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Development of a VLBI Intra-Technique Combination Strategy for CRF Determination Andreas Iddink – 16.09.2013
Development of a VLBI Intra-Technique Combination Strategy for CRF Determination
Andreas Iddink, Axel Nothnagel, Thomas Artz
16.09.2013
Development of a VLBI Intra-Technique Combination Strategy for CRF Determination Andreas Iddink – 16.09.2013
• Motivation• Consistency of ICRF / ITRF / EOPs
• Combination process
• First Results
• Inclusion of X / Ka Sources• Outlook
Outline
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Development of a VLBI Intra-Technique Combination Strategy for CRF Determination Andreas Iddink – 16.09.2013
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ICRF2
Motivation
VTRF
● 1 single monolitic solution ● 1 software package● Only indirect control● Consistency (only) with VTRF2008
VLBI
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Development of a VLBI Intra-Technique Combination Strategy for CRF Determination Andreas Iddink – 16.09.2013
Motivation
3IVS Combination
AC 1..n
IERS Combination & Products
ILRS Combination IDS Combination
ITRF
IGS Combination
AC 1..n AC 1..n AC 1..n
Development of a VLBI Intra-Technique Combination Strategy for CRF Determination Andreas Iddink – 16.09.2013
Motivation
3IVS Combination
AC 1..n
IERS Combination & Products
ILRS Combination IDS Combination
ITRF ICRFEOPs
IGS Combination
AC 1..n AC 1..n AC 1..n
Development of a VLBI Intra-Technique Combination Strategy for CRF Determination Andreas Iddink – 16.09.2013
Single Session Combination
VEVEST
VEST
VEST
VEST
VEST
VEST
VEST
E
SO 1..NAnalysis Centers
VEVE
ST
VEST
VEST
VEST
VEST
VEST
VEST
E
SO
VEVE
VEST
VEST
VEST
VEST
VEST
VEST
E
SO
combined single session NEQs
● Different sofware packages● Different analysis centers● Different analysis strategies
● Station positions (ST)● EOPs (E)● Source positions (SO)
# NEQs
# NEQs
# NEQs
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Development of a VLBI Intra-Technique Combination Strategy for CRF Determination Andreas Iddink – 16.09.2013
Global Combination Strategy
VEVE
VEST
VEST
VEST
VEST
VEST
VEST
E
SO 1..NAnalysis Centers
VEVE
VEST
VEST
VEST
VEST
VEST
VEST
E
SO
VEVE
VEST
VEST
VEST
VEST
VEST
VEST
E
SO
combined single session NEQs
● session selection● arc / global
parameters● parameterization
Free choice of:
VLBI intra-technique NEQ
STVEL
SO
EOPs
# NEQs
# NEQs
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Development of a VLBI Intra-Technique Combination Strategy for CRF Determination Andreas Iddink – 16.09.2013
Single Session Combination Flowchart
ACs SINEX
Transformationto equal epochsto equal a priori values
PreprocessingSINEX-format checksparameter adjustment (e.g., CPWL to offset/rate)...
Computation of individual solutionsdatum definitions inversion
Computation of combined solutionweighting of NEQs (e.g., variance component estimation) accumulation of NEQsdatum definitioninversion
● normal equation matrix● parameter list● apriori values● solution statistics● meta data● ...
Outlier testOutlier existent?
Exclude ACyes
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no
Development of a VLBI Intra-Technique Combination Strategy for CRF Determination Andreas Iddink – 16.09.2013
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Combination EnvironmentBoSC - BonnSolutionCombination
DOGS-CS
ADDNEQ2
BOSC_STACK
database management
support input files
Final estimated results e.g.,● time series of source positions● residuals of EOPs ● global solved CRF or TRF
Consistent datum-free normal equation systemimportant for further processingand investigations
Development of a VLBI Intra-Technique Combination Strategy for CRF Determination Andreas Iddink – 16.09.2013
Residuals AC w.r.t. Combi (0552+398)
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AC Bias [µas] RMS [µas] #Ses
2 120 201
- 4 75 205
12 80 203
9 91 205
Development of a VLBI Intra-Technique Combination Strategy for CRF Determination Andreas Iddink – 16.09.2013
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X/Ka Inclusion
VEVE
VEST
VEST
VEST
VEST
VEST
VEST
E
X/S 1..N-1Analysis Centers
VEVE
VEST
VEST
VEST
VEST
VEST
VEST
E
X/S
VEVE
ST
VEST
VEST
VEST
VEST
VEST
VEST
E
X/S & X/Ka
VLBI intra-technique NEQ
STVEL
EOPs
VEVE
ST
VEST
VEST
VEST
VEST
VEST
VEST
E
X/S & X/Ka
X/S & X/Ka
combined single session NEQs
Development of a VLBI Intra-Technique Combination Strategy for CRF Determination Andreas Iddink – 16.09.2013
Adding X/Ka Catalogs
Issues to be investigated● Non ITRF telescope positions● Frequency dependence● Core shift● „Source Tie“
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*
*
**
**
*X/S catalog** **
X/Ka catalog*
*
Development of a VLBI Intra-Technique Combination Strategy for CRF Determination Andreas Iddink – 16.09.2013
Outlook
• Comparison of ADDNEQ2 / DOGS-CS / BOSC_STACK● Differences, individual shortcomings, numerical problems
• Estimation and comparison of individual CRFs• Parameterization of special handling sources
• Continuous Piecewise Linear (CPWL) Function approach• Astrophysical phenomena background• Cooperation with Max Planck Institute for Radio Astronomy Bonn
→ VLBI Output Contribution to inter-technique (VLBI, GNSS, SLR, DORIS) combination
[IERS Technical Note No. 35]
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