Theoretical and Experimental Determination of the Near-Field Correction for Backscatter Gain at the Arecibo Observatory


  • A. H. Steinfeld,

  • N. M. Brice,

  • J. C. Conrad,

  • L. M. LaLonde


During the summer of 1968, two-beam, incoherent-scatter radar measurements were made at Arecibo. The two beams were formed by two separate feeds for the Arecibo reflector, one a line feed which illuminated essentially all of the reflector, and the other a horn feed which effectively illuminated about 500 feet of the reflector. A by-product of this experiment was the calibration of the near-field correction to the backscatter gain of the line-feed system. This was obtained by comparing the power received as a function of range in the two radar systems. The measured loss of gain in the near field for the line feed was about 1.5 db at a height of 100 km.