Minimum Detectable Radar Cross Sections in a Multistatic OTHR Architecture

Abstract:

We have proposed a high frequency (HF) over the horizon radar (OTHR) architecture with multiple receiving systems which are small and, therefore, relocatable. This Multistatic OTHR (MOTHR) configuration is based on a beamforming on transmit concept, with a very large aperture transmit antenna and a small aperture receive antenna. One consequence of this architecture is that many receivers could be deployed and operated in conjunction with one transmitter, operating multistatically to measure target velocities as well as speed. Such a system should be able to detect and track a wide variety of target velocities.

While this architecture has a number of advantages it also introduces a number of challenges, notably frequency management and coordinate registration over bistatic paths for which ionospheric characterisation via backscatter sounding will not be possible. Consequently, MOTHR requires a real-time ionospheric model, based on data from a variety of ionospheric sensors which may be part of, or independent from the MOTHR facilities. Moreover, to realise the benefits of the architecture it is important that frequencies can be identified which will support propagation to widely separated locations. Clearly, path support over multiple paths will be less likely than over a single path.

The paper will describe the modelling approach, involving a statistical characterisation of the signal propagation across a hypothetical MOTHR network to evaluate the target minimum detectable radar cross section (MDRCS). It will be based on ensembles of realistic ionospheres over a range of environmental conditions (i.e. the equinoxes and solstices at low, mid and high solar activity levels) derived from the Advanced Ensemble electron density (Ne) Assimilation System (AENeAS) in combination with ray tracing.