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

I V S - International VLBI Service for Geodesy and Astrometry IVS is a service of n IAG - International Association of Geodesy n IAU - International Astronomical Union FAGS - Federation of Astronomical and Geophysical Data Analysis Services Main tasks of the IVS u Maintenance of the ICRF (International Celestial Reference Frame) F radio source positions and changes u Provision of products for F ITRF (International Terrestrial Reference Frame) station positions and velocities F EOP - Earth Orientation Parameters monitoring the celestial pole (d , dψ) monitoring Universal Time (UT1) and length of day (LOD) monitoring polar Motion (x p, y p )

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

WG2 on Product Specification and Observing Programs WG 2 established at the 5 th IVS DB-Meeting on February 15 th, 2001 The assignment of WG2 was to l review the usefulness and appropriateness of current IVS products, l recommend guidelines for accuracy, timeliness, and redundancy, l review the quality and appropriateness of observing programs, l set goals for improvements of IVS products, l suggest how these may possibly be achieved in the future, l 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. 14 th, 2002  available: within IVS Annual Report 2001

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

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

IVS products (some examples from WG2 Report) Products StatusGoals( ) n polar motionaccuracy x p ~100  s, y p ~200  sx p, y p :  s latency 1-4 weeks... 4 months4 - 3 days...1day resolution 1 day1 day...1h... 10min freq. of sessions ~3 d/week d/week n UT1accuracy  s  s latency 1 week4 - 3 days.... 1day resolution 1 day1 day min n ,  accuracy  arcsec  arcsec latency 1-4 weeks... 4 months4 - 3days... 1 day resolution 1 day1 day freq. of sessions ~3 d/week d/week n TRF (x,x,z)accuracy 5-20 mm mm n CRFaccuracy mas0.25 mas (improved distribution) freq. of solution 1 y1 y latency 3-6 months month(s) n

More IVS products (see WG2 Report) n EOP- dUT1/dt (lod) - dx p /dt, dy p /dt n TRF- x,y,z time series - episodic events - annual solutions - non-linear changes n CRF- source structure - flux density n Geodynamical Parameters- solid Earth tides h, l - ocean loading A,  - atmospheric loading α n Physical Parameters- tropospheric parameters (zenith delays, gradients) - ionospheric mapping - light deflection parameter 

New IVS observing programs u IVS Program Committee was established in Sept u appropriate observing programs started 2002 for F 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) F Terrestrial Reference Frame (TRF): IVS-T2 <Monthly TRF sessions with 8 stations F Celestial Reference Frame (CRF): IVS-CRF <Bi-monthly RDV sessions using the VLBA and 10 geodetic stations, F 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 F Monthly R&D sessions: IVS-R&D <to investigate instrumental effects, research the network offset problem êObserving program 2002: geodetic VLBI observations will be increased by about 30% êGoal: future increase by ~100% till 2005

Improvements required n weekend gaps, automation for unattended observing needed n reduce time delay and reduce expenses u development of a modern disc based recording system (Mk5) u development of data transfer via the Internet (e-VLBI) n global network configuration has to be improved u especially in the southern hemisphere u encourage additional institutions and include the S2 and K4 technologies u more observing time is required overall n timeliness, shorten turn-around time at the correlators (better logistical organization of tape/disc transport) n robustness of the products, more analysis centers with different software

Finally.... n 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