The Hubble space telescope generated, to my knoweldge, 45TB over its lifetime (this is used for Hubble data). Or that is at least how big the database is.
1TB=10^12 bytes=10^13 bits.
so we have 4.5*10^14 bits of Hubble data
I will assume 1 bit every handful of millisecond (say 5) for encoding neural activities. This calculation depends on firing rates and what exactly we want to encode. But the currently highest reported value is 180 bits/s [1] which is roughly one bit every 5ms. Now, if I wanted to be more precise, the bitrate depends on what you want to encode and how. If we were to encode the neurons varying spatial state we would need far more bits. In any case, the 1bit/ms seems like a good figure.
Brain = 10^11 neurons, 10^3 bits per second = 10^14 bits per second.
So in reasonable approximation the brain produces the amount of hubble space data every 30 seconds.