On 12/18/12, Trevor . <[email protected]> wrote: > The BBC quotes an SSTL engineer as saying It was too early to say that the > satellite was dead. He stressed that any spacecraft would be unstable > immediately after launch, and that North Korea could be trying to rectify > the problem.
But that would depend upon what its rotational geometry is. If it's rotating in a stable mode, then there may be a chance. But if it's marginally stable, the slightest perturbation could make the satellite unmanageable. Shortly after I started grad studies many years ago, I saw a video recording of a satellite made using a ground-based camera. One could see the sunlight reflecting off the photovoltaic arrays and, thereby, determine both its spin rate and its axis of rotation. As I recall, the ground station had lost control of the bird and it started rotating about an axis parallel to the length of the arrays. Over a period of days or weeks, that configuration had become unstable. The satellite slowly moved through about 90 degrees, possibly because the angle of libration became too large . It eventually settled into its new orientation with the rotational axis being through the main body. > > "We take typically two or three days to get a satellite stable, and we know > what we're doing - whereas this is the North Koreans' first try. But if the tumbling is such that the North Koreans can't establish communications, the satellite's a write-off. > > "It would be prudent to wait a little longer and monitor the tumble rate to > see whether there's any attempt to stabilise it." The satellite's been in orbit for several days now. They might not have much time left. > > See http://www.bbc.co.uk/news/world-asia-20769324 > > A Google English Korean newspaper report is at > http://tinyurl.com/cjhpa79 73s Bernhard VA6BMJ @ DO33FL _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
