EFFECT OF AN ARCJET PLUME ON SATELLITE REFLECTOR PERFORMANCE

The effect of an arcjet plume on the performance of satellite reflector antennas is studied. The arcjet plume is modeled as a weakly ionized plasma. Spatial permittivity distribution of the plume is approximated using the measured electron density profile and a cold plasma model. Geometrical optics is applied to determine the ray paths as well as the transmitted fields through the inhomogenous plume. The ray optics results are compared against several exact solutions for scattering from inhomogenous dielectrics and good agreement is observed for sufficiently large scatterer size. The far-field antenna patterns of the reflector in the presence of the plume are calculated from the transmitted ray fields using a ray-tube integration scheme. For arcjet prototypes in the 1-kW class, the plume effect on the antenna performance is small. As the electron density increases (corresponding to higher arcjet power), a gradual degradation of the main beam and sidelobe level is observed. In addition, the main beam tends to squint away from the plume region.