In the evening of October, 21, 2011 between 18.45 and 19.15 CEST in Czech Republic, Austria and Germany spreads of clouds were observed from the northwestern to southwestern horizon at a maximal altitude of 15-20°, which reminded very strongly to noctilucent clouds (NLC). But NLC is not ineligible as explanation for this season of course and also the cloud structure’s altitude calculated from the sun elevation (-8° to -11°) is ca. 60-70 km is too low for NLC.
All known observations with observed direction of clouds (if noted).
Black Points: Observations without photos
Red points: Observations with photos (meteoros-forum)
Violet points: Animations (1 – 2 – 3)
The most probable cause could be the exhaust gases of the Soyuz rocket, which was launched in Kourou, French Guayana at 12.30 o’clock, in order to bring the first satellites for the European navigation system Galileo into the earth orbit. During the overflight above Europe a large extent of water, carbon dioxide and nitrogen containing exhaust gases were ejected with a speed of approximately 4km/s and fell downwards unimpeded. At a height of approx. 70km the water vapour condensed into clouds, which were illuminated – like the NLC – also by the sun, while normal clouds lay long in the shade.
A further possibility of explanation could be a meteor trail. There is one not too much detailed observation, which could refer to a fireball: Report in German and with automatically Bablfish-Translator. But this possible fireball was in this moment, in which would observe the NLC-shaped clouds (18:45 CEST). And as experience teaches a meteor trail needs several hours to develop.
Authors: Landy-Gyebnár Mónika, Claudia Hinz, Wolfgang Hamburg