The orbit,atmospheric dynamics,and initial mass of the Park Forest meteorite

Abstract— The fireball accompanying the Park Forest meteorite fall (L5) was recorded by ground‐based videographers, satellite systems, infrasound, seismic, and acoustic instruments. This meteorite shower produced at least 18 kg of recovered fragments on the ground (Simon et al. 2004). By combining the satellite trajectory solution with precise ground‐based video recording from a single site, we have measured the original entry velocity for the meteoroid to be 19.5 ± 0.3 km/s. The earliest video recording of the fireball was made near the altitude of 82 km. The slope of the trajectory was 29° from the vertical, with a radiant azimuth (astronomical) of 21° and a terminal height measured by infrared satellite systems of 18 km. The meteoroid's orbit has a relatively large semi‐major axis of 2.53 ± 0.19 AU, large aphelion of 4.26 ± 0.38 AU, and low inclination. The fireball reached a peak absolute visual magnitude of ?22, with three major framentation episodes at the altitudes of 37, 29, and 22 km. Acoustic recordings of the fireball airwave suggest that fragmentation was a dominant process in production of sound and that some major fragments from the fireball remained supersonic to heights as low as ?10 km. Seismic and acoustic recordings show evidence of fragmentation at 42, 36, 29, and 17 km. Examination of implied energies/initial masses from all techniques (satellite optical, infrasound, seismic, modeling) leads us to conclude that the most probable initial mass was (11 ± 3) × 10³ kg, corresponding to an original energy of ?0.5 kt TNT (2.1 times 10¹² J) and a diameter of 1.8 m. These values correspond to an integral bolometric efficiency of 7 ± 2%. Early fragmentation ram pressures of <1 MPa and major fragmentations occurring with ram pressures of 2–5 MPa suggest that meter‐class stony near‐Earth asteroids (NEAs) have tensile strengths more than an order of magnitude lower than have been measured for ordinary chondrites. One implication of this observation is that the rotation period for small, fast‐rotating NEAs is likely to be >30 seconds.     

The Villalbeto de la Peña meteorite fall: I. Fireball energy,meteorite recovery,strewn field,and petrography

Abstract— An impressive daylight fireball was observed from Spain, Portugal, and the south of France at 16h46m45s UTC on January 4, 2004. The meteoroid penetrated into the atmosphere, generating shock waves that reached the ground and produced audible booms. The associated airwave was recorded at a seismic station located 90 km north of the fireball trajectory in Spain, and at an infrasound station in France located 750 km north‐east of the fireball. The absolute magnitude of the bolide has been determined to be ?18 ± 1 from a casual video record. The energy released in the atmosphere determined from photometric, seismic, and infrasound data was about 0.02 kilotons (kt). A massive fragmentation occurred at a height of 28 ± 0.2 km, resulting in a meteorite strewn field of 20 × 6 km. The first meteorite specimen was found on January 11, 2004, near the village of Villalbeto de la Peña, in northern Palencia (Spain). To date, about 4.6 kg of meteorite mass have been recovered during several recovery campaigns. The meteorite is a moderately shocked (S4) L6 ordinary chondrite with a cosmic‐ray‐exposure age of 48 ± 5 Ma. Radioisotope analysis shows that the original body had a mass of 760 ± 150 kg, which is in agreement with the estimated mass obtained from photometric and seismic measurements.     

The Hamburg meteorite fall: Fireball trajectory,orbit, and dynamics

The Hamburg (H4) meteorite fell on 17 January 2018 at 01:08 UT approximately 10 km north of Ann Arbor, Michigan. More than two dozen fragments totaling under 1 kg were recovered, primarily from frozen lake surfaces. The fireball initial velocity was 15.83 ± 0.05 km s^?1, based on four independent records showing the fireball above 50 km altitude. The radiant had a zenith angle of 66.14 ± 0.29° and an azimuth of 121.56 ± 1.2°. The resulting low inclination (<1°) Apollo‐type orbit has a large aphelion distance and Tisserand value relative to Jupiter (T_j) of ~3. Two major flares dominate the energy deposition profile, centered at 24.1 and 21.7 km altitude, respectively, under dynamic pressures of 5–7 MPa. The Geostationary Lightning Mapper on the Geostationary Operational Environmental Satellite‐16 also detected the two main flares and their relative timing and peak flux agree with the video‐derived brightness profile. Our preferred total energy for the Hamburg fireball is 2–7 T TNT (8.4–28 × 10⁹ J), which corresponds to a likely initial mass in the range of 60–225 kg or diameter between 0.3 and 0.5 m. Based on the model of Granvik et al. (2018), the meteorite originated in an escape route from the mid to outer asteroid belt. Hamburg is the 14th known H chondrite with an instrumentally derived preatmospheric orbit, half of which have small (<5°) inclinations making connection with (6) Hebe problematic. A definitive parent body consistent with all 14 known H chondrite orbits remains elusive.     

The Villalbeto de la Peña meteorite fall: II. Determination of atmospheric trajectory and orbit

Abstract— The L6 ordinary chondrite Villalbeto de la Peña fall occurred on January 4, 2004, at 16: 46: 45 ± 2 s UTC. The related daylight fireball was witnessed by thousands of people from Spain, Portugal, and southern France, and was also photographed and videotaped from different locations of León and Palencia provinces in Spain. From accurate astrometric calibrations of these records, we have determined the atmospheric trajectory of the meteoroid. The initial fireball velocity, calculated from measurements of 86 video frames, was 16.9 ± 0.4 km/s. The slope of the trajectory was 29.0 ± 0.6° to the horizontal, the recorded velocity during the main fragmentation at a height of 27.9 ± 0.4 km was 14.2 ± 0.2 km/s, and the fireball terminal height was 22.2 ± 0.2 km. The heliocentric orbit of the meteoroid resided in the ecliptic plane (i = 0.0 ± 0.2°), having a perihelion distance of 0.860 ± 0.007 AU and a semimajor axis of 2.3 ± 0.2 AU. Therefore, the meteorite progenitor body came from the Main Belt, like all previous determined meteorite orbits. The Villalbeto de la Peña fireball analysis has provided the ninth known orbit of a meteorite in the solar system.     

The Tajikistan superbolide of July 23, 2008. I. Trajectory,orbit, and preliminary fall data

The results of the atmospheric trajectory, radiant, heliocentric orbit, and preliminary strewn field calculations for an extremely bright slow‐moving fireball are presented. In the evening hours of July 23, 2008, a bright object entered Earth's atmosphere over Tajikistan. The fireball had a ?20.3 maximum absolute magnitude and a spectacularly long persistent dust trail remained visible over a widespread region of Tajikistan for about 28 minutes after sunset. The fireball was also recorded by a visible‐light satellite system at 14 h 45 min 25 s UT, and the dust trail was imaged by video and photocameras. A unique aspect of this event is that it was detected by two infrasound and five seismic stations too. The bolide was first recorded at a height of 38.2 km, reached its maximum brightness at a height of 35.0 km, and finished at a height of 19.6 km. The first breakup occurred under an aerodynamic pressure of approximately 1.6 MPa, similar to the values derived for breakups of the scarcely reported meteorite‐dropping bolides. The fireball's trajectory and dynamic results suggest that meteorite survival is likely. The meteoroid followed an Apollo‐like asteroid orbit comparable to those derived for previously recovered meteorites with accurately known orbits.     

The Berduc L6 chondrite fall: Meteorite characterization,trajectory, and orbital elements

Abstract– The fall of the Berduc meteorite took place on April 7, 2008, at 01 h 02 min 28 s ± 1 s UTC. A daylight fireball was witnessed by hundreds of people from Argentina and Uruguay, and also recorded by an infrasound array in Paraguay. From the available data, the fireball trajectory and radiant have been reconstructed with moderate accuracy. The modeled trajectory was tested to fit the infrasound and strewn field data. From the computed apparent radiant α = 87 ± 2° and δ = ?11 ± 2° and taking into account a range of plausible initial velocities, we obtained a range of orbital solutions. All of them suggest that the progenitor meteoroid originated from the main asteroid belt and followed an orbit of low inclination. Based on petrography, mineral chemistry, magnetic susceptibility, and bulk chemistry, the Berduc meteorite is classified as an L6 ordinary chondrite.     

Orbit and origin of the LL7 chondrite Dishchii'bikoh (Arizona)

The trajectory and orbit of the LL7 ordinary chondrite Dishchii'bikoh are derived from low‐light video observations of a fireball first detected at 10:56:26 UTC on June 2, 2016. Results show a relatively steep ~21° inclined orbit and a short 1.13 AU semimajor axis. Following entry in Earth's atmosphere, the meteor luminosity oscillated corresponding to a meteoroid spin rate of 2.28 ± 0.02 rotations per second. A large fragment broke off at 44 km altitude. Further down, mass was lost to dust during flares at altitudes of 34, 29, and 25 km. Surviving meteorites were detected by Doppler weather radar and several small 0.9–29 g meteorites were recovered under the radar reflection footprint. Based on cosmogenic radionuclides and ground‐based radiometric observations, the Dishchii'bikoh meteoroid was 80 ± 20 cm in diameter assuming the density was 3.5 g/cm³. The meteoroid's collisional history confirms that the unusual petrologic class of LL7 does not require a different parent body than three previously observed LL chondrite falls. Dishchii'bikoh was ejected 11 Ma ago from parent body material that has a 4471 ± 6 Ma U‐Pb age, the same as that of Chelyabinsk (4452 ± 21 Ma). The distribution of the four known pre‐impact LL chondrite orbits is best matched by dynamical modeling if the source of LL chondrites is in the inner asteroid belt in a low inclined orbit, with the highly inclined Dishchii'bikoh being the result of interactions with Earth before impacting.     

The fall of the St-Robert meteorite

Abstract The St-Robert (Québec, Canada) meteorite shower occurred on 1994 June 15 at 0h02m UT accompanied by detonations audible for >200 km from the fireball endpoint. The fireball was recorded by visual observers in Vermont, New York State, New Hampshire, Québec and Ontario as well as by optical and infrared sensors in Earth-orbit. Penetration to an altitude of 36 km occurred ～60 km to the northeast of Montreal, where the bolide experienced several episodes of fragmentation. A total of 20 fragments of this H5 chondrite, comprising a total mass of 25.4 kg, were recovered in an ellipse measuring 8 × 3.5 km. One fragment of the shower partially penetrated the aluminum roof of a shed. Interpretation of the visual and satellite data suggests that the fireball traveled from south-southwest to north-northeast, with a slope from the horizontal of 55°–61°. A statistical evaluation of the likely heliocentric orbits for the body prior to collision with the Earth, coupled with theoretical modeling of the entry, suggests an entry velocity in the range of 12.7–13.3 km/s; the meteoroid had moved in a low-inclination orbit, with orbital perihelion located extremely close to the Earth's orbit. From satellite optical data, it is found that the photometric mass consumed during the largest detonation is ～1200 kg. Estimation of the amplitude of the acoustic signal detected by the most distant observer yields a source energy near 0.5 kt TNT equivalent energy, which corresponds to a mass of order 10 metric tonnes. This measure is uncertain to approximately one order of magnitude. Theoretical modeling of the entry of the object suggests a mass near 1600 kg. Cosmogenic radionuclide activities constrain the lower initial mass to be ～700 kg with an upper limit near 4000 kg. Seismic data possibly associated with the fireball suggest extremely poor coupling between the airwave and the ground. The total mass estimated to have reached the ground is ～100 kg (in material comprising >55 g fragments), while the preatmospheric mass is found to be most probably in the range of 1200–2000 kg.     

The Morávka meteorite fall: 1. Description of the events and determination of the fireball trajectory and orbit from video records

Abstract— The Morávka (Czech Republic) meteorite fall occurred on May 6, 2000, 11:52 UT, during the daytime. Six H5–6 ordinary chondrites with a total mass of 1.4 kg were recovered. The corresponding fireball was witnessed by thousands of people and also videotaped by 3 casual witnesses. Sonic booms were recorded by 16 seismic stations in the Czech Republic and Poland and by one infrasonic station in Germany. A total of 2.5% of the fireball eyewitnesses reported electrophonic sounds. Satellites in Earth orbit detected part of the fireball light curve. In this first paper from a series of 4 papers devoted to the Morávka meteorite fall, we describe the circumstances of the fall and determine the fireball trajectory and orbit from calibrated video records. Morávka becomes one of only 6 meteorites with a known orbit. The slope of the trajectory was 20.4° to the horizontal, the initial velocity was 22.5 km/s, and the terminal height of the fireball was 21 km. The semimajor axis of the orbit was 1.85 AU, the perihelion distance was 0.982 AU, and the inclination was 32.2°. The fireball reached an absolute visual magnitude of ?20 at a height of 33 km.     

The Morávka meteorite fall: 3. Meteoroid initial size,history, structure,and composition

Abstract— The properties and history of the parent meteoroid of the Morávka H5–6 ordinary chondrites have been studied by a combination of various methods. The pre‐atmospheric mass of the meteoroid was computed from fireball radiation, infrasound, seismic signal, and the content of noble gases in the meteorites. All methods gave consistent results. The best estimate of the pre‐atmospheric mass is 1500 ± 500 kg. The fireball integral bolometric luminous efficiency was 9%, and the acoustic efficiency was 0.14%. The meteoroid cosmic ray exposure age was determined to be (6.7 ± 1.0) × 10⁶ yr. The meteorite shows a clear deficit of helium, both ³He and ⁴He. This deficit can be explained by solar heating. Numerical backward integration of the meteoroid orbit (determined in a previous paper from video records of the fireball) shows that the perihelion distance was probably lower than 0.5 AU and possibly as low as 0.1 AU 5 Ma ago. The collision which excavated Morávka probably occurred while the parent body was on a near‐Earth orbit, as opposed to being confined entirely to the main asteroid belt. An overview of meteorite macroscopic properties, petrology, mineralogy, and chemical composition is given. The meteorites show all mineralogical features of H chondrites. The shock level is S2. Minor deviations from other H chondrites in abundances of trace elements La, Ce, Cs, and Rb were found. The ablation crust is enriched with siderophile elements.     

The instrumentally recorded fall of the Križevci meteorite,Croatia, February 4, 2011

The Kri?evci H6 meteorite was recovered on the basis of fireball data obtained by the cameras of the Croatian Meteor Network. The fireball, which occurred on February 4, 2011, 23:20:40 UT, was also observed by meteor cameras in Slovenia and by the Autonomous Fireball Observatory in Martinsberg, Austria, which belongs to the European Fireball Network. Here, we present detailed data on fireball trajectory, velocity, deceleration, light curve, and orbit. We also modeled the atmospheric fragmentation of the meteoroid on the basis of the light curve and deceleration. The initial mass of the meteoroid was between 25–100 kg, most probably about 50 kg. Severe fragmentation occurred at heights of approximately 60 and 31 km, under dynamic pressures of 0.1 and 3 MPa, respectively. The peak absolute magnitude of ?13.7 was reached during the second severe fragmentation event. The recovered 291 g meteorite was probably the only fragment with a terminal mass exceeding 100 g. The orbit had a low inclination of 0.6 degrees, perihelion distance 0.74 AU, and semimajor axis 1.54 AU. Kri?evci can be ranked among the 10 best documented meteorite falls.     

The Morávka meteorite fall: 4. Meteoroid dynamics and fragmentation in the atmosphere

Abstract— Detailed analysis of the fragmentation of the Morávka meteoroid during the atmospheric entry is presented. The analysis is based on the measurement of trajectories and decelerations of fragments seen in a video and at the locations of energetic fragmentation events from seismic data obtained at several stations in the vicinity of the fireball trajectory. About 100 individual fragments are seen on video frames. Significant deceleration of the fireball at heights of ?45 km revealed that the meteoroid had already fragmented into ?10 pieces with masses of 100–200 kg, though the fireball still appeared as a single object. At heights of 37–29 km, all primary fragments broke‐up again under dynamic pressures up to 5 MPa. The cascade fragmentation then continued, even though smaller pieces breaking off from the larger masses were increasingly decelerated and the dynamic pressure acting upon them decreased. At each fragmentation, a significant part of the mass was lost in the form of dust or tiny particles. This was the dominant process of mass loss. The continuous ablation due to melting and evaporation of the meteoroid surface was less efficient with a corresponding ablation coefficient of only 0.003 s² km‐². During fragmentation, some pieces achieved lateral velocities up to 300 m/s, about an order of magnitude more than can be explained by aerodynamic loading. The fragmentation continued even after ablation ceased, as demonstrated by the incomplete fusion crust covering all recovered fragments. We estimate that several hundreds of meteorites of a total mass of ?100 kg landed, mostly in a mountainous area not suitable for systematic meteorite searches. Six meteorites with a total mass of 1.4 kg were recovered up to the end of May 2003. Their positions are consistent with the calculated strewn field.     

Analysis of instrumental observations of the Jesenice meteorite fall on April 9, 2009

Abstract– We report an analysis of instrumental observations of a very bright fireball which terminated with a meteorite fall near the town of Jesenice in Slovenia on April 9, 2009, at 0h59m46s UT. The fireball designated EN090409 was recorded photographically and photoelectrically by two southern stations of the Czech part of the European Fireball Network (EN). Simultaneously, a part of the luminous trajectory was also captured by two all‐sky CCD systems and one video camera of the Slovenian meteor network. In addition to these optical recordings, the sonic booms produced by the Jesenice fireball were detected at 16 seismic stations located within 150 km of the trajectory. From all these records, we reconstructed the fireball’s atmospheric trajectory, basic geophysical data, the possible impact area, and the original heliocentric orbit of the meteoroid. Using a detailed fireball light curve, we modeled the atmospheric fragmentation of the meteoroid. Both the atmospheric behavior and the heliocentric orbit proved to be quite normal in comparison with other observed meteorite falls. The Jesenice orbit is markedly different from the P?íbram and Neuschwanstein orbital meteorite pair, which fell on similar dates (April 7, 1959, and April 6, 2002, respectively). Three meteorites with a total weight of 3.6 kg (until April 2010) were found in a high mountain area near the town of Jesenice. They are classified as L6 ordinary chondrites ( Bischoff et al. 2010 ).     

The Morávka meteorite fall: 2. Interpretation of infrasonic and seismic data

Abstract— The sound production from the Morávka fireball has been examined in detail making use of infrasound and seismic data. A detailed analysis of the production and propagation of sonic waves during the atmospheric entry of the Morávka meteoroid demonstrates that the acoustic energy was produced both by the hypersonic flight of the meteoroid (producing a cylindrical blast wave) and by individual fragmentation events of the meteoroid, which acted as small explosions (producing quasispherical shock waves). The deviation of the ray normals for the fragmentation events was found to be as much as 30° beyond that expected from a purely cylindrical line source blast. The main fragmentation of the bolide was confined to heights above 30 km with a possible maximum in acoustic energy production near 38 km. Seismic stations recorded both the direct arrival of the airwaves (the strongest signal) as well as air‐coupled P‐waves and Rayleigh waves (earlier signals). In addition, deep underground stations detected the seismic signature of the fireball. The seismic data alone permit reconstruction of the fireball trajectory to a precision on the order of a few degrees. The velocity of the meteoroid is much less well‐determined by these seismic data. The more distant infrasonic station detected 3 distinct signals from the fireball, identified as a thermospheric return, a stratospheric return, and an unusual mode propagating through the stratosphere horizontally and then leaking to the receiver.     

An entry model for the Tagish Lake fireball using seismic,satellite and infrasound records

Abstract— We present instrumental observations of the Tagish Lake fireball and interpret the observed characteristics in the context of two different models of ablation. From these models we estimate the pre‐atmospheric mass of the Tagish Lake meteoroid to be ?56 tonnes and its porosity to be between 37 and 58%, with the lowest part of this range most probable. These models further suggest that some 1300 kg of gram‐sized or larger Tagish Lake material survived ablation to reach the Earth's surface, representing an ablation loss of 97% for the fireball. Satellite recordings of the Tagish Lake fireball indicate that 1.1 times 10¹² J of optical energy were emitted by the fireball during the last 4 s of its flight. The fraction of the total kinetic energy converted to light in the satellite pass band is found to be 16%. Infrasonic observations of the airwave associated with the fireball establish a total energy for the event of 1.66 ± 0.70 kT TNT equivalent energy. The fraction of this total energy converted to acoustic signal energy is found to be between 0.10 and 0.23%. Examination of the seismic recordings of the airwave from Tagish Lake have established that the acoustic energy near the sub‐terminal point is converted to seismic body waves in the upper‐most portion of the Earth's crust. The acoustic energy to seismic energy coupling efficiency is found to be near 10^?6 for the Tagish Lake fireball. The resulting energy estimate is near 1.7 kT, corresponding to a meteoroid 4 m in diameter. The seismic record indicates extensive, nearly continuous fragmentation of the body over the height intervals from 50 to 32 km. Seismic and infrasound energy estimates are in close agreement with the pre‐atmospheric mass of 56 tonnes established from the modeling. The observed flight characteristics of the Tagish Lake fireball indicate that the bulk compressive strength of the pre‐atmospheric Tagish Lake meteoroid was near 0.25 MPa, while the material compressive strength (most appropriate to the recovered meteorites) was closer to 0.7 MPa. These are much lower than values found for fireballs of ordinary chondritic composition. The behavior of the Tagish Lake fireball suggests that it represents the lowest end of the strength spectrum of carbonaceous chondrites or the high end of cometary meteoroids. The bulk density and porosity results for the Tagish Lake meteoroid suggest that the low bulk densities measured for some small primitive bodies in the solar system may reflect physical structure dominated by microporosity rather than macroporosity and rubble‐pile assemblages.     

Fragmentation model analysis of the observed atmospheric trajectory of the Tagish Lake fireball

Abstract— A recently published meteoroid fragmentation model (FM) was applied to observational data on the Tagish Lake meteoric fireball. An initial mass of 56,000 kg, derived from seismic and infrasound data by Brown et al. (2002), proved to be consistent with a very low value of intrinsic ablation coefficient of 0.0009 s² km^?2. The average residual of the best fit to the observed light curve was ±0.10 stellar magnitude. The apparent ablation coefficient varied from 0.0009 to 1.52 s² km^?2 with an average value of 0.054 s² km^?2 (determined by the gross fragmentation [GF] model). The FM found 33 individual fragmentation events during the penetration of the 56,000 kg initial mass of the Tagish Lake meteoroid through the atmosphere, with five of the events fragmenting more than 10% of the instantaneous mass of the main body. The largest event fragmented 88% of the mass of the main body at a height of 34.4 km. The velocity of the main body mass of 2660 kg at a height of 29.2 km (the last observed light) was 13.1 km/s. Strong fragmentation at heights lower than 29.2 km is very probable. The extreme fragmentation process of the Tagish Lake meteoroid puts its classification well outside the IIIB type in the direction of less cohesive bodies. The light curve could not be explained at all by making use of only the apparent ablation coefficient and apparent luminous efficiency.     

The typical meteorite event,based on photographic records of 44 fireballs

Abstract— We study the observational data relating to 44 events recorded by the Canadian fireball camera network between 1971 and 1984. Each event is believed to have dropped meteorites, with main masses in the range from 0.1 to 11 kg. Median values are given for 20 parameters describing the atmospheric behavior and orbital elements. A typical duration for a meteoritic fireball is 4 seconds, reaching an end height of 31 km and a velocity of 8 km s^?1 at the end of the luminous path. The peak brightness is typically ?9 magnitude but varies from ?7 to ?15. Meteorites may survive from relatively unspectacular fireballs. Numerous correlations among parameters are investigated. The strong correlations of brightness with initial mass and of duration with slope of the trajectory could be anticipated. Moderate correlations also exist between: (1) initial mass and end height; (2) initial mass and duration of luminosity; (3) initial velocity and beginning height; (4) initial velocity and the fraction of the mass that survives as the largest fragment; (5) initial velocity and the perihelion distance of the orbit. Ablation limits the survival of small masses while fragmentation is usually severe for masses larger than 10 kg. The fractional survival may peak for entry masses between 1 and 10 kg.     

Video observations, atmospheric path, orbit and fragmentation record of the fall of the Peekskill meteorite

Large Near-Earth-Asteroids have played a role in modifying the character of the surface geology of the Earth over long time scales through impacts. Recent modeling of the disruption of large meteoroids during atmospheric flight has emphasized the dramatic effects that smaller objects may also have on the Earth's surface. However, comparison of these models with observations has not been possible until now. Peekskill is only the fourth meteorite to have been recovered for which detailed and precise data exist on the meteoroid atmospheric trajectory and orbit. Consequently, there are few constraints on the position of meteorites in the solar system before impact on Earth. In this paper, the preliminary analysis based on 4 from all 15 video recordings of the fireball of October 9, 1992 which resulted in the fall of a 12.4 kg ordinary chondrite (H6 monomict breccia) in Peekskill, New York, will be given. Preliminary computations revealed that the Peekskill fireball was an Earth-grazing event, the third such case with precise data available. The body with an initial mass of the order of 10⁴ kg was in a pre-collision orbit with a = 1.5 AU, an aphelion of slightly over 2 AU and an inclination of 5. The no-atmosphere geocentric trajectory would have lead to a perigee of 22 km above the Earth's surface, but the body never reached this point due to tremendous fragmentation and other forms of ablation. The dark flight of the recovered meteorite started from a height of 30 km, when the velocity dropped below 3 km/s, and the body continued 50 km more without ablation, until it hit a parked car in Peekskill, New York with a velocity of about 80 m/s. Our observations are the first video records of a bright fireball and the first motion pictures of a fireball with an associated meteorite fall.     

Video observations, atmospheric path, orbit and fragmentation record of the fall of the Peekskill meteorite

Large Near-Earth-Asteroids have played a role in modifying the character of the surface geology of the Earth over long time scales through impacts. Recent modeling of the disruption of large meteoroids during atmospheric flight has emphasized the dramatic effects that smaller objects may also have on the Earth's surface. However, comparison of these models with observations has not been possible until now. Peekskill is only the fourth meteorite to have been recovered for which detailed and precise data exist on the meteoroid atmospheric trajectory and orbit. Consequently, there are few constraints on the position of meteorites in the solar system before impact on Earth. In this paper, the preliminary analysis based on 4 from all 15 video recordings of the fireball of October 9, 1992 which resulted in the fall of a 12.4 kg ordinary chondrite (H6 monomict breccia) in Peekskill, New York, will be given. Preliminary computations revealed that the Peekskill fireball was an Earth-grazing event, the third such case with precise data available. The body with an initial mass of the order of 10(4) kg was in a pre-collision orbit with a = 1.5 AU, an aphelion of slightly over 2 AU and an inclination of 5 degrees. The no-atmosphere geocentric trajectory would have lead to a perigee of 22 km above the Earth's surface, but the body never reached this point due to tremendous fragmentation and other forms of ablation. The dark flight of the recovered meteorite started from a height of 30 km, when the velocity dropped below 3 km/s, and the body continued 50 km more without ablation, until it hit a parked car in Peekskill, New York with a velocity of about 80 m/s. Our observations are the first video records of a bright fireball and the first motion pictures of a fireball with an associated meteorite fall.     

The Žďár nad Sázavou meteorite fall: Fireball trajectory,photometry, dynamics,fragmentation, orbit,and meteorite recovery

We report a comprehensive analysis of the instrumentally observed meteorite fall ??ár nad Sázavou, which occurred in the Czech Republic on December 9, 2014, at 16:16:45–54 UT. The original meteoroid with an estimated initial mass of 150 kg entered the atmosphere with a speed of 21.89 km s^?1 and began a luminous trajectory at an altitude of 98.06 km. At the maximum, it reached ?15.26 absolute magnitude and terminated after a 9.16 s and 170.5 km long flight at an altitude of 24.71 km with a speed of 4.8 km/s. The average slope of the atmospheric trajectory to the Earth's surface was only 25.66°. Before its collision with Earth, the initial meteoroid orbited the Sun on a moderately eccentric orbit with perihelion near Venus orbit, aphelion in the outer main belt, and low inclination. During the atmospheric entry, the meteoroid severely fragmented at a very low dynamic pressure 0.016 MPa and further multiple fragmentations occurred at 1.4–2.5 MPa. Based on our analysis, so far three small meteorites classified as L3.9 ordinary chondrites totaling 87 g have been found almost exactly in the locations predicted for a given mass. Because of very high quality of photographic and radiometric records, taken by the dedicated instruments of the Czech part of the European Fireball Network, ??ár nad Sázavou belongs to the most reliably, accurately, and thoroughly described meteorite falls in history.