Publications

The standard method for GPS occultation data processing of CHAMP at the GeoForschungsZentrum (GFZ) Potsdam is the double differencing method. GPS satellite and ground station data are combined to correct for the clock errors of CHAMP and the occulting and referencing GPS satellites, respectively. The application of the double difference method requires the implementation of a global fiducial network of GPS receivers. By the termination of the Selective Availability (SA) mode on May 2, 2000 at 04:05 UTC the variations in the GPS transmitter clocks were reduced by orders of magnitude. This made the clocks more predictable and enabled the application of less-than-double differencing techniques for occultation data processing to become a potentially attractive alternative. A space based single differencing technique is applied to the CHAMP occultation data processing at GFZ. A set of more than 400 occultation events is analysed using this technique. The processing results, the vertical temperature profiles, are compared with the double difference processing, used as a reference. A similar comparison study (about 900 profiles), is performed at JPL (Jet Propulsion Laboratory). The results of both processing strategies are compared with ECMWF meteorological analysis.

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Wickert, J.; Beyerle, G.; Hajj, G. A.; Kirchengast, G.; Schmidt, T.; Marquardt, C.; König, R. (2002): Space-based single differencing: An alternative approach for CHAMP occultation processing. First Champ Science Meeting (Potsdam 2002).