Catching up on my mail ... Tony Beresford <starman@camtech.net.au> asked: >With all the recently launched satellites that use their own >low thrust rocket motors to get to final orbit, shouldnt we >be seeing some evidence of such activity, like glowing >patches of exhaust gases near such objects. The visibility of propellants depends on the types of propellants and the amount of thrust. For a typical 100 lbf (440 newton) bi-propellant apogee motor on a Hughes HS-601, Lockheed Martin A2100 I doubt it would be visible due to its low thrust. The space shuttle OMS are fairly powerful engines and have been observed during major burns. The Centaur (liquid hydrogen / oxygen) engines were observed during a classified Titan launch from Europe. The burn generated a large comet-like tail and were almost certainly at an appropriate sun-angle which made them visible from the ground. Of course if you've got infrared eyes you've got more of a chance of seeing the burns ... >Perhaps somebody like Phil Chien can comment on when such >activity takes place. I could certainly make some inquiries ahead of time, but most of the time it's dependent on many variables, most notably exactly what time the launch occurs. Philip Chien [M1959.05.31/31.145//KC4YER@amsat.org]