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Project name:ESA-ProdexCN1 - Advanced Topics in Radio Occultation Modeling and Retrieval
Project leader:Gottfried Kirchengast
Project team:Johannes Fritzer
Josef Ramsauer
Marc Schwärz
Susanne Schweitzer
Partners:Michael Gorbunov (Institut for Atmoshperic Physics, Moskau, Russland)
Sponsor:ESA (European Space Agency)



The objectives of the Prodex-CN1 project included work on advanced topics in radio occultation modeling and retrieval along two study lines, the first one on preparing tools, the second one on using them for performance assessments: 1) advancement of modeling, retrieval algorithms and performance evaluation tools, 2) radio occultation performance studies for X/K band inter-satellite links. Meeting these objectives included advancement of End-to-end Generic Occultation Performance Simulator version 5 (EGOPS5) software and consolidation of LEO-LEO radio occultation (LRO) performance knowledge, in particular related to challenging atmospheric sounding conditions in the presence of atmospheric turbulence, which require invoking a wave-optics (WO) modeling approach in the simulation tools and the analysis.

In line with the project tasks, the EGOPS5 software received substantial LRO simulation upgrades, both in wave-optics forward modeling and retrieval, as well as in the full LRO retrieval processing chain. In addition, the so-called EGOPS Joint Development strategy, started in mid 2006, was especially useful to lead to further advancements related to real GNSS radio occultation (GRO) data processing (CHAMP, SAC-C, etc.) and to a completion of the EGOPSv5.2 full release to users by May 2007. Furthermore, it prepared to define a substantial modernization and further improvement in S/W engineering approach, of future work towards EGOPS6 in the Prodex-CN2 project and related projects.

The performance studies consolidated the knowledge, on top of ACE+ heritage, on both adequate system and observational requirements for X/K band and K band LRO systems as well as on the characterization and understanding of the whole LRO technique and its processing. In particular, they consolidated the understanding of the influence of phase and amplitude scintillations in received X/K band signals in presence of (strong) atmospheric turbulence. Evidence was re-enforced that WO-based differential transmission retrieval keeps retrieval errors at small levels also in presence of strong turbulence and enables that X/K band RO phase delay and transmission are a promising future data source for accurate temperature and humidity profiling.

Looking forward to the Prodex-CN2 project, this will allow to fully realize the new approach of EGOPS Joint Development by the UniGraz group and its international development partners. It will transform the present EGOPS5 system (ending with the EGOPSv5.2 release) to a new EGOPS6 system where GRO, LRO, and LEO-LEO infrared laser occultation (LIO), as well as simulated data processing and real data processing, are treated at a joint system development level. This will provide a further enormous boost to the scope and utility of EGOPS for all users, both in-house at UniGraz as well as worldwide, and will ensure further growth of the user community and of the international standing of the EGOPS development partners. For more information on the planned Prodex-CN2 work see the “ESA-ProdexCN2” project description.

Univ.-Prof. Mag. Dr.rer.nat.

Gottfried Kirchengast

Phone:+43 316 380 - 8431

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