First estimates of the second‐order ionospheric effect on radio occultation observations

Abstract

This study examines the impact of the second‐order ionospheric effect on radio occultation (RO) data products. We propose a new linear combination between dual frequency GPS observables, which retrieves slant total electron content free from the second‐order ionospheric effect. Our STEC values differ from those obtained by independent techniques by a maximum of 3 total electron content units (TECU), depending on the geographic location and geomagnetic activity. Additionally, we suggest an alternative method of computing the second‐order ionospheric delay in RO experiments, which does not require the use of geomagnetic and ionospheric models. First estimates show that the second‐order ionospheric delay for the RO experiments falls within the range [−10, −8] mm, which is of the same order of magnitude with second‐order ionospheric delay estimates from ground‐based experiments. Finally, as a by‐product of our model, we retrieve weighted mean geomagnetic field values, which we compare with theoretical estimates computed by the International Geomagnetic Reference Field‐10 (IGRF‐10) model. Our estimations agree with the IGRF‐10 model between 0.23% and 7.0%.