As far as data direct from instruments goes, I'm pretty sure that they usually do encrypt the data before sending, but not with something like PGP. The idea is that data from satellites/probes can easily be scrambled before reaching Earth. Therefore, it's a good idea to include some error correcting facilities in the data stream. In addition, because the data sent back is often huge, compression utilities (which are a form of encryption) are used.

I don't know of any specific space-based examples offhand, but I'm sure if you looked in, for instance, the LIGO documentation, you'd find this. I think I first read about it regarding SOHO, actually.

PGP would be really unwieldy for scientific data. Heck, it's barely useable for Internet transactions. Slow, slow, slow. (Or maybe that's just me living in the early '90s....)

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