Also, with NavSpaSur you can hear reflections of meteors and the moon = when it passes over the fan. I've listened to it some, but others = including one in South Florida that Ted mentioned, have done alot more = work with it, including using DSP I beleive to measure doppler and = attempt element calculations. My own problems with it have been not = having enough time. BTW, it only works on satellites with inclinations greater than 33 or so = degrees. By listening to the return, which may be extermly short or as = long as a second or two for the shuttle (much longer for the moon), you = get an indication of the size of the object too. Bill Bard wtba@eci-esyst.com