I've worked on space-based sythentic aperature radar (SAR) and all the fancy algorithmic stuff can fit on a largish FPGA.
http://en.wikipedia.org/wiki/Synthetic_aperture_radar#Multis...
Here's the thing: technology is moving faster than the military can procure it right now. Way, way faster.
When your procurement cycle is at least 10 years and you want something to work for at least the next 40 years and all that projects take much, much longer and get much, much bigger than they need to.
The SAM sites that people started designing 10 or 20 years ago are big, sure. What about the SAM sites that you COULD design today and build in the next year or two, but which the US military would never accept without the impossible to get sign-offs.
The military is kinda like the FDA. They want to make sure that the stuff that makes it through the process is definitely, for sure, to all reasonable scrutiny, acceptable. There are a TON of really neat devices out there that are 5-10 years from being available to the general public but if you're really dying you can potentially get as a part of a clinical trial.
To judge what's available today after jumping through all the hoops for a decade as "The State of The Art" is understandable, but not entirely correct. I can't fault you for thinking that it is but I won't agree with you either.
