1. IERS Combination WG and CPP Meeting, April 27, 2005, TU of Vienna, Austria Status and Future of the IERS Combination Efforts Markus Rothacher GeoForschungsZentrum Potsdam IERS Combination WG and CPP Meeting April 27, 2004 Technical University of Vienna Vienna, Austria

2. IERS Combination WG and CPP Meeting, April 27, 2005, TU of Vienna, Austria Vision Four Sets of IERS Products Status of Call for Long Time Series Status of Routine SINEX Generation Future Goals Content

3. IERS Combination WG and CPP Meeting, April 27, 2005, TU of Vienna, Austria Vision for a Rigorous Combination Parameter Type VLBIGPS/ GLON. DORIS/ PRARE SLRLLRAlti- metry Quasar Coord. (ICRF)X NutationX (X) X Polar MotionXXXXX UT1X Length of Day (LOD) XXXX Coord.+Veloc.(ITRF) XXXXX(X) GeocenterXXXX Gravity Field XXX(X)X OrbitsXXXXX LEO Orbits XXXX IonosphereXXXX TroposphereXXXX Time/Freq.; Clocks (X)X IERS CPP and ITRF2004/IERS200x at present: red rectangle Parameter space for a rigorous combination: Earth Rotation Gravity Field ITRF Atmosphere ICRF

4. IERS Combination WG and CPP Meeting, April 27, 2005, TU of Vienna, Austria Yearly IERS200x Products: –Based on long time series of SINEX files from a yearly reprocessing and recombination by all techniques including the full time span of global data –Most recent standards in modeling, parameterization, processing strategy to be used in the reprocessing –Combination of the series into an product set: IERS200x = ITRF200x+EOP200x+ICRF200x –Combination should be based on combined weekly intra-technique SINEX file and not on combined weekly inter-technique SINEX files Routine Weekly IERS Products (IERS CPP): –EOPs and station coordinates routinely generated on a weekly basis –Comparable to the IGS Final Products, i.e., based on the final solutions of a technique –Envisaged latency: ca. 3 weeks –Strategy to be discussed at this meeting (IERS CPP, April 27, 2005) Four Sets of IERS Combined Products (1)

5. IERS Combination WG and CPP Meeting, April 27, 2005, TU of Vienna, Austria Daily Rapid IERS Products: –Combination of VLBI Intensive Sessions (e-VLBI) with GPS rapid products and SLR/DORIS rapid solutions –Comparable to the IGS Rapid Products: ca. 24 hour latency –IGS: Generation of combined SINEX files on a daily basis including station coordinates, EOPs, in the future troposphere parameters –VLBI: Rapid generation of VLBI Intensive solutions (1hour), available on a daily basis –SLR/DORIS: Rapid generation of daily solutions –Complementarity: VLBI: UT1 (and scale) GPS: Reference frame, polar motion, LOD SLR/DORIS: geocenter (and scale) Predicted IERS Products: –Prediction of EOPs based on the combined IERS Rapid Products Four Sets of IERS Combined Products (2)

6. IERS Combination WG and CPP Meeting, April 27, 2005, TU of Vienna, Austria IERS Call for Long Time Series (December 2004): Long time series important for two purposes: –ITRF2004: the generation of a new ITRF solution by the ITRF Combination Centers under the responsibility of the ITRF Product Center –IERS CPP complementation: it has become evident, that long time series are essential for the rigorous combination of the space techniques based on “weekly” solutions Yearly ITRF/IERS200x Products: Present Status

7. IERS Combination WG and CPP Meeting, April 27, 2005, TU of Vienna, Austria A few years of additional data available New sites joined the global network Processing strategies of the individual techniques improved Velocities of more recent sites are not available or poorly determined in ITRF2000, which leads to the point that the individual techniques start to use their own TRF realizations Some station positions are no longer valid because of events (earthquakes, equipment changes creating discontinuities in the time series, local tie updates, etc.). Combination of “weekly” SINEX files: a much more rigorous combination possible. More consistent IERS products and time series analysis, especially through a better detection of discontinuous position changes. Make use of the experience gained in rigorous combination strategies through the IERS SINEX Combination Campaign and the IERS CPP. Importance of an ITRF2004 Solution

8. IERS Combination WG and CPP Meeting, April 27, 2005, TU of Vienna, Austria Weekly SINEX solutions routinely generated not sufficient to generate combined inter-technique solutions in a consistent way over many weeks (weighting, local ties, datum) A further step towards the ultimate goal, namely a future rigorously combined, consistent IERS product series IERS200x: “Integrated Earth orientation parameters, Radio sources, and Site coordinates 200x” IERS200x = ITRF200x + EOP200x + ICRF200x Long time series are additional material to test such approaches At present no quasar coordinates are available yet: ICRF not included in the combination Importance for the IERS CPP: IERS200x

9. IERS Combination WG and CPP Meeting, April 27, 2005, TU of Vienna, Austria Status of Call for Long Time Series ServiceTechniqueInstitutionTime Span# Files IGSGPSNRCan021/1996- 361/2004468 IGS*GPSGFZ007/1996-361/2004309 IGS*GPSSIO020/1991-361/20041445 ILRSSLRASI362/1992-361/20041216 IVSVLBIGIUB004/1984-364/20041936 IDS*DORISIGN003/1993-361/20041254 IDS*DORISINA292/1992-165/2004610 IDS*DORISLEGOS-CLS003/1993-361/2004627 IDS*DORISCDDISone year52 * Individual analysis center

10. IERS Combination WG and CPP Meeting, April 27, 2005, TU of Vienna, Austria Status of Call for Long Time Series http://iers1.bkg.bund.de/info/listFileITRF2004.php For the first time: –Intra-technique combined solutions available from all techniques over long time spans (except DORIS) –Homogeneously reprocessed over many years (except IGS)

11. IERS Combination WG and CPP Meeting, April 27, 2005, TU of Vienna, Austria IERS Long Time Series: ITRF2004 Schedule April 27, 2005:IERS CPP Meeting in Vienna to discuss next steps April 28, 2005: IERS DB Meeting (ITRF2004, IERS CPP) May 15, 2005: Submission of ITRF solutions by the ITRF CCs, start of comparison and validation phase August 5, 2005: Final ITRF2004 solution ready after comparisons and validations August 26, 2005: Presentation of the new ITRF2004 at the IAG Scientific Assembly (Cairns, Australia) October 2005: IERS Workshop 2005; Discussion of IERS2005: next level of improvement in parameterization and modeling consistency; Discussions concerning the transitions to new IERS products; IERS Directing Board Meeting for decisions. 200x:Yearly realization of a new IERS200x based on latest standards and strategies, improvements

12. IERS Combination WG and CPP Meeting, April 27, 2005, TU of Vienna, Austria Routine Weekly Products (IERS CPP)

13. IERS Combination WG and CPP Meeting, April 27, 2005, TU of Vienna, Austria IERS CPP Proposals (1) ( = Intra-technique combination)

14. IERS Combination WG and CPP Meeting, April 27, 2005, TU of Vienna, Austria IERS CPP Proposals (2) ( = Inter-technique combination)

15. IERS Combination WG and CPP Meeting, April 27, 2005, TU of Vienna, Austria IERS CPP Proposals (3) ( = Validation)

16. IERS Combination WG and CPP Meeting, April 27, 2005, TU of Vienna, Austria IERS CPP Proposals (4)

17. IERS Combination WG and CPP Meeting, April 27, 2005, TU of Vienna, Austria IERS CPP: Submission Schedule Intra-technique combinations (weekly SINEX files) due 8 weeks after the observations Inter-technique combinations (weekly SINEX files) due 12 weeks after the observations Validation of inter-technique combinations (report) due 16 weeks after the observations Special combined products due 8 weeks after the observations

18. IERS Combination WG and CPP Meeting, April 27, 2005, TU of Vienna, Austria Status of Routine Weekly SINEX Generation http://iers1.bkg.bund.de/info/listFileCPP.php Intra-technique solutions in time and complete Inter-technique solutions not yet available No validation yet TechniqueInstitutionLast Subm.Delay (days) IGSNRCan072/200517 ILRSASI079/200510 IVSGIUB062/200527 IDS *IGN051/200538 Intra-technique combinations (March 30, 089/2005): * Individual analysis center

19. IERS Combination WG and CPP Meeting, April 27, 2005, TU of Vienna, Austria IERS CPP: Conclusions so far It took some time for the technique services to start to compute combined routine intra-technique solutions. Very important to have technique services fully involved, taking their responsibility for the technique-specific products (SINEX) Intra-technique combinations now routinely available from all techniques (except DORIS): a big step forward. 13 months (56 weeks) of weekly solutions available from all techniques. Now complemented and supported by the long time series of weekly SINEX files. All material available to study different strategies for the routine generation of inter-technique combinations. Demonstration of routine generation by October: IERS Workshop 2005

20. IERS Combination WG and CPP Meeting, April 27, 2005, TU of Vienna, Austria IERS CPP: Schedule April 27, 2005:IERS CPP Meeting at the EGU Meeting in Vienna; Discussion of the next steps (inter-technique combination and validation) May-July 2005:Test of strategies for weekly routine generation of products and for their validation August 2005: Results to be presented at the IAG Scientific Assembly (Cairns, Australia) August-October 2005:Set up routine generation of products and their routine validation October 2005:IERS Workshop 2005: Evaluation of the CPP and discussions concerning the transitions to new IERS products

21. IERS Combination WG and CPP Meeting, April 27, 2005, TU of Vienna, Austria IERS CPP: Future Goals Start with weekly generation of (accumulated) inter-technique solutions Start validation of weekly intra-technique and inter-technique combinations Reduce latency of intra-technique solutions (2 months) ITRF2004/IERS2005: Studies of rigorous weekly and multi-year solutions Work towards the combination of daily solutions (Rapid IERS Product) CONT’05: new continuous VLBI campaign coordinated with the IERS CPP and the other techniques; allows detailed studies of combination strategies etc. Encourage combinations on the observation level Add new common parameters to the weekly combinations: –Quasar coordinates (ICRF) –Troposphere zenith delays and gradients –Nutation offsets and rates (to IAU2000) –Subdaily ERPs ? Orbits ? Clocks ?

22. IERS Combination WG and CPP Meeting, April 27, 2005, TU of Vienna, Austria Very useful experiences with the CONT’02 Campaign Possibility to study the details of a rigorous combination (troposphere, local ties, nutation, UT1/LOD, modeling aspects, parameterization, …) Continuous VLBI observations during 2 weeks Inclusion of other observation techniques: –SLR observations to GPS/GLONASS satellites –SLR observations to multi-technique satellites (JASON, CHAMP, …) –DORIS observations (local ties, troposphere, …) Co-location of auxiliary instruments: –As many water vapor radiometers as possible –Meteorological Information –Clock synchronization ? –Gravimeters ? CONT’05 Campaign

23. IERS Combination WG and CPP Meeting, April 27, 2005, TU of Vienna, Austria IERS Combination Pilot Project Parameter Type VLBIGPS/ GLON. DORIS/ PRARE SLRLLRAlti- metry Quasar Coord. (ICRF)X NutationX (X) X Polar MotionXXXXX UT1X Length of Day (LOD) XXXX Coord.+Veloc.(ITRF) XXXXX(X) GeocenterXXXX Gravity Field XXX(X)X OrbitsXXXXX LEO Orbits XXXX IonosphereXXXX TroposphereXXXX Time/Freq.; Clocks (X)X IERS Combination Pilot Project: sub-space (red rectangle) Parameter space for a rigorous combination: Earth Rotation Gravity Field ITRF Atmosphere ICRF