The Experts below are selected from a list of 19923 Experts worldwide ranked by ideXlab platform
Diego Janches - One of the best experts on this subject based on the ideXlab platform.
-
an orbital Meteoroid stream survey using the southern argentina agile Meteor radar saamer based on a wavelet approach
2017Co-Authors: Petr Pokorný, Diego Janches, P Brown, Jose Luis HormaecheaAbstract:Abstract Over a million individually measured Meteoroid orbits were collected with the Southern Argentina Agile Meteor Radar (SAAMER) between 2012–2015. This provides a robust statistical database to perform an initial orbital survey of Meteor showers in the Southern Hemisphere via the application of a 3D wavelet transform. The method results in a composite year from all 4 years of data, enabling us to obtain an undisturbed year of Meteor activity with more than one thousand Meteors per day. Our automated Meteor shower search methodology identified 58 showers. Of these showers, 24 were associated with previously reported showers from the IAU catalogue while 34 showers are new and not listed in the catalogue. Our searching method combined with our large data sample provides unprecedented accuracy in measuring Meteor shower activity and description of shower characteristics in the Southern Hemisphere. Using simple modeling and clustering methods we also propose potential parent bodies for the newly discovered showers.
-
interferometric Meteor head echo observations using the southern argentina agile Meteor radar
2014Co-Authors: Diego Janches, W K Hocking, Steven Pifko, Jose Luis Hormaechea, D C Fritts, C Brunini, R Michell, M SamaraAbstract:A radar Meteor echo is the radar scattering signature from the free electrons generated by the entry of extraterrestrial particles into the atmosphere. Three categories of scattering mechanisms exist: specular, nonspecular trails, and head echoes. Generally, there are two types of radars utilized to detect Meteors. Traditional VHF all-sky Meteor radars primarily detect the specular trails, while high-power, large-aperture (HPLA) radars efficiently detect Meteor head echoes and, in some cases, nonspecular trails. The fact that head echo measurements can be performed only with HPLA radars limits these studies in several ways. HPLA radars are sensitive instruments constraining the studies to the lower masses, and these observations cannot be performed continuously because they take place at national observatories with limited allocated observing time. These drawbacks can be addressed by developing head echo observing techniques with modified all-sky Meteor radars. Such systems would also permit simultaneous detection of all different scattering mechanisms using the same instrument, rather than requiring assorted different classes of radars, which can help clarify observed differences between the different methodologies. In this study, we demonstrate that such concurrent observations are now possible, enabled by the enhanced design of the Southern Argentina Agile Meteor Radar (SAAMER). The results presented here are derived from observations performed over a period of 12 days in August 2011 and include Meteoroid dynamical parameter distributions, radiants, and estimated masses. Overall, the SAAMER's head echo detections appear to be produced by larger particles than those which have been studied thus far using this technique.
-
dynamics of dust particles released from oort cloud comets and their contribution to radar Meteors
2011Co-Authors: David Nesvorny, Petr Pokorný, David Vokrouhlicky, Diego JanchesAbstract:The Oort Cloud Comets (OCCs), exemplified by the Great Comet of 1997 (Hale-Bopp), are occasional visitors from the heatless periphery of the solar system. Previous works hypothesized that a great majority of OCCs must physically disrupt after one or two passages through the inner solar system, where strong thermal gradients can cause phase transitions or volatile pressure buildup. Here we study the fate of small debris particles produced by OCC disruptions to determine whether the imprints of a hypothetical population of OCC Meteoroids can be found in the existing Meteor radar data. We find that OCC particles with diameters D 10 ?m are blown out from the solar system by radiation pressure, while those with D 1 mm have a very low Earth-impact probability. The intermediate particle sizes, D ~ 100 ?m, represent a sweet spot. About 1% of these particles orbitally evolve by Poynting-Robertson drag to reach orbits with semimajor axis a ~ 1 AU. They are expected to produce Meteors with radiants near the apex of Earth's orbital motion. We find that the model distributions of their impact speeds and orbits provide a good match to radar observations of apex Meteors, except for the eccentricity distribution, which is more skewed toward e ~ 1 in our model. Finally, we propose an explanation for the long-standing problem in Meteor science related to the relative strength of apex and helion/antihelion sources. As we show in detail, the observed trend, with the apex Meteors being more prominent in observations of highly sensitive radars, can be related to orbital dynamics of particles released on the long-period orbits.
-
dynamics of dust particles released from oort cloud comets and their contribution to radar Meteors
2011Co-Authors: David Nesvorny, Petr Pokorný, David Vokrouhlicky, Diego JanchesAbstract:The Oort Cloud Comets (OCCs), exemplified by the Great Comet of 1997 (Hale-Bopp), are occasional visitors from the heatless periphery of the solar system. Previous works hypothesized that a great majority of OCCs must physically disrupt after one or two passages through the inner solar system, where strong thermal gradients can cause phase transitions or volatile pressure buildup. Here we study the fate of small debris particles produced by OCC disruptions to determine whether the imprints of a hypothetical population of OCC Meteoroids can be found in the existing Meteor radar data. We find that OCC particles with diameters D 1 um have a very low Earth-impact probability. The intermediate particle sizes, D=100 um, represent a sweet spot. About 1% of these particles orbitally evolve by Poynting-Robertson drag to reach orbits with semimajor axis a=1 AU. They are expected to produce Meteors with radiants near the apex of the Earth's orbital motion. We find that the model distributions of their impact speeds and orbits provide a good match to radar observations of apex Meteors, except for the eccentricity distribution, which is more skewed toward e=1 in our model. Finally, we propose an explanation for the long-standing problem in Meteor science related to the relative strength of apex and helion/antihelion sources. As we show in detail, the observed trend, with the apex Meteors being more prominent in observations of highly sensitive radars, can be related to orbital dynamics of particles released on the long-period orbits.
-
tristatic observations of Meteors using the 930 mhz european incoherent scatter radar system
2002Co-Authors: Diego Janches, D D Meisel, Asta Pellinenwannberg, Gudmund Wannberg, Assar Westman, Ingemar HaggstromAbstract:[1] We report results from the first tristatic measurements of radar Meteors obtained during 17 November 1997 and 1998, using the UHF (930 MHz) European Incoherent Scatter (EISCAT) radar system. The observing technique utilized for these observations was first reported by Pellinen-Wannberg et al. [1998a]. This system consists of three 32-m parabolic antennae located in northern Scandinavia. Since EISCAT observes mostly Meteor head echoes, a general characteristic of high-power/large-aperture radars, direct Doppler velocity (±1 km/s) determinations are possible. In addition, using the technique reported here, absolute geocentric Meteor velocity and good radiant information (±5°) are deduced for those Meteors that are detected simultaneously by all three receivers. An overview of the methodology and a summary of the results obtained so far are reported in this work. We compare the results obtained using this method with those reported by previous large-aperture Meteor radar work at lower frequencies and find general agreement. EISCAT detects mainly sporadic particles extending the fast daily sporadic microMeteor storms first suggested by Janches et al. [2000b] and Mathews et al. [2001] to submillimeter particles. To the best of our knowledge, these observations represent the first of their kind and prove EISCAT to be a crucial instrument for the study of extraterrestrial particles entering the Earth's atmosphere, in particular at very high geocentric latitudes and high geocentric speeds.
Peter Jenniskens - One of the best experts on this subject based on the ideXlab platform.
-
cams newly detected Meteor showers and the sporadic background
2016Co-Authors: Peter Jenniskens, Quentin Nénon, P.s. Gural, Jim Albers, B. Haberman, B. Johnson, R. Morales, Bryant GrigsbyAbstract:Abstract The Cameras for Allsky Meteor Surveillance (CAMS) video-based Meteoroid orbit survey adds 60 newly identified showers to the IAU Working List of Meteor Showers (numbers 427, 445–446, 506–507, and part of 643–750). 28 of these are also detected in the independent SonotaCo survey. In total, 230 Meteor showers and shower components are identified in CAMS data, 177 of which are detected in at least two independent surveys. From the power-law size frequency distribution of detected showers, we extrapolate that 36% of all CAMS-observed Meteors originated from ∼700 showers above the N = 1 per 110,000 shower limit. 71% of mass falling to Earth from streams arrives on Jupiter-family type orbits. The transient Geminids account for another 15%. All Meteoroids not assigned to streams form a sporadic background with highest detected numbers from the apex source, but with 98% of mass falling in from the antihelion source. Even at large ∼7-mm sizes, a Poynting–Robertson drag evolved population is detected, which implies that the Grun et al. collisional lifetimes at these sizes are underestimated by about a factor of 10. While these large grains survive collisions, many fade on a 10 4 -y timescale, possibly because they disintegrate into smaller particles by processes other than collisions, leaving a more resilient population to evolve. The Meteors assigned to the various showers are identified in the CAMS Meteoroid Orbit Database 2.0 submitted to the IAU Meteor Data Center, and can be accessed also at http://cams.seti.org .
-
The established Meteor showers as observed by CAMS
2016Co-Authors: Peter Jenniskens, Quentin Nénon, P.s. Gural, Jim Albers, B. Haberman, D. Holman, R. Morales, Bryant Grigsby, D. Samuels, Carl JohanninkAbstract:Abstract Orbital elements are presented for 70 of the 95 Meteor showers considered “established” by the International Astronomical Union. From 2010 October 21 until 2013 March 31, the low-light-video based Cameras for Allsky Meteor Surveillance project (CAMS) measured a total of 110,367 Meteoroid trajectories and pre-atmospheric orbits from mostly −2 to +4 magnitude Meteors with a precision of
-
The 2011 Draconids: The First European Airborne Meteor Observation Campaign
2015Co-Authors: Jeremie Vaubaillon, P.-D. Pautet, A. Margonis, Joe Zender, R Rudawska, Maria Gritsevich, Pavel Koten, Juraj Toth, Jonathan Mcauliffe, Peter JenniskensAbstract:On 8 October 2011, the Draconid Meteor shower (IAU $$\#8$$ # 8 , DRA) was predicted to cause two brief outbursts of Meteors, visible from locations in Europe. For the first time, a European airborne Meteor observation campaign was organized, supported by ground-based observations. Two aircraft were deployed from Kiruna, Sweden, carrying six scientists, 19 cameras and eight crew members. The flight geometry was chosen such that it was possible to obtain double-station observations of many Meteors. The instrument setup on the aircraft as well as on the ground is described in full detail. The main peak from 1900-dust ejecta happened at the predicted time and at the predicted rate. The second peak was observed from the earlier flight and from the ground, and was caused most likely by trails ejected in the nineteenth century. A total of 250 Meteors were observed, for which light curve data were derived. The trajectory, velocity, deceleration and orbit of 35 double station Meteors were measured. The magnitude distribution index was high, as a result of which there was no excess of Meteors near the horizon. The light curve proved to be extremely flat on average, which was unexpected. Observations of spectra allowed us to derive the compositional information of the Draconids Meteoroids and showed an early release of sodium, usually interpreted as resulting from fragile Meteoroids. Lessons learned from this experience are derived for future airborne Meteor shower observation campaigns.
-
new Meteor showers identified in the cams and sonotaco Meteoroid orbit surveys
2014Co-Authors: R Rudawska, Peter JenniskensAbstract:A cluster analysis was applied to the combined Meteoroid orbit database derived from low-light level video observations by the SonotaCo consortium in Japan (64,650 Meteors observed between 2007 and 2009) and by the Cameras for All-sky Meteor Surveillance (CAMS) project in California, during its first year of operation (40,744 Meteors from Oct. 21, 2010 to Dec. 31, 2011). The objective was to identify known and potentially new Meteoroid streams and identify their parent bodies. The database was examined by a single-linking algorithm using the Southworth and Hawkins D-criterion to identify similar orbits, with a low criterion threshold of D < 0.05. A minimum member threshold of 6 produced a total of 88 Meteoroid streams. 43 are established streams and 45 are newly identified streams. The newly identified streams were included as numbers 448-502 in the IAU Meteor Shower Working List. Potential parent bodies are proposed.
-
characteristics of fe ablation trails observed during the 1998 leonid Meteor shower
2000Co-Authors: Xinzhao Chu, Weilin Pan, George C Papen, Chester S Gardner, G R Swenson, Peter JenniskensAbstract:Eighteen Fe ablation trails were observed during the 17/18 Nov 1998 Leonid Meteor shower with an airborne Fe lidar aboard the NSF/NCAR Electra aircraft over Okinawa. The average altitude of the 18 trails from the high velocity (72 km/s) Leonid Meteors, 95.67±0.93 km, is approximately 6.7 km higher than previously observed for slower (∼30 km/s) sporadic Meteors. This height difference is consistent with the assumption that Meteors ablate when atmospheric drag reaches a critical threshold. The average age of the Fe trails, determined by a diffusion model, is 10.1 min. The youngest ages were observed below 92 km and above 98 km where chemistry and diffusion dominate, respectively. The average abundance of the trails is 10% of the abundance of the background Fe layer. Observations suggest that the 1998 Leonid shower did not have a significant impact on the abundance of the background Fe layer.
Jose Luis Hormaechea - One of the best experts on this subject based on the ideXlab platform.
-
an orbital Meteoroid stream survey using the southern argentina agile Meteor radar saamer based on a wavelet approach
2017Co-Authors: Petr Pokorný, Diego Janches, P Brown, Jose Luis HormaecheaAbstract:Abstract Over a million individually measured Meteoroid orbits were collected with the Southern Argentina Agile Meteor Radar (SAAMER) between 2012–2015. This provides a robust statistical database to perform an initial orbital survey of Meteor showers in the Southern Hemisphere via the application of a 3D wavelet transform. The method results in a composite year from all 4 years of data, enabling us to obtain an undisturbed year of Meteor activity with more than one thousand Meteors per day. Our automated Meteor shower search methodology identified 58 showers. Of these showers, 24 were associated with previously reported showers from the IAU catalogue while 34 showers are new and not listed in the catalogue. Our searching method combined with our large data sample provides unprecedented accuracy in measuring Meteor shower activity and description of shower characteristics in the Southern Hemisphere. Using simple modeling and clustering methods we also propose potential parent bodies for the newly discovered showers.
-
interferometric Meteor head echo observations using the southern argentina agile Meteor radar
2014Co-Authors: Diego Janches, W K Hocking, Steven Pifko, Jose Luis Hormaechea, D C Fritts, C Brunini, R Michell, M SamaraAbstract:A radar Meteor echo is the radar scattering signature from the free electrons generated by the entry of extraterrestrial particles into the atmosphere. Three categories of scattering mechanisms exist: specular, nonspecular trails, and head echoes. Generally, there are two types of radars utilized to detect Meteors. Traditional VHF all-sky Meteor radars primarily detect the specular trails, while high-power, large-aperture (HPLA) radars efficiently detect Meteor head echoes and, in some cases, nonspecular trails. The fact that head echo measurements can be performed only with HPLA radars limits these studies in several ways. HPLA radars are sensitive instruments constraining the studies to the lower masses, and these observations cannot be performed continuously because they take place at national observatories with limited allocated observing time. These drawbacks can be addressed by developing head echo observing techniques with modified all-sky Meteor radars. Such systems would also permit simultaneous detection of all different scattering mechanisms using the same instrument, rather than requiring assorted different classes of radars, which can help clarify observed differences between the different methodologies. In this study, we demonstrate that such concurrent observations are now possible, enabled by the enhanced design of the Southern Argentina Agile Meteor Radar (SAAMER). The results presented here are derived from observations performed over a period of 12 days in August 2011 and include Meteoroid dynamical parameter distributions, radiants, and estimated masses. Overall, the SAAMER's head echo detections appear to be produced by larger particles than those which have been studied thus far using this technique.
Petr Pokorný - One of the best experts on this subject based on the ideXlab platform.
-
an orbital Meteoroid stream survey using the southern argentina agile Meteor radar saamer based on a wavelet approach
2017Co-Authors: Petr Pokorný, Diego Janches, P Brown, Jose Luis HormaecheaAbstract:Abstract Over a million individually measured Meteoroid orbits were collected with the Southern Argentina Agile Meteor Radar (SAAMER) between 2012–2015. This provides a robust statistical database to perform an initial orbital survey of Meteor showers in the Southern Hemisphere via the application of a 3D wavelet transform. The method results in a composite year from all 4 years of data, enabling us to obtain an undisturbed year of Meteor activity with more than one thousand Meteors per day. Our automated Meteor shower search methodology identified 58 showers. Of these showers, 24 were associated with previously reported showers from the IAU catalogue while 34 showers are new and not listed in the catalogue. Our searching method combined with our large data sample provides unprecedented accuracy in measuring Meteor shower activity and description of shower characteristics in the Southern Hemisphere. Using simple modeling and clustering methods we also propose potential parent bodies for the newly discovered showers.
-
dynamics of dust particles released from oort cloud comets and their contribution to radar Meteors
2011Co-Authors: David Nesvorny, Petr Pokorný, David Vokrouhlicky, Diego JanchesAbstract:The Oort Cloud Comets (OCCs), exemplified by the Great Comet of 1997 (Hale-Bopp), are occasional visitors from the heatless periphery of the solar system. Previous works hypothesized that a great majority of OCCs must physically disrupt after one or two passages through the inner solar system, where strong thermal gradients can cause phase transitions or volatile pressure buildup. Here we study the fate of small debris particles produced by OCC disruptions to determine whether the imprints of a hypothetical population of OCC Meteoroids can be found in the existing Meteor radar data. We find that OCC particles with diameters D 10 ?m are blown out from the solar system by radiation pressure, while those with D 1 mm have a very low Earth-impact probability. The intermediate particle sizes, D ~ 100 ?m, represent a sweet spot. About 1% of these particles orbitally evolve by Poynting-Robertson drag to reach orbits with semimajor axis a ~ 1 AU. They are expected to produce Meteors with radiants near the apex of Earth's orbital motion. We find that the model distributions of their impact speeds and orbits provide a good match to radar observations of apex Meteors, except for the eccentricity distribution, which is more skewed toward e ~ 1 in our model. Finally, we propose an explanation for the long-standing problem in Meteor science related to the relative strength of apex and helion/antihelion sources. As we show in detail, the observed trend, with the apex Meteors being more prominent in observations of highly sensitive radars, can be related to orbital dynamics of particles released on the long-period orbits.
-
dynamics of dust particles released from oort cloud comets and their contribution to radar Meteors
2011Co-Authors: David Nesvorny, Petr Pokorný, David Vokrouhlicky, Diego JanchesAbstract:The Oort Cloud Comets (OCCs), exemplified by the Great Comet of 1997 (Hale-Bopp), are occasional visitors from the heatless periphery of the solar system. Previous works hypothesized that a great majority of OCCs must physically disrupt after one or two passages through the inner solar system, where strong thermal gradients can cause phase transitions or volatile pressure buildup. Here we study the fate of small debris particles produced by OCC disruptions to determine whether the imprints of a hypothetical population of OCC Meteoroids can be found in the existing Meteor radar data. We find that OCC particles with diameters D 1 um have a very low Earth-impact probability. The intermediate particle sizes, D=100 um, represent a sweet spot. About 1% of these particles orbitally evolve by Poynting-Robertson drag to reach orbits with semimajor axis a=1 AU. They are expected to produce Meteors with radiants near the apex of the Earth's orbital motion. We find that the model distributions of their impact speeds and orbits provide a good match to radar observations of apex Meteors, except for the eccentricity distribution, which is more skewed toward e=1 in our model. Finally, we propose an explanation for the long-standing problem in Meteor science related to the relative strength of apex and helion/antihelion sources. As we show in detail, the observed trend, with the apex Meteors being more prominent in observations of highly sensitive radars, can be related to orbital dynamics of particles released on the long-period orbits.
M D Campbellbrown - One of the best experts on this subject based on the ideXlab platform.
-
luminous efficiency estimates of Meteors ii application to canadian automated Meteor observatory Meteor events
2018Co-Authors: Dilini Subasinghe, M D CampbellbrownAbstract:Luminous efficiency is a necessary parameter for determining Meteoroid mass from optical emission. Despite this importance, it is very poorly known, with previous results varying by up to two orders of magnitude for a given speed. We present the most recent study of luminous efficiency values determined with modern high-resolution instruments, by directly comparing dynamic and photometric Meteoroid masses. Fifteen non-fragmenting Meteoroids were used, with a further five clearly fragmenting events for comparison. Twelve of the fifteen non-fragmenting Meteoroids had luminous efficiencies less than 1%, while the fragmenting Meteoroids had upper limits of a few tens of percent. No clear trend with speed was seen, but there was a weak negative trend of luminous efficiency on Meteoroid mass, implying that smaller Meteoroids radiate more efficiently.
-
luminous efficiency estimates of Meteors i uncertainty analysis
2017Co-Authors: Dilini Subasinghe, M D Campbellbrown, E StokanAbstract:Abstract The luminous efficiency of Meteors is poorly known, but critical for determining the Meteoroid mass. We present an uncertainty analysis of the luminous efficiency as determined by the classical ablation equations, and suggest a possible method for determining the luminous efficiency of real Meteor events. We find that a two-term exponential fit to simulated lag data is able to reproduce simulated luminous efficiencies reasonably well.
-
transverse motion of fragmenting faint Meteors observed with the canadian automated Meteor observatory
2014Co-Authors: E Stokan, M D CampbellbrownAbstract:Abstract Nine fragmenting, faint Meteors (peak magnitude ∼ + 1 , mass 10 - 4 kg ) were observed with the Canadian Automated Meteor Observatory (CAMO). Fragments for eight of the nine Meteors exhibited significant transverse motion, perpendicular to the Meteor velocity. Transverse speeds of the order 100 m s - 1 were observed, while models of aerodynamic loading predict speeds of the order 0.5 m s - 1 . Acceleration of the fragments in the transverse direction was negligible. Alternate methods of fragmentation, namely rotation and electrostatic charge accumulation, were examined through basic models to explain the observed transverse speeds. Meteoroid strengths of the order 10 6 Pa were derived, matching observed strengths of larger, brighter Meteors.
-
the canadian automated Meteor observatory camo system overview
2013Co-Authors: R J Weryk, M D Campbellbrown, P Brown, P. Wiegert, Z Krzeminski, R MusciAbstract:Abstract We describe the hardware and software for the Canadian Automated Meteor Observatory (CAMO), an automated two-station video Meteor system designed to facilitate simultaneous radar-video Meteor detections, to help constrain numerical ablation models with higher precision Meteor data, and to measure the Meteoroid mass influx at the Earth. A guided system with a wide-field (∼30°) camera detects Meteors ( M ) and positions an optical scanner such that a narrow-field (∼1°) camera tracks the Meteors in real-time. This allows for higher precision deceleration measurements than traditionally available, and for detailed studies of Meteoroid fragmentation. A second system with a wide-field (∼20°) camera detects fainter ( M ) Meteors (in non-real-time) primarily for Meteoroid mass influx measurements. We describe the system architecture, automation control, and instruments of CAMO, and show example detections. We find narrow-field trajectory solutions have precisions in speed of a few tenths of a percent, and radiant precisions of ∼0.01°. Our initial survey shows 75% of all tracked, multi-station Meteor events ( M ) show evidence of fragmentation, either as discrete fragments (17% of total), or in the form of Meteor wake. Our automatic wide-field camera solutions have average radiant errors of ∼3° and speed uncertainties of 3%.