Geodetic Networks: The Supporting Framework Terrestrial Reference Frame is ‘Critical Infrastructure’ for all Earth science research and applications. Global geodetic networks are a fundamental component of all ESE roadmaps. Geodetic network is one of SESWG’s seven observation strategies to address the fundamental solid Earth questions. Maintenance of the global geodetic network, the Terrestrial Reference Frame, and Earth Orientation Parameters is the “supporting framework”: an element of the fully realized solid Earth program.

Geodetic Networks: Production of ITRF Networks include SLR, VLBI, GPS ground system Data and products are provided to the research community via international services: IGS, ILRS, IVS. Techniques are complementary in unique capabilities –SLR provides geocenter –VLBI provides UT1 –GPS provides densification Techniques are interdependent –Sensitive to different systematic errors –Use of UT1 by satellite techniques –Use of satellite origin by VLBI Current consistency and accuracy of ITRF –1-3 cm positions, mm/yr velocities –Xxx pole position –3 µs UT1 –Sub-nanosecond timing distribution (?)

Geodetic Networks: 5-year outcome Reference frame realized by coordinated multi-technique networks and analysis –consistency and accuracy sub-centimeter globally –Vertical component improvement Access to the improved ITRF in real-time for all users, the consistent, robust and accurate global grid Improvement in network and sub-network distributions and characteristics and efficiencies –Real-time GPS global subnetwork –eVLBI –SLR2000 Analysis development and validation to optimize multi-technique combinations Improved data and product access interfaces –Implement SEEDS philosophies at data and information systems (CDDIS - GSFC/CBIS - JPL)

Geodetic Networks: NASA’s role Networks are critical infrastructure and strategic US assets NASA leverages extensive resources by cooperating with international partners International partnerships, cooperation and coordination are unique to NASA and must continue - as only NASA can –Geodetic services coordinating offices are largely funded by NASA (IGS at JPL, ILRS&IVS at GSFC) –International coordination is critical to this success (idea of a standardized approach with global partners) –Benefits? - access to a much larger, enhanced data set, product redundancy

Geodetic Networks: Issues and Challenges Integrating new technology into networks Maintaining and upgrading aging equipment and hardware Developing new analysis techniques as new equipment becomes available Identifying a mechanism by which the support for these vital resources can be shared by all users within NASA

Transition to GPS slides

Geodetic Network: GPS Strengths

Geodetic Networks: GPS Stations Map

Geodetic Networks: GPS Technology Development

Geodetic Networks: IGS Structure

Geodetic Networks: GPS Analysis

Geodetic Networks: GPS Issues and Challenges

Geodetic Networks: GPS 5-year Plan

Transition to SLR slides

Geodetic Networks: SLR Unique Capabilities

Geodetic Networks: SLR Site Map

Geodetic Networks: SLR Current Challenges

Geodetic Networks: SLR Next Generation System

Geodetic Networks: SLR Products

Geodetic Networks: ILRS Structure

Transition to VLBI slides

Geodetic Networks: VLBI Station Map

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

Geodetic Networks: VLBI Unique Capabilities CRF Celestial pole UT1-UTC

Geodetic Networks: VLBI Issues and Challenges Temporal coverage only 3.5 days/week Time delay from data acquisition to products is 15 days Global configuration lacks southern hemisphere stations RFI at S/X Aging antennas Aging data acquisition equipment Currently need to ship media (tapes, disks) from stations to correlator

Geodetic Networks: VLBI Technology Advances Mark 5 disk-based recording system (photo) –Less expensive media than magnetic tapes –Greater capacity for higher bandwidth –Enables automated and unattended operation –Allows electronic data transfer and near real time processing e-VLBI for data transfer (map) –Phase 1: develop e-VLBI compatible data system (Mark 5) –Phase 2: demonstrate Gb/s data transfer. Done on 700 km Westford- GGAO baseline, achieved ~788 Mb/s transfer rate. –Phase 3: demonstrate transfer in global experiments such as the Westford-Kashima (Japan) experiment. –Phase 4: establish new adaptive IP protocol. Tailored to operate in shared-network background mode. Most networks are lightly loaded but have bursty high data requirements.

Geodetic Networks: VLBI 5-year Plan 2004 –Deploy and use Mark 5 at all correlators and stations –Establish e-VLBI for daily UT1 measurements 2005 –Begin replacement of Fairbanks antenna –Begin development of K/Q receivers –Study K/Q and small antenna options 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

Transition to integration slides

Geodetic Networks: Map of NASA Stations

Geodetic Networks: Integration Elements Proposed activities –NGO proposal National Geodetic Observatory proposed in response to NASA solicitation Focus US efforts in space geodesy to integrate techniques, attract new funding –INDIGO proposal Inter-Service Data Integration for Geodetic Operations proposed in response to NASA solicitation 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 technqiues –IAG IGS, ILRS, IVS are all services of IAG, will all contribute to IGGOS: Integrated Global Geodetic Observing System IGGOS is the flagship project under new IAG structure, is expected to play a major role in geodesy community Integration of techniques at a very high level

Geodetic Networks: Co-location Strategy Local ties are essential for combination of data from different techniques Local ties are the limiting factor in closure of the networks Improvements are needed, due to suspect or discrepant ties at the few cm level at some stations Best local ties agree at the few mm level

Geodetic Networks: Issues and Challenges Repeat from intro??? New spin now??

Geodetic Networks: Integration and Coordination Global networks should be considered NASA ‘critical infrastructure’ and strategic US assets Coordinated program management –Appropriate balance of measurements, scientific needs and resources in the mix of VLBI, GPS and SLR –Appropriate balance of resources for scientific research and applications with the demanding requirements of Reference Frame infrastructure Meeting challenges together for mutual strength –Unified management structure for all three techniques –Oriented to the goal of having the most stable and accurate reference frame and tracking capabilities –The three techniques plan to jointly study the structure and budget for the NASA networks and recommend an approach for integration