>Most of the satellites seem to use fairly off-the-shelf parts,
>and they work for the most part. I'm looking for more information
>on what special considerations we should have, besides the obvious
>temperature and pressure differences.
>Especially regarding radiation, etc.

I am currently working on an instrument that is using some COTS parts for 
moon orbit.

COTS and non-radiation tested MILspec parts that we use go to a radiation 
testing lab and samples are suitably tested using a Co60 source.
This then qualifies that batch of these parts for use in radiation 
environments. I don't know off hand what the radiation dosage used for our 
testing is, but do recall that it took several days with stops to check part 
operation after each so many hours. Because of this and the costs associated 
with doing the testing it pays to purchase a reasonable size batch of parts 
for any future projects to ensure that you do not need to go through the 
loop again.

Companies that supply radiation resistant parts avoid the batch problem by 
supplying chips where the die are made to the same process as the qualified 
die. Any mask change to the die requires a re-qualification, which is why so 
many analogue chips have stayed the same for many years without new chips 
coming onto the market.

Typical tests include leakage and operating current (ICs & transistors), and 
on state saturation voltage (transistors), both of which give indicators of 
radiation sensitivity.

Precisely what gets tested with processors and the like I do not know, but 
when we fly EPROMS they get a 1mm thick tantalum shield on both sides of the 
chip. In the UK we buy suitable pieces of tantalum from Goodfellows.

A basic rule of thumb seems to be that parts with geometries of 0.25um and 
smaller are inherently radiation insensitive, but you would need to bee able 
to show test data to confirm this. 

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