I think Bob's dead on with regard to the initial concern about radiation damage. Much of that can be mitigated once the results of the radiation testing are known. At this point we don't have that data. There is also the memory of how AO-10's analog systems continued to function for years long after the digital systems had failed.
We would also do well to head Martin's points about design diversity. We had to blow up a good rocket once on the Eastern Range due to the lack of it. I think the problem with proposing the ACP as providing the diverse backup is that it requires a completely new ground station investment.
There's also added risk by increasing the complexity by adding an analog block to make make an analog transponder. That risk has to be weighed against the benefit of gaining diversity in the overall system as well as the potential to extend the mission even after the SDXs have served a long and productive life. Until some serious work is done on the analog block and the interfaces it would requie, we're trying to compare two unknowns.
My suggestion is to continue the work on an analog path until we have sufficient data to make a reasoned and thoughtful engineering analysis. Then follow that path wherever it may lead.
Lee-KU4OS
On Tue, 2006-10-03 at 01:05 -0400, Robert McGwier wrote:
I think the issue is that people are worried about radiation damage to the SDX CPU. If the DSP dies so are we. We really need to subject that puppy to a brutal amount of radiation in our testing and indeed test to destruction.
Bob N4HY
Matt Ettus wrote:
I know that the current documented thinking is to have two SDX's and no analog transponder, however we did say we'd bring up for discussion at a telecon prior to the Symposium. I know that this was brought up in July 2005 where it was clear that the answer to the members was yes, we'd have a backup _analog_ linear transponder.
Why stop there? We should have a backup to the analog transponder in the form of a CW transponder. Then we can back that up with a spark transponder. Finally, we should have some sort of semaphores or smoke signals to back that up.
Seriously, if we have 2 SDX's, aren't they backups for each other?
Matt
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