Science and the First Upgrade

The early research results described in Chap. 7 were just the beginning of a flood of results in the lead up to the first upgrading of the telescope, the replacement of the reflector and installation of a high-powered transmitter for planetary radar observations, and a deluge of them post-upgrade. Despite the reduced sensitivity due to the feed problems, Arecibo was one of the most powerful radar systems in the world and it was used to make significant advances in our knowledge of the Moon and terrestrial planets as well as of the Earth’s ionosphere. With the discovery of pulsars in 1967 (approximately 20 km in diameter balls of mainly neutrons, neutron stars, with masses about 1.4 times that of the Sun left over from the supernova explosions of massive stars), Arecibo came into its own as a radio astronomical telescope. The resurfacing of the telescope’s primary reflector with aluminum panels and the installation of a high-powered transmitter operating at 2.38 GHz in the early 1970s, opened up new research areas in radio astronomy and greatly boosted Arecibo’s sensitivity for radar studies of the terrestrial planets, satellites and asteroids and comets.