Encountering the Teeth of the Dragon: The hazard posed to satellites by the anticipated Draconid meteor storm on 2011 October 08

Duncan Steel
Australian Centre for Astrobiology, University of NSW

David Asher
Armagh Observatory, Northern Ireland

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     Last modified: July 29, 2011

Abstract
The Draconid meteor shower – the radiant lies in the constellation Draco, the Dragon – is annually active from October 8–10 with naked-eye count rates near 20 per hour, but with storms (counts of thousands per hour) occurring if the Earth passes through filaments of meteoroids yet incompletely dispersed since liberation from the parent comet (21P/Giacobini-Zinner) within the past few centuries. The comet’s orbital period being 6.6 years, a cyclicity near 13 years is anticipated, as exemplified by the storms observed in 1933 and 1946. Because 2011 is 65 (= 5×13) years after 1946, a storm is feasible this year. Modelling of meteoroids released over the past two centuries indicates a series of peaks between 17:00 and 21:00 UTC on October 8th, and meteor rates up to a thousand per hour. Only observers in tropical Australia might witness anything unusual in the pre-dawn hours on October 9th (local time), because the radiant is well north (declination +54 degrees).

This anticipated event is of significance with regard to satellite safety: it would be the first Draconid storm since the start of the Space Age. Spacecraft operators could benefit by being forewarned and so ready for possible malfunctions, perhaps orienting their platforms to minimise the probability of damage. In 1993 August an intense Perseid meteor shower was forecast, linked to the appearance of 109P/Swift-Tuttle in the preceding year: one functioning geostationary communications satellite, ESA’s Olympus, suffered an end-of-life anomaly during that outburst. Various other spacecraft are suspected to have received damaging impacts at the times of other intense stream intersections. During the Leonid shower outbursts in 1998–2003 the Hubble Space Telescope’s optical axis was directed away from the radiant for a few hours during pre-calculated peak activity times, following the parent comet (55P/Tempel-Tuttle) passing perihelion in early 1998.

The Draconid outburst of 2011 is due shortly after this conference. In this presentation we review the available predictions; later, when writing up this paper for publication, we will be able to compare those predictions with reality!