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Improving IVS Observing Program for Global Reference Frames

This article discusses the importance of the International VLBI Service for Geodesy and Astrometry (IVS) in maintaining accurate global reference frames and related products. It highlights the role of Very Long Baseline Interferometry (VLBI) in determining celestial pole, UT1-UTC, and Earth Orientation Parameters (EOPs). The article also presents the goals and achievements of the IVS Product Specification and Observing Programs working group.

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Improving IVS Observing Program for Global Reference Frames

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  1. Evolving the IVS Observing Program for Improvements of Global Reference Frames and Related Products Wolfgang Schlüter IVS Chair Bundesamt für Kartographie und Geodäsie Fundamentalstation Wettzell Nancy Vandenberg IVSCC Director NASA Goddard Space Flight Center http://ivscc.gsfc.nasa.gov IAG-Symposium, Santiago de Chile

  2. Gloabal Reference Frames and Related Products ICRF EOP’s • ICRF: • Radio Source Positions • ITRF: • Station Positions • Velocities • EOP’s: • Celestial Pole (d, dψ) • Polar Motion (xP, yP) • UT1-UTC (DUT1) • Importance documented: coming up IAG Project IGGOS with demand for • mm-accuracy • consistent for decades • ….. ITRF IAG-Symposium, Santiago de Chile

  3. Very Long Baseline Interferometry- fundamental role - • Unique Technique for • CRF • Celestial Pole • UT1-UTC • Primary Technique for • EOP’s (Complete set of Parameter) • TRF (most precise technique for long baselines - scale!) IAG-Symposium, Santiago de Chile

  4. I V S - International VLBI Servicefor Geodesy and Astrometry IVS is a service of • IAG - International Association of Geodesy • IAU - International Astronomical Union • FAGS - Federation of Astronomical and Geophysical Data Analysis Services Main tasks of the IVS coordination of VLBI components, guarantee the provision of the products for CRF, TRF and the set of EOP’s • IVS inauguration was on 1st of March, 1999 • Demand for continuity in maintaining the reference frames forced to employ at first the • existing observing programs (NEOS, CORE, .... INT) • 2001 review of products and observing programs ==> WG2 • Basis for improving products and evolving observing programs to meet service requirements IAG-Symposium, Santiago de Chile

  5. Concepcion Hobart 2 new stations IAG-Symposium, Santiago de Chile

  6. WG2: “Product Specification and Observing Programs” WG 2 established at the 5th IVS DB-Meeting on February 15th, 2001 The assignment of WG2 was to • review the usefulness and appropriateness of current IVS products, • recommend guidelines for accuracy, timeliness, and redundancy, • review the quality and appropriateness of observing programs, • set goals for improvements of IVS products, • suggest how these may possibly be achieved in the future, • suggest a realistic set of observing programs, taking into account existing agency programs. • Complete report was presented in November 2001 and accepted by the IVS Directing Board on Feb. 14th, 2002 available: http://ivscc.gsfc.nasa.gov within IVS Annual Report 2001 IAG-Symposium, Santiago de Chile

  7. Harald Schuh (chair), TU Vienna (A) Patrick Charlot, Obs. Bordeaux (F) Hayo Hase, BKG (D) Ed Himwich, NASA/GSFC (USA) Kerry Kingham, USNO (USA) Calvin Klatt, EMR (Canada) Chopo Ma, NASA/GSFC (USA) Zinovy Malkin, IAA (RU) Arthur Niell, MIT Haystack (USA) Axel Nothnagel, Univ. Bonn (D) Wolfgang Schlüter, BKG (D) Kazuhiro Takashima, GSI (JP) Nancy Vandenberg, NASA/GSFC (USA) Members of the WG2 • Experts in various fields of VLBI • Involving many agencies • Different nations • to obtain broad acceptance within IVS IAG-Symposium, Santiago de Chile

  8. Products Status Goals(2002-2005) polar motion accuracy xp ~100 as, yp ~200 as xp, yp: 50 ... 25 as latency 1-4 weeks... 4 months 4 - 3 days...1day resolution 1 day 1 day...1h... 10min freq. of sessions ~3 d/week .........7d/week UT1 accuracy 5... 20 s 3.................. 2 s latency 1 week 4 - 3 days .... 1day resolution 1 day 1 day ....... 10min ,  accuracy 100... 400 as 50...25 as latency 1-4 weeks... 4 months 4 - 3days... 1 day resolution 1 day 1 day freq. of sessions ~3 d/week .......... 7 d/week TRF (x,x,z) accuracy 5-20 mm 5 .............. 2 mm .... .... .... CRF accuracy 0.25-3 mas 0.25 mas (improved distribution) freq. of solution 1 y 1 y latency 3-6 months 3 ............. 1 month(s) ...... ....... ....... ....... IVS Products (some examples from WG2 Report) IAG-Symposium, Santiago de Chile

  9. More IVS Products (see WG2 Report) • EOP - dUT1/dt (lod) - dxp/dt, dyp/dt • TRF - x,y,z time series - episodic events - annual solutions - non-linear changes • CRF - source structure - flux density • Geodynamical Parameter - solid Earth tides h, l - ocean loading A,  - atmospheric loading α • Physical Parameter - tropospheric parameters (zenith delays, gradients) - ionospheric mapping - light deflection parameter  IAG-Symposium, Santiago de Chile

  10. New IVS Observing Programs • Appropriate observing programs started 2002 for • Earth Orientation Parameters (EOP): IVS-R1 ... IVS-R4, IVS-INT1 • Two rapid turn-around sessions each week, • Comparable xp, yp results. • Additional sessions employing S2 and K4 techniques (IVS-E3, IVS-INT2) • Terrestrial Reference Frame (TRF): IVS-T2 • Monthly TRF sessions with 8 stations • Celestial Reference Frame (CRF): IVS-CRF • Bi-monthly RDV sessions using the VLBA and 10 geodetic stations, • CONT, annually or semi-annually IVS-CONT02 • 14-day continuous sessions to demonstrate the best results that VLBI can offer • in 2002: CONT-session, October 16-31, 2002 • Monthly R&D sessions: IVS-R&D • to investigate instrumental effects, research the network offset problem • Observing program 2002: geodetic VLBI observations increased by • about 30% IAG-Symposium, Santiago de Chile

  11. Delay from observation to product availability • 2 time series • IVS R1 (Bo, Hay) • IVS R4 (Wash) • Results in general after two weeks available now • Improvements still required • Transportation • Correlator processing IAG-Symposium, Santiago de Chile

  12. Combined EOP’s are regular IVS Products Example: DUT1 form R1 and R4 • Complete set of EOP’s • Combined Solution from 6 Analysis Centers • 20-30% improved • accuracy • robustness • R1 & R4 since 2002 IAG-Symposium, Santiago de Chile

  13. UT1-UTC from INTENSIVES with reference to CO4MK4: Wettzell - Kokee Park and K4: Wettzell - Tsukuba IAG-Symposium, Santiago de Chile

  14. Tropospheric ParameterPilot Project to prepare WZD as IVS product • Wet Zenith Delay • Regular for each R1 or R4 • Hourly • Solution of 5 Analysis Centers • Combined IVS product • 2-3mm • Comparable to GPS (or better?) 1day example for Wettzell (R4) in GPS week 1180 IAG-Symposium, Santiago de Chile

  15. IVS Observing Program 2003 IAG-Symposium, Santiago de Chile

  16. Further improvements required • weekend gaps, automation for unattended observing needed • reduce time delay and reduce expenses • employment of a modern disc based recording system (Mk5) • development of data transfer via the Internet (e-VLBI) • global network configuration has to be improved • especially in the southern hemisphere • encourage additional institutions and include the S2 and K4 technologies • more observing time will required overall • timeliness, shorten turn-around time at the correlators • better logistical organization of tape/disc transport or e-VLBI, • improving the correlation factor (MK5) • robustness of the products, more analysis centerswith different software IAG-Symposium, Santiago de Chile

  17. MK 5 Development • Replacing tape drives (MK4) with disk systems (MK5) • Reducing costs • E-VLBI • More than 20 MK5 systems already deployed MK4 vs. MK5 IAG-Symposium, Santiago de Chile

  18. e-VLBI is coming as the world is being wiredonly a question of time and money • Surfnet • USA-Europa • 2,4 Gbit/s • TransPAC • USA-Japan • 655Mbits/s • APAN • USA-Japan • 655 Mbits/s IAG-Symposium, Santiago de Chile

  19. Summary • EOP’s as Combined IVS products (more precise and robust) • Two rapid turn around programs per week (R1, R4) • Involving different Techniques (K4, S2) • Pilot Project: Tropspheric Parameter • Data Acquisition (MK5, e-VLBI) • Network improvements (Concepcion, Hobart) • WG2: Goals for Improvements • “VISION REPORT 2010” in work Thank you IAG-Symposium, Santiago de Chile

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