Ionspheric Error Removal in the Positioning of LEO Satellites Based on Low cost GPS Receivers

Abstract

A novel technique for the ionspheric correction of single frequency GPS measurements from satellites in low Earth orbit (LEO) is presented. The fractional total electron content (TEC) above the receiver altitude is obtained from global TEC maps of the IGS network and an altitude dependent scale factor. By choosing a suitable effective height of the residual ionosphere, the resulting path delay for positive elevations from the LEO satellite to the GPS satellites is computed using a thin layer approximation. The scale factor can either be predicted assuming a Chapman profile for the altitude variation of the electron density or adjusted as a free parameter in the processing of an extended set of singel frequency measurements. Based on flight data from the Champ satellite, that orbis the Earth at an altitude of 450 km, the developed algorithm allows for a 90 % correction of the ionospheric error in a reduced dynamic orbit determination, based on single frequency C/A code measurements.