IVS’ contribution to the IERS Combination Pilot Project and the ITRF2005 – Status & Results

1. IVS’ contribution to the IERS Combination Pilot Project and the ITRF2005 –Status & Results Markus Vennebusch, Sarah Böckmann VLBI – group of the Geodetic Institute of the University of Bonn IVS-General Meeting 2006 M. Vennebusch, S. Böckmann – IVS’ contribution to the IERS CPP and the ITRF2005 January 9, 2006 slide 1

2. IERS Combination Pilot Project (IERS CPP): - Combination of VLBI, GPS, SLR, DORIS (based on normal equations)=> Consistent combination of TRF, EOP, (CRF, ATM, …) IERS Combination Pilot Project VLBI – Intra-technique combination(GIUB for IVS) Intra-techniquecombination Inter-techniquecombination (IERS CPP Call for Participation) M. Vennebusch, S. Böckmann – IVS’ contribution to the IERS CPP and the ITRF2005 January 9, 2006 slide 2

3. VLBI Intra-technique combination • Analysis centers generating SINEX files: • CALC/SOLVE : BKG, GSFC, SHA, USNO- OCCAM : AUS (Kalman), DGFI (LSM) • SteelBreeze: : MAO • => For each session up to seven contributions / individual solutions Data available (January 6, 2005): • For ITRF2005: • Every technique performed intra-technique combination of all data available for so-called long-term solution - IVS combined ~3600 VLBI sessions (1979-now, real datum-free NEQ) • IERS WS in Potsdam => combined sessions used by DGFI, IGN, ... M. Vennebusch, S. Böckmann – IVS’ contribution to the IERS CPP and the ITRF2005 January 9, 2006 slide 3

4. VLBI Intra-technique combination VLBI SINEX-datadatum-free NEQs (all station coordinates, EOP+Rates, Nutation free) IVS‘ contribution to IERS CPP IVS‘ contribution to IERS CPP Internal VLBI investigations - Combination of TRF, EOP, (CRF)- Contribution to ITRF2005- other parameters (mainly ATM)=> datum-free NEQs = no solutions! Computation of solutions Long-term-solution:data for ITRF2005(1979 - 2005) Routine combination(2005 - now) EOP or site positions series(will replace combination on the basis of results) M. Vennebusch, S. Böckmann – IVS’ contribution to the IERS CPP and the ITRF2005 January 9, 2006 slide 4

5. EOP Comparisons Examples for differences between VLBI-SINEX EOP series and C04: M. Vennebusch, S. Böckmann – IVS’ contribution to the IERS CPP and the ITRF2005 January 9, 2006 slide 5

6. EOP Comparisons Examples for differences between VLBI-SINEX EOP series and IGS EOP series: M. Vennebusch, S. Böckmann – IVS’ contribution to the IERS CPP and the ITRF2005 January 9, 2006 slide 6

7. Site position comparisons Example for SINEX-site position series (combined VLBI-SINEX – data vs. GPS): M. Vennebusch, S. Böckmann – IVS’ contribution to the IERS CPP and the ITRF2005 January 9, 2006 slide 7

8. Site position comparisons Helmert Parameters (between individual SINEX solutions and ITRF2000): scale WRMS M. Vennebusch, S. Böckmann – IVS’ contribution to the IERS CPP and the ITRF2005 January 9, 2006 slide 8

9. Weighting / Variance component estimation Weighting procedure (for individual solutions of one session): Reasons for determination of weighting factors: 1. Determination of quality of contributions (smaller weight for solutions with lower quality)2. normal equation matrices might be differently scaled and weighted(caused by use of different stochastic models = different quality of observations)=> Variance component estimation: For each session: One variance factor per contribution / individual solution M. Vennebusch, S. Böckmann – IVS’ contribution to the IERS CPP and the ITRF2005 January 9, 2006 slide 9

10. Weighting / Variance component estimation Iterate until Computation of variance components:(k = Iteration counter, p = no. of indiv. solutions) Accumulation of NEQs: Computation of residuals: Computation of residuals (with W.S.S.O-C and r.h.s. of NEQ): Group redundancy(part of contribution to total redundancy): Variance component: inverted vc => weighting factor M. Vennebusch, S. Böckmann – IVS’ contribution to the IERS CPP and the ITRF2005 January 9, 2006 slide 10

11. Weighting / Variance component estimation Examples of variance component estimation (14 months of data): M. Vennebusch, S. Böckmann – IVS’ contribution to the IERS CPP and the ITRF2005 January 9, 2006 slide 11

12. Conclusions and outlook • Conclusions from VCE: • more realistic estimates of accuracy => realistic weighting procedure • impact on parameters / combined solution ? • Problems to be solved: • Reference epoch: 12 UTC (IVS) • Use of identical nutation models (IVS) • Atmosphere parameters included in SINEX file (IVS) • Correlations between analysis centers (GIUB) • Conclusions: • SINEX results show agreement with results of other techniques • VLBI SINEX data is suitable for ITRF2005 (different checks passed) M. Vennebusch, S. Böckmann – IVS’ contribution to the IERS CPP and the ITRF2005 January 9, 2006 slide 12

13. IVS’ contribution to the IERS Combination Pilot Project and the ITRF2005 –Status & Results Markus Vennebusch, Sarah Böckmann VLBI – group of the Geodetic Institute of the University of Bonn IVS-General Meeting 2006 M. Vennebusch, S. Böckmann – IVS’ contribution to the IERS CPP and the ITRF2005 January 9, 2006 slide 13