Assessment of satellite altimeter's dual frequency ionospheric delay in tropical regions compared to global ionospheric models

Abstract

The rapid development of satellite altimeters has brought about a remarkable feat of innovation in the field of ionosphere studies as they can measure the ionosphere using an on-board instrument called dual frequency sensor. Some methods that can be used to measure the ionosphere are by using satellite altimeters, Global Positioning Systems (GPS), and Ionosondes. Most of the wellknown agencies such as NASA and ESA are working hard to study the ionosphere by producing their own Global Ionospheric Models (GIMs). However, factors like point based monitoring techniques and the scarcity of monitoring stations in tropical regions could deteriorate the quality of these GIMs. This study aimed to assess the performance of the satellite altimeter derived ionospheric delay compared to GIMs over tropical regions especially in Malaysian Seas. Three GIMs were used for the purpose of this study namely the IRI2007, Jet Propulsion Lab (JPL) GIM and the NOAA Ionosphere Climatology 2009 (NIC09). This study used the Radar Altimeter Database System (RADS) to extract ionospheric corrections from Malaysian seas. The expected result was to evaluate the ionospheric delay pattern in marine areas in tropical regions from 2009 until 2016. It was found that the performance of the satellite altimeter's ionospheric delay works best with the IRI2007 with a root mean square error (RMSE) value of 1.1115cm. Furthermore, the data from satellite altimeter was in a good understanding with the latitudinal variation of the ionosphere since the study area's ionosphere is characterized by the presence of the Equatorial Ionospheric Anomaly (EIA) and a strong amplitude magnetic signature of the equatorial electrojet (EEJ). In conclusion, satellite altimetry could be a useful data source for the under observed areas such as the tropical regions.