Determination of Meteoroid Orbits and Spatial Fluxes by Using High-Resolution All-Sky CCD Cameras

By using high-resolution, low-scan-rate, all-sky CCD cameras, the SPanish Meteor Network (SPMN) is currently monitoring meteor and fireball activity on a year round basis. Here are presented just a sampling of the accurate trajectory, radiant and orbital data obtained for meteors imaged simultaneously from two SPMN stations during the continuous 2006–2007 coverage of meteor and fireball monitoring. Typical astrometric uncertainty is 1–2 arc min, while velocity determination errors are of the order of 0.1–0.5 km/s, which is dependent on the distance of each event to the station and its particular viewing geometry. The cameras have demonstrated excellent performance for detecting meteor outbursts. The recent development of automatic detection software is also providing real-time information on the global meteor activity. Finally, some examples of the all-sky CCD cameras applications for detecting unexpected meteor activity are given.     

The Southern Ontario All-sky Meteor Camera Network

We have developed an automated network of all-sky CCD video systems to detect medium–large meteoroids ablating over Southern Ontario, Canada. The system currently consists of five stations with the largest baseline being 180 km. Each site runs a video rate recorder with sufficient resolution to determine meteoroid trajectories with a typical precision of about 300 m but no worse than 1 km. The sensitivity of the camera is close to a stellar visual magnitude of +1 which allows for astrometric calibrations using field stars. Photometric procedures have also been developed and tested. The system has a limiting magnitude for meteors of about −2 with the current detection algorithm.     

The outburst of the κ Cygnids in 2007: clues about the catastrophic break up of a comet to produce an Earth-crossing meteoroid stream

Using high-resolution, low-scan-rate, all-sky CCD cameras and high-level CCD video cameras, the SPanish Meteor and fireball Network (SPMN) recorded the 2007 κ Cygnid fireball outburst from several observing stations. Here, accurate trajectory, radiant and orbital data obtained for the κ Cygnid meteor are presented. The typical astrometric uncertainty is 1–2 arcmin, while velocity determination errors are of the order of 0.3–0.6 km s⁻¹, though this depends on the distance of each event to the station and its particular viewing geometry. The observed orbital differences among 1993 and 2007 outbursts support the hypothesis that the formation of this meteoroid stream is a consequence of the fragmentation of a comet nucleus. Such disruptive process proceed as a cascade, where the break up of the progenitor body leads to produce small remnants, some fully disintegrate into different clumps of particles and other remaining as dormant objects such as 2008ED69, 2001MG1 and 2004LA12 which are now observed as near-Earth asteroids. In addition to the orbital data, we present a unique spectrum of a bright  κ  Cygnid fireball revealing that the main rocky components have chondritic abundances, and estimations of the tensile strength of those fireballs that exhibited a catastrophic disruption behaviour. All this evidence of the structure and composition of the κ Cygnid meteoroids is consistent with being composed by fine-grained materials typically released from comets.     

Automated Meteor Detection by All-Sky Digital Camera Systems

We have developed a set of methods to detect meteor light traces captured by all-sky CCD cameras. Operating at small automatic observatories (stations), these cameras create a network spread over a large territory. Image data coming from these stations are merged in one central node. Since a vast amount of data is collected by the stations in a single night, robotic storage and analysis are essential to processing. The proposed methodology is adapted to data from a network of automatic stations equipped with digital fish-eye cameras and includes data capturing, preparation, pre-processing, analysis, and finally recognition of objects in time sequences. In our experiments we utilized real observed data from two stations.     

Photographic observations of fireballs in Tajikistan

Since 2006, systematic double-station photographic observations of fireballs using all-sky cameras equipped with Zeiss Distagon “fisheye” objectives (f/3.5, f = 30 mm) with a 180° field of view have been carried out at two observatories, Gissar (GisAO) and Sanglokh (IAOS), of the Institute of Astrophysics of the Tajik Academy of Sciences. In the method of astrometric reduction of fireball photographs, the empirical formulae for converting the measured coordinates to horizontal celestial coordinates are used. These formulae contain 12 unknown constants to be determined by the least-squares method and the iteration method. Such an approach enables the determination of the coordinates of an object at any point of the celestial hemisphere with a precision close to the theoretical limit whose value is quite comparable with the measurement errors. In the photometric reduction, the dependence of the measured width of the diurnal star trails on their magnitudes was used. As a result of astrometric and photometric reduction of the double-station photographs of five fireballs, the data on atmospheric trajectories, the coordinates of radiants, orbits in interplanetary space, light curves, and photometric masses of meteoroids which produced fireballs were obtained, and the belonging of fireballs to the known meteor showers was determined as well.     

Coordinated observations of two large Leonid meteor fireballs over northern New Mexico,and computer model comparisons

Abstract— This paper describes the coordinated results of several sets of measurements of two Leonid meteor fireballs over northern New Mexico at 1:32 and 3:06 MST, respectively, on the night of 1998 November 17. The measurements included visible band photometry on both events, as well as filtered 5890 Å all-sky images of the Na airglow. Also, for the 3:06 a.m. event, we obtained an infrasound measurement of the hydrodynamic yield. For the 1:32 a.m. event, we obtained a set of visible band charge-coupled device (CCD) camera images of the meteor train for times extending to 30 min after the initial impact. The measurement results have been combined to derive an optical efficiency for the intense early-time optical flash, and the total explosion yields and masses for both of the meteors. We have also done a set of numerical radiation, hydrodynamic, and chemistry computations to investigate the nature and distribution of the long-lasting airglow. We attribute the brightest visible airglow to atomic O 5577 Å line emission, with additional contributions from atomic Na emission and NO₂ chemiluminescence. The near-infrared atmospheric bands of molecular O₂ should be very strong as well. All of the band emissions are expected to show a hollow limb-brightened structure.     

Multi-Instrument Observations of Bright Meteors in the Czech Republic

We present detailed data on 8 bright meteors recorded simultaneously by different observational techniques. All meteors were recorded by all-sky cameras at the Czech stations of the European Fireball Network and by image intensified TV cameras placed at Ondrejov and Kunzak observatories. As well as direct photographic and LLLTV recordings, most of meteors were recorded also by the spectral TV camera and some also by photographic spectral cameras. For 6 cases, lightcurves from radiometers with very high time resolution (1200 s⁻¹) are also available. From all these detections we found a significant difference between TV and photographic beginning heights. TV beginnings are in average about 40 km higher than the photographic ones. We found that meteor brightness is up to 2 magnitudes higher in the photographic system than in the TV system. This difference for high velocity meteors is mainly caused by the presence of strong Ca⁺ lines in the blue part of the spectrum, where the image intensifier is only marginally sensitive. At heights above 110 km, the Na line is usually brighter than the Mg line, while at lower heights both lines have comparable brightness. In one of two captured spectra of short duration luminous trains, a small initial brightening of the Mg and Na lines caused by recombination processes was observed.     

Apex I and Apex II software packages for the reduction of astronomical CCD observations

We describe in detail the Apex I and Apex II software packages created for astrometric and photometric reductions of astronomical observations with CCD cameras. The Apex I software package has been created for the semiautomatic reduction of astronomical observations and has a convenient user interface. The Apex II software package allows for the completely automatic reduction of astrometric and photometric observations to be performed.     

一种基于全天相机组网的区域火流星监测网的实现和应用

流星监测网是小尺寸近地小天体撞击监测、判断陨石落点的主要工具. 提出了一种基于多站布局的全天视频相机组网监测系统, 并在江苏及周边构建了一个区域级原型系统, 实现了火流星监测组网控制、视频数据采集、数据处理及流星体定轨的完整流程. 通过1yr的实测运行表明, 该系统可观测流星极限视星等为-1.0等, 可以实现绝对星等-2.5等流星的完备检测; 根据监测数据得到火流星通量为2.68×10^-7km^-2 ·h^-1;群流星和偶发流星占比分别为46%和54%,偶发流星中类小行星轨道和类彗星轨道比例分别为27.1%和72.9,统计结果与国际主要流星监测网相接近,验证了监测网系统在实际组网使用中的监测能力.     

The “European Fireball Network”: Current status and future prospects

Abstract— Among the three large camera networks carrying out fireball observations through the seventies and eighties, the “European Fireball Network” is the last one still in operation. The network today consists of more than 34 all-sky and fish-eye cameras deployed with ～100 km spacing and covering an area of ～10⁶ km², in the Czech and Slovak Republics, Germany, as well as parts of Belgium, Switzerland, and Austria. Network operation results in ～10 000 image exposures per year, which represent on average 1200 h of clear sky observations—as imaging periods are restricted due to daylight, moonlight, and clouds. The cameras detect currently large meteors at a rate of ～50 per year; this is in good agreement with the encounter rates determined in previous fireball studies. From sightings of “meteorite candidates” (fireballs that may have deposited meteorites) and meteorite recoveries in the network area, we estimate that 15% of the influx of meteoritic matter is currently observed by the cameras, whereas <1% is recovered on the ground. Issues to be addressed by future fireball observations include the study of very large meteoroids (>1000 kg) for which statistics are currently very poor and an examination of their relationship to NEOs (near-Earth objects) identified by current NEO search programs.     

The Armagh Observatory Meteor Camera Cluster: Overview and Status

Armagh Observatory installed a sky monitoring system consisting of two wide angle (90° × 52°) and one medium angle (52° × 35°) cameras in July 2005. The medium angle camera is part of a double station setup with a similar camera in Bangor, ∼73 km ENE of Armagh. All cameras use UFOCapture to record meteors automatically; software for off-line photometry, astrometry and double station calculations is currently being developed. The specifications of the cameras and cluster configuration are described in detail. 2425 single station meteors (1167, 861 and 806 by the medium-angle and the wide-angle cameras respectively) and 547 double station meteors were recorded during the months July 2005 to Dec 2006. About 212 double station meteors were recorded by more than one camera in the cluster. The effects of weather conditions on camera productivity are discussed. The distribution of single and double station meteor counts observed for the years 2005 and 2006 and calibrated for weather conditions are presented.     

Estimated Visual Magnitudes of the EISCAT UHF Meteors

We have investigated the conditions for simultaneous meteor observations with the EISCAT UHF radar system and telescopic optical devices. The observed characteristics of 410 meteors detected by all three UHF receivers are compared with model simulations and their luminosity is calculated as a part of a meteoroid ablation model using a fifth order Runge–Kutta numerical integration technique. The estimated absolute visual magnitudes are in the range of +9 to +5. The meteors should therefore be observable using intensified CCD or EMCCD (Electron Multiplying CCD) cameras with telephoto lenses. A possible setup of a coordinated radar and optical campaign is suggested.     

Transient Detection Using Panoramic All-Sky Cameras

A method of using on-going panoramic all-sky monitors for the purpose of bright optical transient detection is described. The detection is performed by comparing all-sky images to canonical images taken at the same sidereal time. The described approach has been implemented and tested using the infrastructure of the Night Sky Live network of panoramic all-sky cameras. Preliminary results of detected bright flashes are presented in the paper.     

A New Analysis of Fireball Data from the Meteorite Observation and Recovery Project (MORP)

Sixty fireball cameras operated in Western Canada from 1971 to 1985. Over one thousand (1016) fireballs were recorded at more than one station, but only 367 were reduced, of which 285 have been published, including that of the Innisfree meteorite. Digitization of all the data is underway, and procedures are being developed which will allow the automatic reduction of events not previously examined. The results of the analysis of 80 fireballs reduced but not previously published are presented. When the new analysis is complete, the MORP archive will be a valuable source of information on meteoroid orbits.     

Exceptional Fireball Activity of Orionids in 2006

We report exceptional fireball activity of the Orionid meteor shower in 2006. During four nights in October 2006 the autonomous fireball observatories of the Czech part of the European Fireball Network (EN) recorded 48 fireballs belonging to the Orionids. This is significantly more than the total number of Orionids recorded during about five decades long continuous operation of the EN. Based on precise multi-station photographic and radiometric data we present accurate atmospheric trajectories, heliocentric orbits, light curves and basic physical properties of 10 Orionid fireballs with atmospheric trajectories that were long enough and, with one exception, were observed from at least three stations. Seven were recorded in within a 2-h interval in the night of 20/21 October. Their basic parameters such as radiant positions and heliocentric orbits are very similar. This high fireball activity originated from a very compact geocentric radiant defined by α = 95.10° ± 0.10° and δ = 15.50° ± 0.06°. These fireballs most likely belonged to a distinct filament of larger meteoroids trapped in 1:5 resonance with Jupiter. From detailed light curves and basic fireball classification we found that these meteoroids appertain to the weakest component of interplanetary matter.     

Atmospheric behavior and extreme beginning heights of the thirteen brightest photographic Leonid meteors from the ground‐based expedition to China

Abstract— Precise atmospheric trajectories including dynamic and photometric data on thirteen of the brightest Leonid fireballs have been determined from the double‐station photographic observations of Leonid meteors during the ground‐based expedition to China in 1998 November. the expedition was organized as a collaboration between the dutch and chinese academy of sciences and was supported by the leonid multi‐instrument aircraft campaign (mac) program (jenniskens and butow, 1999). All data presented here were taken at Xinglong Observatory and at a remote station, Lin Ting Kou near Beijing, on the night of 1998 November 16/17. At the Xinglong station, photographic cameras were accompanied by an all‐sky television camera equipped with an image intensifier and 15 mm fish‐eye objective in order to obtain precise timings for all observed meteors up to magnitude +2. Whereas beginning heights of photographed meteors are all lower than 130 km, those observed by the all‐sky television system are at ～160 km, and for three brightest events, even > 180 km. Such high beginnings for meteors have never before been observed. We also obtained a precise dynamic single‐body solution for the Leonid meteor 98003, including the ablation coefficient, which is an important material and structural quantity (0.16 s² km^?2). From this and from known photometry, we derived a density of this meteoroid of 0.7 g/cm³. Also, all PE coefficients indicate that these Leonid meteors belonged to the fireball group IIIB, which is typical for the most fragile and weak interplanetary bodies. From a photometric study of the meteor lightcurves, we found two typical shapes of light curves for these Leonid meteors.     

Radiants of the Leonids 1999 and 2001 Obtained by Lltv Systems Using Automatic Software Tools

Both amateur and professional meteor groups are more frequently using Low-Light level TV (LLTV) systems to record meteors. Double-station observations can yield orbit data. However, data analysis normally is still done by hand and thus time consuming. This paper addresses the question of whether available automated tools can be used to determine reasonably accurate orbits with minimum human intervention. The European Space Agency performed several observing campaigns to observe the Leonid meteor stream. In November 1999, the ESA meteor group was stationed at two locations in Southern Spain, in November 2001 at two stations close to Broome in North-Western Australia. Double-station observations with LLTV systems were conducted. The data was recorded on S-VHS video tapes. The tapes were processed using automatic detection software from which meteor heights, velocities and radiants were computed. This paper shows the results for the two maximum nights. The radiants determined in 1999 show a very large scatter due to unfortunate observing geometry and inaccurate position determination since one of the cameras was moving because of the wind. The 2001 data is excellent and the radiant was determined to be at RA = 153.96°±0.3° and Dec = 21.09°±0.2°. The error bars for individual meteor radiants are about 0.2° to 0.4°. This demonstrates that is indeed possible to determine good radiant positions using totally automated tools. Orbits, on the other hand, are not well defined due to the fact that the velocity of individual meteors shows large errors. Reasons for this are described.     

Radiation pressure correction to meteor orbits

We present a method to calculate the radiation pressure force to gravity ratio on meteoroids from their atmospheric flight. Radiation pressure corrections to meteor orbits are negligible for fireballs; of the order of or less than the measurement errors (≈ 1%) for photographic meteors; of the order of and in some cases substantially larger than the measurement errors (≈ 10%) for radar meteors.     

HIGH SPATIAL AND TEMPORAL RESOLUTION OPTICAL SEARCH FOR EVIDENCE OF METEOROID FRAGMENTATION

A digital image intensified CCD camera with an electronically gated image intensifier was used to produce very short duration images of meteors. The observational system employed a 0.40 m F/4.5 Newtonian telescope to obtain high spatial resolution. A second intensified CCD camera was used to yield height information using parallax. At a typical meteor height one pixel (for the vertically oriented system) corresponded to about 1.1 m. A sampling of 59 mainly sporadic meteors was analyzed. There is clear variability from meteor to meteor, with many meteors (nearly 50%) showing only a small amount of wake, while some meteors (approximately 20%) have the off segments completely filled in.