Effects of the orbital uncertainties on atmosphere profiles retrieved with the GNSS radio occultation technique

In the last decade the use of GPS radio occultation technique (GPS RO) bas been deeply and widely investigated for retrieving physical and chemical parameters of Earth atmosphere. The technique proved to be particularly precise in retrieving temperature profiles with an high vertical resolution (1 km) and accuracy (1st1K). The use of such technique for numerical weather prediction is the most challenging application. In fact a good knowledge of the orbits, in turn of the LEO satellite with the GPS receivers and the GPS satellites, is needed. Another severe requirement is that such orbits must be provided in Near-Real-Time (1 hour). Such severe requirement limits dramatically the precision of the estimated- predicted orbits. We will investigate in the present work the sensitiveness of the atmosphere profiles, namely pressure, temperature and humidity, to the LEO and GPS satellites orbital uncertainties. In the second part we will discuss about the requirements and specs to be fulfilled by the estimates of the orbits to assure a meteorological service based on the GNSS radio occultation technique.