Effect of the ionospheric delay on passive bistatic radar using spaceborne UHF illuminators

The unknown radio propagation delay of the ionosphere is well-known as a potentially-limiting effect of microwave navigation systems such as GPS. We report on an analysis on the effects of the ionosphere on passive bistatic radar using non-cooperative satellite-based transmitters. Ionospheric data for a one-year period during 2010 are analyzed in the context of the bistatic geometry. Both geostationary (e.g., XM-Radio) and low Earth-orbiting spacecraft (e.g., Iridium) are considered. It is found that the worst-case effects of the ionosphere on a radar of this type might be meaningful for systems attempting to achieve the best accuracy at the longest range, but that the effect is small enough to be neglected for close-range measurements.