1. Science Mission Directorate Earth Surface and Interior Focus Area John LaBrecque / Focus Area Lead Craig Dobson / InSAR Devel. Lead Herbert Frey / GSFC-Cntr. Prog. Manager Ronald Blom / JPL- Cntr. Prog. Manager Adriana Ocampo / JPL Earth-Sun Division Science Review October 29, 2004

2. Earth Surface and Interior Focus Area ESI Strategic Goals- ESI Achievements in FY04 ESI Programmatic Opportunities & Challenges 1.What is the nature of deformation at plate boundaries and what are the implications for earthquake hazards? 2.How do tectonics and climate interact to shape the Earth’s surface and create natural hazards? 3.What are the interactions among ice masses, oceans, and the solid Earth and their implications for sea level change? 4.How do magmatic systems evolve and under what conditions do volcanoes erupt? 5.What are the dynamics of the mantle and crust and how does the Earth’s surface respond? 6.What are the dynamics of the Earth’s magnetic field and its interactions with the Earth system? Earthquake Prediction SRTM 13 of 14 Earthquakes 1st Uniform Global Topography GRACE:1st Time Variable Gravity & Mass Flux Performance Measures: Enable 30 Day volcanic Eruption Forecasts with > 50% confidence by 2014 Enable estimation of earthquake likelihood in North American plate boundary with > 50% confidence by 2014 Overview of ESI Focus Area Renew NASA’s Planetary Geodetic Network Approach:Develop NGO: Work with DSN, ESTO, GGOS, INDIGO Develop Geodetic Imaging and Geohazards Natural Laboratories Approach: TerraScope Initiative/UAVSAR ESI Component Programs Gravity and Geomagnetic Field Exploration : Approach: Technology Development & Partnerships (International, DoD, Focus Areas) Natural Hazards Predictive Models Remote Sensing Natural Laboratories Space Geodesy Celestial Ref Frame Terrestrial Ref Frame Earth Rotation Crustal Dynamics Planetary Interior Geomagnetic Models Gravity Models Geodynamic Models

3. How is the Earth changing and what are the consequences for life on Earth? 1.What is the nature of deformation at plate boundaries and what are the implications for earthquake hazards? 2.How do tectonics and climate interact to shape the Earth’s surface and create natural hazards? 3.What are the interactions among ice masses, oceans, and the solid Earth and their implications for sea level change? 4.How do magmatic systems evolve and under what conditions do volcanoes erupt? 5.What are the dynamics of the mantle and crust and how does the Earth’s surface respond? 6.What are the dynamics of the Earth’s magnetic field and its interactions with the Earth system? Prediction: How can knowledge of Earth’s surface change be used to predict and mitigate natural hazards? Variability: How is the Earth’s surface being transformed by naturally occurring tectonic and climatic processes? Response: How is global sea level affected by natural variability and human induced change in the Earth system? Forcing: What are the dynamics of the Earth’s interior and how do these forces drive change at the Earth’s surface? Goal Research Questions SESWG Challenge NASA Solid Earth Strategic Goals

5. Shared Observational Strategies Space Geodesy Planetary Interior (Atmospheric Limb sounding, network observations & gravity modeling)

6. Shared Observational Strategies Space Geodesy Natural Hazards Planetary Interior (ITRF, EOP, POD, Atmos. Limb Sounding, Gravity, InSAR, Lidar)

7. Geodetic Imaging Optical Imaging Radar,Topography, VNIR Natural Hazards ( SAR, Lidar, Topography, VNIR) Shared Observational Strategies

8. Space Geodesy Natural Hazards (Water vapor, TIR, UV volcanic ash)

9. Shared Observational Strategies Space Geodesy Planetary Interior Natural Hazards (Water vapor, SAR, Lidar, Gravity)

10. Shared Observational Strategies Space Geodesy Planetary Interior Geomagnetic Fields Ionospheric Modeling

11. Shared Observational Strategies Space Geodesy Planetary Interiors Natural Hazards Geopotential Fields, Geodetic Imaging Ionospheric Modeling

12. Earth Surface and Interior Focus Area ESI Strategic Goals- ESI Achievements in FY04 ESI Programmatic Opportunities & Challenges 1.What is the nature of deformation at plate boundaries and what are the implications for earthquake hazards? 2.How do tectonics and climate interact to shape the Earth’s surface and create natural hazards? 3.What are the interactions among ice masses, oceans, and the solid Earth and their implications for sea level change? 4.How do magmatic systems evolve and under what conditions do volcanoes erupt? 5.What are the dynamics of the mantle and crust and how does the Earth’s surface respond? 6.What are the dynamics of the Earth’s magnetic field and its interactions with the Earth system? Earthquake Prediction SRTM 13 of 14 Earthquakes 1st Uniform Global Topography GRACE:1st Time Variable Gravity & Mass Flux Performance Measures: Enable 30 Day volcanic Eruption Forecasts with > 50% confidence by 2014 Enable estimation of earthquake likelihood in North American plate boundary with > 50% confidence by 2014 Renew NASA’s Planetary Geodetic Network Approach:Develop NGO: Work with DSN, ESTO, GGOS, INDIGO Develop Geodetic Imaging and Geohazards Natural Laboratories Approach: TerraScope Initiative/UAVSAR ESI Component Programs Gravity and Geomagnetic Field Exploration : Approach: Technology Development & Partnerships (International, DoD, Focus Areas) Natural Hazards Predictive Models Remote Sensing Natural Laboratories Space Geodesy Celestial Ref Frame Terrestrial Ref Frame Earth Rotation Crustal Dynamics Planetary Interior Geomagnetic Models Gravity Models Geodynamic Models

13. Earth Surface and Interior Focus Area ESI Strategic Goals- ESI Achievements in FY04 ESI Programmatic Opportunities & Challenges 1.What is the nature of deformation at plate boundaries and what are the implications for earthquake hazards? 2.How do tectonics and climate interact to shape the Earth’s surface and create natural hazards? 3.What are the interactions among ice masses, oceans, and the solid Earth and their implications for sea level change? 4.How do magmatic systems evolve and under what conditions do volcanoes erupt? 5.What are the dynamics of the mantle and crust and how does the Earth’s surface respond? 6.What are the dynamics of the Earth’s magnetic field and its interactions with the Earth system? Earthquake Prediction SRTM 13 of 14 Earthquakes 1st Uniform Global Topography GRACE:1st Time Variable Gravity & Mass Flux Performance Measures: Enable 30 Day volcanic Eruption Forecasts with > 50% confidence by 2014 Enable estimation of earthquake likelihood in North American plate boundary with > 50% confidence by 2014 Renew NASA’s Planetary Geodetic Network Approach:Develop NGO: Work with DSN, ESTO, GGOS, INDIGO Develop Geodetic Imaging and Geohazards Natural Laboratories Approach: TerraScope Initiative/UAVSAR ESI Component Programs Gravity and Geomagnetic Field Exploration : Approach: Technology Development & Partnerships (International, DoD, Focus Areas) Natural Hazards Predictive Models Remote Sensing Natural Laboratories Space Geodesy Celestial Ref Frame Terrestrial Ref Frame Earth Rotation Crustal Dynamics Planetary Interior Geomagnetic Models Gravity Models Geodynamic Models

14. 2002200420072006200520102011200320082009 Airborne remote sensing of surface change for long duration monitoring of earthquake, volcano, landslide, erosion, storm damage. Focus on geohazards natural laboratories e.g. Earthscope, Asia-Pacific Arc Natural Laboratory (A-PANL) 2004200720062005201020112003201220082009 GPS Remote Sensing, COSMIC, etc High sensitivity Gravity & Geomagnetic Satellite Constellation First uniform topography of land and ice surface, sparse hyperspectral visible & thermal imaging of land surface change GRACE and GOCE All Weather Surface Deformation Mission (InSAR) Coordinated international global observation of land surface change for volcano,earthquake prediction, land and ice cover, natural disaster management NASA mission leads in with instrument to target plate boundaries, coastal zones to measure surface deformation InSAR data service provides science data access from international missions Required fourth component of EarthScope Natural Lab Wide Swath high spectral & spatial resolution visible through thermal infrared imaging mission T SAC-C CHAMP,Oersted Gravity and geomagnetic models from this data provide estimates of water, atmospheric transport, plate boundary deformation, Earth interior forces, structure and deformation, geomagnetic field generation International SAR Information Service Shared grid computing, seamless archive and capabilities for enhanced modeling and and sharing of databases ICESat, EO-1, TERRA, MASTER, AVIRIS Ionospheric dynamics for geomagnetic modeling, atmospheric pressure for satellite gravity analysis, improved GPS orbits for geodesy Models & Prediction: mm accuracy of terrestrial reference frame, reliable and timely volcanic eruption & earthquake predictions, improved Earth system mass transport and geodynamo models, Earth interior models for glacial rebound and ocean loading. T Advanced airborne, Repeat pass InSAR, High spatial & spectral visible & thermal imaging, high altitude Lidar altimeter Distributed Solid Earth computing & modeling environment International InSAR Satellite Constellation 1 meter global topography T 2014 High-Res topography to measure erosion, flooding, landslides, faults, & coastal zones, etc. T NASA Agency Partners Internat’ l Unfunde d 2013 T T SRTM Knowledge Base Global Geodetic Networks T T GOALS: How do magmatic systems evolve and volcanoes erupt? How the dynamics of the mantle and crust deform Earth’s surface? What are the dynamics of the Earth’s magnetic field and its interactions with the Earth system? How do plate boundaries deform & create earthquake hazards? How do tectonics and climate interact to shape the Earth’s surface? What are sea level implications from ice masses, oceans, and the solid Earth? Earth Surface and Interior Focus Area Roadmap High-Res optical for earthquake, volcano, land surface change Terrestrial Reference Fame, Celestial Reference Frame, Earth orientation, angular momentum, time transfer; Required for planetary surface and interior measurements,and interplanetary nav. National Geodetic Observatory T

15. InSAR Science Contributions Volcano Eruption Prediction

16. TerraScope: Geodetic Imaging Development Build the InSAR we need todayDevelop the technology for tomorrow Enable an international collaboration on civilian SAR data and applications 3. Accelerate development of data handling and modeling capacity VHF UHF P-band L-band C-band X-band

17. TerraScout: A Roadmap to Understanding Surface Change 3-D Displacement Accuracy (mm) Revisit Frequency (days) 0.1 5 10 20 50 100 10 1 0.1 0.01 2025 Systematic data acquisition Modeling of faults in crust/mantle system Fine resolution hazard maps Community Based Data System Geohazards Natural Laboratories Modeling-Project Columbia National/ International Partnerships-GEOSS/ GMES Continuous observations Understanding earthquake physics and prediction Precise hazard maps continuously updated Foreign Satellites/National Partnerships Low Earth Orbit InSAR GeoSynchronous InSAR Improved models and forecasts High-resolution topography Possible InSAR in medium Earth orbit 2010 UAVSAR Repeat pass InSAR for regional studies Advanced concept testbed 2008 Technology & Modeling 2005

18. Earth Surface and Interior Focus Area ESI Strategic Goals- ESI Achievements in FY04 ESI Programmatic Opportunities & Challenges 1.What is the nature of deformation at plate boundaries and what are the implications for earthquake hazards? 2.How do tectonics and climate interact to shape the Earth’s surface and create natural hazards? 3.What are the interactions among ice masses, oceans, and the solid Earth and their implications for sea level change? 4.How do magmatic systems evolve and under what conditions do volcanoes erupt? 5.What are the dynamics of the mantle and crust and how does the Earth’s surface respond? 6.What are the dynamics of the Earth’s magnetic field and its interactions with the Earth system? Earthquake Prediction SRTM 13 of 14 Earthquakes 1st Uniform Global Topography GRACE:1st Time Variable Gravity & Mass Flux Performance Measures: Enable 30 Day volcanic Eruption Forecasts with > 50% confidence by 2014 Enable estimation of earthquake likelihood in North American plate boundary with > 50% confidence by 2014 Overview of ESI Focus Area Renew NASA’s Planetary Geodetic Network Approach:Develop NGO: Work with DSN, ESTO, GGOS, INDIGO Develop Geodetic Imaging and Geohazards Natural Laboratories Approach: TerraScope Initiative/UAVSAR ESI Component Programs Gravity and Geomagnetic Field Exploration : Approach: Technology Development & Partnerships (International, DoD, Focus Areas) Natural Hazards Predictive Models Remote Sensing Natural Laboratories Space Geodesy Celestial Ref Frame Terrestrial Ref Frame Earth Rotation Crustal Dynamics Planetary Interior Geomagnetic Models Gravity Models Geodynamic Models

19. 2002200420072006200520102011200320082009 Airborne remote sensing of surface change for long duration monitoring of earthquake, volcano, landslide, erosion, storm damage. Focus on geohazards natural laboratories e.g. Earthscope, Asia-Pacific Arc Natural Laboratory (A-PANL) 2004200720062005201020112003201220082009 GPS Remote Sensing, COSMIC, etc High sensitivity Gravity & Geomagnetic Satellite Constellation First uniform topography of land and ice surface, sparse hyperspectral visible & thermal imaging of land surface change GRACE and GOCE All Weather Surface Deformation Mission (InSAR) Coordinated international global observation of land surface change for volcano,earthquake prediction, land and ice cover, natural disaster management NASA mission leads in with instrument to target plate boundaries, coastal zones to measure surface deformation InSAR data service provides science data access from international missions Required fourth component of EarthScope Natural Lab Wide Swath high spectral & spatial resolution visible through thermal infrared imaging mission T SAC-C CHAMP,Oersted Gravity and geomagnetic models from this data provide estimates of water, atmospheric transport, plate boundary deformation, Earth interior forces, structure and deformation, geomagnetic field generation International SAR Information Service Shared grid computing, seamless archive and capabilities for enhanced modeling and and sharing of databases ICESat, EO-1, TERRA, MASTER, AVIRIS Ionospheric dynamics for geomagnetic modeling, atmospheric pressure for satellite gravity analysis, improved GPS orbits for geodesy Models & Prediction: mm accuracy of terrestrial reference frame, reliable and timely volcanic eruption & earthquake predictions, improved Earth system mass transport and geodynamo models, Earth interior models for glacial rebound and ocean loading. T Advanced airborne, Repeat pass InSAR, High spatial & spectral visible & thermal imaging, high altitude Lidar altimeter Distributed Solid Earth computing & modeling environment International InSAR Satellite Constellation 1 meter global topography T 2014 High-Res topography to measure erosion, flooding, landslides, faults, & coastal zones, etc. T NASA Agency Partners Internat’ l Unfunde d 2013 T T SRTM Knowledge Base Global Geodetic Networks T T GOALS: How do magmatic systems evolve and volcanoes erupt? How the dynamics of the mantle and crust deform Earth’s surface? What are the dynamics of the Earth’s magnetic field and its interactions with the Earth system? How do plate boundaries deform & create earthquake hazards? How do tectonics and climate interact to shape the Earth’s surface? What are sea level implications from ice masses, oceans, and the solid Earth? Earth Surface and Interior Focus Area Roadmap High-Res optical for earthquake, volcano, land surface change Terrestrial Reference Fame, Celestial Reference Frame, Earth orientation, angular momentum, time transfer; Required for planetary surface and interior measurements,and interplanetary nav. National Geodetic Observatory T

20. NASA’s Space Geodetic Network Very Long Baseline Interferometry (VLBI) Very Long Baseline Interferometry (VLBI) Satellite Laser Ranging (SLR) Satellite Laser Ranging (SLR) Global Positioning System (GPS) Global Positioning System (GPS) 30 Station Network International VLBI Service (IVS) Strength: Earth Orientation 30 Station Network International VLBI Service (IVS) Strength: Earth Orientation >300 Station Network International GPS Service (IGS) Strength: Crustal Motion >300 Station Network International GPS Service (IGS) Strength: Crustal Motion 37 Station Network International Laser Ranging Service (ILRS) Strength: Center of Mass Scale 37 Station Network International Laser Ranging Service (ILRS) Strength: Center of Mass Scale Celestial Reference Frame: Planetary ExplorationCelestial Reference Frame: Planetary Exploration Terrestrial Reference Frame: NASA POD, Sealevel, DoD, CivilianTerrestrial Reference Frame: NASA POD, Sealevel, DoD, Civilian Earth Orientation:Earth Circulation, Planetary ExplorationEarth Orientation:Earth Circulation, Planetary Exploration Enables Exploration and New NASA CapabilitiesEnables Exploration and New NASA Capabilities Civilian and DoD ApplicationsCivilian and DoD Applications

21. Earth Surface and Interior Focus Area ESI Strategic Goals- ESI Achievements in FY04 ESI Programmatic Opportunities & Challenges 1.What is the nature of deformation at plate boundaries and what are the implications for earthquake hazards? 2.How do tectonics and climate interact to shape the Earth’s surface and create natural hazards? 3.What are the interactions among ice masses, oceans, and the solid Earth and their implications for sea level change? 4.How do magmatic systems evolve and under what conditions do volcanoes erupt? 5.What are the dynamics of the mantle and crust and how does the Earth’s surface respond? 6.What are the dynamics of the Earth’s magnetic field and its interactions with the Earth system? Earthquake Prediction SRTM 13 of 14 Earthquakes 1st Uniform Global Topography GRACE:1st Time Variable Gravity & Mass Flux Performance Measures: Enable 30 Day volcanic Eruption Forecasts with > 50% confidence by 2014 Enable estimation of earthquake likelihood in North American plate boundary with > 50% confidence by 2014 Overview of ESI Focus Area Renew NASA’s Planetary Geodetic Network Approach:Develop NGO: Work with DSN, ESTO, GGOS, INDIGO Develop Geodetic Imaging and Geohazards Natural Laboratories Approach: TerraScope Initiative/UAVSAR ESI Component Programs Gravity and Geomagnetic Field Exploration : Approach: Technology Development & Partnerships (International, DoD, Focus Areas) Natural Hazards Predictive Models Remote Sensing Natural Laboratories Space Geodesy Celestial Ref Frame Terrestrial Ref Frame Earth Rotation Crustal Dynamics Planetary Interior Geomagnetic Models Gravity Models Geodynamic Models

22. 2002200420072006200520102011200320082009 Airborne remote sensing of surface change for long duration monitoring of earthquake, volcano, landslide, erosion, storm damage. Focus on geohazards natural laboratories e.g. Earthscope, Asia-Pacific Arc Natural Laboratory (A-PANL) 2004200720062005201020112003201220082009 GPS Remote Sensing, COSMIC, etc High sensitivity Gravity & Geomagnetic Satellite Constellation First uniform topography of land and ice surface, sparse hyperspectral visible & thermal imaging of land surface change GRACE and GOCE All Weather Surface Deformation Mission (InSAR) Coordinated international global observation of land surface change for volcano,earthquake prediction, land and ice cover, natural disaster management NASA mission leads in with instrument to target plate boundaries, coastal zones to measure surface deformation InSAR data service provides science data access from international missions Required fourth component of EarthScope Natural Lab Wide Swath high spectral & spatial resolution visible through thermal infrared imaging mission T SAC-C CHAMP,Oersted Gravity and geomagnetic models from this data provide estimates of water, atmospheric transport, plate boundary deformation, Earth interior forces, structure and deformation, geomagnetic field generation International SAR Information Service Shared grid computing, seamless archive and capabilities for enhanced modeling and and sharing of databases ICESat, EO-1, TERRA, MASTER, AVIRIS Ionospheric dynamics for geomagnetic modeling, atmospheric pressure for satellite gravity analysis, improved GPS orbits for geodesy Models & Prediction: mm accuracy of terrestrial reference frame, reliable and timely volcanic eruption & earthquake predictions, improved Earth system mass transport and geodynamo models, Earth interior models for glacial rebound and ocean loading. T Advanced airborne, Repeat pass InSAR, High spatial & spectral visible & thermal imaging, high altitude Lidar altimeter Distributed Solid Earth computing & modeling environment International InSAR Satellite Constellation 1 meter global topography T 2014 High-Res topography to measure erosion, flooding, landslides, faults, & coastal zones, etc. T NASA Agency Partners Internat’ l Unfunde d 2013 T T SRTM Knowledge Base Global Geodetic Networks T T GOALS: How do magmatic systems evolve and volcanoes erupt? How the dynamics of the mantle and crust deform Earth’s surface? What are the dynamics of the Earth’s magnetic field and its interactions with the Earth system? How do plate boundaries deform & create earthquake hazards? How do tectonics and climate interact to shape the Earth’s surface? What are sea level implications from ice masses, oceans, and the solid Earth? Earth Surface and Interior Focus Area Roadmap High-Res optical for earthquake, volcano, land surface change Terrestrial Reference Fame, Celestial Reference Frame, Earth orientation, angular momentum, time transfer; Required for planetary surface and interior measurements,and interplanetary nav. National Geodetic Observatory T

23. Comprehensive Geomagnetic Model-4: 1960-2002 Sabaka,Olsen,Purucker, 2004 (Geophys. J. Int) Separation of Geomagnetic Field Sources Geodynamic modeling of the Earth Interior requires the separation and precise modeling of all geomagnetic components. The GSFC CM-4 model is the most successful to date

24. GRACE (Mar 2002) CHAMP (Jul 2000) SAC-C (Nov 2000)SWARM (2009)Oersted (Nov 1999) COSMIC (Jan 2006) GOCE (2007)

25. Technology is being developed and tested for the Geomagnetic Constellation GRACE has demonstrated an integrated BlackJack GPS receiver and non-magnetic Star Imager Integration of GRACE/GPS and IIP technologies will provide essentials for geomagnetic nano-satellites and missions of opportunity. Instrument Incubator Program is developing Miniature Self Calibrating Vector Helium Magnetometer Three-Axis Coil System RF  network InGaAs Detector Laser Input Optics Internal 6 cm 3 Helium Cell

26. Back-up Viewgraphs

27. Future Geodetic Science Contributions Earthquake Prediction Space-based Seismology Volcano Eruption Prediction Mass Flux

30. International Satellite Laser Ranging Network Legend: NASA NASA Partner NASA Partner (Proposed) International Cooperating

31. International VLBI Network

32. 4. SLR2000 SLR2000 Deployment Strategy; 12 Station Global Network by 2008 Optical Communications Option 1. E-VLBI vs Aging Equipment 2. New GNSS signals-New equipment/New Strategies 3. Global Geodetic Fiducial Network: Realtime fully automated mm-VLBI, GPS, SLR Geodetic Network Challenges

33. One of several optical fiber networks as Backbone to the International Geodetic Observatory One of several optical fiber networks as Backbone to the International Geodetic Observatory

34. Renovation of the Space Geodetic Network Importance of NASA’s Space Geodesy Program Enables New Exploration Capabilities GRACE, UAVSAR, ICESat, COSMIC, SCIGN/PBO, SRTM, J2, Lense-Thirring, Gravity Probe B Provides long term continuity of observations e.g. sea-level, ice volume, land subsidence and erosion, crustal deformation Supports Navigation of Satellites, Space Probes, Telescopes Topex-Poseidon, Jason I, Cassini, DSN, VLBA Maintains International Leadership and collaboration in Space Geodesy e.g. IGS,IVS,ILRS,IERS- over 50 Int’l agreements Supports National Defense and Civilian Activities e.g. radar calibration, trajectory tracking, gravity fields, navigation, surveying, commerce, flight safety, USNO, NRL, NOAA, EarthScope partnerships Science and Technology Challenges Science requires better than 1 mm reference frame accuracy Sea-level change, glacial mass balance, gravity field variability, ocean topography and circulation Present Frame accuracy is 1 cm or worse Geodetic systems require replacement before 2010 Creaking bearings and sagging antennas- –Yarragadee laser station and Gilmore Creek VLBI antenna celebrating 25th and 40th anniversaries Moving on: –GPS,Galileo,GLONASS GNSS signals in transformation Invasion of XM Radio: –VLBI S band spectrum contaminated by commercial and government users Strategy for Meeting These Challenges Technology Development VLBI- test small S, X, K broad- band antenna systems SLR- Continue development of SLR2000 GPS- Develop GNSS capable software receiver Continue development of real time e-VLBI, GDGPS Develop integrated modeling and analysis algorithms Program Development Develop roadmap- National Geodetic Observatory, INDIGO,GGOS Develop partnership funding –ESTO, DSN, Exploration Directorate –USNO, FAA, DoD –International Partnerships Integrate Geodetic Operations Management Strategy for Meeting These Challenges Technology Development VLBI- test small S, X, K broad- band antenna systems SLR- Continue development of SLR2000 GPS- Develop GNSS capable software receiver Continue development of real time e-VLBI, GDGPS Develop integrated modeling and analysis algorithms Program Development Develop roadmap- National Geodetic Observatory, INDIGO,GGOS Develop partnership funding –ESTO, DSN, Exploration Directorate –USNO, FAA, DoD –International Partnerships Integrate Geodetic Operations Management Very Long Baseline Interferometry Very Long Baseline Interferometry Satellite Laser Ranging Satellite Laser Ranging Global Positioning System Global Positioning System 30 Station Network International VLBI Service (IVS) Strength: Earth Orientation 30 Station Network International VLBI Service (IVS) Strength: Earth Orientation >300 Station Network International GPS Service (IGS) Strength: Site velocity >300 Station Network International GPS Service (IGS) Strength: Site velocity NASA’s Space Geodetic Network 37 Station Network International Laser Ranging Service (ILRS) Strength: Center of Mass Scale 37 Station Network International Laser Ranging Service (ILRS) Strength: Center of Mass Scale