Are you sure it was hydrazine? There have been a number of sightings of clouds of (I think) sodium released by sounding rockets launched from Poker Flat, Alaska. patrick On 05 Jan 2009, at 23:22, Canopus56 wrote:

I am looking for a reference to a 2008 event where amateurs observed a hydrazine cloud from a satellite. I'm thinking it may have been the USA 193 satellite destruction in Feb. 2008? Any guesses? - Kurt