A cylindrically stratified model of the plasma wake of a dipole antenna entering a planetary atmosphere

The interaction between the ionized wake of a capsule entering the Martian atmosphere and the circularly polarized radiation emitted by a turnstile antenna located a quarter wave above the aft part of the capsule is studied. Numerical results for 400 MHz show that the effects of the plasma on the radiation from the antenna begin to appear at an electron density of 1 x 10 to the 7th per cu cm. In particular, the radiation patterns of the antenna develop a null region for small values of theta; sharp peaks occur within the null region of patterns for electron densities approaching the cutoff value 1.99 x 10 to the 9th per cu cm. It is found that, for the low velocity case, no serious motional or depolarization effects occur, and that communications with the capsule can be satisfactorily carried out when the condition of blackout does not exist.