THE EFFECTS OF THE PROPOSED SATELLITE POWER SYSTEM ON THE VLA A. R. Thompson The Very Large Array (VLA) is being constructed on the Plains of San Augustin, New Mexico as a facility to map the sky at centimetre wavelengths with angular resolution down to a few tenths of an arcsecond. The array, when completed, will consist of 27 fully steerable paraboloid antennas of 25-m diameter, located on a three-armed array with nine on each arm. The antennas can be moved between foundations so that the scale of the array can be varied in four steps in which the distance of the furthest antenna from the center varies between 0.6 and 21 km. A general description of the array has been given by Heeschen (1975), and more detailed accounts can be found in NRAO technical reports. The array operates in the Fourier Synthesis mode in which signals from all possible pairs of antennas are combined to form a two-dimensional visibility function. To obtain sufficient data the point in the sky being observed is usually tracked over a range of at least -4 to +4 hours in hour angle. The sky brightness function is then obtained from the visibility by Fourier transformation. For an account of the principles involved see, for example, Swenson and Mathur (1968) or Fomalont and Wright (1974). Table 1 gives the four wavelength bands in which the VLA is equipped to operate at the present time. Each of these VLA bands encompasses a narrower band assigned to radio astronomy. Note that harmonics of the SPS frequency at 4.9, 14.7 and 22.05 GHz fall within VLA operating bands. The receiving equipment is capable of operation with an instantaneous bandwidth of up to 100 MHz in two orthogonal polarizations. Bandwidths wider than the assigned radio astronomy bands are often used, if no other signals are encountered, to maximize the sensitivity. Two effects in the operation of such an array reduce the response to radiation from directions in the sky other than that desired. First, the unwanted source does not have the expected motion across the sky of the point
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