The Evolution of the Telescope Design

The initial design of the telescope as laid out by William Gordon during his May 1958 seminar was a 1000 ft (305 m) fixed parabolic antenna with a central tower and equipped with a 1 MW transmitter and a receiving system. While the emphasis was on using the radar system to study the Earth’s ionosphere, the strong desire to also use it for studies of the Sun and nearby planets dictated that it had to be sited in the tropics, resulting in the selection of two possible sites in Puerto Rico. A proposal to build the telescope and radar system was submitted to the Advanced Research Projects Agency (ARPA) of the US Department of Defense in November 1958. Driven by the desire to improve the telescope’s capabilities for radar studies of the Sun and nearby planets, the decision was made to change the telescope’s reflector from a parabolic shape to a spherical one despite the difficulties of devising a device that would complete the focusing of incoming radio waves. This change allowed the telescope to point up to 20° from the zenith. A new site for the telescope south of the city of Arecibo in Puerto Rico was selected. A revised proposal was submitted to ARPA in June 1959, which was given approval in September. As a result of a design competition, a contract for the design of a cable suspended structure and a cable supported reflector was awarded to the Von Seb Joint Venture, a consortium of companies, in April 1960.