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

2

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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