I flew to San Juan Puerto Rico to catch the ship. Those who registered on time had an opportunity to register for a tour to Aricebo Observatory before the cruise started; I was too late for that, so I decided to rent a car and do it on my own. This would be a little challenging, navigating a rental car half way across the island knowing about 15 words of spanish, but hey -- I'm a big boy. Fortunately, I managed to acquire a navigator and assistant navigator on the plane. It seems that carrying a tripod down the aisle of a 767 heading for an eclipse cruise constitutes an instant introduction to the other 50 people flying down for the same event.Two of them were in the same situation of having missed out on the Aricebo tour, so I was happy to pick them up at their hotel and take them along.
I got into my rental car in San Juan, immediately missed a turn right outside the airport, and spent the next hour doing the 10-minute drive from there to the airport. During that hour, I learned all my directions in spanish, plus the words for "stop", "no parking", "entrance", "exit", and "one way", so I guess the time wasn't wasted.
Next morning, I picked up my passengers and we drove off to Aricebo. We learned some more spanish: "Pay toll, 25 cents", got lost a few times, saw lots of territory, drove some really exciting back roads, and finally found the observatory way up in the hills.
They have a really nice visitor's center which just opened recently. ( http://aosun.naic.edu/home.htm ) The walls are covered with descriptions of the science being done there: atmospheric studies (which the dish was originally constructed for), planetary and asteroid work with the dish being used as a radar, and various deep-sky observations, including one Nobel Prize winning study of a pulsar which showed the existence of gravitational waves, predicted by Einstein about 70 years ago.
The dish has had two major upgrades since it was first built. The first one was to replace the original wire-mesh reflector surface with light-weight aluminum panels.
These enable the shape of the dish to be kept spherical to millimeter accuracy, and make it possible to reflect radio waves with wavelengths down in the couple of centimeter range which are emitted by some of the more interesting gasses in deep space. (The funny thing with straps in the picture is a "snowshoe" that can be used for walking around on the aluminum panels when they need to be serviced.)
The dish is spherical, not parabolic. A parabola focuses energy to a single point, but it has to be moved to point it at various parts of the sky.This is obviously difficult to accomplish when the dish is wired to the ground. A sphere focuses to a straight line, but you can "steer" the direction it looks without moving the dish by waving a wand-shaped antenna around at the proper distance from the reflecting surface. This wand has to be carefully built for the wavelength being observed, and isn't nearly as efficient at collecting energy as a smaller antenna would be. To address this issue, the second major renovation of the observatory added a "Gregorian" antenna -- the large half-sphere in the picture. Inside the sphere are two carefully-shaped secondary reflectors which refocus the radio energy to a point. This immensely improves the sensitivity of the telescope, and makes it much easier to observe at different radio frequencies.
Additional guy wires were also added to the supporting structure to allow the position of the antenna to be maintained to millimeter accuracy.
Why?
P.R.
Ship
USVI
Dominica
Grenada
Astro
L.G.
Eclipse
Aruba
Bday
Buzz
