1. IGS Analysis Center Workshop, Miami Beach, 2-6 June 2008 M. Fritsche, R. Dietrich, A. Rülke Institut für Planetare Geodäsie (IPG), Technische Universität Dresden, Germany Reprocessing of a Global GPS Network  Experiences and Results M. Rothacher GeoForschungsZentrum Potsdam (GFZ), Germany P. Steigenberger Institut für Astronomische und Physikalische Geodäsie, Technische Universität München, Germany

2. IGS Analysis Center Workshop, Miami Beach, 2-6 June 2008 Outline  Basic Facts: Database, Software, Resources  Observation Modeling and Adjustment  Results  Conclusions

3. IGS Analysis Center Workshop, Miami Beach, 2-6 June 2008 Basic Facts Project fundedDeutscheForschungsGemeinschaft, 2003-2006 Processed periodJanuary 1994 – December 2007 GPS data202 nominal GPS stations Softwaremodiefied Bernese GPS Software Version 5.0 Strategymodified processing scheme adapted from CODE IGS Analysis Center

4. IGS Analysis Center Workshop, Miami Beach, 2-6 June 2008 Processing on Cluster of Linux PCs -1-day solution ~ 2.5h from raw level -1-day solution ~ 15min from screened DD-level -7-day solution ~ 2h on NEQ level Labor input invested ~ 15000 man hours -40% software development and processing setup -40% data handling and screening -20% analysis of results and publication Results -3 complete processing runs -~ 20 additional solutions based on 1-day solutions Basic Facts

5. IGS Analysis Center Workshop, Miami Beach, 2-6 June 2008 Bernese GPS Software frozen version from !May 2005! - absolue PCVs (!w.r.t. IGb00!) - 2 nd & 3 rd –order IONO - IMF for TROPO 1-day Normal Equations (NEQs) ZD-code observations: - ION,DCB,CLK DD-phase observations: - XYZ, TRP - ORB, PCV - ERP Modeling and Adjustment

6. IGS Analysis Center Workshop, Miami Beach, 2-6 June 2008 Higher-order ionospheric effects mean coordinate residuals for the year 2002 (GRL, Fritsche et al. 2005) compared to standard solution Modeling and Adjustment

7. IGS Analysis Center Workshop, Miami Beach, 2-6 June 2008 mean NMF-IMFdifferences for 2002 at 5° elevation (GRL, Vey et al. 2006) Modeling and Adjustment A Priori Tropospheric Delay

8. IGS Analysis Center Workshop, Miami Beach, 2-6 June 2008 1-day NEQs weekly solution 3-day solution coordinates, Earth rotation parameter satellite orbits long term solution Reference Frame Modeling and Adjustment

9. IGS Analysis Center Workshop, Miami Beach, 2-6 June 2008 Orbit Accuracy SLR residuals for IGS, CODE and Reprocessing GPS orbits (JoG, Steigenberger et al. 2008)

10. IGS Analysis Center Workshop, Miami Beach, 2-6 June 2008 Equipment change at Horn Point (HNPT) Coordinate Discontinuities abs. PCVs  U= -0.5 mm rel. PCVs  U= -15.8 mm AOAD/M_TA_NGS NONE ASH700936E SNOW  U= 15.3 mm

11. IGS Analysis Center Workshop, Miami Beach, 2-6 June 2008 Altogether 134 discontinuities considered between 1 January 1994 and 31 December 2005 Type# Antenna/Radome change35 Receiver change5 Antenna & Receiver change29 Earthquakes17 Other5 Unknown43 Coordinate Discontinuities directly equipment related further equipment changes not reported?

12. IGS Analysis Center Workshop, Miami Beach, 2-6 June 2008 GPS TRF – PDR05 Terrestrial Reference System Realization - absolute PCVs for satellites and receiver antennas (scale) - preelimination of weekly satellite arcs (CM) - station coordinates, velocities: NNR w.r.t. IGb00 - Xpol, Ypol: freely estimated - spherical harmonics for a surface load redistribution (JGR, Rülke et al. 2008)

13. IGS Analysis Center Workshop, Miami Beach, 2-6 June 2008 Degree-1 Surface Load Coefficients GPS TRF – PDR05

14. IGS Analysis Center Workshop, Miami Beach, 2-6 June 2008 TRS space geodetic observations + random erros additional constaints systematic modeling errors TRF = „Estimate“ Comparison of TRFs: instead of 14-parameter transformation weekly 7-parameter transformations GPS TRF – PDR05

15. IGS Analysis Center Workshop, Miami Beach, 2-6 June 2008 Weekly 7-Parameter Transformations w.r.t. ITRF2000 / ITRF2005 ITRF2000 ITRF2005 GPS TRF – PDR05

16. IGS Analysis Center Workshop, Miami Beach, 2-6 June 2008 Conclusions (1)Reprocessing results show improved quality and homogeneity of estimated parameter time series (2)Reference system realization based on homogeneously reprocessed GPS observations (3)Concept of simultaneous estimation of satellite orbits, station positions and large-scale surface load deformation in the CM frame

17. IGS Analysis Center Workshop, Miami Beach, 2-6 June 2008 Fritsche M., R. Dietrich, C. Knöfel, M. Rothacher, A. Rülke, S.Vey, P. Steigenberger, (2005), Impact of higher-order ionospheric terms on GPS-estimates; GRL, doi:10.1029/2005GL024342 Vey S., M. Fritsche, R. Dietrich, M. Rothacher, A. Rülke, P. Steigenberger, (2006), Influence of mapping function parameters on global GPS network analyses – comparison between NMF and IMF, GRL, doi:10.1029/2005GL024361 Steigenberger P., M. Rothacher, R. Dietrich, Fritsche, M., A. Rülke, and S. Vey, (2006), Reprocessing of a global GPS network, JGR, doi:10.1029/2005JB003747 References Steigenberger P., M. Rothacher, M. Fritsche, A. Rülke and R. Dietrich (2008), Quality of Reproccessed GPS Satellite Orbits, Journal of Geodesy, doi:10.1007/s00190-008-0228-7 (accepted) Rülke A., R. Dietrich, M. Fritsche, M. Rothacher, and P. Steigenberger (2008), Realization of the Terrestrial Reference System by a reprocessed global GPS network, J. Geophys. Res., doi:10.1029/2007JB005231 (accepted)