Geocentric Velocity Research Articles

A statistical analysis of over three thousand meteors and their spectra

ABSTRACT In this article, over three thousand meteor spectra recorded in Saitama, Japan, between 2018 and 2021 are analysed. We performed a principal component analysis of the intensity of the sodium and magnesium lines and the iron band of each meteor in combination with the orbital elements and the kinematic parameters such as the geocentric velocity and the initial and final altitudes to determine the relative importance of each of these variables in the composition of a meteor’s spectrum. We found that for meteor showers such as GEM, LEO, QUA, and PER, the orbital elements or kinematic parameters are important parameters that determine the intensity of these spectral lines, which could indicate the influence of gravitational and/or non-gravitational forces in distinguishing the composition or variations in the strength of the meteoroid material in each meteor shower. The normal spectral type in our sample ranges from 39.5 per cent to 96.8 per cent, corresponding to GEM and PER, respectively. The COM meteors have a similar sodium content to the components of the LEO and PER showers, suggesting a comet as a possible parent body. The sodium and magnesium content of the iron-class meteoroids is the lowest of all our samples, but it is not zero, suggesting that there are no pure iron meteoroids. The sodium content of the GEM meteor shower shows temporal variations in 2021 compared to the 2019 and 2020 observing seasons. We found no correlation between the sodium content and the perihelion distance for other meteor showers.

“Cold capture” of micrometeorites in Archean and Quaternary atmospheres: Effects of dilute exospheres

Micrometeorites (MM) that undergo low heating could have provided a source of organic material to the Earth during the Archean (4-2.5 Ga ago) before life emerged, given that the density of interplanetary dust and larger grains were much higher than today. Amino acids are destroyed on atmospheric entry if the temperature rises above the pyrolysis temperature of few hundred degrees Celsius, depending on type of amino acid. A numerical study was carried out to obtain temperature statistics along relatively rare grazing angle trajectories in the Quaternary (modern) and Archean atmospheres to determine the probability of “cold capture” below pyrolysis temperatures. Effects of the thermospheric temperature and density was considered for the Quaternary atmosphere, and an extended hydrogen/helium envelope remnant from the protosolar nebula was considered for the Archean atmosphere.An important result for the Archean is an elevated “cold capture” probability (twice the capture probability of the modern atmosphere, up to 7%–8%) for low heating below 500 °C of small asteroidal grains around 20μm in diameter, and geocentric velocities in the range 3–5 km/s, provided that there was a remnant envelope. Cometary 20μm grains of higher geocentric velocities did not have such an elevated capture probability. If the Archean atmosphere did not have an envelope, it was found that these capture probabilities were lower than for the modern atmosphere for both cometary and asteroidal grains, due to smaller density scale height of the lower Archean atmosphere leading to faster heating rate. Radiative degradation of amino acids in these relatively small grains should be considered more closely since the X-ray and XUV-flux from the Sun was larger by a factor of about 5–10 in the Archean.Very low maximum temperatures were found for 20μm asteroidal and cometary grains in the Quternary atmosphere, with temperatures in the range 150–200 °C, but with a very small capture probability in this range of typically less than 0.3%. All 300μm asteroidal grains were heated to temperatures above 500 °C for all atmosphere models. The probability of heating to temperatures < 500 °C of 100μm asteroidal grains, was estimated to 0.3% or less for all models. Most 100μm cometary grains were heated to temperatures > 500 °C for all models.

A Numerical Approach to Study Ablation of Large Bolides: Application to Chelyabinsk

In this study, we investigate the ablation properties of bolides capable of producing meteorites. The casual dashcam recordings from many locations of the Chelyabinsk superbolide associated with the atmospheric entry of an 18 m in diameter near-Earth object (NEO) have provided an excellent opportunity to reconstruct its atmospheric trajectory, deceleration, and heliocentric orbit. In this study, we focus on the study of the ablation properties of the Chelyabinsk bolide on the basis of its deceleration and fragmentation. We explore whether meteoroids exhibiting abrupt fragmentation can be studied by analyzing segments of the trajectory that do not include a disruption episode. We apply that approach to the lower part of the trajectory of the Chelyabinsk bolide to demonstrate that the obtained parameters are consistent. To do that, we implemented a numerical (Runge–Kutta) method appropriate for deriving the ablation properties of bolides based on observations. The method was successfully tested with the cases previously published in the literature. Our model yields fits that agree with observations reasonably well. It also produces a good fit to the main observed characteristics of Chelyabinsk superbolide and provides its averaged ablation coefficient σ = 0.034 s2 km−2. Our study also explores the main implications for impact hazard, concluding that tens of meters in diameter NEOs encountering the Earth in grazing trajectories and exhibiting low geocentric velocities are penetrating deeper into the atmosphere than previously thought and, as such, are capable of producing meteorites and even damage on the ground.

Quantifying the Hypervolatile Abundances in Jupiter-family Comet 46P/Wirtanen

Abstract We present analysis of IR and optical spectroscopy of Jupiter-family comet (JFC) 46P/Wirtanen obtained in 2019 January, when the comet had sufficient geocentric velocity to enable studies of the hypervolatiles CO and CH4, as well as [O i] emission. These species could not be studied near closest approach in mid-December because there was insufficient Doppler shift to separate the cometary emission from their corresponding telluric absorption lines. We employed the [O i] observations as a proxy for the CO2/H2O ratio, as CO2 cannot be observed directly from the ground, and space-based assets sensitive to CO2 were not able to observe 46P during this apparition. We focused our analysis on H2O, CO, CH4, C2H6, CH3OH, and CO2 (via [O i] emission). We detected strong emissions from H2O, C2H6, and CH3OH. Over the 3 nights, we found evidence for changing mixing ratios, mostly due to a variable H2O production rate. In 46P, C2H6 and CH3OH are enriched compared to cometary averages, with mixing ratios relative to H2O of ∼1% and ∼3%, respectively. Measurements of CH4 and CO have been especially rare in JFCs. We report significant 3σ upper limits on CH4/H2O &lt; 0.97% and CO/H2O &lt; 0.54%. They place CH4 being near-average or depleted, and CO being strongly depleted in 46P compared with Oort cloud comets. 46P has comparable CO/H2O to the few other measurements in JFCs, but enriched in C2H6 and CH3OH. Our inferred CO2/H2O mixing ratio is ∼15%, though accounting for systematic uncertainties from the lack of knowledge of [O i] photochemistry means a value between 10% and 20% is likely. The compositional profile of 46P is similar to another small, hyperactive comet: 103P/Hartley 2. The mechanism of CO2-driven water-rich ice grain production proposed for 103P/Hartley 2 may be operating on 46P as well.

The κ-Cygnid Meteor Shower and Its Relationship with Near-Earth Asteroids

This study is focused on the relationships between the κ-Cygnid meteor shower and different groups of asteroids crossing the Earth’s orbit (the so-called near-Earth objects (NEOs)). The analysis is based on the visible structure of the meteor shower and a comprehensive strategy for estimating the proximity of orbits of two bodies. The κ-Cygnid meteor shower (abbreviated as KCG) is observed from August 3 to August 25 every year; it is classified as a minor shower, and the size of its mean orbit is around 3.2 AU, while the geocentric velocity is 20.9 km/s. No parent body (PB) of the shower has been found among comets so far. Relationships between the shower and asteroids, as potential PBs of the shower, are under active examination; some hypotheses on this subject can be found on the website of the Meteor Data Center (MDC) of the International Astronomical Union (IAU).

Updated Mean Sea-Level Analysis: Australia

Watson, P.J., 2020. Updated mean sea-level analysis: Australia. Journal of Coastal Research, 36(5), 915–931. Coconut Creek (Florida), ISSN 0749-0208.As an island nation with 60,000 km of open coastline and extensive margins of increasingly urbanised intertidal estuarine foreshores, Australia is critically exposed to the global threat posed by rising sea levels into the future. This study provides a contemporary assessment of sea-level rise around Australia to the end of 2018, based on all available tide gauge records and satellite altimetry. The study provides the first national assessment of vertical land motion (VLM) around the coast, identifying margins more prevalent to subsidence, which in turn exacerbate the localised effects of a rising global mean sea level. These areas include coastlines between Townsville and Coffs Harbour, Burnie to Port Pirie, and Fremantle to Wyndham. State-of-the-art time-series analysis techniques applied to all high-quality tide gauge records exceeding 75 years in length (four sites) enabled improved insights into the temporal resolution of current rates of rise and accelerations in mean sea level around Australia than were previously available. Averaged across these four records in 2018, approximately 40% of the “relative” velocity observed (∼2.2 ± 1.8 mm/y, 95% confidence limit [CL]) is attributable to VLM. When corrected for VLM, only the Fort Denison site exhibits “geocentric” mean sea-level velocity in 2018 exceeding 2 mm/y. The average geocentric velocity across all four sites in 2018 equates to 1.3 ± 2.0 mm/y (95% CL). Interestingly, each long record exhibits similar temporal characteristics, whereby a low point in the velocity time series occurs sometime in the period from 1970 to 1990, after which velocity increases over time to a peak occurring sometime after ca. 2010, suggesting the presence of a small acceleration (albeit not statistically different to zero at the 95% CL) in the record.

Observations of an Unexpected Meteor Shower Outburst at High Ecliptic Southern Latitude and Its Potential Origin

Abstract A strong and unexpected meteor shower outburst was observed by the Southern Argentina Agile MEteor Radar Orbital System (SAAMER-OS) at high southern ecliptic latitude within the South Toroidal region. The outburst, which was active throughout solar longitudes 351° and 352°, peaked at 09:30 UT on 2020 March 12, has a mean Sun-centered ecliptic radiant of λ − λ 0 ∼ 307.°5 and β ∼ −77.°2 and a geocentric velocity of 30.7 km s−1. Using the parameter criterion, we find the corresponding orbital elements of the outburst to match well with both the β Tucanid and δ Mensid meteor showers, suggesting these are in fact the same shower. We also find a promising parent candidate in asteroid (248590) 2006 CS, a large (D ∼ 2 km) highly inclined 52° near-Earth object.

RESULTS OF POSITIONAL AND PHOTOMETRIC MEASURE- MENTS OF METEOR TRAJECTORIES OBSERVED IN MYKOLAIV 2017-2018

Regular meteor observation using TV CCD unintensified techniques was started in 2011 in RI «Mykolaiv astronomical observatory» (RI MAO). The method of meteor registration is based on using “track- and-stack” technique for obtaining frames with reference stars and online meteor detection software developed at RI NAO. The main accent of the research is made on precise astrometry and meteoroid orbits calculation. New observa- tional campaign with baselines 11.7 and 100 km was start- ed in 2017-2018 in collaboration with Astronomical Ob- servatory of the I.I. Mechnikov Odessa National Universi- ty. Eight telescopes with narrow field lens (f=50 mm, f/1.2) were installed in Mykolaiv and Odessa. More than 3000 single station meteors and 221 double station mete- ors were detected during 2017-2018. Uncertainties of me- teor trajectory and orbital parameters are calculated using Monte Carlo method. Catalog of meteor trajectory posi- tions and photometric parameters has created. Standard deviation of approximation of a meteoric trajectory in a large circle is (15-20). Kinematic parameters of atmos- pheric meteoric trajectories and elements of heliocentric orbits for 3 meteors were calculated based on the results of television observations with cameras with a field of view <10° at a baseline distance 100 km. The average uncertainty of visible radiant estimation is in (0.3-0.7)o with baseline 100 km. The geocentric velocity estimation uncertainty is 0.5 km/s, elevation uncertainty is 50-150 m.

The Possibility of Harmless Destruction of an Asteroid Threatening the Earth

One possible means of counteraction against a hazardous asteroid is discussed: destruction of the object with a nuclear device during an earlier encounter with the Earth. This is feasible, since virtually all hazardous asteroids appear in near-Earth space several times before they hit the Earth. Computations show that this method is effective and essentially harmless if certain conditions are satisfied. Two possibilities are acceptable. In the first, a spacecraft overtakes the asteroid in a heliocentric orbit. In the second, the asteroid overtakes the spacecraft, which demands a substantially lower characteristic geocentric velocity for the spacecraft. This method for eliminating this cosmic threat is reasonable in two cases: when it is not possible to achieve a soft departure of the object from the collision orbit, and when the object continuously returns to the Earth. A soft departure from a collision orbit can be required multiple times, whereas the destruction of such an object must occur only once.

A Tale of “Two” Comets: The Primary Volatile Composition of Comet 2P/Encke Across Apparitions and Implications for Cometary Science

Abstract The highly favorable 2017 apparition of 2P/Encke allowed the first comprehensive comparison of primary volatile abundances in a given comet across multiple apparitions. This apparition offered opportunities to address pressing questions in cometary science, including investigating evolutionary and/or heliocentric distance (R h) effects on volatile production, sampling the hypervolatiles CO and CH4 in an ecliptic comet, and measuring volatile release at small R h. The faintness and frequently low geocentric velocity of ecliptic comets during most apparitions make our near-infrared observations of these hypervolatiles rare and of high scientific impact. We characterized the volatile composition of 2P/Encke on three post-perihelion dates using the iSHELL spectrograph at the NASA Infrared Telescope Facility on Maunakea, HI. We detected fluorescent emission from nine primary volatiles (H2O, CO, C2H6, CH3OH, CH4, H2CO, NH3, OCS, and HCN) and three fragment species (OH*, NH2, and CN), and obtained a sensitive upper limit for C2H2. We report rotational temperatures, production rates, and mixing ratios (abundances relative to H2O). Compared to mean abundances in comets observed to date in the near-infrared, mixing ratios of trace gases in 2P/Encke were depleted for all species except H2CO and NH3, which were “normal.” The detection of the hypervolatiles CO and CH4 is particularly notable given the paucity of measurements in ecliptic comets. We observed significant differences in primary volatile composition compared to published pre-perihelion results from 2003 at larger R h. We discuss possible mechanisms for these differences and discuss these results in the context of findings from the Rosetta mission and ground-based studies of comets.

Enhanced activity of the Southern Taurids in 2005 and 2015

The paper presents an analysis of Polish Fireball Network (PFN) observations of enhanced activity of the Southern Taurid meteor shower in 2005 and 2015. In 2005, between October 20 and November 10, seven stations of PFN determined 107 accurate orbits with 37 of them belonging to the Southern Taurid shower. In the same period of 2015, 25 stations of PFN recorded 719 accurate orbits with 215 orbits of the Southern Taurids. Both maxima were rich in fireballs which accounted to 17% of all observed Taurids. The whole sample of Taurid fireballs is quite uniform in the sense of starting and terminal heights of the trajectory. On the other hand a clear decreasing trend in geocentric velocity with increasing solar longitude was observed. Orbital parameters of observed Southern Taurids were compared to orbital elements of Near Earth Objects (NEO) from the NEODYS-2 database. Using the Drummond criterion $D'$ with threshold as low as 0.06, we found over 100 fireballs strikingly similar to the orbit of asteroid 2015 TX24. Several dozens of Southern Taurids have orbits similar to three other asteroids, namely: 2005 TF50, 2005 UR and 2010 TU149. All mentioned NEOs have orbital periods very close to the 7:2 resonance with Jupiter's orbit. It confirms a theory of a "resonant meteoroid swarm" within the Taurid complex that predicts that in specific years, the Earth is hit by a greater number of meteoroids capable of producing fireballs.

Meteor shower detection with density‐based clustering

AbstractWe present a new method to detect meteor showers using the density‐based spatial clustering of applications with noise algorithm (DBSCAN; Ester et al. ). The DBSCAN algorithm is a modern cluster detection algorithm that is well suited to the problem of extracting meteor showers from all‐sky camera data because of its ability to efficiently extract clusters of different shapes and sizes from large data sets. We apply this shower detection algorithm on a data set that contains 25,885 meteor trajectories and orbits obtained from the NASA All‐Sky Fireball Network and the Southern Ontario Meteor Network (SOMN). Using a distance metric based on solar longitude, geocentric velocity, and Sun‐centered ecliptic radiant, we find 25 strong cluster detections and six weak detections in the data, all of which are good matches to known showers. We include measurement errors in our analysis to quantify the reliability of cluster occurrence and the probability that each meteor belongs to a given cluster. We validate our method through false‐positive/negative analysis and with a comparison to an established shower detection algorithm.

TRIO OF STELLAR OCCULTATIONS BY PLUTO ONE YEAR PRIOR TO NEW HORIZONS’ ARRIVAL

ABSTRACT We observed occultations by Pluto during a predicted series of events in 2014 July with the 1 m telescope of the Mt. John Observatory in New Zealand. The predictions were based on updated astrometry obtained in the previous months at the USNO, CTIO, and Lowell Observatories. We successfully detected occultations by Pluto of an R = 18 mag star on July 23 (14:23:32 ± 00:00:04 UTC to 14:25:30 ± 00:00:04 UTC), with a drop of 75% of the unocculted stellar signal, and of an R = 17 star on July 24 (11:41:30 ± 00:00:08 UTC to 11:43:28 ± 00:00:08 UTC), with a drop of 80% of the unocculted stellar signal, both with 20 s exposures with our frame-transfer Portable Occultation, Eclipse, and Transit System. Since Pluto had a geocentric velocity of 22.51 km s−1 on July 23 and 22.35 km s−1 on July 24, these intervals yield limits on the chord lengths (surface and lower atmosphere) of 2700 ± 130 km and 2640 ± 250 km, respectively, indicating that the events were near central, and therefore provide astrometric constraints on the prediction method. Our coordinated observations with the 4 m AAT in Australia on July 23 and the 6.5 m Magellan/Clay on Las Campanas, the 4.1 m Southern Astrophysical Research Telescope on Cerro Pachön, the 2.5 m DuPont on Las Campanas (LCO), the 0.6 m SARA-South on Cerro Tololo of the Southeastern Association for Research in Astronomy (SARA), the MPI/ESO 2.2 m on La Silla, and the 0.45 m Cerro Calán telescope and 0.36 telescope in Constitución in Chile on July 27 and 31, which would have provided higher-cadence observations for studies of Pluto’s atmosphere, were largely foiled by clouds, but led to detection with the LCO Magellan/Clay and DuPont Telescopes on July 31 of the grazing occultation of a previously unknown 15th-magnitude star, completing the trio of occultations successfully observed and reported in this paper.

TV observations of the Perseid meteor shower in 2012–2013

The results of television meteor observations during the Perseid meteor shower activity in 2012–2013 are presented. The observations were carried out in the Moscow region using the television system PatrolCa – the patrol camera with the field of view of 56°×44° and limiting magnitude (for meteors) of +4m. The distribution of the Index of Meteors Activity of the Perseid meteor shower in 2012–2013 was estimated. The maximum activity occurs on August 12 with the Index of Meteors Activity (IMA) (λ=140.4°) 192 (±0.03)*103 particles to the Earth per 1h in 2012 and 122 (±0.06)*103 particles to the Earth per 1h in 2013 (λ=140.2°). In total for 91 meteoroids radiants, geocentric velocities and orbit parameters were calculated. The daily drift of Perseid radiant was determined. The dependence of the beginning and ending heights by absolute magnitude is presented.

Dynamical features of hazardous near-Earth objects

We discuss the dynamical features of near-Earth objects moving in dangerous proximity to Earth. We report the computation results for the motions of all observed near-Earth objects over a 600-year-long time period: 300 years in the past and 300 years in the future. We analyze the dynamical features of Earth-approaching objects. In particular, we established that the observed distribution of geocentric velocities of dangerous objects depends on their size. No bodies with geocentric velocities smaller that 5 kms-1 have been found among hazardous objects with absolute magnitudes H 29. We estimated the distribution of absolute magnitudes of hazardous objects based on our analysis of the data for the asteroids that have passed close to Earth. We inferred the Earth-impact frequencies for objects of different sizes. Impacts of objects with H <18 with Earth occur on average once every 0.53 Myr, and impacts of objects with H <27—once every 130–240 years. We show that currently about 0.1% of all near-Earth objects with diameters greater than 10 m have been discovered. We point out the discrepancies between the estimates of impact rates of Chelyabinsk-type objects, determined from fireball observations and from the data of telescopic asteroid tracking surveys. These estimates can be reconciled assuming that Chelyabinsk-sized asteroids have very low albedos (about 0.02 on average).

On the orbital evolution of the Lyrid meteoroid stream

A detailed analysis of the Lyrid video orbits from the EDMOND database is performed. Applying selective methods, the weighted mean orbit and mean geophysical parameters are derived. The occurrence of orbits with the semimajor axes smaller than 35AU, in comparison with the value of 55AU of the parent comet Thatcher, is about 80%, in the set of higher quality data of the Lyrids in the EDMOND database.The gravitational orbital evolutions of Thatcher and modelled particles ejected in five perihelion passages of the comet in the past are studied. Both, orbits of the comet and modelled particles, are under quite strong disturbing influence of Jupiter, Saturn and Earth. After the integration to the present, the mean theoretical radiants, the mean geocentric velocities and periods of activity of particles approaching the Earth's orbit were calculated. The mean orbits of the modelled streams of particles ejected from different perihelia match well the mean Lyrid orbit from the IAU MDC and the observed video Lyrids from the EDMOND database. The particles released in the two oldest simulated perihelion passages of the parent comet are most responsible for the occurrence of the Earth-crossing orbits with the semimajor axes smaller than 35AU, but no one below 20AU.The influence of non-gravitational effects, mainly solar radiation, may shorten semimajor axis of a submilimeter particle with density of 0.3g/cm3 by more than half during an evolution of 50000 years. A common influence of gravitational perturbations and non-gravitational effects can provide a dynamical way to the short-period orbits. However, this process is for millimeter and larger particles (video and photographic) less effective.

Observations of the new Camelopardalids meteor shower using a 38.9 MHz radar at Mohe, China

The Camelopardalids meteor shower was predicted to occur for the first time on 24 May 2014, based on optical observations of the comet 209P/LINEAR. Using a 38.9MHz meteor radar located at Mohe, China, we were able to detect approximately 590 shower meteors originating from an average pre-infall radiant of R.A.=129.1°±9.8°, declination=79.4°±1.6° (J2000) with a geocentric velocity of 16.0±1.6kms−1. Measurements of the shower duration, direction, velocity, and individual meteor detection heights facilitated a detailed analysis of the parent debris stream. Orbital parameters were calculated including a semi-major axis of 2.86AU, eccentricity of 0.659, and inclination of 21.1°. Combining orbital parameters with the shower activity duration FWHM of 5.09h, it was found that the stream has a FWHM of at least 211,000km at 1AU, as measured perpendicular to the direction of orbital motion. A comparison of shower meteor detection heights and diffusion coefficient estimates with the sporadic background is consistent the prediction of Ye and Wiegert (Ye, Q., Wiegert, P. [2014]. Mon. Not. R. Astron. Soc. 437, 3283–3287) that Camelopardalid meteoroids are biased towards larger sizes or that Cameloppardalid meteoroids are less fragile than sporadic background meteoroids.

Draconids 2011: Outburst Observations by the Croatian Meteor Network

The predicted Draconid meteor shower outburst during October 2011 had been observed by a portion of the Croatian Meteor Network whose stations encountered clear weather. A total of 95 Draconid orbits have been calculated from 18 contributing stations, and in this paper we present results for 63 orbits obtained from the fully automatic observation and processing pipeline. Two methods of trajectory estimation were applied, showing better fit results using a linearly changing velocity model versus a constant velocity model. The estimated mean radiant position has been found to be at RA = 262.6°, Dec = +55.7°, with estimated geocentric velocity Vg = 20.7 km/s.

Real-Time Flux Density Measurements of the 2011 Draconid Meteor Outburst

During the 2011 outburst of the Draconid meteor shower, members of the Video Meteor Network of the International Meteor Organization (IMO) provided, for the first time, fully automated flux density measurements in the optical domain. The data set revealed a primary maximum at 20:09 UT $\pm$5 min on 8 October 2011 (195.036 deg solar longitude) with an equivalent meteoroid flux density of (118 $\pm$10) x 10^-3 km^-2 h^-1 at a meteor limiting magnitude of +6.5, which is thought to be caused by the 1900 dust trail of comet 21P/Giacobini-Zinner. We also find that the outburst had a full width at half maximum (FWHM) of 80 minutes, a mean radiant position of alpha=262.2 deg, delta=+56.2 deg ($\pm$1.3 deg) and geocentric velocity of v_geo=17.4 km/s ($\pm$0.5 km/s). Finally, our data set appears to be consistent with a small sub-maximum at 19:34 UT $\pm$7 min (195.036 deg solar longitude) which has earlier been reported by radio observations and may be attributed to the 1907 dust trail.

Radar observations of the 2011 October Draconid outburst

A strong outburst of the October Draconid meteor shower was predicted for 2011 October 8. Here we present the observations obtained by the Canadian Meteor Orbit Radar (CMOR) during the 2011 outburst. CMOR recorded 61 multistation Draconid echoes and 179 single-station overdense Draconid echoes (covering the magnitude range of +3 ≤ MV ≤ +7) between 16 and 20 h ut on 2011 October 8. The mean radiant for the outburst was determined to be αg = 261| $_{.}^{\circ}$|9 ± 0| $_{.}^{\circ}$|3, δg = +55| $_{.}^{\circ}$|3 ± 0| $_{.}^{\circ}$|3 (J2000) from observations of the underdense multistation echoes. This radiant location agrees with model predictions to ∼1°. The determined geocentric velocity was found to be ∼10–15 per cent lower than the model value (17.0–19.1 km s−1 versus 20.4 km s−1), a discrepancy we attribute to undercorrection for atmospheric deceleration of low-density Draconid meteoroids as well as to poor radar radiant geometry during the outburst peak. The mass index at the time of the outburst was determined to be ∼1.75 using the amplitude distribution of underdense echoes, in general agreement with the value of ∼1.72 found using the diffusion-limited durations of overdense Draconid echoes. The relative flux derived from overdense echo counts showed a similar variation to the meteor rate derived from visual observations. We were unable to measure the peak flux due to the high elevation of the radiant (and hence low elevation of specular Draconid echoes). Using the observed speed and electron line density measured by CMOR for all underdense Draconid echoes as a function of height as a constraint, we have applied the ablation model developed by Campbell-Brown & Koschny. From these model comparisons, we find that Draconid meteoroids at radar sizes are consistent with a fixed grain number ngrain = 100 and a variable grain mass mgrain between 2 × 10−8 and 5 × 10−7 kg, with bulk and grain density of 300 and 3000 kg m−3, respectively. One particular Draconid underdense echo displayed well-defined Fresnel amplitude oscillations at four stations. The internal synchronization allowing us to measure absolute length as a function of time by combining the absolute timing offsets between stations. This event showed clear deceleration and modelling suggests that the number of grains for this meteoroid was of the order of 1000 with grain masses between 10−10 and 10−9 kg, and a total mass of 2 × 10−6 kg.