Radar tracking is used for Earth satellites and big enough asteroids. As the FH-launched Tesla Roadster is leaving the Earth-Moon system and it is quite small object (the car + the payload adapter are much smaller than telco satellites, but the second stage is possibly still attached and is a bit bigger), my question is:
For how long (or how far from Earth) will it be picked by orbital tracking radars? Can it be significantly longer if it is specifically targetted? Could for example the Arecibo Observatory be used to pick it even in the asteroid belt or is it just too small?