KOrea-Multi-Purpose-SATellite (KOMPSAT)-5 is the first Korean satellite to perform synthetic aperture radar (SAR) mission and support radio occultation. In order to process SAR and radio occultation data, precise position and velocity are required. KOMPSAT-5 orbit determination system consists of Operational orbit determination (OOD) and precise orbit determination (POD). The satellite operational orbit supporting satellite operation is adjusted using satellite on-board global-positioning-system (GPS) navigation solutions data as well as ground-based satellite tracking and ranging data. KOMPSAT-5 carries two GPS receivers, TOPSTAR 3000 and IGOR, to perform orbit determination (OD) based on GPS data. IGOR dual-frequency GPS receiver is mainly operated for a primary mission support and TOPSTAR 3000 is a backup single-frequency GPS receiver. The POD result is validated using satellite lager ranging (SLR) data and the daily precise satellite position data are transferred to the international laser raging service (ILRS) site. KOMPSAT-5 POD and OOD are designed to meet the requirements of 20 cm and 5 m (one-sigma) positioning accuracy in three-dimension, respectively. However, KOMPSAT-5 OD using ranging and antenna pointing data is normally operated when GPS data is not available or before GPS receiver is activated on. The position error based on the range, azimuth, and elevation data should be satisfied within ±1000m (three-sigma) for processing three-day measurement data. The requirement of OD performance is fully validated showing all OD requirements are satisfied for normal operation.
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