1. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S The Global Geodetic Observing System and the IVS Service Markus Rothacher GeoForschungsZentrum Potsdam (GFZ) Fourth IVS General Meeting January 9-13, 2006, Concepción, Chile GG S

2. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Contents Motivation Vision and Objectives of GGOS GGOS Structure International GGOS Activities Contributions of IAG Services (IVS) on 4 levels: –First Level: Raw Data Collection –Second Level: Three Pillars of Geodesy –Third Level: Integration/Combination –Fourth Level: Modeling/Interpretation Conclusions

3. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Motivation Helplessness in the face of natural disasters demonstrates that our knowledge of the Earth’s complex system is rather limited. Deeper insight into the processes and interactions within this system is one of the most urgent challenges for our society. To monitor changes in the Earth system and the processes causing natural disasters a global Earth observing system has to be established; GGOS = geodetic part of the system. IAG Services: space geodetic techniques (VLBI, SLR/LLR, GNSS, DORIS), altimetry, InSAR, gravity missions, in-situ measurements etc. allow the monitoring of the Earth system with an unprecedented accuracy (10 -9 )

4. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Mission of GGOS as an IAG-Projekt Mission: To collect, archive and ensure the accessibility of geodetic observations and models; To ensure the robustness of the three fundamental fields of geodesy: geometry, orientation, and gravity; To identify a consistent set of products and establish requirements concerning its accuracy and reliability; To identify IAG service gaps and to close them; to stimulate close cooperation between IAG services; To promote and improve the visibility of the scientific research in geodesy; To achieve maximum benefit for the scientific community and society in general. http://www.ggos.org

5. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Objectives of GGOS as an IAG Project Objectives: Maintain the stability of and providing the ready access to geometric and gravimetric reference frames. Ensure the consistency of geometric and gravimetric products. The targeted overall accuracy and consistency of products is in the order of 10 -9 or better (deformation, Earth rotation, gravity) Ensures the consistency between different geodetic standards used in the geosciences community. Improve the geodetic models at the level required by the observations. To become an official partner in the IGOS, the United Nation’s Integrated Global Observing Strategy. http://www.ggos.org

6. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Structure until new Terms of Reference officially adopted at IUGG/IAG Meeting 2007 Perugia GGOS Steering Committee: Chair: M. Rothacher; Co-Chairs: R. Neilan, H.-P. Plag; Represented: all services, commissions, … GGOS Executive Committee: Chair, Co-Chairs, 3 SC members GGOS Science Panel: Science rationale, overall goals, vision GGOS Working Groups GGOS Secretariat IAG Services IAG Commissions GEO Representatives GGOS Retreat February 15-17, 2006, in Munich; formal approval by the IAG EC, EGU Meeting, April 2006, in Vienna Proposed Structure of GGOS 2006-2007

7. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Goals: Contribute to the international/interdisciplinary efforts to establish a global Earth Observing System Increase the visibility of geodesy Establish international relationships, funding mechanisms GEO and GEOSS: GEO = Group on Earth Observation; members are organizations and groups of organizations GEOSS = Global Earth Observation System of Systems; Members: Contributing Global Earth Observing Systems IAG has become a member of GEO represented by GGOS (representatives: Markus Rothacher, Ruth Neilan) Significant contributions to the GEOSS 10-year plan GGOS International Activities (1)

8. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S IGOS-P: IGOS-P = Integrated Global Observation Strategy Partnership Members of IGOS-P: ICSU, UNESCO, UNEP, IOC, WMO, GCOS, GOOS, GTOS, CEOS, … GGOS will soon become an official member of IGOS-P (positive discussion at IGOS-P Meeting, November 17, 2005) Prepare the theme „Earth System Dynamics“ for IGOS-P for meeting in May 2006 Other themes are: -Geohazards -Integrated Global Water Cycle Observatio -Atmospheric Chemistry -Coasts (including Coral reefs) -… GGOS International Activities (2)

9. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S IAG Services: Backbone of GGOS IERS: International Earth Rotation and Reference Systems Service IGS: International GNSS Service IVS: International VLBI Service ILRS: International Laser Ranging Service IDS: International DORIS Service IGFS: International Gravity Field Service BGI: Bureau Gravimetrique International IGeS: International Geoid Service ICET: International Center for Earth Tides ICGEM:International Center for Global Earth Models PSMSL:Permanent Service for Mean Sea Level IAS: International Altimetry Service (in preparation) BIPM: Bureau International des Poids et Mesures IBS: IAG Bibliographic Service

10. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Others The IAG Services IERS IGSIVS ILRSIDS IGFS BGIIGeS ICETICGEM PSMSLIASBIPMIBS GeometryGravity Sea Level Global Geodetic Observing System (GGOS)

11. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S GGOS: Measuring and Modeling the Earth‘s System MeasuringInformation about Earth System Influence / Modelling Observation Modelling Space Geodetic Techniques VLBI SLR/LLR GNSS DORIS Altimetry InSAR Gravity Missions Terrestrial Techniques Levelling Abs./Rel. Gravimetry Tide Gauges Air-/Shipborne Geometry Station Position/Motion, Sea Level Change, Deformation Earth Rotation Precession/Nutation, Polar Motion, UT1, LOD Gravity Geocenter Gravity field, Temporal variations Earth System Sun/Moon (Planets) Atmosphere Ocean Hydrosphere Cryosphere Core Mantle Crust COMBINATION COMBINATION INTERACTIONS INTERACTIONS

12. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S First Level: Raw Data Collection Three major contributions: 1)Space geodetic techniques: VLBI, SLR/LLR, GPS/GNSS, DORIS; global networks = backbone 2)Satellite missions (altimetry, gravity, atmosphere, …) 3)Terrestrial, airborne, shipborne measurements or campaigns (regional densification, refinement, validation, …) VLBI: Data of a global VLBI network (expensive infrastructure), correlation of the data Future: more stations (?); VLBI observations of GNSS satellites (direct link between ICRF and GNSS orbit frame) Technological innovations by VLBI2010

13. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Satellite Missions Relevant to GGOS MissionTypeMission Duration CHAMPGravity/ magnetic field/ atmosphere2000 – 2007 GRACEGravity (static+ temporal), atmosphere 2002 – 2010 GOCEGravity (stationary, high-resolution)2006 – 2008 TOPEX-POSEIDONOcean altimetry1992 – 2004 Jason-1Ocean altimetry2001 – 2006 ICESATIce altimetry2003 – 2008 CRYOSATIce altimetry2004 – 2007 ERS-2Altimetry/ climate/ environment1995 – 2005 ENVISATAltimetry/ climate/ environment2002 – 2007 TerraSAR-XSAR/ InSAR/ atmosphere2005 – 2010 SWARMMagnetic field2009 - 2014 LAGEOS-1 & 2Reference system, gravity1975 - open GPS/GLONASSNavigation/ positioning, orbits, time transfer/ Earth rotation,… 1978 - open GALILEONavigation/ positioning,…2008 - open

14. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Second Level: Three Pillars of GGOS GEOMETRY GPS, Altimetry, INSAR Remote Sensing Leveling Sea Level EARTH ROTATION VLBI, SLR, LLR, GPS, DORIS Classical: Astronomy New: Ringlasers, Gyros GRAVITY FIELD Orbit Analysis Satellite Gradiometry Ship-& Airborne Gravimetry Absolute Gravimetry Gravity Field Determination REFERENCE SYSTEMS VLBI, SLR, LLR, GPS, DORIS VLBI contributions with darker colors

15. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Level 2: VLBI Contributions to GGOS International Celestial Reference Frame (ICRF), quasar coordinates (only available from VLBI) Full set of Earth Orientation Parameters (EOP: polar motion, UT1/LOD, nutation) Station coordinates and velocities Global scale: stable and absolute Atmospheric products (troposphere and ionosphere) Time/frequency products (time/frequency transfer)

16. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Quasars and Satellite Orbits (VLBI and GPS) VLBI: Kinematic definition of an inertial frame (ICRF) Quasars ideal for the establishment of such a frame (ICRF) Critical: quasars are no point sources, developing with time  Very stable inertial frame from VLBI GPS: Dynamic definition of an inertial frame Stable only over a few days due to force modeling problems Good enough for short-term inertial frame (  LOD, nutation rates) Resonances between Earth Rotation and orbital periods  Inertial frame has to come from VLBI  LOD and nutation rates are important contributions for short-term variations, for interpolation between VLBI experiments

17. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S GNSS Resonance: Orbit - Earth Rotation GALILEO

18. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Scale and Antennas (VLBI and GPS) GPS: Receiver and satellite antenna exhibit antenna phase center variations (different for each antenna type and mounting) Absolute GPS satellite antenna calibration is extremely difficult (determined from global solutions fixing the ITRF scale) Considerable amount of multipath especially at low elevations  Scale not absolutely defined, critical variations with time  Problems with station heights VLBI: Pointing antenna: no problems with antenna phase center variations, only marginal multipath effects Critical: deformation by temperature changes and gravitational sag  Very stable, almost absolute scale

19. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S GPS Satellite Antenna PCVs and Offsets Estimation of satellite antenna phase center variations and offsets from global GPS solutions using absolute antenna calibrations for receivers (robot)

20. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Scale Compared to ITRF2000 (IGb00) Significantly smaller scale drift for absolute PCVs 0.34 ppb/y 0.15 ppb/y

21. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Level 3: Integration/Combination Ensure the consistency and can improve the accuracy of the resulting geodetic products Complementary use of the individual techniques to strengthen the solutions Benefits from observing instruments co-located at the same site/satellite Distinguish genuine geodetic/geo- physical signals from technique- specific systematic biases Crucial to get a more detailed view and understanding of the complexity of the "System Earth" and its geophysical processes.

22. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Steps Toward a Full Combination Parameter Type VLBIGPS/ GLON. DORIS/ PRARE SLRLLRAlti- metry Quasar Coord. (ICRF)X NutationX (X) X Polar Motion X UT1 X Length of Day (LOD) XXXX Coord.+Veloc.(ITRF) XXXXX(X) GeocenterXXXX Gravity Field XXX(X)X OrbitsXXXXX LEO Orbits XXXX IonosphereXXXX TroposphereXXXX Time/Freq.; Clocks XX(X) ICRF ITRF Earth Rotation Gravity Field Atmosphere X XXXX ITRF2000

23. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Coordinate Time Series: Westford 30-day median

24. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Steps Toward a Full Combination Parameter Type VLBIGPS/ GLON. DORIS/ PRARE SLRLLRAlti- metry Quasar Coord. (ICRF)X NutationX (X) X Polar Motion X UT1 X Length of Day (LOD) XXXX Coord.+Veloc.(ITRF) XXXXX(X) GeocenterXXXX Gravity Field XXX(X)X OrbitsXXXXX LEO Orbits XXXX IonosphereXXXX TroposphereXXXX Time/Freq.; Clocks X(X) ICRF ITRF Earth Rotation Gravity Field Atmosphere X XXXX ITRF2005 X

25. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Combination of Polar Motion CONT’02: X/Y-Pole Combination w.r.t. IERS2000 Model 1-hour time resolution

26. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Steps Toward a Full Combination Parameter Type VLBIGPS/ GLON. DORIS/ PRARE SLRLLRAlti- metry Quasar Coord. (ICRF)X NutationX (X) X Polar Motion X UT1 X Length of Day (LOD) XXXX Coord.+Veloc.(ITRF) XXXXX(X) GeocenterXXXX Gravity Field XXX(X)X OrbitsXXXXX LEO Orbits XXXX IonosphereXXXX TroposphereXXXX Time/Freq.; Clocks X(X) ICRF ITRF Earth Rotation Gravity Field Atmosphere X XXXX ITRF2005 (?) X

27. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S CONT’02: Combination UT1 (VLBI) + LOD (GPS)

28. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S CONT’02: Combination UT1 (VLBI) + LOD (GPS) Formal errors of LOD from GPS grow with time Formal errors of UT1 from VLBI stay at a constant level  The long-term behavior is given by VLBI, GPS helps in the interpolation (densification)

29. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Examples: Rapid Combined IERS Daily Products Combination of VLBI Intensive Sessions (e-VLBI) with GPS rapid products and SLR/DORIS rapid solutions Main purpose: daily EOPs available within ~ 24 hours Near-real-time monitoring of the reference frame and individual stations: Eathquakes, Tsunami, station problems, … IGS: Generation of combined SINEX files on a daily basis including EOPs and station coordinates, VLBI: Use e-VLBI for rapid generation of VLBI Intensive solutions (1hour); Intensives are observed on a daily basis SLR/DORIS: Rapid generation of daily solutions (???) Complementarity: -VLBI: UT1 (and scale) -GPS: Reference frame, polar motion (and LOD) -SLR/DORIS: geocenter (and scale)

30. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Steps Toward a Full Combination Parameter Type VLBIGPS/ GLON. DORIS/ PRARE SLRLLRAlti- metry Quasar Coord. (ICRF)X NutationX (X) X Polar Motion X UT1 X Length of Day (LOD) XXXX Coord.+Veloc.(ITRF) XXXXX(X) GeocenterXXXX Gravity Field XXX(X)X OrbitsXXXXX LEO Orbits XXXX IonosphereXXXX TroposphereXXXX Time/Freq.; Clocks XX(X) ICRF ITRF Earth Rotation Gravity Field Atmosphere X XXXX IERS2007=ITRF2007+EOP2007+ICRF2007 ?

31. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Steps Toward a Full Combination Parameter Type VLBIGPS/ GLON. DORIS/ PRARE SLRLLRAlti- metry Quasar Coord. (ICRF)X NutationX (X) X Polar Motion X UT1 X Length of Day (LOD) XXXX Coord.+Veloc.(ITRF) XXXXX(X) GeocenterXXXX Gravity Field XXX(X)X OrbitsXXXXX LEO Orbits XXXX IonosphereXXXX TroposphereXXXX Time/Freq.; Clocks XX(X) ICRF ITRF Earth Rotation Gravity Field Atmosphere X XXXX IERS2008=ITRF2008+EOP2008+ICRF2008 ?

32. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Zenith Wet Delay (VLBI+GPS) : Wettzell Correlation 0.994 Bias 0.1 mm dH=3.1 m Bias corrected 1.1 mm RMS 4.6 mm

33. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Zenith Wet Delay (VLBI+GPS): Kokee Park Correlation 0.961 Bias -7.7 mm dH=9.2 m Bias corrected -5.1 mm RMS 10.9 mm

34. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Tracking Problems at Kokee Park (1) dZWD [cm]Up [cm]Obs. Rate [%] Decorrelation of troposphere and station height problematic due to degraded tracking at low elevations

35. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Tracking Problems at Kokee Park (2) Antenna degradation (July 1996)After antenna replacement

36. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Mean Biases 5.3 mm -2.5 mm -0.8 mm Excluded due to large dH: HART,HARKU RUM Troposphere Parameters: Comparison GPS+VLBI

37. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Tropospheric Gradient Time Series: Wettzell Often good agreement, especially in the last years 30-day median

38. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Steps Toward a Full Combination Parameter Type VLBIGPS/ GLON. DORIS/ PRARE SLRLLRAlti- metry Quasar Coord. (ICRF)X NutationX (X) X Polar Motion X UT1 X Length of Day (LOD) XXXX Coord.+Veloc.(ITRF) XXXXX(X) GeocenterXXXX Gravity Field XXX(X)X OrbitsXXXXX LEO Orbits XXXX IonosphereXXXX TroposphereXXXX Time/Freq.; Clocks XX(X) ICRF ITRF Earth Rotation Gravity Field Atmosphere X XXXX IERS2009=ITRF2009+EOP2009+ICRF2009 ?

39. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Complexer Combination (e.g. Clocks) Clock Combination: Co-located VLBI and GPS receivers running on the same high-accuracy clock Temperature stability on the few picosecond level necessary Ideal goal: common clock parameters with just one offset to be estimated between the techniques Combination on the observation level necessary

40. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Steps Toward a Full Combination Parameter Type VLBIGPS/ GLON. DORIS/ PRARE SLRLLRAlti- metry Quasar Coord. (ICRF)X NutationX (X) X Polar Motion X UT1 X Length of Day (LOD) XXXX Coord.+Veloc.(ITRF) XXXXX(X) GeocenterXXXX Gravity Field XXX(X)X OrbitsXXXXX LEO Orbits XXXX IonosphereXXXX TroposphereXXXX Time/Freq.; Clocks XX(X) ICRF ITRF Earth Rotation Gravity Field Atmosphere X XXXX GGOS2010 = ITRF20010+EOP2010+ICRF2010+IGRF2010 ? IGRF = International Gravity Reference Frame/Field

41. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S 2010: Dense GPS networks: ca. 10‘000 stations 1200 Japan 1000 Plate Boundary Observatory 400 Europe 29 Switzerland 100 Hz, near real-time Vision 2010: Intergation of 4 Levels into a GGOS 2010: ca. 90 MEO and GEO satellites 29 GPS 30 GALILEO 24 GLONASS 3 ZQSS Augmentation systems (GEO) 2010: ca. 40 Low Earth Orbiters (LEO) CHAMP, GRACE-A/B, GOCE T/P, ERS-1/2, Jason-1, Jason-2, Icesat, Envisat GPS/MET, OERSTED, SAC-C 6 COSMIC, 3 SWARM 20 SLR satellites Satellite constellations 2010: ca. 600 radio sources

42. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Fourth Level: Modeling and Interpretation GEOSPHERE Plate Tectonics, Subduc- tion,Convection,Earth‘s Core ATMOSPHERE Wind, Pressure Distribution HYDROSPHERE Ocean Currents, Ground Water CRYOSPHERE Melting of Pole Caps, Glaciers BIOSPHERE Change in Vegetation KINEMATICS OF POINTS Coordinates, Velocities EARTH ROTATION VARIATIONS Polar Motion, UT1 VARIATIONS OF THE EARTH‘S GRAVITY FIELD Potential Coefficients Geodetic Parameters Geophysical Processes ? Common effort of all Services/Commissions!

43. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Modeling / Interpretation Links: global time series of geodetic parameters ↔ relevant geophysical models Highly interdisciplinary task: cooperation with geophysicists / geologists, glaciologists, oceanographers, hydrologists, atmosphere physicists, … Final goal: comprehensive global Earth models that can assimilate global surface deformations, mass transport and exchange Deeper understanding of: –Solid Earth processes (GIA, tectonics, Earthquakes, volcanoes, …) –Ice mass dynamics and balance, sea ice –Ocean circulation, mass and heat transport in the oceans –Sea level change, global water cycle –Atmosphere dynamics –Global energy budget, global mass balance, … Additional information, e.g., from global geophysical fluids is required to separate different contributions

44. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S Conclusions IVS in special, and IAG Services in general, can contribute significantly to the monitoring and understanding of the Earth system: Stable, highly accurate reference frames for all other global observing systems and monitoring activities Many contributions to geo-hazards: Earthquakes, volcanoes, land slides, de-glaciation, sea level rise, floods, storms, global warming, tsunamis, … Integration into one observing system: GGOS, not a flood of individual, inconsistent products Not only delivery of basic products: step by step reach the level of consistent modeling and interpretation of the Earth’s processes and interactions With its unique contributions the IVS has a particularly important in reaching these goals

45. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S We are looking forward to work with all of you on this challenging endeavor ! Thank you for your attention ! GG S

46. Fourth IVS General Meeting, January 9-13, 2006, Concepción, Chile GG S First GGOS Workshop in Potsdam