DEIMOS-2 captured the two world’s largest radio telescopes: the Arecibo Observatory and the Five-hundred-meter Aperture Spherical Telescope (FAST). The images show the proportions of both, allowing to appreciate the great difference between their diameters.

The Arecibo observatory is located inside the depression left by a karst sinkhole in Arecibo, Puerto Rico. With a 305-meters diameter, it was the world’s largest single-aperture telescope from its completion in 1963 until July 2016, when the Five hundred meter Aperture Spherical Telescope (FAST) achieved first light. The FAST is also sitting in a karst valley, in Pingtang County, a mountainous area in southwest China. In fact, the idea of constructing this large spherical dish in a karst depression was rooted in its precursor. However, when comparing both radio telescopes, differences are noticeable, and not only regarding their size.

While Arecibo has a fixed spherical curvature and thus focuses radio waves into a single line, FAST can reshape into a paraboloidal surface, being able to rotate 40 degrees and to cover two to three times more areas of the sky area thanks to its innovative design of active primary surface. Moreover, FAST has a much better angular resolution.

Arecibo’s reflector and the feed cabin are solidly connected, but the design is different in the case of the FAST: its feed cabin is supported and driven by cables and servomechanism and a secondary adjustable system is employed to achieve the required accuracy.

DEIMOS-2 imagery is an extremely useful and cost-effective information source. It provides regular monitoring services of high and uniform quality that can support assessment of change in facilities and infrastructures located in remote locations and extreme environments.