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Gravity Field

Gravity Field. Main task Exploitation of science data collected by space-geodetic techniques Main research topics Dynamic orbit determination/prediction Trajectories from SLR and radio science measurements Gravity field Static and time-variable gravity field recovery

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Gravity Field

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  1. Gravity Field Main task • Exploitation of science data collected by space-geodetic techniques Main research topics • Dynamic orbit determination/prediction • Trajectories from SLR and radio science measurements • Gravity field • Static and time-variable gravity field recovery • Mass variation from time-variable gravity • Satellite accelerometry • Atmosphere evolution studies Refereed publications (since Jan 2013) • Total: 7 (first author: 6) • Educational activities (since Jan 2013) • PhD thesis: 1, Master thesis: 1 • Teaching at Graz University of Technology IWF/ÖAW

  2. Who are we? Lead: Oliver Baur Members • Staff: S. Krauss, K. Yamamoto • Students: PhD: A. Maier, H. Wirnsberger Master: B. Klinger, A. Purkhauser, S. Reimond • Cooperation within IWF • SLR Group (Kirchner et al.): SLR orbit determination/prediction • Atmosphere-Plasma (Lammer et al.): Atmosphere response to solar activity • Key external collaboration • Australia: Curtin University of Technology; Austria: TU Graz, KFU Graz; Czech Republic: University of West Bohemia; Germany: University of Stuttgart, TU Munich; Greece: TU Crete; Luxembourg: University of Luxembourg; Switzerland: University of Bern; The Netherlands: TU Delft IWF/ÖAW

  3. Orbit Determination - SLR • Geodetic satellites • Participation in the international GOCO project • Dynamic flattening of the Earth can best be recovered by SLR • Analysis of laser measurements to six satellites • Results accessible via ILRS website Space debris • Sparse data; parameterization challenging • SLR-based orbit determination and prediction superior to radar (TLEs) • “Traditional“ ranging successfully augmented by bi-static measurements • Orbit predictions accessible via ILRS website TLE SLR SLR and bi-static Accuracy of ENVISAT orbit depending on observation technique please visit poster Exemplary availability of SLR observations to ENVISAT (01 Jul to 18 Aug 2013) IWF/ÖAW

  4. Orbit Determination - Doppler please visit poster LRO • Tracked by optical (laser ranges) and radiometric (Doppler shifts, ranges) techniques • “Pilot endeavor“ at IWF for orbit determination from radio science • Modeling and parameterization challenging • Very promising results achieved • GRAIL • First experiences in the framework of simulation studies • Satellites tracked by the Deep Space Network • Data freely available via PDS • Software development started (as alternative to Geodyn) Inter-satellite and ground-based tracking of the GRAIL spacecraft (credits: NASA) Differences between IWF (Doppler-only) and NASA orbits (Doppler, ranges) IWF/ÖAW

  5. Static Gravity Field GOCE • Tuning gravity field recovery from GPS-tracked satellites • Motivated by the potentially more pronounced role of orbit analysis • Several methods have been developed in the last decade • Large-scale study: comparison of results from different approaches • GRAIL • Relevance for geophysics • Transfer of experience from GRACE • Analysis of Ka-band data from the nominal science mission phase • First lunar gravity field model (GrazLGM200a) released • Cooperation with TU Graz GrazLGM200a model in terms of free-air gravity anomalies Degree-error RMS values of recovered spherical harmonic coefficients IWF/ÖAW

  6. Time-Variable Gravity Field GRACE • Detection of mass changes (secular, periodic) on the Earth’s surface • Important source of information for climate research (cf. IPCC-AR5) • Continental balance, impact on sea level • Outlived nominal lifetime by far (follow-on mission approved) • CHAMP/Swarm • Motivated by the likely gap between GRACE and GRACE-FO • Orbit analysis (cf. GOCE, SLR) • CHAMP as case study for Swarm (promising bridging candidate) • Potential for glaciology/hydrology has been demonstrated • Swarm tracking data supposed to be released in mid-2014 GRACE CHAMP Spatial mass variation patterns from time-variable gravity GRACE-derived secular mass change; strongest signals over Greenland & Antarctica IWF/ÖAW

  7. Thermospheric density variation Determination of neutral densities from GRACE accelerations Response of the Earth’s upper atmosphere to extreme solar events Proxy for the young Sun ICMEs/solar flares Comparisons with empirical and theoretical thermosphere models Atmosphere ICME characterization Cooperation with KFU Graz Speed, magnetic field (magnitude, orientation) Regular measurements at L1 (NASA Wind, ACE) Relation between geomagnetic disturbances and density variation Atmospheric neutral density from GRACE Correlation diagram IWF/ÖAW

  8. Future Plans: 2015-2018 • Dynamic orbit determination • SLR: incorporation of multi-static (and pointing angle) measurements • Doppler: trajectories of planetary orbiters • Software development • Gravity field • GRAIL and Swarm data processing • Inference of mass variation from gravity (Swarm, GRACE, GRACE-FO) • Gravity field determination of irregularly shaped bodies (e.g., comets) • Combination of gravity with altimetry-based topography (geophysical studies) • Depending on funds (project proposals) • Atmosphere: relations with ICMEs • Austrian contribution to GGOS SWARM configuration (credits: ESA) GGOS & the three pillars of geodesy IWF/ÖAW

  9. Thank you IWF/ÖAW

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