GPS atmosphere and ionosphere methods used on Orsted data and initial application on CHAMP data

The launch of the Orsted satellite started a range of activities to verify GPS occultation measurements of the Earth atmosphere and ionosphere based on observations of GPS signal delay from a low Earth orbiting satellite. The Orsted satellite followed the GPS/MET satellite experiment as the second mission in space to perform these types of measurements. Now the CHAMP satellite and also the SAC-C satellite are producing GPS occultation measurements in large numbers in long time-series and the data are just available since November 2001. The aim of this paper is to present an overview of the retrieval techniques used on the observations with the TurboRogue receiver on Orsted and the results obtained both for the atmosphere and ionosphere. The results of CHAMP occultations using Orsted processing tools will be presented and compared with Orsted.