RIP Arecibo, 1963–2020

Photo by Adrian Pelletier on Unsplash

The news this week that the Big Dish at Arecibo has reached the end of its life has hit the astronomy and SETI communities hard. Let’s look back over the working life of this amazing telescope.

An Ambitious Project

In the early 1960s, William E. Gordon from Cornell University designed a telescope to study the ionosphere.

The site on Puerto Rico was chosen for two reasons:

1. It was close to the equator, which is always a good site for large telescopes.
2. The karst geography was prone to large sinkholes, which allowed for the easy construction of the big dish.

The initial design was a fixed parabolic reflector with a 150 m tower, but designers soon realized that this would greatly limit its utility, and the tower was redesigned to have an azimuth arm, which would carry the actual antennae to receive the signal and allow them to be pointed at any part of the sky. Thus, the only limitation was the Earth’s rotation; sometimes astronomers would have to wait for their target to come into view.

The big dish was at the time the largest single aperture telescope constructed; and it held that title until the Five hundred meter Aperture Spherical Telescope was constructed in 2016.