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Geodetic VLBI Wishes and Limitations

Geodetic VLBI Wishes and Limitations. Wolfgang Schlüter Bundesamt für Kartographie und Geodäsie Fundamentalstation Wettzell, Products of geodetic VLBI (global reference frames) Events relevant for geodetic VLBI IVS International VLBI Service for Geodesy and Astrometry

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Geodetic VLBI Wishes and Limitations

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  1. Geodetic VLBIWishes and Limitations Wolfgang Schlüter Bundesamt für Kartographie und Geodäsie Fundamentalstation Wettzell, Products of geodetic VLBI (global reference frames) Events relevant for geodetic VLBI IVS International VLBI Service for Geodesy and Astrometry IVS WG2: “Review of Products and Observing Programs” Status and improvements of products Considering geodetic aspects (collocation with other techniques, Fundamentalstation) New Technologies in VLBI, Korea 2002

  2. Key role for geodetic VLBI: Global Reference Frames ICRF EOP’s • ICRF: • Radio Source Positions • Variations in Source Structure • ITRF: • Station Positions • Velocities • EOP’s: • Celestial Pole (d, dψ) • Polar Motion (xP, yP) • UT1-UTC (DUT1) • Importance is documented: coming up IAG Project IGGOS with demand for • mm-accuracy • consistent for decades • ….. ITRF New Technologies in VLBI, Korea 2002

  3. VLBI plays a fundamental roleas geodetic space technique • 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!) New Technologies in VLBI, Korea 2002

  4. Events important for the development of geodetic VLBI • 1931 Karl Jansky detected radio waves from outer space (birth of Radio Astronomy) • In the 60ies and 70ies relevant technology developments for Long Baseline Radiointerferometry: • Atomic clocks (H-Maser) • Large Scale Antenna • Recording Technology • Signal Processing • Potential of VLBI for Geophysics described in Shapiro, I.I. and Knight, C.A. in 1969: ” Geophysical Application of Long Baseline Radio Interferometry” presented at Conference “Earthquake Displacement fields and the Rotation of the Earth” held in London/Canada 1969 New Technologies in VLBI, Korea 2002

  5. International projects promoting geodetic VLBI • PPME (Pacific Plate Motion Experiment) Haystack - Onsala • 1st geodetic intercontinental baseline, Sept 1977, February and May 1978 (MK1) • NASA Crustal Dynamics Project (CDP), 1979 -1993 • All VLBI facilities available in US, Europe, Asia, Australia, South Africa and South America involved • Regular Experiments • Important Milestone: Herring et al. (1986): baseline rate 17+/- 2mm/y; Haystack-Onsala; Sept 1980- August 1984 observed with MKIII • Monitor Earth Rotation and Intercompare the Techniques (MERIT), 1983 - 1986 • VLBI: POLARIS (Carter et. al. (NGS) Westford-Ft.Davis, ext. Onsala and Wettzell 83); • IRIS, 1984-1990, regular observations, 5 day interval, 6 Stations • NEOS (USNO); continuation of IRIS (weekly) • INTENSIV (“daily UT1”)since 1984 • Establishment of the International Earth Rotation Service (1986) • Continuous Observation of the Rotation of the Earth (CORE, 1996) • …… and more …… New Technologies in VLBI, Korea 2002

  6. IERS (International Earth Rotation Service) established as result of MERIT in 1986 Aiming in the realization and maintenance of • CRF, Celestial Reference Frame • TRF, Terrestrial Reference Frame • ITRF 89, 93, 97, 2000 • Based on different techniques (VLBI, SLR/LLR and GPS) • EOP’s, Earth Orientation Parameters on behalf of • International Association of Geodesy (IAG) • International Astronomical Union (IAU) New Technologies in VLBI, Korea 2002

  7. Westford – Wettzell(NASA Goddard Space Flight Center VLBI Group, Data products available electronically at http://lupus.gsfc.nasa.gov/global) New Technologies in VLBI, Korea 2002

  8. 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 EOP’s regular and in time • 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) • review of products and observing programs  WG2 in 2001 • Basis for improving products and evolving observing programs to meet service requirements ( wishes and limitations) New Technologies in VLBI, Korea 2002

  9. Wish: KVN, supporting IVS with new components soon! Concepcion Hobart 2 new IVS stations in 2002 New Technologies in VLBI, Korea 2002

  10. 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 • accepted by the IVS Directing Board on Feb. 14th, 2002 available: http://ivscc.gsfc.nasa.gov within IVS Annual Report 2001 New Technologies in VLBI, Korea 2002

  11. 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 New Technologies in VLBI, Korea 2002

  12. Products Status Goals(2002-2005) polar motion accuracy xp ~100 as, yp ~200 as xp, yp: 50 ... 25 as xP, yP 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-UTC accuracy 5... 20 s 3.................. 2 s latency 1 week 4 - 3 days .... 1day resolution 1 day 1 day ....... 10min celest. pole 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,y,z) accuracy 5-20 mm 5 .............. 2 mm .... .... .... CRF(a, d) 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) New Technologies in VLBI, Korea 2002

  13. 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  New Technologies in VLBI, Korea 2002

  14. Evolving IVS Observing Programs since 2002 • 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% New Technologies in VLBI, Korea 2002

  15. Combined EOP’s are regular IVS Products Example: DUT1 from NEOS, R1 and R4 • Complete set of EOP’s • Celestial Pole (d, dψ) • Polar Motion (xP, yP) • UT1-UTC (DUT1) • Combined Solution from 6 Analysis Centers • 20-30% improved • accuracy • robustness • R1 & R4 since 2002 • Wishes: R1, R2, R3… (daily EOP’s series) NEOS IVS R1 + R4 New Technologies in VLBI, Korea 2002

  16. Delay from observation (R1 & R4) 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 • Wishes • Product availability 1 day after observation New Technologies in VLBI, Korea 2002

  17. UT1-UTC from INTENSIVES with reference to CO4observed by Wettzell-Kokee Park (MK4/MK5) controlled by Wettzell–Tsukuba (K4) Candidate for e-VLBI New Technologies in VLBI, Korea 2002

  18. New Product: tropospheric ParameterPilot Project to prepare WZD as IVS product • Wet Zenith Delay (WZD) • 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 New Technologies in VLBI, Korea 2002

  19. IVS Observing Program 2003 New Technologies in VLBI, Korea 2002

  20. Further Improvements required (Wishes and limitations) • automation for unattended observing needed • Weekend gaps • Remote controlled stations • 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 and central Asia • encourage additional institutions and include the S2 and K4 technologies • more observing time will be 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 New Technologies in VLBI, Korea 2002

  21. MK5 - Development • Replacing tape drives (MK4) with disk systems (MK5) • Reducing costs • e-VLBI • More than 20 MK5 systems already deployed • IVS supports deployment MK4 vs. MK5 New Technologies in VLBI, Korea 2002

  22. Estimated amount of data and media required • Amount of data: • 24 h-observation of IVS R1 (~400 Scans) 1, 2 TByte • 24 h-observation of IVS R4 (~180 Scans) 0, 9 TByte • 1 h-observation of IVS INT 0,04 Tbyte • Number of required media R 1 R 4 INT • Videotapes 2 1 1 (Babytape) • Classical recording with MKIV • Harddisks 20GByte capacity 60 45 2 • Not realistic • Harddisks 120GByte capacity 12 8 1 • Harddisks 200GByte capacity 7 5 (1) New Technologies in VLBI, Korea 2002

  23. Time required for data transmission (max. 60% through put) transmission rate R1 R4 INT estimated cost/ year (WIN) • 64 kbit/s - - 100 d • 2 Mbit/s 93 d 69 d 3 d • 34 Mbit/s 6 d 4 d 5 h ~ 50.-k€ • 155 Mbit/s 1,2 d 1 d 1 h ~180.-k€ • 622 Mbit/s 7 h 5 h 15 m ~450.-k€ • 2,4 Gbit/s 1,9 h 1,3 h 4 m New Technologies in VLBI, Korea 2002

  24. 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 New Technologies in VLBI, Korea 2002

  25. Considering geodetic requirements • Reference point of the Antenna • Clear defined, e.g. intersection of axis • Stable at all • Connection to geodetic marker (Fundamentalstation) • Internal delays stable and controlled (Phase Cal) New Technologies in VLBI, Korea 2002

  26. Fundamentalstations- collocation of geodetic techniques - • VLBI advantages • CRF • Complete set of EOP’s • Unique: celestial pole and DUT1 • Scale of TRF • SLR/LLR advantages • Gravityfield sensitivity • Center of Mass • Optical observations (calibration, refraction, scale) • GPS-advantages • Densification of VLBI/SLR-networks • Provision of TRF to general applications • Easy , economic, precise • Combination of techniques • Local survey for the ties New Technologies in VLBI, Korea 2002

  27. 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: tropospheric Parameter • Data Acquisition (MK5, e-VLBI) • Network improvements (Concepcion, Hobart, ….) • WG2: Goals for Improvements • Improve products in accuracy, latency • Improve geometry in the network • Improve stations in automation, stability, reliability, e-VLBI, less disturbances (interferences) • Geodetic ties to markers • Collocated with other techniques (Fundamentalstation) • “VISION REPORT 2010” in work Thank you for the attention! New Technologies in VLBI, Korea 2002

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