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 CPU.
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 disputable. 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 project.
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 shining.
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.