Much later than I’d originally intended while I was still SPA Meteor Director, I’m now starting to catch-up with the outstanding meteor shower analyses from late 2011, hopefully in roughly chronological order!
A recent IMO video analysis of the 2011 Draconids (see their journal “WGN”, 40:1, 2012 February, pp. 41-47 for details) essentially confirmed the timing and strength of the moonlit peak already found in the preliminary IMO visual online assessment of the shower’s outburst, where a maximum estimated ZHR of around 300 was found at 20:12 UT on October 8-9, give or take a minute or two. The activity was at or above half this peak level from circa 19:20-20:40 UT. Fresh video information included a radiant derivation at RA 17h29m, Dec +56°, each value ± 1.3° (that is, ± 5.2m in RA), the meteors having an average atmospheric-entry velocity of about 21 ± 0.5 km/sec. This compared very favourably with the standard values usually adopted for the shower of RA 17h28m, Dec +54°, velocity 20 km/sec.
Although too little visual data was received by the SPA to carry out an analysis comparable to the IMO’s, it has now been possible to perform an analysis of the radio results the Meteor Section collected, which is discussed here. Most of the radio meteor observers provided data in hour-long segments only, which showed that probable Draconid activity had been present from about 14h UT on October 8 through until 02h UT on October 9, at least at a level liable to be readily detected visually or by video, with a distinct peak signature in the hour beginning at 20:00 UT. This pattern was quite closely comparable to that found in the IMO visual results (albeit with at least hourly datapoints available only between 14:30-23:55 UT on October 8; the IMO video information, where most observers were based in Europe, ran near-continuously from just 17:10 to 23:35). It also confirmed that despite a variety of predicted maximum timings in advance for the UT evening hours, only one clear peak had happened.
Four radio observers provided counts of meteor echoes in shorter periods across the Draconid peak as well, lasting between 5-10 minutes, which allowed a more detailed examination of activity in the hours around the maximum. A direct comparison between the IMO’s visual and the SPA radio results showed again a closely similar pattern, with seemingly even many of the minor fluctuations between individual datapoints found in both sets. The radio information also found activity at or above half the maximum flux had been present from 19:20 to 20:45 UT or so, virtually identical to what the video results showed.
This was naturally a very pleasing outcome, allowing further confirmation of what the earlier analyses had indicated.
In Britain, only a few observers in southern England and the Channel Islands seemed to have had any luck in seeing something of the Draconid outburst, and then often far less than they might have hoped. Elsewhere in mainland Europe, conditions were thankfully often much better.
A full list of observers whose data were included in this analysis can be found on the SPA Forum at forum.popastro.com/viewtopic.php
Assistant Meteor Director, Society for Popular Astronomy
2012 June 2