[eth0ws]

I thought you were being handwave-y about the signal being returned because that's an obscenely small amount of power, but you're right. Hardware that is probably 50 years old at this stage, in the cold of (interstellar)space, and we're still able to talk to it despite the signal after its long journey back being ~0.000000000000000001w.

[brcmthrowaway]

I still havent figured out how people decide signals under the noise floor

[tails4e]

Essentially averaging. To put it simply, noise is random while the signal is not. So if you average 2x the noise reduces but sqrt(2) but the signal remains. Keep doing that and you have the signal appear out of the noise.

GPS operates at a negative SNR. That also uses code division multiple access to allow multiple transmitters to operate on the same frequency and the signals do not interfere.

[Vecr]

A lot of the signal processioning/decoding gear is cryogenic. Maybe everything to the ADC?

[toomuchtodo]

Applied radio astronomy with a transmit component.