My cable company (Verizon FIOS) doesn't carry NASA TV channel (according to the NASA TV FAQ they can have it at no cost, which means they must not carry it because they hate space, America, freedom, and puppies).
Since it is on very late in my timezone, I was hoping to Tivo it but since I don't get the channel that wasn't going to work. Luckily I found this script that lets me easily record the stream to disk using mplayer. On my mac I installed mplayer using MacPorts ("sudo port install mplayer") and the script worked on my first try.
I've put a copy of the script here: http://whatexit.org/tal/record-nasa.sh.txt