[amsat-bb] Re: Keep It Simple, MM
David B. Toth
ve3gyq at amsat.org
Mon Oct 1 19:20:55 PDT 2007
At 08:06 AM 10/1/2007, MM wrote:
>Keep It Simple Silly KISS
>By Miles WF1F
>The direction of this tread is caution. I am not
>suggesting that we do not use digital technology for
>satellites, just that we need to be careful of the
>technology. The Space environment is not kind to
>digital circuits. Digital circuits are easily
>corrupted by solar radiation and thermal stresses. A
>digital circuit designed for use on Earth many not
>survive the rigors of outer space. This is partially
>because of the Size of a transistor inside a modern
>In 1978 a computer transistor was made up of wires 3
>microns in size. Today's CPU Itanium, uses wires 0.18
>microns in size. The new DSP chips used on Digital
>radio will be some where in-between. With the wire
>sizes in the 0.20-micron range, it's much easier for
>solar radiation to cause temporary shorts, which can
>cause system crashes.
The SDX is a software-defined radio ... it does not necessarily, and
probably does not, use a DSP chip.
>Keep It simple. A small satellite that does one or
>two features is better than one big satellite that
>does 10 big features.
At the cost of launches and satellites, i think this point is easily
I am sure that the engineers are looking at an overall systems approach, AND
they've done this before. The difference is the addition of a
software-defined approach, which WILL be space-tested in SuitSat2 anyway
>Axle lead Resistor and through-hole mounting of
>components are much more resilient in space than
>surface mount components.
Miles, do you have any data to support this statement because right
off-hand, I can't see why this would be true.
>Hardware is not your only problem; you also need to
>Extensively Test the software that runs the satellite
This is not the first satellite these guys have built - I think they
had this somewhere on their "To-Do List" ...
>The Analog satellites AO-7 (launched Nov 1974) and
>AO-10 (June 1983) are still there when the sun is
Well, that is actually a bug, not a feature. We need to have a way
that we can guarantee that when a satellite dies, it STAYS dead. That
was a real sticking point with Larry Kayser when he was still alive.
These things pop up, un-controlled, and if we had enough of them,
they'd be an interference problem.
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