The IGS contribution to ITRF2013 – Preliminary results from the IGS repro2 SINEX combinations Paul Rebischung, Bruno Garayt, Xavier Collilieux, Zuheir Altamimi AGU Fall Meeting 2014, Abstract G11C-07, San Francisco, 15 December

The IGS 2 nd reprocessing (repro2) 2 Re-analysis of GNSS data collected by the IGS network since 1994 using the latest models and methodology –Reduce systematic errors in IGS products –Provide IGS contribution to ITRF2013 Main updates since repro1: –Daily data integrations (instead of weekly) –GLONASS data processed by some ACs –IGb08/igs08.atx framework –IERS2010 Conventions –New yaw attitude models for eclipsing satellites –A priori modeling of Earth radiation pressure and antenna thrust –See details at:

Analysis Center submissions 3 Contributions from 7 operational ACs + 2 TIGA contributions Submitted products include: –Satellite orbits and clocks –Terrestrial frames and EOPs (daily SINEX files)

1 st combinations (1/2) 4 WRMS of station position residuals (i.e., of daily « AC – combined » differences) –Outlying days for several ACs: ongoing re-submissions

1 st combinations (2/2) 5 Smoothed WRMS ULR: –Large systematic errors in East –Issue in sub-network combos –Ongoing re-submissions GRG: –Large systematic errors in Up –Pronounced semi-annual variations in North and Up –Under investigation →2 nd combinations with GRG, ULR & GTZ included for comparison only

MIT seems to dominate in Up (and North). –Because « classical » WRMS are biased in favor of ACs with non-common stations. →Use Sillard (1999)’s unbiased WRMS 2 nd combinations (1/2) 6 Smoothed WRMSSmoothed, unbiased WRMS # stations in AC solutions

GFZ’s North WRMS vs. mean ionosphere TEC: –Error in 2 nd order ionospheric corrections –New products submitted, but still affected by several issues →3 rd combinations with GFZ included for comparison only 2 nd combinations (2/2) 7 Smoothed, unbiased WRMS ― GFZ’s North WRMS ― a + (b x mean_TEC)

3 rd combinations 8 Smoothed, unbiased WRMS Inter-AC agreement after 2004: –Horizontal: ≈ 1 – 1.5 mm –Vertical: ≈ 3 – 4 mm –Comparable to the weekly repro1 results Substantial degradation before 2000 (and 1997) –Much less marked in repro1: 3D RMS of repro1 combination residuals

Spectral analysis Stacked periodograms of station position residuals (computed using stations with > 3000 days of data) EastNorth Up Background: flicker + white noise Spectral peaks at: –Annual period; GPS draconitic harmonics –Fortnightly periods (14.8, 14.2, 13.7 & 13.2 d) –9.1 d (MIT); 8.2 & 7.8 d (COD, ESA, MIT); 7.0 d (MIT); 3.65 & 2.2 d (GRG) 9

Scale 10 AC / ig2 scale offsets ACOffset (mm) Rate (mm/yr) WRMS (mm) cod emr esa jpl mit Inter-AC agreement: 0.3 – 0.5 mm –Scale rate differences < 0.1 mm/yr Combined scale rate wrt IGb08: mm/yr –Contribution to ITRF2013 scale rate? ig2 / IGb08 scale offsets

Origin: Y component AC / ig2 Y origin offsets ACOffset (mm) Rate (mm/yr) WRMS (mm) cod emr esa jpl mit ― ig2 / IGb08 Y origin offsets ― SLR / ITRF2008 Y origin offsets (cf. G11C-08) Inter-AC agreement: ≈ 3 – 5 mm –nearly 10 times larger than for scale Y component of combined origin: –Good agreement in phase with SLR –Annual amplitude slightly over-estimated 11

Origin: X component AC / ig2 X origin offsets ACOffset (mm) Rate (mm/yr) WRMS (mm) cod emr esa jpl mit ― ig2 / IGb08 X origin offsets ― SLR / ITRF2008 X origin offsets (cf. G11C-08) Inter-AC agreement: ≈ 3 – 5 mm –nearly 10 times larger than for scale X component of combined origin: –Annual amplitude under-estimated –Broad spectral peak around 3.12 cpy 12

Origin: Z component AC / ig2 Z origin offsets ACOffset (mm) Rate (mm/yr) WRMS (mm) cod emr esa jpl mit ― ig2 / IGb08 Z origin offsets ― SLR / ITRF2008 Z origin offsets (cf. G11C-08) Inter-AC agreement: ≈ 6 – 9 mm –nearly 20 times larger than for scale Z component of combined origin: –Spoiled by GPS draconitic harmonics –Annual signal out-of-phase with SLR 13

Earth Orientation Parameters 14 AC / ig2 X-pole differences AC / ig2 Y-pole differences AC / ig2 X-pole rate differencesAC / ig2 Y-pole rate differences AC / ig2 LOD differences ACXPO μ as YPO μ as XPOR μ as/d YPOR μ as/d LOD μ s/d cod emr esa jpl mit WRMS of EOP residual time series Inter-AC agreement: ≈ 30 μas; μas/d; μs/d

Summary 15 Station positions: –Post-2004 inter-AC agreement comparable to weekly repro1 results –Substantially worse in early years Scale: –Excellent inter-AC agreement –Contribution to ITRF2013 scale rate? Origin: –No substantial improvement EOPs: –Inter-AC agreement slightly improved compared to repro1

Next steps 16 Expected by end of January 2015: –Re-submissions (COD, GFZ) –Extensions to 2014 (COD, ESA, MIT) Final combined solutions due by end of February 2015 If time allows, study station residual time series: Form long-term cumulative solution –Revised discontinuity list –Modeling of post-seismic deformations ULAB North residuals

Thanks for your attention! 17

Pole coordinates 18 AC / ig2 X-pole differences AC / ig2 Y-pole differences

Pole rates 19 AC / ig2 X-pole rate differences AC / ig2 Y-pole rate differences

Length of day 20 AC / ig2 LOD differences Normalized periodograms

Origin: X component 21 AC / ig2 X origin offsets Normalized periodograms

Origin: Y component 22 AC / ig2 Y origin offsets Normalized periodograms

Origin: Z component 23 AC / ig2 Z origin offsets Normalized periodograms

Annual – East cod emr esa gfz grg jpl mit gtz ulr 24

Annual – North cod emr esa gfz grg jpl mit gtz ulr 25

Annual – Up cod emr esa gfz grg jpl mit gtz ulr 26

Relative formal errors: pole coordinates 27 σ XPO / median(σ sta ) [mas/mm] σ YPO / median(σ sta ) [mas/mm]

Relative formal errors: pole rates & LOD 28 σ XPOR / median(σ sta ) [mas/d/mm] σ YPOR / median(σ sta ) [mas/d/mm] σ LOD / median(σ sta ) [ms/d/mm]

Relative formal errors: geocenter 29 σ XGC / median(σ sta ) [mm/mm] σ YGC / median(σ sta ) [mm/mm] σ ZGC / median(σ sta ) [mm/mm]