A comparison between TEC obtained by the TOPEX/Poseidon borne GPS receiver and TEC from the Gallagher model

JPL archived RINEX files relative to the GPS receiver of TOPEX at the site bodhi.jplnasa.gov/pub/topex/rinex for years 1992, 1993, 1994, 1995, 1997. The GPS receiver on board was intended as a tool for precise orbitography, but from such data it is possible to extract Differential Phase and Group Delays providing with a biased estimate of slant Total Electron Content (TEC) from TOPEX to GPS. This means a very useful information about TEC in an area above 1340 up to 20000 km, or high topside and plasmasphere. It was possible to get some estimate of the minimum magnitude of slants that can be observed in such region. A comparison with slants obtained by the Gallagher was carried out, with interesting results.