Arecibo Observatory: into the telescope

If you visit Arecibo Observatory, you’ll probably see the suspended platform from the visitor center.

Platform and dome

It’s a great view.  Better is the view from the cable car, or the platform itself.  Best is from inside the receiver dome housing.

Rising above the ground screen



Weighing around 90,000 pounds, the platform is very stable for being suspended 500 feet in the air.  We took the cable car to tour the structure.



Tallest mountains




After alighting from the cable car, you walk down a staircase to the “rotary joint”, the hub around which the platform rotates.  Photons/waves come out of the grey box in the upper left.

Rotating joint

Climbing through the rotary joint is a bit awkward, but the rest of the trip involves stairs and ladders.


Down the stairs

Hello, line feed!

Line feed

Another few more staircases we were in the dome proper where both transmitters and receivers dwell.

Alignment guides

Shadow through the dome

Supports and alignment guides inside the secondary mirror

Tertiary mirror below the secondary in the dome over the dish

After some dire warnings, we went into the transmitter room where several klystrons stood.  These beasts are what produce our megawatt radar wave, similar to the klystrons at SLAC (though theirs can produce 50 megawatts at about the same frequency).  Signals from the klystrons are focused by the telescope and sent to bounce off asteroids, whether near-Earth or out in the main asteroid belt.



Klystron with a BREW MASTER cooling tube

65,000 volts DC


Down another staircase, now to the receivers’ instrument room.

Out toward the platform

Instrument room

And down another level to the receivers themselves: “business end” of the telescope.  These strange plates receive the tiny radio signals from galaxies, pulsars, and yes, asteroids.  The largest is about three feet across.  When you’re getting just a few parts in a billion back of your signal, you need all the sensitivity you can get.


Instruments above the dome

The business end of the telescope


At this point you couldn’t go any lower without falling out of the dome, or into the tertiary mirror, below.

Tertiary mirror

Looming over us as we emerged from the receiver and transmitter rooms was the 8 o’clock tower.

8 o'clock tower

The 16-meter dish toward the Atlantic.

16 meter dish

We just missed the 10 o’clock cable car down to the control room, but we opted to take the catwalk to the visitor center.

Cable car


Anatomy of the telescope

Visitor's center; two towers; platform

Platform and dome

It’s an IEEE Milestone in Electrical Engineering & Computing, as well as an ASME Mechanical Engineering Landmark!

IEEE Milestone in Electrical Engineering and Computing


Looks much smaller from down here!

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