Earth Surface and Interior Focus Area Space Geodetic Networks for Maintaining the Reference Frame Geodesy's Critical Contributions to NASA (Earth Science) –Defines, maintains and improves the Reference Frame Staying ahead of NASA’s evolving scientific requirements –Inter-Connects measurements over space (globally) and time (decades) and technology evolution All observations/instruments placed within this one framework –This infrastructure is composed of the: Physical networks Technologies that compose them, and Ongoing scientific analysis and model development that define the reference frame Why NASA? –Needed to support NASA science programs, goals and missions –NASA is one of the foremost space technology agencies in the world Geodetic Challenges to Achieve Roadmap Goals –Erosion of geodetic capabilities in face of declining resources and increasing demands –Integrating new technologies seamlessly while maintaining the long-term stability of the reference frame –Achieving 1 mm reference frame stability Strategies for Meeting Challenges –Implementation of new technologies –Unified & balanced approach to utilization of available measurement techniques –Continued evolution of geophysical models and analysis –Leveraging the benefits available to NASA through established international cooperation –Earthscope and NGS cannot meet national priority objectives without valuable global NASA assets (domestic agencies?) –Better overall program focus and integration Current and Future Requirements –Science Areas Definition of the ocean surface, sea level change (altimetry) Land surface change (with INSAR) Ice budget Static and time-varying gravity field (?), mass distribution, tides Tests of relativity POD capability of GPS and SLR…. –1mm over ten years for sea and ice level change studies –SESWG report quote -” ITRF and EOP, hence the networks [VLBI, SLR, GPS], should continue to be maintained and improved and their data routinely acquired at the best possible accuracy and temporal resolution.” –Roadmaps: Earth science, oceans - [ John - cite the relevant or implied roadmaps that require geodetic networks]

Technologies –SLR kHz lasers Automation and 7/24 operations More accurate retroreflector targets –Saved missions: ERS1, GFO1,METEOR3,…. GPS and SLR combined provide very accurate POD –VLBI Smaller antennas e-VLBI Higher rate recording –GNSS (GPS, GLONASS, Galileo) More frequencies better suited for analysis Densification of ground systems Upgraded receivers (better S/N, signal structure, etc.) Expanded LEO tracking –Integration of techniques Knowledge base integration Solution-level integration Observation-level integration

Linking Requirements to Sources Tapley Ries GLOSS - 1mm over ten years- Woodworth SESWG report pg 31 report 1mm/year surface displacement over 50 km

Earth Surface and Interior Focus Area Reference Frame of Space Geodetic Networks Why do we need a reference frame? –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 Current and Future Requirements First among the requirements is the realization and maintenance of the terrestrial reference system, since this is the background to which all local and global variability is tied. Errors in the frame map directly into errors in observable motions and mass changes. (ref Tapley ) 1mm over ten years for Sea level change studies SESWG report quote -” ITRF and EOP, hence the networks[ VLBI, SLR, GPS], should continue to be maintained and improved and their data routinely acquired at the best possible accuracy and temporal resolution.” GGOS? Challenges –Rusty network and stations, declining resources –Losing capabilities –Need to maintain existing reference frame geodetic systems –New capabilities and technologies must be integrated New Technologies –SLR improvements in automation and. (SLR 200) –- VLBI smaller antennas, e-VLBI –- GPS - modernization, Galileo, collective GNSS, densification of reference frame