We present a new generation of model calculations for cosmogenic production rates in various types of solar system bodies. The model is based on the spectra for primary and secondary particles calculated using the INCL++6 code, which is the most reliable and most sophisticated code available for spallation reactions. Thanks to the recent improvements (extending the code to lower and higher energies and considering light charged particles as ejectiles and projectiles), we can for the first time directly consider primary and secondary Galactic α particles. We calculate production rates for 22Na, 10Be, and 26Al in an L-chondrite with a radius of 45 cm and in the Apollo 15 drill core, and we determine the long-term average Galactic cosmic-ray (GCR) spectrum (represented by the solar modulation potential Φ) in the meteoroid orbits at ∼3 au of Φ = 600 MV and at 1 au, i.e., for Earth and Moon of Φ = 660 MV. From this, we calculate a long-term average GCR gradient in the inner solar system of ∼5% au−1. Finally, we discuss the possibility of studying temporal GCR variations and meteoroid orbits using production rate ratios of short- and long-lived radionuclides.