1. Geodetic Networks SENH Program Executive Review Geodetic Networks "In all things it is a good idea to hang a question mark now and then on the things we have taken for granted." Bertrand Russell

2. Geodetic Networks NASA ESE Needs for Geodetic Networks Long term, systematic measurements of the Earth system require the availability of a terrestrial reference frame (TRF) that is stable over decades and independent of the technology used to define it. The space geodetic networks provide the critical infrastructure necessary to develop and maintain the TRF and the needed terrestrial and space borne technology to support the Earth Science Enterprise goals and missions. This infrastructure is composed of the: - Physical networks, - Technologies that compose them, and - Scientific models and model development that define a TRF. A TRF is a set of positions and a model for how those positions evolve with time

3. Geodetic Networks Geodetic Networks: A stable and accurate TRF underlies Solid Earth and Climate roadmaps SESWG report –Geodetic networks are one of seven observation strategies to address the fundamental solid Earth questions. –Maintenance of the global geodetic network, the TRF, and Earth Orientation Parameters is the “supporting framework”: an element of the fully realized solid Earth program.

4. Geodetic Networks Geodetic Networks: Realization of TRF TRF is a set of station positions and velocities Networks of SLR, VLBI, and GPS ground systems enable TRF realization Techniques have unique yet complementary capabilities –Allowing for evaluation of systematic error sources Techniques are interdependent for TRF definition Data and products are provided to the research community via international services of the IAG: IGS, ILRS, IVS. Current consistency and accuracy of space geodetic systems –1-3 cm positions, mm/yr velocities –0.1 mas/day pole position –3 µs UT1 –Sub-nanosecond timing distribution Technique Signal Source Obs. Type VLBI Microwave Quasars Time difference SLR Optical Satellite Two-way range GPS Microwave Satellites Range change Celestial Frame UT1 Yes No Scale Yes GeocenterNo Yes Geographic density No Yes Real-timeYesNo Yes

5. Geodetic Networks Geodetic Networks: 5-year outcome TRF realized by coordinated multi-technique networks and analysis –Sub-centimeter consistency and accuracy globally –Improvement in the vertical component Consistent and robust access to the improved TRF in real-time for all users Improvement in network distributions, characteristics and efficiencies –Real-time GPS global sub-network, GNSS, GPS3 –eVLBI –SLR2000 Analysis development and validation to optimize multi-technique methods Improved data and product access interfaces via –Proposed collaborative project to implement state-of-the-art services aligned with SEEDS

6. Geodetic Networks Geodetic Networks: NASA’s role among global collaborators Networks, through the TRF, provide critical infrastructure to support flight projects. –This support is assumed by current and future missions to be provided yet is rarely budgeted or planned. NASA leverages its resources by cooperating with international partners. –NASA supports and coordinates the geodetic services through central offices at JPL (IGS) and GSFC (ILRS and IVS). –This NASA coordination is a highly successful international activity endorsed by international organizations such as the IAG. –NASA’s space geodetic data sets are augmented by data contributed by other agencies to the international pool. –These activities are supported by the Crustal Dynamics Data Information System (CDDIS), a key data center supporting the IGS, ILRS, IVS, and IERS. –This results in access to greater and enhanced data sets and products.

7. Geodetic Networks Geodetic Networks: Issues and Challenges Maintaining and upgrading aging equipment and hardware Transitioning new technology into the definition of the TRF Developing new analysis techniques to address evolving requirements and new opportunities Identifying a mechanism by which the support for this vital infrastructure can be shared by all users within NASA

8. Geodetic Networks Introduction wrap-up Geodetic networks support the TRF requirements of NASA ESE missions Each of SLR, VLBI, GPS substantially and uniquely contributes to TRF determination NASA’s SLR, VLBI, and GPS groups collaborate toward wide- ranging improvements in the next 5 years NASA leverages considerable resources through its significant activity in international services NASA faces certain challenges in continuing and advancing these activities

9. Geodetic Networks Geodetic Networks: GPS

10. Geodetic Networks Geodetic Networks: GPS Stations Map

11. Geodetic Networks Geodetic Network: GPS Strengths Relatively low cost –Hardware –Station operations –Analysis Dense ground networks High temporal resolution – 1 Hz Universal access to TRF for ground stations and vehicles, aircraft, and spacecraft Supports the objectives and goals of many users and agencies –Solid Earth Science ( e. g., NASA, NSF, USGS) –Climate Science (e. g., NASA, NSF, NOAA, USGS) –National security (DoD) –Space weather (NASA, USAF, NOAA) –Flight projects POD (e. g., TOPEX, Jason, GRACE) Opportunities for new and novel applications –Ocean reflections –Atmospheric occultations

12. Geodetic Networks Geodetic Networks: GPS Technology Development TRF realization as a System Ground and flight hardware capabilities with analysis software Ground stations –Continuous GPS Networks –Receiver tracking technology –Network Communications –Real-time Internet (RTNT) Flight segment –Receiver development –Hardware deliveries to flight projects Analysis –Computational efficiency ~ (Number of stations) 3 –Optimal combinations –POD and positioning accuracy in real time and in post processing

13. Geodetic Networks JPL processing center running IGDG Remote user Running IGDG NASA’s Global Differential GPS System Internet Broadcast Revolutionary new capability: decimeter real time positioning, anywhere, anytime Broadcast Internet For more info see: http://gipsy.jpl.nasa.gov/igdg NASA’s global real time network

14. Geodetic Networks Special Value to NASA and Society Autonomous operations in Earth orbit to enable smart sensor webs and reduce operational costs and communications bandwidth Prototype GDGPS flight receiver being developed Precise time transfer for interferometric SAR Aviation safety and efficiency Dryden plans to offer GDGPS services on all platforms Safe operations for NASA missions RLV navigation payload based on GDGPS Timely monitoring and response to natural hazards NRT sea surface height Many commercial applications Many national security applications GPS integrity monitoring GPS enhancements GPS capabilities to exceed Galileo’s

15. Geodetic Networks International Union of Geodesy and Geophysics International Council for Science Federation of Astronomical and Geophysical Data Service International GPS Service 200 Organizations in 80 Countries International GPS Service 200 Organizations in 80 Countries International Association of Geodesy International Governing Board NASA Involvement: 4 of 27 International Governing Board NASA Involvement: 4 of 27 Central Bureau Network Coordinator Central Bureau Network Coordinator Data Centers USERS Global (3) Regional (5) Operational (23) Network Stations (358) NASA Involvement: 72 Network Stations (358) NASA Involvement: 72 Pilot Projects and Working Groups Associate Analysis Centers Analysis Centers (8) IGS Reference Frame Coordinator Analysis Coordinator IGS Pilot Projects and Working Groups Precise Time and Frequency Project (IGS/BIPM) International GLONASS Service Pilot Project (IGLOS-PP) LEO Pilot Project Tide Gauge Benchmark Monitoring Project for Sea Level (TIGA) Ionosphere Working Group Atmosphere Working Group IGS Reference Frame Working Group Real-Time Working Group IGS Pilot Projects and Working Groups Precise Time and Frequency Project (IGS/BIPM) International GLONASS Service Pilot Project (IGLOS-PP) LEO Pilot Project Tide Gauge Benchmark Monitoring Project for Sea Level (TIGA) Ionosphere Working Group Atmosphere Working Group IGS Reference Frame Working Group Real-Time Working Group Note: Red indicates NASA involvement Geodetic Networks: IGS Structure

16. Geodetic Networks Geodetic Networks: GPS Analysis Geophysical models –Required to maintain TRF Support mission enabling Precise Orbit Determination –Repeat Orbit Interferometry for InSAR –GRACE –TOPEX, Jason, other LEO’s –Formation Flying Collateral science support –Solid Earth, such as - SCIGN (NASA, WM Keck, NSF, USGS) - Plate Boundary Observatory (NSF, USGS) - Post Glacial Rebound Studies Atmospheric occultations

17. Geodetic Networks BlackJack is a Software Radio software-driven allows –mission-independent hardware –post-launch reconfigurability –mission-specific functionality software-driven requires –mission-specific configuration & testing Single Antenna RF Sampler Board, Diplexer & Amp Modules CPU & Memory Board Digital Signal Processing Board Host I/O Board optional 1553 Interface Board single antenna version (eg, Jason)

18. Geodetic Networks Current Missions with BlackJack Receivers precise orbit atmospheric remote sensing gravity ionospheric remote sensing ocean surface reflections CHAMP ( Jul 2000) SAC-C ( Nov 2000) JASON-1 ( Dec 2001) GRACE ( Mar 2002) FEDSat ( Dec 2002) ICESat ( Jan 2003) precise orbit (on-board, real-time) atmospheric remote sensing ionospheric remote sensing ocean surface reflections precise orbit ionospheric remote sensing precise orbit atmospheric remote sensing gravity ionospheric remote sensing LEGEND solid  full functionality shaded  limited functionality

19. Geodetic Networks Upcoming Missions with BlackJack Receivers C/NOFS ( 2003) COSMIC ( 2005) OSTM ( 2007) PARCS ( 2009) ionospheric remote sensing precise orbit atmospheric remote sensing ionospheric remote sensing precise orbit and time precise orbit

20. Geodetic Networks Direct solid Earth science from the ground stations: How is the surface of the Earth changing?

21. Geodetic Networks Geodetic Networks: GPS Issues and Challenges Current and pending issues (0-3 years): Aging ground receivers “Ownership” of the global network Integration of new techniques, e. g. GALILEO Communications infrastructure for real-time Geophysical model development International partnering Future issues (2-10 years): Improved system redundancy Verification and validation of TRF stability Technology independence of the TRF Integrated operation with the other techniques Co-location Smooth infusion of new technology

22. Geodetic Networks Geodetic Networks: GPS 5-year Plan New GPS signals –L2C (June 2004) –L5 (June 2005) New GPS satellites –GPS III (2005) New GNSS systems –Galileo (2004) Network hardware –Replace aging and obsolete equipment (2003-2004) –Track new signals and satellites (2004-2007) –Increase number of real-time stations –Optimize station distribution and improve performance –Harden reference frame station subset Upgrade analysis capability to support system evolution

23. Geodetic Networks Geodetic Networks: SLR

24. Geodetic Networks Geodetic Networks: SLR Unique Capabilities The SLR Technique Precise range measurements to satellites Passive space segment Near real-time global data availability Satellite orbit accuracy ~1-2 cm on LAGEOS Science and Applications Terrestrial Reference Frame –3-D coordinates and velocities of the ILRS tracking stations –Time varying Earth Center of Mass and Scale (GM) Static and time-varying coefficients of the Earth's gravity field Earth Tides Measure of the total Earth mass Earth Orientation Parameters (EOP): polar motion, length of day Special Missions - Tether Dynamics, etc. Accurate satellite ephemerides: calibration, and validation of altimetry missions Backup precise orbit determination (POD) for other missions

25. Geodetic Networks Geodetic Networks: Monitoring Temporal Gravity Changes Using SLR Anomalistic behavior of J 2 time series First detection of large-scale unanticipated mass redistribution Reported by Cox and Chao, (SCIENCE, 2002) +0.6 correlation between S 2,2 time series and the SOI when S 2,2 is shifted forward in time by 12 months. Evidence of El Nino prediction? Reported by Cox, Chao et al. (AGU, 2003)

26. Geodetic Networks Geodetic Networks: SLR Site Map

27. Geodetic Networks Geodetic Networks: SLR Site Map (and co-locations)

28. Geodetic Networks Geodetic Networks: Satellite Tracking List

29. Geodetic Networks Geodetic Networks: ILRS Structure NASA operates the ILRS Central Bureau NASA actively participates in all ILRS entities (Governing Board, Working Groups, operational components) ILRS supports NASA Missions and Programs Over 70 organizations located in 27 countries participate in the ILRS

30. Geodetic Networks Geodetic Networks: SLR Current Challenges SLR Cost Per Pass Down Current NASA Systems have improved data quality and quantity over last 10 years Decreased operating costs thru system improvements and automation More satellite missions supported Sub-centimeter performance Performance limits have been reached with existing systems Aging technology, very difficult to replace parts Costly to operate and maintain Chemical & HV Hazards Further automation not cost effective

31. Geodetic Networks Geodetic Networks: SLR 2000, the Future of SLR Innovative hardware and intelligent computer systems Fully automated, tracks 7/24 Subcentimeter ranging accuracy No ocular, chemical, or electrical hazards Increased reliability Lower replication and operating costs Self-monitoring, low maintenance SLR Network 5-Year Plan: Integrate and checkout prototype by April 2004 Replicate and deploy 12 NASA systems over the next 5 years, transitioning from existing system. Possible use of SLR2000 as ground link in laser communications and transponder experiments.

32. Geodetic Networks Geodetic Networks: SLR Backup Slides

33. Geodetic Networks Geodetic Networks: SLR Technology Tall Poles Solved Innovative hardware developed –New quadrant micro-channel plate pmt –Full aperture telescope use (eyesafe) –Passive 2 khz trans/rec switch –Risley prism point ahead –All sky thermal ir camera –2 khz event timer/gate generator –Mtbf of several months –Tracking loop closed with qmcp-pmt

34. Geodetic Networks Geodetic Networks: SLR Satellites Reflector Microsatellite

35. Geodetic Networks Geodetic Networks: VLBI

36. Geodetic Networks Geodetic Networks: VLBI Station Map

37. Geodetic Networks Geodetic Networks: IVS Structure IVS has 73 permanent components, representing 37 institutions in 17 countries. NASA supports the IVS Coordinating Center, Network Coordinator, and 7 permanent components

38. Geodetic Networks Geodetic Networks: VLBI Unique Capabilities Celestial Reference Frame - quasars Celestial pole UT1-UTC Differential navigation for spacecraft

39. Geodetic Networks Geodetic Networks: VLBI Issues and Challenges Improve temporal coverage from 3.5 days/week to full time. Decrease processing delay from 15 days to near-real time. Improve global configuration with more stations in the southern hemisphere. Address serious RFI problem at S/X (2.2/8.4 GHz) by moving to higher RF bandwidths, e.g. K/Q (24/42 GHz). Replace aging antennas. Upgrade aging data acquisition equipment. Establish fiber networks for electronic data transfer to remove the need to ship media from stations to correlator.

40. Geodetic Networks Geodetic Networks: VLBI Technology Advances Mark 5 disk-based recording system –Media cost only $1.25/GB (half of tape) –Allows higher bandwidth recording –Enables automated/unattended operation –Allows electronic data transfer and near real time processing e-VLBI for data transfer –Gb/s data transfer demonstrated –Global experimental program for international transfer near Gb/s rates –New adaptive IP protocol studies

41. Geodetic Networks Geodetic Networks: VLBI 5-year Plan 2004 –Deploy and use Mark 5 at all correlators and stations –Establish e-VLBI for daily UT1 measurements –Study K/Q for using higher dual-frequency RF bands 2005 –Begin replacement of Fairbanks antenna –Begin development of K/Q receivers 2006 –Establish e-VLBI network of NASA stations with international partner stations –Begin replacement of data acquisition hardware with digital interfaces 2007 –Fairbanks antenna complete 2008 –e-VLBI networks in use for 3-4 days/week EOP and TRF measurements –Initial K/Q test installations

42. Geodetic Networks Transition to integration slides

43. Geodetic Networks Geodetic Networks: Integration Elements Proposed activities –NGO proposal: National Geodetic Observatory Focus US efforts in space geodesy to integrate techniques, attract new funding –INDIGO proposal: Inter-Service Data Integration for Geodetic Operations Goal: to enable improved performance, accuracy, and efficiency in support of NASA’s Earth science and international user community by developing and providing uniform access to heterogeneous space geodetic data systems. International organizations –IERS: International Earth rotation and Reference systems Service. Compiles and distributes ITRF, ICRF, EOP time series Pilot project on rigorous combination of data from all techniques –IAG: International Association of Geodesy IGGOS: Integrated Global Geodetic Observing System, flagship project IGGOS is expected to play a major role in geodesy community with integration of techniques at a very high level

44. Geodetic Networks Geodetic Networks: Co-location Strategy Importance of co-location –Co-location ties techniques together, enables combination for TRF –Local ties accurate measurements of vectors between reference points for different techniques at a site essential for combination of data from different techniques limiting factor in closure of the networks Approach and strategy –Improve local tie measurements. –Understand different solution results for each technique at a site. –Improve the co-location network. –Investigate new technology approaches to measuring local ties.

45. Geodetic Networks Geodetic Networks: Next Steps Toward Integration Global networks are NASA ‘critical infrastructure’ and strategic US assets. Meeting challenges together for mutual strength –Continue and extend cross-technique coordination. –The goal of integration is the most stable and accurate reference frame and tracking capabilities. –The three techniques plan to jointly assess the structure and budget for the NASA networks and recommend an approach for integration. –An integrated program should achieve appropriate balance of measurements, scientific needs and resources in the mix of SLR, VLBI and GPS. appropriate balance of resources for scientific research and applications with the demanding requirements of the TRF and the geodetic networks infrastructure.