Prospective Improvements of IVS Products and Evolvement of Observing Programs

1. Prospective Improvements of IVS Products and Evolvement of Observing Programs Harald Schuh WG2 Chair Vienna University of Technology hschuh@luna.tuwien.ac.at Wolfgang Schlüter IVS Chair Bundesamt für Kartographie und Geodäsie Fundamentalstation Wettzell Nancy Vandenberg IVSCC Director NASA Goddard Space Flight Center

2. 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 • Maintenance of the ICRF(International Celestial Reference Frame) • radio source positions and changes • Provision of products for • ITRF (International Terrestrial Reference Frame) • station positions and velocities • EOP - Earth Orientation Parameters • monitoring the celestial pole (d, dψ) • monitoring Universal Time (UT1) and length of day (LOD) • monitoring polar Motion (xp, yp)

3. The IVS 1999 - 2001 • IVS inauguration was on 1st of March, 1999 • Demand for continuity in maintaining the reference frames forced to employ and accept the • existing infrastructure • existing observing programs (NEOS, CORE, ....) • related data handling • IVS efforts in 1999 - 2001 • installation of its structure and components • Get used to the new tasks • 2001 review of products and observing programs ==> WG2 • Basis for improving products and evolving observing programs to meet service requirements

4. WG2 onProduct 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

5. 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

6. Rationale and motivation for the work of WG2 • Fundamental role of VLBI for the realization and maintenance of global reference frames • unique for the ICRF, essential for EOPs and scale of the ITRF • Requirement for precise reference frames (10-9), consistent for decades:  IGGOS - Integrated Global Geodetic Observing System • Demand for combination of all techniques • to achieve the required accuracy • to eliminate systematic errors • to generate reliable and redundant results • Collaboration of all IAG Services (IVS, ILRS, IGS, IDS, ... IERS)

7. Products Status Goals(2002-2005) polar motion accuracy xp ~100 s, yp ~200 s xp, yp: 50 ... 25 s 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 arcsec 50...25 arcsec 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)

8. 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 Parameters - solid Earth tides h, l - ocean loading A,  - atmospheric loading α • Physical Parameters - tropospheric parameters (zenith delays, gradients) - ionospheric mapping - light deflection parameter 

9. New IVS observing programs • IVS Program Committee was established in Sept. 2001 • 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 will be increased by about 30% • Goal: future increase by ~100% till 2005

10. Improvements required • weekend gaps, automation for unattended observing needed • reduce time delay and reduce expenses • development 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 is required overall • timeliness, shorten turn-around time at the correlators (better logistical organization of tape/disc transport) • robustness of the products, more analysis centerswith different software

11. Finally .... • To meet the ambitious goals all responsible members of the contributing agencies are kindly asked to support the IVS as much as possible Thank you