The 305m diameter radio dish of the Arecibo Observatory in Puerto Rico. Photo credit: NAIC

There are big telescopes, and then there are the truly humongous telescopes, like some of the radio telescopes. These bad boys are so big that the largest of them takes up an entire valley. This is the well-known Arecibo Observatory in Puerto Rico, that a lot of people likely know from Golden Eye, X-files or Contact, to name a few times it has been used in popular culture.

The observatories are, of course, mainly used to do astronomical observations, and not as fancy movie sets. The planetary radar transmitter here, and at the Goldstone Deep Space Network site in California are used extensively to observe asteroids, the terrestrial planets, and the larger satellites of Jupiter and Saturn.  To do this, they run hundreds of kilowatts of UHF signal out through each telescope.  By the time the beam is distributed across the many thousands of square meters of the primary telescope reflector, it’s diluted to the point that it doesn’t pose a hazard to anything.  However, along the beam path from the transmitter feed to the tertiary and then to the secondary reflectors, it is significantly more concentrated. This means that every now and then, the telescopes turn into something very different from instruments for peacefully observing the Universe.

The Gregorian dome of the Arecibo Observatory. Finding your way out is not as easy as it seems. Photo credit: NAIC

At Arecibo, the transmitters, receivers, tertiary, and secondary are all contained inside a Gregorian dome. Birds tend to fly in and get confused about how to exit again. As interesting as it may be to inspect the inside of the world’s largest radio telescope, this is not without risk! If the birds happen to be between the transmitter and the tertiary reflector when the transmitter goes on, they are very rapidly microwaved. The birds’ remains may then land on the tertiary, where they get cooked into char. They can be removed from the tertiary’s surface from the access platform by using sophisticated tools, like a large wad of sticky tape on the end of a stick.

At Goldstone, birds can fly out of the beam line more easily, since the transmitter is not contained within a dome. But on one occasion, a swarm of bees were in the beam when the radar started transmitting. The telescope briefly acted as the world’s most expensive bug zapper. The resulting cloud of steam and fried bees caused a dramatic back-reflection of the beam until it dispersed.

There are no reports (yet) of larger things being fried by any of these instruments, and, admittedly, it would take quite some work to get anything without wings to be in the right place. But you could host a rather impressive and efficient BBQ party there. Just be mindful of  where you are, once the beam goes off. We don’t want any accidents!

Thanks to Michael Busch for providing this anecdote.

One of the Goldstone Deep Space Network Antennas. Photo courtesy NASA/JPL-Caltech