An Overview of the Very Large Array (VLA FAQ) History: 1972 August: approved by Congress 1973 April: construction started 1975 September 22: first antenna put in place 1976 February 18: first fringes 1980: formal dedication of the VLA The total cost was $78,578,000 (in 1972 dollars), roughly $1 per taxpayer at the time; the project was completed nearly one year early, and within the allotted budget. Location: Plains of San Augustin, west of Socorro, New Mexico. latitude = 3404'43.497" north longitude = 10737'03.819" west elevation = 2124 m (6970 ft) Size: 27 antennas. Each antenna is 25 m (82 ft) in diameter, 230 tons. The Array: The “Y” shaped Array with 9 antennas on each arm has “Four Configurations” A,B,C,&D: A Array- maximum antenna separation is 36 km; B Array - 10 km; C Array - 3.6 km; and D Array - 1 km. Resolution: 0.04 arcseconds The resolution of the VLA is set by the configuration of the array -- up to 36 km (22 miles) across. Highest frequency (43 GHz) this gives a resolution of 0.04 arcseconds: sufficient to see a golf ball held by a friend 150 km (100 miles) away. Of course, very few golf balls contain high-power radio transmitters... Misc. antenna information: Slew rates: 40 per minute in azimuth, 20 per minute in elevation Minimum elevation angle: 8 above the horizon Frequency coverage: The VLA can observe at various bands between 74 and 50,000 MHz (400 to 0.7 cm) How does it work? The VLA is an interferometer; this means that it operates by multiplying the data from each pair of telescopes together to form interference patterns. The structure of those interference patterns, and how they change with time as the earth rotates, reflect the structure of radio sources on the sky: we can take these patterns and use a mathematical technique called the Fourier transform to make maps. Who uses it? The VLA is used primarily by astronomers from around the world. It's also occasionally used for atmospheric/weather studies, satellite tracking, and other miscellaneous science.