How did radar allow astronomers to study Venus through its thick clouds?

Because Venus is completely enshrouded by thick clouds, astronomers utilize radar to study its surface. When a large radio telescope is equipped with an appropriate high-power transmitter, it can bounce radio signals off the planet and detect their return.12

Unlike visible light, radio wavelengths are capable of penetrating the dense Venusian atmosphere. By measuring the time of flight and the spectrum of these reflected signals, astronomers can probe the surface, deduce rotation rates, and map topographical features such as valleys and mountains with high resolution. This technique has been instrumental in unveiling surface details that remain hidden from optical observation, including the identification of major features like Alpha Regio, Beta Regio, and Maxwell Montes.132