FFT Integration

Hello, I am relatively new to Gnuradio and GRC

I am looking to use Gnuradio for Radio Astronomy

I am doing some measurements and I need the whole FFT spectrum from my
RTL SDR to be integrated for at least half an hour for my observations.

Is there any way that I can export all of the data (i.e. the full
bandwidth(FFT)) coming from my RTL SDR, into a file on my HDD with
Gnuradio (preferably as a csv file or similar) so that it can be
analyzed further?

Or is there a way of constantly integrating all the samples from the SDR
for all of the bandwidth over this time period?

I realize that this will create a lot of data

Many thanks

Jon - M0ZJO