|An SPA Meteor Section Special ReportDecember 2002 produced three fireballs seen from multiple sites in the UK, on December 4, 17 and 19. In addition, at least two other fireballs occurred on the night of December 17-18, seen by single observers at 20h42m UT from north-west England, and about 00h30m UT from South Wales (a bright meteor seen from indoors). Such a relative “cluster” of fireballs on December 17-18 is unusual, though not unprecedented, and following the analysis leading to this report, it is very unlikely that they all derived from a single source. A casual report of four faint binocular meteors in only 2 or 3 seconds around 05h30m UT on December 17-18 was received too, but this was probably unrelated to the fireballs. Here, we concentrate on the three multiple-observer events.
2002 December 4-5, 19h17m +/- 2m UT
Six observers in Devon, Hertfordshire, Northamptonshire, London, Essex and Nottinghamshire reported details on this probably magnitude -5/-8 fireball. Several of these people were out to spot the ISS pass at around the same time, which led to a degree of scatter in the timings for the event, with outlying estimates between 19h15m-19h25m UT. The mean was 19h17m +/- 2m UT. This also led to few accurate sky-positions for the start and end of the visible trail being received, and it has not proven possible to derive even an approximate surface track from the estimates that were made. The fireball probably passed high above the general area of south Wales to the Severn Valley/Bristol Channel, possibly on a roughly north-west to south-east trajectory, but this direction of motion is uncertain. Two of the observers noted fragmentation took place, probably late in its flight, and almost all agreed it was bright green in colour.
2002 December 17-18, 16h51m +/- 1m UT
Eight reports on this event were received from Lancashire southwards across England. The sketch map of mainland Britain here shows their distribution, where most of the observers are indicated by individual small red target symbols. Selected cities are shown as named open black circles, while the most likely position for the fireball’s surface track is given as the red arrowed line. As with the December 4-5 fireball, there was some scatter in the timing estimates of between 16h40m-16h53m UT, but the majority were closer to the mean value of 16h51m +/- 1m UT adopted here. Details about the object’s appearance and apparent flight path were hampered by the presence of the almost-full Moon, but there was a reasonable degree of consistency between most of the sightings, allowing an approximate surface track and atmospheric trajectory to be suggested.
Derived details based on this track were as follows. The meteor probably started at about 130 km altitude above the River Crouch area north of Southend in Essex, at roughly latitude 51 degrees 38′ N, longitude 0 degrees 47′ E, both positions with errors of at least +/- 10′. Its visible flight carried it south-westwards from here, high over south-east England and the Isle of Wight, to end approximately 20 km offshore south of Brighstone, IoW, at ~ 90 km altitude above the Channel waters (latitude ~ 50 degrees 26′ N, longitude ~ 1 degree 25′ W, again both parameters with a minimum +/- 10′ error). This gives a surface track length of some 210 +/- 20 km, and an atmospheric trajectory of ~ 213 +/- 20 km length at an angle to the horizontal of just 11 degrees +/- 1 degree, very nearly grazing the atmosphere, if correct. The best estimates for the fireball’s entire visible duration were between 3 to 3.5 seconds, which equates to a mean atmospheric velocity not allowing for deceleration of ~ 66 +/- 11 km/sec. Such a very high velocity is consistent with the higher than average start and end heights for so bright a meteor.
The observers generally agreed that the meteor had been a very bright green colour, and that it flared to around magnitude -4/-8, breaking up into several fragments, perhaps two to four main pieces, late in its flight. Some people described the fragments as being orange in colour. Given such a high speed, fragmenting, atmospheric flight, it is most unlikely that any sizeable meteorites would survive to reach the surface, but any that continued to follow the same mean path as the fireball would have splashed-down into the Atlantic Ocean around 150 km west of the south-west tip of Brittany, the Pointe du Raz.
2002 December 18-19, 06h29m +/- 1m UT
Despite eleven sightings being received on this probably magnitude -5/-10 object, only two observers were able to give reasonably accurate sky-positions for the trail, and it has not been possible to derive a plausible surface track from these, as they were made by observers too close to one another in southern England. There were two main clusters of observers, in Berkshire-Surrey and Hampshire-Wiltshire-Dorset, plus outlying single witnesses in Worcestershire and Cardiff. The meteor most likely passed high over the Cotswold Hills on an east to west, perhaps north-east to south-west, trajectory, but this is only a best guess. Several observers mentioned the meteor was golden-yellow in colour, and it seems to have been quite slow-moving. For once, the majority of timings were within one minute of 06h29m UT!
As always, my thanks go to all the observers for their data, and also to John Lambert of Newcastle and Northumberland AS’s for rounding up several of the December 4-5 and 17-18 sightings particularly, Mike Dale of Royal Observatory Edinburgh, John L Roberts, and Paul Sutherland of the SPA for forwarding additional observations of the December 18-19 fireball.
|Report prepared by Alastair McBeath Email: firstname.lastname@example.org|