Accession Number : ADP006394

Title :   Reduction of Target Scattering by Tropospheric Modification,

Corporate Author : RUTHERFORD AND APPLETON LABS CHILTON (UNITED KINGDOM)

Personal Author(s) : Craig, K. H.

Report Date : SEP 1991

Pagination or Media Count : 12

Abstract : This paper examines the possibility of reducing the effective radar cross-section of an aircraft by actively modifying the refractive index of the air surrounding it. The mechanism proposed is heating of the atmosphere by a laser mounted on the aircraft. The equations for the refractive index changes caused by absorption of laser radiation are derived, and refractive index profiles are calculated. A shielding factor specifying the reduction in target cross-section is introduced. The shielding factor is evaluated for typical laser beam geometries by using these profiles in a parabolic equation based electromagnetic propagation model. A parametric study is presented in order to optimise the laser wavelength and beam geometry. It is concluded that laser powers in the megawatt range can yield shielding factors greater than 10 dB. A 10.6-micron C02 laser appears to be optimum in terms of efficiency of cross-section reduction, and is also the laser type for which the highest CW powers are achievable.

Descriptors :   *AIRCRAFT, *RADAR CROSS SECTIONS, *TARGET DETECTION, ABSORPTION, AIR, ATMOSPHERES, CROSS SECTIONS, EFFICIENCY, EQUATIONS, GEOMETRY, HEATING, LASER BEAMS, LASERS, MODELS, PROFILES, PROPAGATION, RADAR, RADIATION, REDUCTION, REFRACTIVE INDEX, SHIELDING, TARGETS, YIELD, MILITARY EQUIPMENT.

Subject Categories : Active & Passive Radar Detection & Equipment
      Aircraft
      Lasers and Masers

Distribution Statement : APPROVED FOR PUBLIC RELEASE