Rocket Measurements of Faraday Rotation and Differential Absorption

Abstract

A system for high resolution measurements of Faraday rotation and differential absorption in the D region is described. Closed loop feedback between the rocket receiver and ground transmitter increases accuracy through the use of a null seeking technique which minimizes nonlinear receiver effects and transfers the differential absorption measurement to precision attenuators on the ground. Faraday rotation, which is superimposed on rocket roll, is separated from layer reflection, standing wave interference by increasing the effective roll rate through artificial rotation of the transmitter antenna produced by a 500 Hz difference frequency between the two oppositely polarized transmitted waves. Resolutions of 1° in Faraday rotation and 0.2 dB in differential absorption are obtained.