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Re: CMOS flight heritage



>>> "W.J.Ubbels" <w.j.ubbels@student.tudelft.nl> 4/28/2005 
>does anyone know whether the following 
>C-MOS chips have flown successfully on AMSAT 
>missions?

PCsat uses a CD4040 for its 72 hour fail safe timer.
(Re boots the TNC's if we dont clear the timer at
least once every 3 days.)  And PCsat is still "working".

But this is *absolutely in no way* an endorsement
of such use for the following reasons:

1.  What does "work" mean?
2.  PCsat spends more time resetting itself on
     every orbit due to low power budget that
     the occassional 72 hour reset is not an issue.
    It is only a few times a year of full sun that
    it ever runs more than a fwe hours at a time
    anyway. (then we have to watch the timer
    carefully...
3.  Our satellite was a "nobody-cares-risk"
    mission.  Meaning the "building" was the
    educational value, not reliability.

Having said that, it is interesting to note that we
will NEVER use a 72 hour timer again.  Because
PCsat's orbit actually made its first pass on the
3rd day about 73 hours after the similar pass
on the Fridday before.  Meaning, over weekends
and we missed a pass on the weekend, by the
first pass on monday was too late!

And all it takes is a reset and poor sun and we
cannot recover until the next full sun period.
So on PCSAT2, we did the following:

The timer is 96 hours. (covers a 4 day weekend)

Not the answer you needed, but an anechdote
none-the-less.

Bob
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