How planetary radar works at Arecibo Observatory

We know Arecibo Observatory for its 305-meter (1000-foot) diameter telescope and its appearances in Goldeneye and Contact.  Aside from battling Bond villains and driving red diesel Jeeps around the telescope (grousing at the site director about the funding status of projects is optional), several hundred hours a year of telescope time at Arecibo go toward radar studies of asteroids.  Tasked to “find asteroids before they find us”, a group of us four planetary radar astronomers at Arecibo (as well as collaborators and colleagues at institutions outside of Puerto Rico) observes asteroids for NASA’s Near-Earth Object Observation program. We study the orbits and surface properties of our rowdy neighbors, near-Earth asteroids.

William E. Gordon telescopeHow do we transmit and receive radio waves using the klystrons and radio receivers at the observatory, and how do we turn these into images of asteroids?  Read more on my guest post at the Planetary Society on how planetary radar at Arecibo Observatory works.


On Friday’s holiday, a postdoc and I trundled down to the beach to go swimming.  Protected by rocky arms, this tiny cove remained still as giant waves broke over the brown barriers.

I swum out in the flat water, enjoying not being pummeled by waves.  A man and a boy rode up on Paso Fino Horses, then tied them up under the coconut palms.  As we were swimming, the boy rode the larger horse, a dapple grey, into the water and they both began swimming.  He asked me if I could hold the bridle as he tied his shoes, then he hopped off the horse and swam alongside the equine.  The horse was non-plussed, but compliant.  The boy rode the horse up onto the beach, exchanging him for a smaller brown Paso Fino.

The second horse, spirited and younger than the first, held no interest in going in the water.  The boy led him toward the waterline where the horse bucked and flicked his tail, but eventually he gave in and followed the boy into the water, still bucking and kicking.

The boy lunged the horse in water about shoulder height, then took him out toward deeper water, and eventually rode the horse as it swum.

Back at the observatory, the coqui sang into the gathering darkness.

Saturday evening we were due to get rinsed by Tropical Storm Raphael.  I wanted to go for a run around the dish, so I checked in at the control room to tell the operator that I was going.  I looked out the window to see a raptor sitting on the railing, looking at us.

I pointed out the raptor to the TO.

“A Puerto Rican eagle!  I’ve never seen one.”  He ran off to grab his camera as the eagle and I stared at one another.  The eagle turned around, fluffed his plumage, turned around to eye me some more, then flew off after the TO returned with his camera, along with someone from electronics whose lens fogged up in the chilly control room.

Creatures, everywhere.

I ran around the dish, listening to the frogs sing.

The storm never arrived.