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The first radio occultation measurements of the CHAMP (CHAllenging Minisatellite Payload) satellite using Global Positioning System (GPS) signals have been performed on February 11, 2001. By the end of April 2001 more than 3000 occultations were recorded. Globally distributed vertical profiles of dry temperature and specific humidity are derived, of which a(More)
CHAMP (CHAllenging Minisatellite Payload) and GRACE (Gravity Recovery And Climate Experiment) formed a satellite configuration for precise atmospheric sounding during the first activation of the GPS (Global Positioning System) radio occultation experiment aboard GRACE on 28 and 29 July 2004. 338 occultations were recorded aboard both satellites, providing(More)
Radio occultation events recorded on 28–29 July 2004 by the " BlackJack " GPS receiver aboard the GRACE-B satellite are analyzed. The high stability of the receiver clock allows for the implementation of a zero difference technique rendering clock calibrations with concurrent observations of a reference GPS satellite unnecessary. Thereby the usage of(More)
Fig. 1. Geometry for double difference processing of CHAMP's GPS radio occultation data. Involved are two satellite to satellite links (occulting and referencing GPS satellite to CHAMP) and two satellite to ground links (GPS satellites to the ground station). The atmospheric influence on the propagation of the GPS signal is characterized by the bending(More)
[1] The observation of GPS slant delays from ground GPS networks can be used to reconstruct spatially resolved humidity fields in the troposphere by means of tomographic techniques. Tomography is always related to the solution of inverse problems which are very sensitive to the quality of the input data. Prior to a tomographic reconstruction, it is(More)
An analysis of 205,633 atmospheric refractivity profiles ob-reveals significant biases compared to ECMWF meteorological fields at altitudes below 5 km. The mean bias decreases down to −2% at altitudes below 2 km; in the Amazon region positive biases exceeding +1% are observed. In order to separate bias contributions caused by critical refraction from(More)
[1] The GPS (Global Positioning System) radio occultation experiment onboard the German CHAMP (CHAllenging Minisatellite Payload) satellite was successfully started in February 2001. By the end of July 2001 more than 11,000 globally distributed vertical profiles of atmospheric temperature were derived. Operational data processing is based on the double(More)
The operational data analysis of the GPS radio occultation experiment aboard the German CHAMP (CHAllenging Minisatellite Payload) satellite mission is described. Continuous Near-Real-Time processing with average time delay of ~5 hours between measurement and provision of analysis results is demonstrated. A delay of less than 3 hours is reached for(More)
A GNSS water vapour tomography system developed to reconstruct spatially resolved humidity fields in the troposphere is described. The tomography system was designed to process the slant path delays of about 270 German GNSS stations in near real-time with a temporal resolution of 30 min, a horizontal resolution of 40 km and a vertical resolution of 500 m or(More)