Abstract

For frequencies below 1 GHz, the ionosphere behaves as a refractive medium, delaying signals passing through. These delays can cause timing errors, leading to much larger problems when the signal transit time is used in the positioning of objects. For the Navy Space Surveillance (NAVSPASUR) Fence, a ground based space observation radar system, these timing errors translate into positioning errors. Modeling the ionosphere is problematic, as any climatological model is prone to significant errors. As an alternative, this research examines the possibility of applying ionospheric measurements from the Low Resolution Airglow and Aurora Spectrograph (LORAAS) sensor to radar data obtained from the Navy Space Surveillance Fence for the purpose of correcting these ionospheric errors. The LORAAS sensor, flown aboard the Advanced Research and Global Observation Satellite (ARGOS), obtains ionospheric information by scanning the ultraviolet airglow of the atmosphere. This research examines the validity of using ionospheric measurements on a localized scale to accurately estimate the ionospheric delays between the radar site and its target. Night-side measurements from the LORAAS instrument covering six months with various solar conditions were compared to total electron content (TEC) values obtained from the International Reference Ionosphere (IRI), the TOPEX satellite, and GPS-based Global Ionosphere Maps (GIM). Ionospheric corrections were then calculated for the data from the Navy Space Surveillance Fence using the LORAAS, IRI, and GIM data, in order to determine how effective LORAAS TEC measurements are at correcting these observations.