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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
300
400
500
600
# 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
−200
0
200
400
600
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