(Ref. a) Evidently, I am reading too much into this "echo" effect;
(Ref b) As a treat, I recommend the youtube video: "JointSTARS.wmv (2:54 long). This features the nondescript looking airplane in the depiction- gets my juices flowing- enjoy. Cheers.
Ref. to (a) above - Anybody here heard 'round the world echo on 20 Meters ? ... it's an awesome phenom to behold, and today with propagation 'in the ditch' so to speak it will be hard to demonstrate 'live', but when things are good it's not that rare. The echoes from the DOD's multisite-originated multicast/simulcast system are due to the time delay the other poster pointed out; the delays could also be due to satellite echo delay, I say, I do not know as a certainty, but, if using geostationary sats for links the time delay to and from the geo sats are not insignificant either ...
For some HF echo, round-the-earth paths of recordings check out:
http://www.aa5tb.com/recordings.html the section titled: "Radio Echoes - Short and Long Path"
Ref. to (b) above - JSTARS is pretty impressive, it is quite amazing the detail that can be 'rendered' when you pepper a target area with a nearly continuous barrage of short, interspersed RADAR pulses then work with both the Doppler shifts imposed plus the amplitudes returned and integrating the returns over time ... the effect is as if you had a much larger, more sharply defined RADAR antenna, leading to the term SAR (Synthetic Aperture RADAR) ... the rendered detail can be quite amazing ...
Just to be clear: JSTARS <> AWACS
AWACS - rotating dish on top, meant for detection and control/direction of aircraft in the 'theater'
JSTARS - longish stationary pod attached/beneath the aircraft, meant to look at targets (kinda sideways to the aircraft, not straight down) on the ground ..
Edit: Update JSTARS desrip.