At 11:22 PM +0000 2/8/09, Nigel Gunn G8IFF/W8IFF wrote:
Oscars 10 and 13 handled the propulsion issues without mishap.
Not really.
Quoting from The Satellite Experimenter's Handbook, Second Edition, page 15-19, about AO-10:
"The first burn went relatively well -- there was a small deviation from the expected burn duration, which placed the spacecraft perigee somewhat higher than planned. The second burn could not be accomplished because a slow leak in the high-pressure helium system during the week the spacecraft was being reoriented prevented the opening of valves feeding fuel to the thrust assembly."
The "small deviation" is known to be due to a design error in the simple digital logic circuit that controlled the burn duration.
On AO-13, the kick motor worked exactly as planned, and the spacecraft achieved the intended orbit. But that orbit could have been chosen better, as it turned out. The early re-entry after only 8.5 years was not anticipated, and probably could have been avoided if we had been smart enough, soon enough. Reference: AMSAT-DL press release, http://www.amsat.org/amsat/sats/n7hpr/ao13pressrel.html
73 -Paul kb5mu@amsat.org