Hallo [hier könnte Dein Vorname stehen],
erstmal willkommen im Forum!
Wo Du schon danach fragst - andere wird das ja auch interessieren ... im Smalltalk habe ich in ganz anderem Kontext mal dazu etwas geschrieben, aber das können dort nur Mitglieder lesen, also zitier ich mich hier mal selbst:
Es geht um den Staubschweif des wiederkehrenden
Kometen 21P/Giacobini-Zinner, und der ist eigentlich nix Neues.
Vielmehr ist der
Draconiden-Sternschnuppenschauer schon mehrfach in der Spitze relativ intensiv ausgefallen, und nach einer Meteoriten-Konferenz im Mai nahm bereits der englische
"Telegraph" am 17.06. die vermeintlich neue Meldung auf, und
space.com war am Vortag noch schneller, aber dennoch seriöser.
Tatsächlich wurden schon 2005 wegen der Bahnberechnungen für Staubteile des Kometenschweifs für 2011 Sternschnuppenschauer berechnet (The Orbital Debris Quarterly News/NASA, Seite 6/7:
"No Fire from the Dragon this Year"). Und Watanabe/Sato gingen 2008 in
"Activities of Parent Comets and Related Meteor Showers" von theoretischen Spitzenwerten von 200 bis zu 600 Sternschnuppen je Stunde in 2011 aus.
Hier ist noch das Abstract des Vortrags, auf den sich jetzt so viele Meldungen angeblich stützen:
The 2011 Draconid shower risk to Earth-orbiting satellites
William J. Cooke(1) and Danielle E. Moser(2)
(1) Meteoroid Environment Office, Marshall Space Flight Center, Huntsville, AL 35812
(2) Stanley, Inc., Huntsville, AL 35812
william.j.cooke@nasa.gov
Current meteor shower forecast models project a strong Draconid outburst, possibly a storm, on October 8, 2011, with a duration of approximately 7 hours and peaking between 19 and 21 hours UT. Predicted rates span an order of magnitude, with maximum ZHRs ranging from a few tens to several hundred. Calibration of the NASA MSFC Meteoroid Stream Model(70) to radar and optical observations of past apparitions, particularly the 2005 Draconid outburst(71), suggest that the maximum rate will be several hundreds per hour. Given the high spatial density of the Draconid stream, this implies a maximum meteoroid flux of 5-10 Draconids km-2 hr-1 (to a limiting diameter of 1 mm), some 25-50 times greater than the normal sporadic flux of 0.2 km-2 hr-1 for particles of this size. Total outburst fluence, assuming a maximum ZHR of 750, is 15.5 Draconids km-2, resulting in an overall 10x risk increase to spacecraft surfaces vulnerable to hypervelocity impacts by 1 mm particles.
It is now established that a significant fraction of spacecraft anomalies produced by shower meteoroids (e.g. OLYMPUS and LandSat 5(72) are caused by electrostatic discharges produced by meteoroid impacts. In these cases, the charge generated is roughly proportional to v3.5(73), giving a Draconid moving at 20 km s-1 approximately 1/80th the electrical damage potential of a Leonid of the same mass. In other words, a Draconid outburst with a maximum ZHR of 800 presents the same electrical risk as a normal Leonid shower with a ZHR of 15, assuming the mass indices and shower durations are the same. This is supported by the fact that no spacecraft electrical anomalies were reported during the strong Draconid outbursts of 1985 and 1998. However, the lack of past anomalies should not be taken as carte blanche for satellite operators to ignore the 2011 Draconids, as the upcoming outburst will constitute a period of enhanced risk for vehicles in near-Earth space. Each spacecraft is unique, and components have differing damage thresholds; programs are encouraged to conduct analyses to determine whether or not mitigation strategies are necessary for their vehicles.
(70) D. E. Moser and W. J. Cooke, Earth Moon Planet., 102, 285 (2008).
(71) M. Campbell-Brown et al., Astron. Astrophys., 451, 339 (2006).
(72) S. Close, personal communication (2009).
(73) R. D. Caswell et al., Int. J. Impact Eng., 17, 139 (1995).
Schaun' wir also 'mal ...
Gruß+cs,
Dietmar
