Combined assimilation of GPS based TEC data from CHAMP and SAC-C for ionosphere/plasmasphere imaging

Abstract

Ground based GPS measurements are well proved in terms of monitoring the vertical Total Electron Content (TEC) of the ionosphere. The GPS receivers installed on board of LEO (Low Earth Orbiting) satellites such as CHAMP and SAC-C provide a rather new data source for ionospheric remote sensing on global scale. Both satellites CHAMP and SAC-C track permanently several GPS satellites using zenith looking antennas dedicated for precise orbit determination. These 0.1 Hz sampled dual frequency navigation measurements provide valuable information on the ionization state of the upper ionosphere and plasmasphere up to GPS altitude on global scale. After preprocessing and calibration, link related TEC measurements are derived from the GPS navigation observations. The three dimensional electron density distribution is reconstructed by assimilating these TEC measurements into the Parameterized Ionospheric Model (PIM) which includes also the Gallagher model of the plasmasphere. Due to the orbit properties of CHAMP and SAC-C there are time intervals of about 2 weeks when both satellites circle the earth at nearly the same orbit plane but at different altitudes.We focus on these constellations which are of special interest for the combined assimilation of TEC measurements from both satellites. In this talk reconstruction results are presented for selected assimilation examples by means of two dimensional slices along the respective CHAMP/SAC-C orbit plane. The assimilation technique will be described briefly. We present validation results using electron density measurements from the Langmuir Probe on board CHAMP and compare reconstructions based on TEC data from only one and from both satellites. Potentials for space weather monitoring will be addressed.