Ionosphere/Plasmasphere Imaging Based on GPS Navigation Measurements from CHAMP and SAC-C

Both the CHAMP and SAC-C satellites permanently track several GPS satellites using dedicated zenith looking antennas 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 altitudes on a global scale. After preprocessing and calibration, link related TEC measurements are derived from the GPS navigation observations. Three-dimensional electron density information is retrieved by assimilating these TEC data into the Parameterized Ionospheric Model (PIM). In specific periods CHAMP and SAC-C circle the earth in nearly the same orbit plane due to their different orbit properties. We focus on these constellations which are of special interest for the combined assimilation of TEC measurements from both satellites. Reconstruction results for selected assimilation examples are presented by means of two dimensional slices along the respective CHAMP/SAC-C orbit plane. Using electron density measurements from the CHAMP Langmuir Probe we validate our reconstruction results along the CHAMP path and discuss the impact of the TEC measurements from SAC-C on the reconstruction result at CHAMP orbit altitudes.