This proposal introduces a unique first principles approach that applies physics-based system-level modeling of HF propagation, oceanic and ionospheric clutter, and target scattering. Our approach, which incorporates both cooperatively controlled and non-anthropogenic "noise" sources, is a departure from traditional methods. We treat the latter statistically using parameters that are dependent on space- and tropospheric weather conditions. Our work will explore the estimation of both target and environmental properties as a function of the observing geometry, sea and ionospheric conditions, and source distributions using simulations and will apply the methods developed with government-furnished measured data. Nonlinear sparse estimation techniques that account for both system and environmental noise effects will be developed through correlation and subspace projections. Interferometric techniques among multiple receive arrays that have been successfully employed for blind channel estimation in geophysics and oceanography will also be examined for both target tracking and environmental sensing applications.