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Project name:

OPSCLIMPROP –  Occultation Processing System for Cal/Val and Climate: Level 1 Processing with Integrated Uncertainty Propagation

Project leader:

Gottfried Kirchengast

Projekt team:

Johannes Fritzer (Senior Scientist)
Jakob Schwarz (Scientist)
Marc Schwärz (Senior Scientist)

Andrea Steiner (Senior Sci. Adviser)
Barbara Scherllin-Pirscher (PostDoc Sci. Adviser)




FFG- ALR (Austrian Research Promotion Agency- Austrian Aeronautics and Space Agency); ASAP - 9 Programme


Oct. 2013 - May 2016






Monitoring the atmosphere to gain accurate and long-term stable records of essential climate variables (ECVs) such as temperature is the backbone of contemporary atmospheric and climate science and observation from space is the key to obtain such data globally in Earth’s atmosphere. Currently, however, not any existing satellite-based atmospheric ECV record can serve as authoritative reference over months to decades so that atmospheric variability and change are not yet reliably monitored.

GPS radio occultation (RO) provides a unique opportunity to solve this problem in the free atmosphere for core ECVs: the thermodynamic variables temperature and pressure, and to some degree water vapor, which are key parameters both for governing atmospheric chemistry and for tracking climate change. RO accurately measures time delays from atmospheric refraction of the GPS signals, which enables to tie RO-derived ECVs and their uncertainty to fundamental time standards, effectively the SI second, and to their unique long-term stability and narrow uncertainty. However, despite impressive advances since the pioneering RO mission GPS/Met in the mid-1990ties, not least due to work at WEGC, no rigorous trace from fundamental time to the ECVs exists so far.

Establishing such a trace first-time in form of the Reference Occultation Processing System OPS, providing reference RO data for calibration/validation and climate monitoring, research and services, is therefore a current cornerstone endeavor at the WEGC over 2011 to 2014. It demands to process the full chain from the SI-tied raw data to the ECVs with integrated uncertainty propagation, including a first step to so-called excess phase level (Level 1a), a second one to atmospheric bending angle level (Level 1b), a third one to refractivity/dry-air level (Level 2a), and a forth one to final thermodynamic ECV profiles (Level 2b).

The OPSCLIMPROP project—following the ESA project OPSGRAS—aims to help complete the novel Level 1 and Level 2 processing of the OPS as follows: 1. complete the chain by adding a Level 1a processor to the Level 1b and Level 2a/2b processors from OPSGRAS, 2. integrate Level 1a/1b uncertainty propagation capabilities. This will enable first-time to trace and propagate the fundamental-time uncertainty and relevant side influences from RO raw tracking data and high-accuracy GPS orbit data to atmospheric bending angles. An ESA/ESRIN project scheduled in parallel (MMValRO-4) will complete the trace with Level 2 uncertainty propagation down to the atmospheric ECVs.

Based on this new OPS, the WEGC is scheduled to serve as of 2015 as the primary global distribution center for benchmark-quality RO data from the CICERO community initiative RO mission (launch of two-satellite pathfinder scheduled in late 2014). We will also (re-)process data from other RO missions, like the European MetOp/GRAS and the Formosat-3/COSMIC mission, with the aim to broadly provide a new reference standard for thermodynamic ECVs for atmosphere and climate research and applications.


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

Gottfried Kirchengast

Phone:+43 316 380 - 8431

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