IAG School on Reference Systems June 7 June 12, 2010 Aegean University, Department of Geography Mytilene, Lesvos Island, Greece SCHOOL PROGRAM

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1 IAG School on Reference Systems June 7 June 12, 2010 Aegean University, Department of Geography Mytilene, Lesvos Island, Greece SCHOOL PROGRAM Monday June 7 8:00-9:00 Registration 9:00-10:00 Opening Session 10:00-10:30 Coffee Break 10:30-13:00 A. Dermanis: Basic Concepts of Reference Systems in Geodesy, Astronomy and Geophysics 14:30-16:00 A. Dermanis: (cont.) 16:30-18:00 A. Dermanis: (cont.) Tuesday June 8 8:30-10:30 E. Pavlis: Models and Strategies for Global SLR Networks 10:30-11:00 Coffee Break 11:00-13:00 E. Pavlis: (cont.) 14:30-16:00 T. Herring: Models and Strategies for Global VLBI Networks 16:30-18:00 T. Herring: (cont.) Wednesday June 9 8:30-10:30 T. Herring: Models and Strategies for Global GNSS Networks 10:30-11:00 Coffee Break 11:00-13:00 T. Herring: (cont.) 14:30-16:00 T. Herring: (cont.) 16:30-18:00 T. Herring: (cont.) Thursday June 10 8:30-10:30 M. Sideris: Height Systems 10:30-11:00 Coffee Break 11:00-13:00 M. Sideris: (cont.) 14:30-16:00 P. Willis: Models and Strategies for Global DORIS Networks 16:30-18:00 P. Willis: (cont.) Friday June 11 8:30-10:30 Z. Altamimi: Reference Frame Combination and Time Series Analysis 10:30-11:00 Coffee Break 11:00-13:00 Z. Altamimi: (cont.) 14:30-16:00 Z. Altamimi: (cont.) 16:30-18:00 Z. Altamimi: (cont.)

2 Saturday June 12 9:30-11:00 Closing Session 11:00-12:00 Coffee Break 12:00-23:00 Excursion

3 Basic Concepts of Reference Systems in Geodesy, Astronomy and Geophysics Lecturer: A. Dermanis Introduction: Definition of a reference system. Relation to coordinate systems. Transformations between reference systems. The role of the reference system in geodetic datums and cartographic projections. Reference systems in motion: Inertial and accelerated systems, pseudo-forces. Rigid body rotation, instantaneous rotation vector. Generalized Euler s kinematic equations. Reference systems for deformable bodies. Figure axes and Tisserand axes. Reference systems and earth rotation: Celestial, terrestrial and intermediate reference systems, separation into precessionnutation, diurnal rotation and polar motion. From the instantaneous rotation vector to the Celestial Intermediate Pole (CIP). The Non-Rotating Origin (NRO) principle, the Celestial and Terrestrial Intermediate Origins (CIO and TIO). Diurnal rotation and time. The role of earth rotation theories. Relativistic reference systems and time systems. The IERS representation of earth rotation. Basic algorithms and procedures. Comparison with reference systems and concepts in classical geodetic astronomy. Reference systems in space geodetic methods. Comparison of spatial techniques and their contributions in establishing a global terrestrial reference system (ITRF). The geodetic datum problem. The datum problem in classical control networks, its relation to stochastic estimability and the solution of linear systems without full rank. Basic models for ITRF construction from individual technique-based coordinates series and solutions of the ITRF datum problem. Geophysical causes of coordinate variations. Tectonic motions, tides, loading effects. The geophysical representation of residual ITRF coordinate variations and open problems.

4 SLR Data Analysis for Terrestrial Reference Frame Development: Lecturer: E.C. Pavlis Preamble: The Satellite Laser Ranging (SLR) technique, a brief introduction (concept, targets, hardware, network, operations, the observable), the ILRS--Int. Laser Ranging Service of IAG, emphasis on the Analysis Working Group and its official products. The observable two-way range: Development of the observation equation and discussion of the parameters of interest and their estimability. The unique contributions of SLR in the development of a TRF product: origin and absolute scale. The official archives of SLR observations and related topics (QC and QA, availability, access, etc.). Data quality and relative weighting. Theoretical aspects: Orbital dynamics theory (PPN metric), force models, reference frames involved and their relationship. Description of the observer (station), its instantaneous position and various motions. Propagation media effects (atmospheric refraction delay). Coupling of SLR measurement process with Earth System processes (atmospheric, oceanic, hydrologic, etc.). Practical aspects: Choice of underlying models and standards with an emphasis on the current ILRS AWG practice. The role of IERS Conventions and the ILRS AWG Standards. The daily and weekly routine of generating the official ILRS TRF products. Target signature and its effect on the quality of SLR products. Geodetic (e.g. LAGEOS, Starlette, etc.) versus other targets (e.g. remote sensing platforms such as JASON-2, ENVISAT, GRACE, etc.) and their modeling complications. The synergism between SLR and GNSS techniques. Official ILRS Products: Station position and velocity estimates, Earth Orientation Parameter (EOP) series, geocenter motion series, orbits, etc. Description of the analysis step and the intratechnique combination for the generation of the official ILRS contributions to ITRF. Practicum: Analysis of sample SLR data and generation of a weekly TRF and EOP product using NASA Goddard s GEODYN II and SOLVE II s/w package.

5 Models and Strategies for Global VLBI Networks (3 hours of classes) Lecturer: Tom Herring. (1) VLBI observables and how they relate to reference frames (2) Rotation transformations: Critical aspects of transformation from inertial to earth fixed coordinates. Here I would like to use some simple Matlab programs to demonstrate how the separation between inertial and earth fixed rotations changes are accommodated. (3) Critical models in VLBI e.g., radio source structure, atmospheric delay models, tidal and non-tidal loading Models and Strategies for Global GNSS Networks (7 hours of classes) Lecturer: Tom Herring. (1) GNSS observables and how they related to reference frames. Start here with GPS and then examine impact of Glonass, Galileo and Compass. (2) Propagation medium, include multipath, second order ionosphere, relativity. Examples will be largely based on GPS. (2) Orbit determination and reference frame effects from orbit modeling and estimation. Treatment of radiation parameters will be carefully examined since this is critical to GPS global reference frames (and not so critical to regional ones). (3) Ambiguity resolution on global and regional scales; issues and methods and effects on reference frames. (4) Critical models for GPS not already covered: e.g., Phase center models (5) Reference frame realization methods in loose to unconstrained solutions. Applications here to global and regional GPS analyses. (6) Deformation effects on reference frames e.g., co-seismic and post-seismic motions, episodic tremor and slip; water and loading effects.

6 Height Systems (4 hours of classes) Lecturer: M.G. Sideris Basic theory of gravity field and height systems Determination of geometric and physical heights, geopotential numbers and geoid undulations Transformation between height systems GNSS leveling Definition of a vertical reference system (VRS) Geometrical and physical components, and its relation to ITRS Boundary value problems for the definition of a VRS VRS, mean sea level and tides Realization of a vertical reference system The vertical reference frame Solving the vertical datum problem using terrestrial and satellite data Determination of gravity potential values (WP) The role of high resolution gravity field models and other data Determination of the reference potential Wo Connection/unification of existing vertical datums Determination of temporal variations of elevations and the vertical datum time series of absolute/superconducting gravimetry, GNSS, tide gauge, and altimetry data Realization of a World Height System

7 Models and Strategies for Global DORIS data analysis Lecturer: P. Willis Introduction: Historical aspects related to the DORIS system (main goals, key technical evolution for instruments), ground tracking network, the International DORIS Service Estimating geodetic products using a free-network approach General description of DORIS data processing using GIPSY/OASIS II software package: From Doppler data to daily, weekly time series of station coordinates, geocenter motion, and derived products (EOPs, station velocities). Phase center corrections and frame definition: an example of systematic errors on geodetic products and derived mean sea level. Expressing DORIS coordinates in specific terrestrial reference frame. Solar radiation pressure Current models used for TOPEX/Poseidon, Jason1&2, Envisat and SPOTs, current limitation, empirical estimation strategies and consequences in terms of systematic errors on station vertical position and geocenter motion. Atmospheric drag Current models and limitations, estimation strategies and consequences on derived geodetic products Tropospheric estimation using DORIS data Current analysis strategies related to tropospheric estimation using DORIS data, current limitations, comparison with results from other techniques, consequences on station coordinates estimation. Possible future improvements.

8 Reference Frame Combination and Time Series Analysis Lecturer: Zuheir Altamimi Introduction: Brief history of ITRF combination activities. Basic equations for reference frame combination, 14-parameter similarity transformation. Combination model: Inputs and Outputs. Basic observation equations for combination of station positions and Earth Orientation Parameters. Linearized unknowns. Construction of the Normal Equation. Constraint handling: Type of constraints used by space geodesy analysis centers. Removal of constraints for the purpose of combination. Datum Definition of the combined solution: Rank deficiency of the Normal Equation. Possible types of datum definition for the combined solution. Usage of Minimum Constraints for the datum definition Quality estimators: Variance component estimation. Weighting of individual input solutions. RMS, WRMS Introduction to CATREF Software: CATREF Combination Strategy. Usage of CATREF software for: Intra-technique combination (rigorously stacking) of time series of station positions and EOPs Multi-technique combinations using local ties Numerical Applications: Illustrating examples of intra and multi-technique combinations Quality evaluation: analysis of residuals, outliers, variance component estimation, RMS, WRMS Analysis of the outputs of an intra-technique combination: time series of frame parameters (geocenter and scale) and residual of station positions, outliers and discontinuities.