The investigators will advance the state of ionospheric tomography by: (1) refining the "weighted, damped, least-squares" (WDLS) technique for tomographically inverting total electron content (TEC) records, (2) formalizing partition of over- and under-determined image parameters estimated by the WDLS technique, (3) constraining plasma density estimated in image cells to nonnegative values, and (4) generalizing the WDLS technique to permit systematic augmentation of TEC data with plasma-density measurements from any external source.
