A natural pixel decomposition for tomographic imaging of the ionosphere

We apply a natural pixel (NP) decomposition to the problem of computerized ionospheric tomography (CIT). For tomography from very few angles, the NP approach provides some distinct advantages over standard basis expansions. The NP solution requires no prior assumption and as such embeds into the solution the natural spatial resolution supported by the data. For the uniquely constrained CIT geometry, however, NP estimated fields will contain significant negative values. We propose a method of improving the NP estimates by enforcing positivity through an entropy regularization algorithm. These techniques are demonstrated in an example