A Radio Telescope is nothing more than a giant Radio Receiving Antenna, and the Green Bank Telescope is 100 Meters across.
An antenna can not only receive, it can also TRANSMIT.
Connect a Radar Frequency TRANSMITTER to it and it becomes a Steerable Radar System, without having to build a new dish.
And Radio Telescope can be modified to do this.
If they really wanted to, Aracaibo could be rebuilt and refurbished to do this as well, although it isn’t as steerable................
Thanks for the extra insight.
I was trying to emphasize the point that Earth threatening space rocks and ice balls do not generate their own radio waves, at least until they enter the atmosphere, at which time they become an unavoidable catastrophe that is just minutes away.
My impression is that most people do not understand that radio waves are a form of light energy, and that huge radio telescopes do not send out radar signals to bounce off of distant space objects.