[1] The Cassini radio science facility provided 13 occultation electron density profiles of Titan during the period of 2006 and 2009. This paper presents the results of all of these occultation observations. It shows that ten of the observed electron density profiles are similar, but three are significantly different. The number of observations is relatively small for meaningful statistical con...

In this study different approaches based on multilayer perceptron neural networks are proposed and evaluated with the aim to retrieve tropospheric profiles by using GPS radio occultation data. We employed a data set of 445 occultations covering the land surface within the Tropics, split into desert and vegetation zone. The neural networks were trained with refractivity profiles as input compute...

Validation studies of current GPS radio occultation experiments using meteorological analyses consistently report on a negative refractivity bias in the lower troposphere. It is shown that refractivity profiles obtained from Doppler-inverted bending angle profiles not only deviate significantly within zones of multipath propagation but also depend on the selected end point of the occultation si...

In this work we have proposed a method based on neural networks to directly retrieve dry and wet refractivity and dry pressure profiles in troposphere (which in turn can be used to obtain temperature and humidity profiles) by using COSMIC GPS radio occultation (RO) data. To overcome the constraint of an independent knowledge of one atmospheric parameter at each GPS occultation, we trained diffe...

The atmosphere sounding experiment of the German CHAMP (CHAllenging Minisatellite Payload) satellite mission was activated on February 11, 2001. Since then more than 110,000 occultations were recorded as of mid-December 2002. The results of nearly two years CHAMP GPS (Global Positioning System) occultation measurements and data analysis have shown, that significant improvements of the GPS radio...

The possibility of simplifying the retrieval scheme required to produce GNSS radio occultation refractivity climatologies is described. In a new, simplified retrieval approach, the main statistical analysis is performed in bending angle space and an estimate of the average bending angle profile is then propagated through an Abel transform. The average is composed of means and medians of ionosph...

Introduction On July 17, 1995 the U.S. Air Force announced “ .. that today the Global Positioning System (GPS) satellite constellation has met all requirements for Full Operational Capability”. Apart from precise positioning GPS signals also can be used to derive characteristic properties of the propagation medium (neutral atmosphere and ionosphere). Onboard the Low-Earth-Orbiting MICROLAB-1 sa...

The atmospheric propagation of GPS signals under multipath conditions and their detection are simulated. Using the multiple phase screen method C/A-code modulated L1 signals are propagated through a spherically symmetric refractivity field derived from a high-resolution radio sonde observation. The propagated signals are tracked by GPS receivers implemented in software and converted to refracti...

GPS radio occultation (RO) measurements are a potentially important new source of profile information that can be used in numerical weather prediction (NWP). This paper outlines the options for assimilating the RO measurements into an operational NWP system. The importance of realistic estimates for the observation error estimates is discussed.