The 2016 International Meteor Conference (IMC2016) took place in Egmond in the Netherlands during June 2-5. The number of attendees was 157 – a record. Most were from Europe, but there were also a good number of attendees from locations further afield, including Japan, Australia, Turkey, Canada and the USA. Attendees from the UK included the SPA’s Megan Argo, Paul Sutherland, Bill Ward and Tony Markham. Concern was expressed that only two presentations this year related to visual work, with the majority being related to radio and video observations.
With many of the attendees wishing to give presentations, talks were strictly limited to 12 minutes (including questions) and some were persuaded to produce posters for display rather than give presentations. Below is a summary of a selection of the presentations:
Peter Jenniskens (USA) provided an update on the CAMS video network that has been operating in California since 2010 and has recorded 320000 meteors. Their map of the distribution of meteor radiants is showing increasing amounts of structure in the Apex, Antihelion and Toroidal concentrations.
Joel Younger (Australia) reported on radar observations of the recently discovered Volantid meteor shower that is active Dec 31-Jan 2 and was originally detected by CAMS New Zealand. Observations made from Davis Station in Antarctica and Buckland Park in Australia have shown their velocity distribution to peak just below 30km/s
Giancarlo Tommezzoli (Germany) reported on attempts to detect the Daytime Sextantids during Sep 30 to Oct 5 using radio methods. Their results showed no clear evidence for any activity from the shower.
Paul Roggemans (Belgium) reported on the CAMS Benelux network. This has operated since 2012 and now includes 56 cameras located at 17 stations. Results are forwarded on to Peter Jenniskens. August’s Kappa Cygnids were rather active in 2014, but produced little activity in 2015. The recently discovered Chi Cygnid shower appears to be active throughout September.
Przemyslaw Zoladek (Poland) reported on observations of the 2015 Taurids from Poland. Southern Taurid rates were enhanced. The Northern Taurids had a flat maximum. Two fireballs were observed five hours apart on October 31. Both had orbits similar to asteroids 2005UR and 2005TF50 and also to asteroid 2015TX24 which had passed close to the Earth two days earlier.
Juergen Rendtel (Germany) reported on minor shower activity outburst predictions and the issues faced in deciding which to mention in each year’s IMO shower calendar. Comparison of visual and video results does help assess whether peaks and dips in ZHR plots are genuine. There is some evidence for long term periodicities in Kappa Cygnid and Delta Aurigid rates, but we need to keep collecting visual observations in order to extend the data sets.
Thomas Weiland (Austria) reported on observations of the southern Delta Aquarids from Crete in 2014. Only 1% of SDAs were trained and none produced any flares. This fits in with the expectation that the long term heating of cometary meteoroids reduces train and flare production. Many SDAs are, however, described as being yellow and orange, suggesting that not all volatile content has been lost.
Pavel Spurny (Czech Rep) described three recently documented meteorite falls recorded by the European Fireball network. Three meteorites were found in the predicted fall area for the Zd’ar event of 2014 Dec 9, six in the predicted area for the Stubenberg event of 2016 Mar 6, and 10kg of meteorites were recovered from the Copenhagen event of 2016 Feb 6, some being found before the predicted fall area had been published.
Vincent Perlerin (France) and Mike Hankey (USA) gave accounts of two recent fireballs. One was seen on 2016 Jan 24 from the USA, with 124 reports being received. The other was seen from France on 2016 Feb 25, with 341 reports received. Radar data was available for the former event but not for the latter. Meteorites have been recovered for the former (from a swampy area) but not from the latter (impact area near a military base).
Francois Cola (France) gave an overview if the French FRIPON fireball camera network. This uses digital cameras with 1.2 megapixel chips. A 0.000001 sec exposure time allows the cameras to operate during daytime, but many false detections are seen in daylight. Doppler measurements are obtained using GRAVES. All PCs involved are connected to the network. The software used can be downloaded from https://github.com/fripon/freeture . It is low cost and open source.
Lukas Shrbeny (Czech Rep) described the activities of the Australian Desert camera network. This operated from October 2003, with the final film exposure before the switch to digital being taken in April 2015. During this period, 950 fireballs were recorded, 267 of these being multi-station. Several fireball activity peaks were seen, including March 8, May 27, July 31 and Dec 6.
Sirko Molau (Germany) flagged up unexpected patterns in flux density and population index studies. These revealed sinusoidal patterns, with calculated flux densities being 15% higher at full moon and calculated population index values being 10% higher at new moon. The explanation is not yet clear, although it may in part relate to inaccuracies in automated limiting magnitude determinations.
Abedin Abedin (Canada) reported on investigations to determine the age of the Daytime Arietid meteor shower and whether it was linked to comet 96P/Machholz or to a recent break up producing a group of sun-skirting comets. The results, based on radar observations and fireball network data have shown the stream’s age to be at least 12000 years and support the 96P/Machholz link.
Jeremie Vaubaillon (France) outlined a system that could be used to give an indication as to whether outburst predictions will come true. This would take into account factors such as whether an associated dust trail has been identified, whether the parent body has been identified and on the stability of the orbit of the parent body. The resulting “code” would consist of a series of numbers and letters. Several attendees commented that a simple “colour code” or a “Torino scale” type rating would be preferable.
David Capek (Czech Rep) reported on investigations into the ablation of small iron meteoroids. These meteors contain no spectral lines other than those of Fe and typically have low start heights and unusual light curves. Various ablation models were tested. The most promising involves the immediate removal of a liquid Fe layer from the ablating particle. This model produces the best match in terms of light curves and start heights.
Vlastimil Vojacek (Czech Rep) reported on the production of a catalogue of meteor spectra types. This has been made publically available. It includes 84 spectra and covers particle sizes from 1mm to 10mm and magnitudes from +2 to -3. Spectra are classified based on the strengths of lines of Mg, Fe and Na.
Shinsuke Abe (Japan) described plans for the release of test meteoroids from an altitude of 500-600km at a speed of 7-8 km/s. The first test will occur in 2018. Business applications would involve “wishing upon a falling star” and controlling the colours of the artificial meteors produced.
Denis Vida (Croatia) described his work in developing an open source meteor-detection program that can run on a single board computer, such as a Raspberry Pi. This involves video capture, conversion to CAMS format and fireball detection. Meteors need to be detected on at least four video frames. Frames containing no stars are not processed – it is assumed that the lack of stars is due to cloud.
Pete Gural (USA) reported on work he is carrying out to develop a faster meteor-detection algorithm. Faster detection is needed to cater for observers increasingly running multiple cameras, for the advent of HD cameras and for the use of large format cameras. The work is focussing on those parts of the detection process that are speed-critical. A particular challenge is that the detection algorithm being replaced has over the years become embedded within other software.
Theresa Ott (Germany) & Esther Drolshagen (Germany) described how the PaDe system developed to find dust particles in images from the Rosetta/OSIRIS cameras is being adjusted to work with meteor videos. This is looking promising, although one issue is that the presence of a wake or trail can move a meteor’s photometric centre.
Stijn Calders (Belgium) reported on the Radio Meteor Zoo. The BRAMS network has 30 stations and captures over 8500 spectrograms per day. There is a desire to automate the detection algorithms, but the system needs calibrating. The human eye is very good at recognizing meteor signals in spectrograms and so a Zooniverse project has been created. Initial investigations indicate that if ten volunteers view a set of images, they will identify 95% of the meteors and only 6% will be false detections.
Herve Lamy (Belgium) reported on investigations into the feasibility of retrieving meteor trajectories from BRAMS data. Any meteor detected will be travelling tangentially to an ellipsoid whose foci are the transmitter and receiving station. Thus combining detections of the same meteor from multiple stations could yield trajectories. Reliable trajectories would need at least six stations to have recorded the same meteor. Unfortunately, it is rare for so many stations to record the same meteor.
Detlef Koschny (Netherlands) described how as a schoolboy he calculated the height of a fireball seen by himself and from Switzerland, using the cosine function about which he had recently been taught.
Eleanor Samson (Australia) described a mobile phone app that can be used to report fireballs. This works in a similar way to the IMO fireball report form but does not yet store reports in an on-line database.
Mariusz Wisniewski (Poland) described the work of the Polish Fireball network. This has 40 continuously operating stations including nearly 80 cameras. During 2011-2015, this has generated around 34K Q0 orbits and 24K Q1 orbits, with 2015 being the most productive. During this period, the increase in camera numbers has led to the fraction of Q1 orbits increasing from 67% to 75%, with multi-station meteors increasing from 12% to 17%.
Hadrien Devillepoix (Australia) reported on the meteorite searching activities of the Australian Desert Fireball Network. This currently includes 50 digital cameras with fisheye lenses spread across an area of 2.5 million square kilometres. Cameras can be installed in less than 2 hours. The only moving parts are two fans. Power comes from solar power and a car battery. The cameras have two 8TB drives and can run unattended for 11 months. Hadrien also gave an account of the recovery of meteorites from the Lake Eyre event of Dec 2013.
Chris Peterson (USA) compared the accuracy of position measurements from analogue and digital cameras. In analogue cameras, an issue is that the processing loses the link with the original image pixels. The processed pixels may be spread across 3 of 4 pixels, leading to a positional uncertainty of +/- 2 pixels. The position of the image centroid can therefore “jump around”.
Martin Dubs (Switzerland) gave an overview of meteor spectroscopy and calibration. Wide angle lenses produce curved meteors. Spectra need to be linearized and wavelength calibrated. Flux calibration is needed to correct for vignetting, grating efficiency, camera spectral sensitivity and atmospheric extinction.
Waleed Madkour (Japan) gave an overview of the Kochi University of Technology (KUT) meteor radar system that has operated since 1996 at 50.75MHz and 50W. The studies include meteor echo counts, durations, directions (through interferometry) and meteor burst communication options. There is a lack of long-duration signals – this may be due to oxidization of meteoric ions in the ozone layer. Upper limits are 45-50s for Perseids 12-13s for Geminids.
Anna Kartashova (Russia) described work being carried out since 2014 that combines optical and acoustic (pressure) observations. Infrasound signals are searched for events that are coincident with double-station optical meteors. In 2016, the set up will include five optical stations and three infrasound stations.
Margaret Campbell-Brown (Canada) described the work of the Canadian Automated Meteor Observatory. Despite this Ontario based group already collecting much radar data via CMOR, optical data is also required as it leads to better orbits, produces light curves and covers a different particle size range. They operate two sets of cameras located 45km apart. At each station, an “influx system” uses auto-detection and manual processing and mostly captures slower meteors and a “mirror system” uses a wide field camera for detection and a 1.5-degree camera for tracking. This latter system uses automated reduction and typically captures faster meteors. They have not yet conclusively identified any hyperbolic meteors.
A new version of the IMO website is being developed by Vincent Perlerin and will go live shortly.
The next IMC will be held in Petnica, Serbia during 21-24 September 2017.