Here we continue the descend into the space under the Arecibo 300-m reflector, which we began in the previous blog post. Again, it is hard to grasp the size of this facility. The photo above shows a panoramic image taken from the road about half-way down to the bottom of the sinkhole under the reflector.
The reflector is kept in precisely spherical shape by a multitude of wires underneath, each mounted to a concrete anchor point. Now and again, the spherical shape is verified with lasers from the platform above, and then adjusted by tightening or loosening the wires underneath.
There are three places under the reflector, where two cables go all the way up to the outriggers of the platform high above. These are stabilising the platform, and are mounted on the ground via a set of shock absorbers (above).
In the centre of the reflector, there's a small platform one can climb on top of. When standing there, the bottom of the reflector is about waist high. Here's a super wide-angle photo taken from there towards two of the heating antennae. These are huge crossed dipoles, which will be used in due time for ionospheric active modification experiments.
Photos: Thomas Ulich.