Radio wave propagation through a characterized CO2 plasma flow

• Design and characterization of a radome for testing signal propagation through an impinging flow in a plasma facility • CO 2 plasma temperature and frequency characterization by emission spectroscopy • Experimental measurements of radio signal propagation through a stagnant CO 2 plasma flow • Signal attenuation and Faraday rotation dependent with signal frequency The high levels of ionization of the plasma layer created around a spacecraft during the reentry in planetary atmospheres can cause disruption of the communications, leading to a radio blackout phenomenon. The entry, descending and landing phase of a Mars mission includes degradation and complete loss of the signal for a few minutes. This work, as part of the Horizon 2020 Magnetohydrodynamics Enhanced Entry System for Space Transportation (MEESST) project, presents experimental measurements of radio signal propagation for the first time through a stagnant flow of a CO 2 plasma, representative of Mars entry flows. The measurements are conducted at the VKI plasma wind tunnel, the Plasmatron facility, using conical horn antennas at the K a -band, transmitting inside an optimally designed probe. The probe designed at VKI and its characterization at the UPC anechoic chamber are detailed. The temperature of the plasma flow is measured by means of optical emission spectroscopy, to estimate the plasma frequency and to correlate it with the experimental signal propagation results. The measurements at the plasma wind tunnel show that the signal propagates almost undisturbed for low electric powers (and plasma frequencies), being its magnitude attenuated and its polarization rotated at higher electric powers, when the electron number densities are higher.