A MODEL-INDEPENDENT ALGORITHM FOR IONOSPHERIC TOMOGRAPHY - 1 - THEORYAND TESTS

This paper presents a model-independent algorithm for tomography of th e ionosphere. Prior knowledge consists of the following pieces of info rmation: electron density cannot be negative, the ionosphere is basica lly smooth and stratified, and electron density is low at high (greate r than or similar to 700 km) and low (less than or similar to 100 km) altitudes. Tests based on simulated measurements show that the method recovers the latitudinal structure well, whereas the vertical structur e is recovered with moderate success: the estimated height of the laye r of maximum electron density may be as much as 90 km in error. Becaus e of the imposed smoothness the method tends to underestimate the peak in electron density by as much as one third in unfavorable cases.