Previously discussed
here
The biggest problem isn't the computer nor the software. That like evulish said, is relatively simple, run a few programs and config. The BIGGEST problem you will have is getting bandwidth. Not at the encoding computer but at the server which will host the feeds others will see. NASA is running probably something like an DS3 (
45Mbps) (http://www.cybercon.com/oc.html) (http://www.broadband.com/Business/ba...ml?R=googleoc3)and costs THOUSANDS to connect. Many users get a high download speed, big deal, you need a big UPLOAD speed. With the DS3 you could get a good connection at 300Kbps could get you about 150 connected with little lag, and a good quality video. At which point you would THEN need to worry about the server.
Now, one possibility would be to get ahold of someone with NASA and see about uploading to their servers and have them host your webcast. Just a thought.
-Mike