Audacious -- that's how I describe the Arecibo radio telescope. For me, it was just hard to believe what I was seeing. I have just returned from my first Planetary Society-sponsored trip to Puerto Rico and this historic, remarkable, big idea of a telescope.
If you're not familiar with this machine designed to explore the cosmos and our own ionosphere, it was conceived in 1958, built by 1963, upgraded and refined in the decades since.
The premise of the story (as we say in writing) was to build a telescope so big that it could and can detect electromagnetic signals at astonishingly low energy levels. These would be signals emanating from high in our own atmosphere as well as from fantastic astronomical distances. The reflector of this machine is too big to move. It fills a whole valley, an ancient sinkhole actually, a bowl created by the collapsed roof of an ancient underground limestone cave. The valley has been fitted with a reflective section of a sphere 1000 feet (305 meters) across that's round to within plus-or-minus 1.5 millimeters (1/16th of an inch). It is amazing in its construction. But for me, the more amazing aspect of the machine is the conception, the idea that humans could build such a thing? and have it work.
The receivers above the reflector are suspended on an almost crazy system of wire ropes (twisted steel cables) and pulleys. The receiving and broadcasting antennae for this thing are enormous. They appear to be suited for the Jolly Silver Giant, were he to exist, of radio astronomy. With a sphere for a reflector, rather than a parabola, the antenna is a stick, 25 meters long. Or, it's a detector big enough for a family of four to camp out in comfortably.
This machine not only receives deep space waves; it can create them. In a separate building, we have a microwave-making klystron. High above the big dish, are two other klystrons in tandem. They're just like the one in your microwave oven; only these reckon their power in Megawatts. Radar signals can travel to 100-kilometer-diameter asteroids, millions of kilometers away, and record surface features just a few meters across, all in less than a second. When investigating Saturn, the astronomers have to plan for the Earth rotating as they wait the hour and a half for the electromagnetic waves to make the trip there and back. The wave-guide for the signals travels 1600 feet of perfectly machined square tubing. Its interfaces transmit microwaves, like in your oven, only these go into deep space with barely 3% of loss.
The whole machine with its accompanying instruments and its dedicated staff is audacious. It's the work of a citizenry dedicated to exploration and learning more of our place in space. It is the product of the best use of our intellect and treasure. If you have a chance, consider a trip with the Planetary Society. We'll take you to remarkable places like the Arecibo telescope. There are many worlds out there; to learn about them, try a trip around ours.