Le plus grand radiotélescope du monde: le "Very Large Array".

The VLA consists of 28 radio antennas arranged in formations extending for up to 21 km in the high altitude dry lake bed of St. Augustine, NM. The functioning principle of the instrument is synthetic aperture interferometry (SAI), i.e., the separate signals received by the antennas are digitally processed with inverse Fourier transformations to form a single image. The procedure permits arcsec imaging resolution, the same accuracy available from large optical telescopes. The rotation of the earth furnishes the interferometric information on the signal sources. The identical Cassegrain antennas are mounted on rails to allow altering the array layout for particular measurements. Each antenna can scan 270 deg azimuthally and 125 deg in elevation, and all move in unison to lock onto a designated target. Usage of the VLA for radiospectroscopy, image processing at millimeter wavelengths and for mapping regions of the sky and the sun at various wavelengths are described, and sample images of DG Tau and Herculis A are provided.