After two days of deliberations I finally think I know exactly what it was that I've seen with the fabulous Centaur pass on Sunday evening. The clouds (and also the concentric rings) must have been produced by the hydrazine thrusters rather than the actual firing of the Centaur engine because this engine burns liquid hydrogen and oxygen which would leave pure water vapor (and unless it condenses would not be seen). Just before the escape trajectory burn some attitude maneuvers would be done by the Centaur to get into the right attitude for the burn. This must have caused the first bright cloud which remained near the position of the DMSP F18 satellite. The actual firing did not produce a visible cloud but after that firing some more attitude maneuvers were done to get into the right venting attitude. This caused the fresh cloud which was now at the new (escape trajectory) position. Having looked at it with 10x50 binoculars I definitely saw a red dot (the engine was still hot from the firing) and clouds did not emerge continuously but as *puffs of smoke*. There was a brief pause of cloud generation after the new attitude maneuver and the cloud just expanded and became weaker but then the venting started and caused a continuous cloud generation and the cloud grew brighter again. I wouldn't mind if they launch more Atlas Centaur rockets perfoming such maneuvers! Gerhard HOLTKAMP Darmstadt, Germany ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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