I have worked a few satellites over the years, through the hobby of amateur radio.

I have of late been making use of the digital repeater (digipeater) mounted on the International Space Station.

The ISS makes a few passes per day and gives you a small window of opportunity to pass signals to other stations.

A Linux platform can be used to track and correct for doppler frequency shift. 

Check out the sat panel here

Here is a block diagram of my satellite ground station.