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Project name:OPSGRAS - Reference Occultation Processing System for GRAS on MetOp and other Past and Future RO Missions
Project leader:Gottfried Kirchengast
Project team:Gottfried Kirchengast
Marc Schwärz
Johannes Fritzer

Team Support and Advice:
Ulrich Foelsche
Andrea Steiner
Barbara Pirscher
Susanne Schweitzer
Veronika Proschek
Florian Ladstädter

Michael Gorbunov (expert wave-optics algorithms and tools), Inst. of Atmospheric Physics, Moscow, RU
Kent B. Lauritsen (expert GRAS-SAF/ROPP software and wave-optics), Danish Meteorological Inst., Copenhagen, DK


European Space Agency ESA



Recognizing the strong need for a fresh approach despite six main RO processing centers (and other less known ones) running systems worldwide, the aim of the OPSGRAS project is to implement a new reference Occultation Processing System (OPS). The OPS will process data of the currently most modern RO sensor GRAS (GNSS Receiver for Atmospheric Sounding on EUMETSAT’s polar-orbiting meteorological operational satellites MetOp) as well as data from other past and future RO missions (CHAMP, Formosat-3/COSMIC, GRACE, Formosat-7/COSMIC-2, etc). It will interface to the Level 1a data (phase/amplitude and orbit data) of the respective RO raw data providers. In designing and implementing the OPS, OPSGRAS aims to bring to fruition the best of RO know-how learned over the last decade and more and to realize a range of innovative ideas. The goal is to have a new system that is better fit for enabling climate monitoring with benchmark quality than existing systems.

More specifically, the new OPS will be intentionally developed as a system separate from the existing EGOPS software, whereby the OPSGRAS work includes the following main components:

  • A renewed 3D atmosphere modeling compared to EGOPS, needed to adequately serve the OPS with reliable background information from ECMWF analyses and forecasts, including serving a new implementation of consistent forward modeling to Level 1 profiles (bending angle, Doppler shift, excess phase) from background refractivity fields.
  •  A new Level 1b processing system (retrieving atmospheric bending angles from Level 1a phase/amplitude and orbit data) with an innovative approach to use background profiles in supporting the algorithmic chain from pre-processing of phase/amplitude data to high-altitude initialization of raw bending angle data.
  • A new Level 2 processing system (retrieving refractivity and further atmospheric profiles like temperature and humidity from bending angles) with a renewed refractivity retrieval optimally matching the new Level 1b bending angles and another innovative algorithmic chain for dry air retrieval and moist air retrieval, including moist air optimal-estimation retrieval.

Provision of the OPS, including the necessary system development, testing and validation work, as a complete OPS software and documentation system that fulfils the “Reference OPS User Requirements” serving as basis for the functionality and performance to be achieved by the work.

Publications on the new OPS for the peer-reviewed scientific literature will be prepared as integral part of the project work, regarding both its algorithms and its performance relative to best-available existing systems. This “work-to-publication approach”, less common in ESA projects which usually lead to ex-post publications of selected results, serves to integrate high-quality feedback from independent peers during the project as well as to make the algorithms fully transparent and broadly known as a potential reference for developments at other RO centers.

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

Gottfried Kirchengast

Phone:+43 316 380 - 8431

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