NASA you can
Angel One is another
The rest are scrambled. To get C-Span and the other PI channels you have to subscribe to something on Dish.
This is pretty old, but it is not true. You can get the PI channels from a tech support person. I used that route to get mine. I pay dish about $18 every month so I can use my 2 522 machines, so I should I am "their customer". I also have an account on dishnetwork.com. I did get a CSR to refuse me when I first tried, but I just jumped to the tech support lady on my second attempt and it worked.
Brad