It’s worth noting that this sort of thing is done for closer objects: https://en.wikipedia.org/wiki/Radar_astronomy

The problem is that the power requirements go up sharply with distance. The amount that hits the object decreases with the square of the distance, as does the amount that’s returned. The end result is that your power requirements are proportional to the fourth power of the distance. Twice as far means you need sixteen times more power.

Now extrapolate that to something hundreds of times farther away than the closer planets....