Design and Commissioning of the LWA1 Radio Telescope

LWA1 is a new large radio telescope array operating in the frequency range 10-88 MHz, located in central New Mexico. The telescope consists of 260 pairs of dipole-type antennas whose outputs are individually digitized and formed into beams. Simultaneously, signals from all dipoles can be recorded using one of the telescope's "all dipoles" modes, facilitating all-sky imaging. Notable features of the instrument include four independently-steerable beams utilizing digital "true time delay" beamforming, high intrinsic sensitivity (about 6 kJy zenith system equivalent flux density), large instantaneous bandwidth (up to 78 MHz), and large field of view (about 3-10 degrees, depending on frequency and zenith angle of pointing). This paper summarizes the design of LWA1, its performance as determined in commissioning experiments, and results from early science observations demonstrating the capabilities of the instrument.