How do you even begin to deal with that much data per second? What do they do with it? Storing more than a few minutes of data isn't practical is it? Do they process it in realtime?
You're right in the last point, the raw data has such a high rate that they have to process it on the fly, which has its drawbacks. The reason that these instruments output so much data is that the process of correlating the signal between each unique pair of antennas is O(n^2) in the number of antennas. Now 36 antennas (when complete) is not very large, that's approximately the size of the VLA[1], but because of the…
Whoops! I misremembered in my post above, data rates on the VLA should have been around 20 MB/s not 10 GB/s, but I can't seem to edit my response above now.