UDP isn't a form of data; it's a transmission protocol. You can use it over any transmission method at all, but frankly, I highly advise against using it for satellite communications. UDP is fast and lightweight because it doesn't do anything about reliability. It just tosses the packet over the fence and assumes it got there okay. In space, you have to worry about interference in a big way, much more so than on Earth, and many of your transmissions may be mission-critical, especially if they contain instructions for a satellite's attitude control or something like that. I'd use something a tad more reliable, personally, even if it does eat into bandwidth. You want the spacecraft to know if there's been data loss.<br /><br />I'm afraid data compression isn't one of my areas of expertise, however, but there are lots of algorithms that can be used to squeeze the most out of your bandwidth. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em> -- The Tenth Doctor, "Blink"</font></p> </div>