For more than two decades, the planetary radar installed at the Arecibo Telescope was the most sensitive instrument of its kind, harnessing the penetrating power of radio waves to perform observations of the (sub)surface of planets, moons, and asteroids in the Solar System—providing a unique perspective on those bodies that helped to drive in situ exploration. This Colloquium presents an overview of the scientific legacy of the Arecibo radar system, focusing on the period posterior to the Gregorian Update in the late 1990s until the unexpected demise of the telescope in 2020. After recalling the basics of planetary radar techniques, it reviews key Arecibo observations of Mercury, Venus, Mars, our Moon, and the Saturn system, and highlights its essential role in the characterization of a large sample of near-Earth asteroids and comets.

From the article:

Colloquium: Planetary radar at the Arecibo Observatory
Michael C. Nolan, Lynn M. Carter, and Edgard G. Rivera-Valentín
Rev. Mod. Phys. 98, 011003 (2026)

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