The ability to do atmospheric sensing of the neutral atmosphere (troposphere and statosphere) by space geodetic techniques has improved considerably over the last years. This is a result of technological advances, larger regional and global ground networks, satellite-based missions (CHAMP, GRACE, COSMIC, MetOp, TerraSAR-X, OceanSat-2,…) and developments of appropriate models and algorithms. The availability of new additional GNSS signals and constellations, as the forthcoming Galileo, is expected to increase the quality of derived atmospheric parameters. Accurate atmospheric observations based on space geodetic techniques can significantly improve our understanding on the physical and dynamic characteristics of weather and climate at various scales. We welcome contributions on the following subjects: Physical modelling of the neutral atmosphere using ground-based and radio-occultation data. Usage of GNSS measurements in weather forecasting (e.g., NWP and now-casting) and the impact of it. Use of GNSS data in climate monitoring. Technique validation or inter-technique comparisons (e.g. against other satellite instruments or radiosonde) and inter-system calibration. Assessment and discussion of neutral atmospheric effects on the GNSS signals and on other techniques at radio wavelengths, such as VLBI, InSAR and spacecraft ranging, as well as current techniques to perform neutral atmosphere media calibration. Studies on how to mitigate such effects for improving GNSS positioning, navigation, and observations at radio wavelengths. Contributions about empirical or numerical correction models, user services and receiver technology to handle atmospheric corrections, real-time estimate and related issues.