Aims. Here we report on precise metric and photometric observations of 107 optical meteors, which were simultaneously recorded at multiple stations using three different intensified video camera systems. The purpose is to estimate bulk meteoroid density, link small meteoroids to their parent bodies based on dynamical and physical density values expected for different small body populations, to better understand and explain the dynamical evolution of meteoroids after release from their parent bodies. Methods. The video systems used had image sizes ranging from 640 × 480 to 1360 × 1036 pixels, with pixel scales from 0.01 • per pixel to 0.05 • per pixel, and limiting meteor magnitudes ranging from M v = +2.5 to +6.0. We find that 78% of our sample show noticeable deceleration, allowing more robust constraints to be placed on density estimates. The density of each meteoroid is estimated by simultaneously fitting the observed deceleration and lightcurve using a model based on thermal fragmentation, conservation of energy and momentum. The entire phase space of the model free parameters is explored for each event to find ranges of parameters which fit the observations within the measurement uncertainty. Results. (a) We have analysed our data by first associating each of our events with one of the five meteoroid classes. The average density of meteoroids whose orbits are asteroidal and chondritic (AC) is 4200 kg m −3 suggesting an asteroidal parentage, possibly related to the high-iron content population. Meteoroids with orbits belonging to Jupiter family comets (JFCs) have an average density of 3100 ± 300 kg m −3 . This high density is found for all meteoroids with JFC-like orbits and supports the notion that the refractory material reported from the Stardust measurements of 81P/Wild 2 dust is common among the broader JFC population. This high density is also the average bulk density for the 4 meteoroids with orbits belonging to the Ecliptic shower-type class (ES) also related to JFCs. Both categories we suggest are chondritic based on their high bulk density. Meteoroids of HT (Halley type) orbits have a minimum bulk density value of 360 +400 −100 kg m −3 and a maximum value of 1510 +400 −900 kg m −3 . This is consistent with many previous works which suggest bulk cometary meteoroid density is low. SA (Sun-approaching)-type meteoroids show a density spread from 1000 kg m −3 to 4000 kg m −3 , reflecting multiple origins. (b) We found two different meteor showers in our sample: Perseids (10 meteoroids, ∼11% of our sample) with an average bulk density of 620 kg m −3 and Northern Iota Aquariids (4 meteoroids) with an average bulk density of 3200 kg m −3 , consistent with the notion that the NIA derive from 2P/Encke.
We have optically recorded faint meteors using a large aperture LLLTV (low light level television) system based on second generation image intensifiers. These data consist of 42 two-station meteors of which 13 were captured during an observing campaign near London, Ontario (Canada) in May 2004, and 29 during a campaign near Kiruna (Sweden) in October 2007. Among 13 meteors recorded in the London campaign, where the baseline between the two sites was 5 km, only four meteors satisfied our requirement for complete lightcurves and deceleration profiles by starting in the field of view, of at least one station and also ending in the field of view of at least one station. From the second set of 29 meteors captured in Sweden, with a baseline of 117.7 km, only two satisfied these criteria. The cameras used in both campaigns had fields of view of 6 degrees, which with an assumed range of 100 km, gives a scale of 13 m/pixel at ∼60 interlaced fields per second. This resolution allows precise measurement of the deceleration of very faint meteors. The limiting magnitude for meteors on these systems is near V = +8, while +11th magnitude stars are visible in the individual fields. The meteors detected in these two campaigns have peak brightnesses between absolute magnitude +6.2 and +7.4. Their photometric masses range from 4.2 mg to 0.35 mg. An ablation model was applied to fit each complete two-station event using the high-precision metric and photometric data as a constraint, in an attempt to compute bulk meteoroid densities. Interestingly, a large proportion of our faint meteor events were found to ablate at low altitudes, a result partly of our observing biases. The orbits of these events are consistent with either asteroidal or a Jupiter-family comet origin. The meteoroids' physical properties, as determined through model fits, suggest high densities, which favors an asteroidal interpretation. The high percentage of apparently dense asteroidal meteoroids at these small sizes may call into question earlier findings that only ∼1% of meteoroids at these masses are asteroidal in origin. Our results are similar to others that find ∼15% of faint TV meteors had spectra consistent with pure iron meteoroids. We find that many of these apparently asteroidal objects also undergo extensive fragmentation, which may reflect melting and spraying of droplets rather than mechanical fragmentation. Some individual cases in our small dataset will be highlighted where high bulk densities (approaching that of iron) are required to adequately match the end height, peak brightness, and observed deceleration. We speculate that these meteoroids may represent metallic condensates from impact-processed asteroid regolith.
In order to correct for the effect of saturation on photometric measurements of meteors, we have developed a numerical model for saturation and apply it to data gathered using two generation III image intensified video systems on two nights (2008 October 31 and 2008 November 6). The two cameras were pointed in the same direction, and the aperture of one camera was set two stops below the aperture of the other. With these conditions, some meteors saturated one camera but not the other (group I); some saturated both cameras (group II); and some did not saturate either of them (group III). A model of meteor saturation has been developed which uses the image background value, angular meteor speed and the lateral width of the meteor image to simulate the true and saturated light curve of meteors. For group I meteors, we computed a saturation correction and applied it to the saturated light curve. We then compared the corrected saturated curve to the unsaturated curve from the other camera to validate the model. For group II meteors, a saturation correction is calculated and applied to both observed light curves, which have different degrees of saturation, and the corrected curves are compared. We collected 516 meteors, of which 30 were of group I, and seven of group II. For meteors in group I, an average residual of less than 0.4 mag was found between the observed unsaturated light curve and the model‐corrected saturated light curve. For meteors in group II, the average residual between the two corrected light curves was 0.3 mag. For our data, the saturation correction goes from 0.5 to 1.9 mag for meteors in group I, and 1.2 to 2.5 mag for meteors in group II. Based on the agreement between the observed and modelled light curves (less than 0.4 mag over all meteors of all groups), we conclude that our model for saturation correction is valid. It can be used to extract the true luminosity of a saturated meteor, which is necessary to calculate photometric mass. Our model also demonstrates that fixed corrections to saturated meteor photometry, not accounting for background levels or angular velocities, do introduce significant error to meteor photometric analyses.
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