The radar cross section of ogives, double-backed cones, double-rounded cones, and cone spheres

Experimental measurements have been made of the nose-on backscattering radar cross section over a range of diameters from 0.05 to 1.0 wavelengths of a series of ogives with total included nose angles of40\deg,75\deg, and120\deg; of cone spheres with nose angles of15\deg,30\deg,40\deg60\degand120\deg; of double-rounded cones with nose angles of15\deg,40\deg, and75\deg; and of double-backed cones with nose angles of40\deg. Further, a series of ogives of approximately the same diameter and with nose angles of25\deg,40\deg,60\deg,75\deg,95\deg,120\deg,160\degand180\deghave also been measured. All the present results have been obtained using two monostatic phase-locked CW balanced-bridge model measurement radars operating at frequencies of 9 Gc and 35 Gc. For targets with maximum dimensions less than two inches, cross sections of less than10^{-7}square meters at 9Gc and10^{-6}square meters at 35 Gc can be measured with an accuracy of \pm0.5 db. The experimental data is sufficiently comprehensive to provide qualitative explanations of the scattering mechanism in the Rayleigh and resonance regions, and to make rigorous tests of the various theoretical predictions. An extension of the physical optics theory of Adachi was found to predict accurately the echo area of the ogive, the double-rounded cone, and double-backed cone in the resonance region. The Rayleigh theory was found to be generally accurate for all the models considered. The impulse analysis of Kennaugh and Moffatt was found to be accurate for the cone sphere.