Comparisons of Ion Density From IVM With the GNSS Differential TEC-Derived Electron Density on the FORMOSAT-7/COSMIC-2 Mission

We report on a new method to derive the on-orbit electron density using the Tri Global Navigation Satellite System (GNSS) Radio-occultation System (Tri-GNSS Radio occultation System (TGRS)) differential total electron content data and compare it to the Constellation Observing System for Meteorology Ionosphere and Climate-2 Ion Velocity Meter (IVM) ion density data. We found that the IVM ion density is about 8%–15% lower than the TGRS derived density at the insertion orbit (∼710 km) and 5% higher at the mission operation orbit (∼540 km) for reasons that are currently unknown. Using a linear coefficient, we scaled the IVM data to remove the offset between TGRS-derived electron density and the IVM ion density for the two orbital heights. We believe the scaled IVM densities eliminate any inter-spacecraft discrepancy, making the IVM data suitable for use in high precision multi-satellite scientific investigations of longitudinal and local time variations of non-migrating tides, planetary waves and space weather operational applications.