slr-gnss analysis in the framework of the itrf2013 ... - nasa · gnss-slr combination: satellite...

1) Bundesamt für Kartographie und Geodäsie, Frankfurt am Main, Germany2) Astronomical Institute, University of Bern, Switzerland

3) Institut für Astronomische und Physikalische Geodäsie, TU München, Germany

SLR-GNSS analysisin the framework of theITRF2013 computation

D. Thaller1), O. Roggenbuck1), K. Sosnica2), P. Steigenberger 3), M. Mareyen1), C. Baumann 2), R. Dach2), A. Jäggi2)

Overview

▪ ITRF2013 called for pre-combined solutions (forcomparison purposes)

▪ SLR-GNSS combined solutions:− GPS / GLONASS: microwave observations− LAGEOS and Etalon: SLR observations− GPS / GLONASS: SLR observations

▪ Impact of datum definition on pre-combined solutions:− Geocenter− Scale− Earth Rotation Parameters (ERPs)

ILRS Workshop 2013, Fujiyoshida, Japan11.-16. Sept. 2013 2

GNSS-SLR combination:Satellite co-location

ILRS Workshop 2013, Fujiyoshida, Japan 311.-16. Sept. 2013

1-day

1-day NEQ

GNSS-SLR combination:Satellite co-location

ILRS Workshop 2013, Fujiyoshida, Japan 411.-16. Sept. 2013

1-day

1-day NEQ

IGS processing at the CODE Analysis Center

ILRS processing at the BKG Analysis Center

GNSS-SLR combination:Satellite co-location

Using co-locations at GNSS satellites for connecting both techniques

ILRS Workshop 2013, Fujiyoshida, Japan 511.-16. Sept. 2013

1-day

1-day NEQ

GNSS tracking

Studies presented here: 2009/Jan – 2013/Oct

ILRS Workshop 2013, Fujiyoshida, Japan11.-16. Sept. 2013 6

1996 1998 2000 2002 2004 2006 2008 2010 2012 20140

100

200

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# O

bs /

Day

GPS (2) GPS (2) + GLONASS

2 3 6 6 - 24

Strategy for datum definition

1) Use GNSS core network (~ 90 sites)− Dense network / many stations− (almost) identical network for each week− Orientation (= ERPs) should be defined well− Problems in geocenter may occur (artefacts from GNSS orbit modeling)

2) Use SLR core network (usually < 10 sites)− Sparse network− Changing network configuration from week to week− Orientation (= ERPs) may suffer− Geocenter should be unaffected by GNSS orbit modeling issues

3) Use combined GNSS+SLR core network− Benefit from GNSS (-> ERPs) and SLR (-> origin) ???− Not independent from local ties used in reference frame (ITRF2008)

ILRS Workshop 2013, Fujiyoshida, Japan11.-16. Sept. 2013 7

Geocenter coordinates

▪ Using GNSS sites shows slightly different signal than using SLR sites

▪ Using SLR sites reproduces SLR-only solutionILRS Workshop 2013, Fujiyoshida, Japan11.-16. Sept. 2013 8

2009 2010 2011 2012 2013 2014−30

−20

−10

0

10

20

30

GC

C−Y

[mm

]

LAGEOS−Etalon: NNR+NNTSLR−GNSS: NNR+NNT GNSSSLR−GNSS: NNR+NNT SLR

Geocenter coordinates

▪ Using GNSS sites shows clearly different signal than using SLR sites: draconitic year

▪ Using SLR sites reproduces SLR-only solutionILRS Workshop 2013, Fujiyoshida, Japan11.-16. Sept. 2013 9

2009 2010 2011 2012 2013 2014−80

−60

−40

−20

0

20

40

60

80

GC

C−Z

[mm

]

LAGEOS−Etalon: NNR+NNTSLR−GNSS: NNR+NNT GNSSSLR−GNSS: NNR+NNT SLR

Geocenter coordinates

▪ Using GNSS+SLR sites for datum definition does not improve situation: GNSS is still dominating

▪ GNSS orbit modelling issues propagate into combinationILRS Workshop 2013, Fujiyoshida, Japan11.-16. Sept. 2013 10

2009 2010 2011 2012 2013 2014−80

−60

−40

−20

0

20

40

60

80

GC

C−Z

[mm

]

NNR+NNT GNSS sitesNNR+NNT SLR sitesNNR+NNT GNSS+SLR sites

Earth rotation parameters

▪ Using SLR core sites results in noisier time series than using GNSS core sites

▪ Using GNSS+SLR sites slightly better than GNSS-only

ILRS Workshop 2013, Fujiyoshida, Japan11.-16. Sept. 2013 11

2009 2010 2011 2012 2013 2014−800

−600

−400

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0

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800

Δ X

−pol

e [μ

as]

NNR+NNT SLR sitesNNR+NNT GNSS sitesNNR+NNT GNSS+SLR sites

Summary and outlook -1-

▪ Weekly pre-combined GNSS-SLR solutions using satellite co-locations were studied

− SLR observations to GPS/GLONASS are additionally used (compared to „standard“ ITRF contributions)

▪ Geocenter coordinates are highly influenced by GNSS orbit modelling as soon as GNSS core network is included in datum definition

▪ ERPs are more stable if dense GNSS core network is included in datum definition

▪ Scale is independent of the set of core sites used (not shown here)

ILRS Workshop 2013, Fujiyoshida, Japan 1211.-16. Sept. 2013

Summary and outlook -2-

▪ There is no set of core sites that is optimal for all parameters of interest

▪ GNSS orbit modelling (solar radiation pressure) is still a big issue:

− Using 3-day orbits (instead of 1-day orbits) would help already

− Constraining of once-per-rev parameters reduces the impact on geocenter

▪ The increased amount of SLR tracking to GLONASS helps to strengthen the connection via satellites

ILRS Workshop 2013, Fujiyoshida, Japan 1311.-16. Sept. 2013

Thanks for your attention!

ILRS Workshop 2013, Fujiyoshida, Japan 1411.-16. Sept. 2013

This work was partly funded by the DFG Research Project (FOR1503): „Space-Time Reference Systems for Monitoring Global Change and for Precise Navigation in Space“

Earth rotation parameters

▪ Using SLR core sites results in noisier time series than using GNSS core sites

▪ Using GNSS+SLR sites slightly better than GNSS-only

ILRS Workshop 2013, Fujiyoshida, Japan11.-16. Sept. 2013 15

2009 2010 2011 2012 2013 2014−800

−600

−400

−200

0

200

400

600

800

Δ Y

−pol

e [μ

as]

NNR+NNT SLR sitesNNR+NNT GNSS sitesNNR+NNT GNSS+SLR sites

Geocenter coordinates

ILRS Workshop 2013, Fujiyoshida, Japan11.-16. Sept. 2013 16

2009 2010 2011 2012 2013 2014−30

−20

−10

0

10

20

30

GC

C−X

[mm

]

LAGEOS−Etalon: NNR+NNTSLR−GNSS: NNR+NNT GNSSSLR−GNSS: NNR+NNT SLR

Scale

ILRS Workshop 2013, Fujiyoshida, Japan11.-16. Sept. 2013 17

2009 2010 2011 2012 2013 2014−2

−1.5

−1

−0.5

0

0.5

1

1.5

2

2.5

3

Sca

le w

.r.t.

SLR

F200

8 [p

pb]

NNR+NNT GNSSNNR+NNT GNSS/SLRNNR+NNT SLR