There are two neat concepts from the early days of communications experiments using satellites and Echo is one of them (the other is SCORE).
There were a lot of "ideas" for follow on echos...one used a gravity gradient "pole" to stop the balloon from spinning and keeping it pointed to the earth, allowing a directional reflector to be installed in the balloon...another used a radar reflector like concept inside the balloon to increase the amount of DB that returned...
The problems were "large" however. Doppler shift and tracking were issues at the time (and probably still are)..the antennas were going to have to be large (really large).
My elmer in Dallas when he was in the USAF did some radar experiments with echo...I got to see it a few times.
SCORE probably has more relevance to todays possibilities.
Robert WB5MZO _________________________________________________________________ New Windows 7: Find the right PC for you. Learn more. http://www.microsoft.com/windows/pc-scout/default.aspx?CBID=wl&ocid=PID2...