Swarm-E GPS Observations of the Polar Cap Ionosphere

The Global Positioning System (GPS) Attitude, Positioning, and Profiling (GAP) instrument is one of eight components of the scientific instrument suite onboard the Swarm-E satellite (previously CASSIOPE/e-POP). The Swarm-E instrument suite was designed to primarily study the physical processes coupling the polar ionosphere to the solar wind and magnetosphere. The GAP instrument consists of three GPS antennas oriented towards spacecraft zenith and one antenna oriented in the anti-ram direction, along with associated GPS receivers. This configuration allows for both radio occultation and topside ionosphere measurements, which are collected at data rates of up to 100 Hz. The elliptical, polar orbit of Swarm-E and high data rate of GAP allows for unique radio occultation and topside ionosphere observations, which is particularly useful for polar regions where much of the ionospheric structure and dynamic behaviour are not well observed or understood.