High up in the mountains fifty miles west of Socorro, New Mexico, the Plains of San Augustin stretch out flat and bare, providing the perfect NRAO entrance sign spot for an antenna farm. The Very Large Array (VLA) is an assembly of 27 high-tech radio antennas which for more than twenty years have been collecting data from far beyond our solar system.
Since celestial objects emit radiation at radio frequencies as well as light, they can be observed with radio telescopes, which magnify the extremely weak signals from remote objects using large parabolic dish antennas and powerful radio amplifiers.
But even so, radio telescope images were blurred compared with optical telescopes, so scientists planned to employ interferometric techniques using an array of precisely spaced radio telescopes pointing in the same direction. The result is the VLA, funded by the National Science A straight line of antennas Foundation and taking years to build in the 1970s.
The twenty-seven identical radio telescopes are placed on three radii of a circle on the Plains of San Augustin. The radii are spaced 120 degrees apart, and are 13 miles in length. The result is an instrument equivalent to a single radio telescope with a diameter of twenty miles. The 27 telescopes are mounted on rails and can be brought in to a tighter configuration for higher resolution. They are all controlled by a central computer, their data converted to IF frequencies and sent by waveguides to the main building, where they are combined and digitized for electronic shipment to scientists anywhere in the world.
Of the nine astronomers who have received the Nobel prize in astronomy, six have used radio telescope observations to study the universe. Bigger than your average truck Unlike optical telescopes, radio telescopes operate as well during the day as at night.
The VLA is so powerful that it can detect signals from the outer edge of the universe, in other words, dating back to the time of the big bang. Thus the VLA has helped gather data for cosmologists.
Other arrays of radio telescopes are in use, including another U.S. effort combining information from a large but irregular array of radio telescopes in the Virgini Islands, Hawaii, and across the North American continent. And a new international effort is under way to locate a precise array of radio telescopes in Chile. But for now, VLA occupies a unique place in radio astronomy. Focusing elements
The VLA conducts about 50 astronomical experiments each month, providing information to scientists studying black holes, galaxies, quasars, cosmic interactions, etc.
To a non-scientist the process is entirely mystifying, but there's a visitor center with a short video and lots of nifty celestial pictures derived from VLA data. At one point you could look out the window and see a small (three-foot diameter) radio telescope, looking just like a satellite TV antenna. It was connected to and controlled by a little PC inside the visitor center, and was "looking" at the sun. The result was a computer screen full of information about the current condition of the sun, and its eruptions of gaseous material. ... and the antelope play ...
To an astronomer, the sun might have been changing quite a bit, but it felt nice and warm to us as we took the self-guided walk around the outside of the lab and got a close up view of one of the giant telescopes. They're beautiful to see. An experiment was taking place (there's always an experiment going on -- this is a 24/7 operation) and every now and then we'd hear the motors grind and the telescope would slew a little one way or another. At the same time the other 26 telescopes were slewing the same way. Up in the center of each one the radio receiver is cooled to near absolute zero.
The three radii are each marked by two parallel standard-gauge railroad tracks, which are used for moving the radio telescopes in or out as the needs of the experiments change. The tracks are also used for ferrying the instruments to the maintenance shed. Actually maintenance isn't the correct word, for the telescopes are continually upgraded as new technology becomes available and affordable. Another interesting feature of the VLA itself is that the staff consists mostly of technologists. This is a test facility, whose measurements are gathered and shipped off to Sacred Heart Church, Quemado astronomers who analyze the data in the comfort of their university laboratories, located in big cities with shopping malls and movie theaters.
And speaking of movie theaters, parts of the Jodie Foster movie "Contact" were filmed on location here, with schoolchildren from the nearby Magdalena, New Mexico elementary school playing extras. Which is kind of interesting, because Magdalena, once the largest railroad shipping point for cattle in the country, is now nearly a ghost town. The old railroad station is used as a library, most of the buildings are falling down, and there's certainly no movie theater! Thirty miles west of the observatory is Quemado, with a quaint parish church.
Internet Note: www.nrao.edu.