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Requirements for Potential Analysis Centers

This document describes the requirements for potential Analysis Centers to take part in the regular IVS combination as proposed by the IVS Combination Center at BKG.

   

Introduction

In order to contribute to any IVS product, it is required to be at least an IVS Associate Analysis Center. The application form can be found in the appendix below.

   

Basic Requirements

First, verify that the SINEX files have the correct format (in form and content) and can be read by the combination routines and their corresponding pre-combination programs. Currently, the agreed data are unconstrained normal equations in the SINEX format. The submitted files must contain at least the following blocks (in addition to the Header Line):

  • FILE/REFERENCE,
  • SOURCE/ID,
  • SITE/ID,
  • SITE/ECCENTRICITY,
  • SOLUTION/EPOCHS,
  • SOLUTION/STATISTICS,
  • SOLUTION/APRIORI,
  • SOLUTION/NORMAL_EQUATION_VECTOR,
  • SOLUTION/NORMAL_EQUATION_MATRIX.

A guideline for SINEX files can be found here. The input data must contain station coordinates, EOP (X- and Y-Pole, UT1-UTC, LOD, X- and Y-Pole-Rate, Nutation dX and dY) as unconstrained normal equations. It is preferable if they also include source positions. The analysis must meet the current standards of the IERS and the IVS.

Currently, only 24h rapid sessions R1 and R4 are combined as they can be found at the IVS Data Center. For preliminary tests, it is sufficient to submit some test files for approximately one year, i.e. about 100 sessions (for practical reasons via ftp if possible). These files can be checked at the Combination Center for the right format and content. After a positive preliminary test, a test on a longer time span will follow which should include sessions of approximately the last ten years.

  

Inclusion in Routine Combination Process

The second step is a test-wise inclusion of the new contribution into the rapid routine combination process. As soon as the analyst is ready to submit on a regular basis, data should be submitted following the announcements of the IVS analysis messages (the technical part has to be determined yet). To subscribe for the IVS Analysis message please follow the instructions at IVS analysis topics mailing list. This test phase is meant for demonstrating how the new solution matches into the combination and the reliability of data submission.

Before the new solution enters the testingphase, the candidate institution has to formally submit an application to be an IVS Associate Analysis Center to the IVS Directing Board (see Approval by the IVS, below). Within the testingphase, the contribution will be checked for:

  1. Format correctness (in co-ordination with the IVS Combination Center).
  2. Timeliness/reliability of the contribution.
  3. The quality within the combined solution, regarding outlier, data gaps or systematic effects within the solution.

The testingphase may last from several months to one year or longer, depending on occurrence of analysis or software problems, availability of man-power, etc.

        

How to become an IVS operational Analysis Center

After a successful completion of the testingphase, the applying institution must formally apply to become an IVS operational Analysis Center. After this, the solution will be incorporated with the combined solution without additional tests.

           

Bid for Analysis Centers

        

Additional Data

In addition to the data which are needed for the combination, the SINEX files should, by default, contain information (metadata) describing the analysis process. To cover this issue, the IVS Analysis Coordinator drafted a document which contains a template for analysis description. The document can be found in the appendix (below).

Approval by the IVS

Candidate members will be tested to ensure compatibility with the regular processes at the IVS Combination Center, after which the candidate institution should contact the IVS Analysis Coordinator and submit a formal proposal for approval as an operational Analysis Center to the IVS Directing Board. The process is explained in greater detail here. Candidates should also already be an IVS Associate Member.
The application form to become an IVS Analysis Center can be found below (Appendix II OPAC-form). A formal description of the definition of IVS components can be found in the IVS Terms of Reference.

         

Questions

The IVS attempts to increase the number of independent software packages, and encourages institutions to apply to become an IVS Analysis Center and/or contribute to IVS products. For further information, please contact the staff of the IVS Combination Center.

1. Origin of input data

               a) Correlator output from IVS Data Center (Version 1)    
               b) Databases from IVS Data Center (please state Version number)    
               c) NGS file from IVS Data Center    
               d) other (please state details)
       

2. Authentication processing steps after data retrieval

               a) Re-Calc    
               b) Re-Calibration (which)    
               c) other (please state details, e.g. if fully processed)
           

3. Origin of meteorological data

               a) Use database content    
               b) Use NGS file content    
               c) other (please state details)
        

4. Use of numerical weather model

               a) none    
               b) other (state origin and describe procedure)
       

5. Setting of mapping functions

               a) use database content    
               b) other (please state details)
    

6. Origin of cable cal data

                a) Use database content    
                b) Use NGS file content    
                c) other (please state details)
       

7. Application of cable cal flags

                 a) all on by default    
                 b) use database settings    
                 c) other (please state details)
       

8. Selection/settings of geophysical models. If detailed information on geophysical models and a priori interpolation schemes is given in a separate comment section, options are:

                 a) use database settings  
                 b) replace database settings (state which)   
                 c) other (please state details)  
                 If no further information on geophysical models is given elsewhere, please describe all models here.  
       
       8.1 A priori Earth orientation:   
                 - A priori precession/nutation model: (e.g. IAU2000A  precession-nutation, IAU2006 precession model)   
                 - A priori short-period tidal variations in X, Y and UT1: e.g. IERS Conventions 20xx  
     
       8.2 A priori geophysical models:   
                 - Solid Earth tide: e.g. IERS Conventions 20xx   
                 - Ocean loading    
                 - Pole tide: e.g. Mean pole coordinates according to IERS Conventions 20xx   
                 - Atmospheric loading   
                 - Antenna thermal deformation: e.g. IVS antenna thermal expansion model of Nothnagel (2009) using daily mean temperatures   
                 - Axis offsets: e.g. Taken from the IVS Analysis Coordinator's file antenna-info.txt 
   

9. Parameterization N.B.: Pre-reduced datum-free normal equations are only interim products, not solutions as such. For analyses of the IVS, it is mandatory that these normal equations contain coefficients for all site position X,Y and Z components, as well as all EOP components (Xp, Yp, dXp/dt, dYp/dt, UT1-TAI, LOD (dUT1-TAI/dt), dX, dY (dX/dt, dY/dt optional, but desirable for the combination with GPS) and all source positions in RA and DEC. Pre-reduced parameters should be described below.

       9.1 Clocks   
                 a) use database settings   
                 b) other (please state details)  
   
       9.2 Atmospheres   
                 a) use database settings   
                 b) other (please state details)  
       9.3 Other parameters   
                  please state details
   

10. Outlier elimination

                  a) use database settings   
                  b) re-activate all flagged observations and re-identify outliers (please state detailed procedure)   
                  c) other (please state details)
   

11. Handling of source positions if not yet in normal equations

                  a) fix all positions to their respective a priori states (identify which a priori)   
                  b) Select individual sources to be estimated for this session (please state details)   
                  c) other (please state details)
      

12. Generation of pre-reduced datum-free normal equations

                  a) Unknown - using standard Solve routines   
                  b) Program is based on authentic classical least squares adjustment and matrix elements of interest are squeezed out by inversion steps 
                  (please state how the square sum of residuals is computed)   
                  c) other (Please state original estimation process and procedure to generate and extract pre-reduced normal equations 
                  Please also state how the square sum of residuals is computed)
       

13. Further details e.g. if EOP are estimated and reported in SINEX file --> Datum constraints (NNR/NNT conditions on stations, or NNR on sources)

   

Appendix II OPAC-form

International VLBI Service for Geodesy and Astrometry (IVS)

Analysis Center Proposal Form

   

Analysis Center Name

   

Type of Analysis Center: Operational ( ) Associate ( ) SAC-SOS ( )

    

Parent/Funding Organization

   

Name of Administrative Contact

   

Name of Primary Technical Contact

    

Local Mailing Address

   
Phone Number                       Fax number
  
E-mail address                     Web address
  

Indicate the software package(s) you use for analysis. Please provide information about where documentation of your software can be found if software is not in use by other IVS Analysis Centers (e.g., publications, Webpage).

   

Describe your specific analysis interests and indicate how you select the data you analyze.

  

Personnel assigned to Analysis Center functions

  

How many years have the personnel been involved in VLBI data analysis?

  

Please indicate in sufficient detail which Analysis Center functions you will perform:

  

Please provide any other information that you feel will be helpful indemonstrating your Analysis Center capabilities to participate in the IVS.

  

This form should be signed by someone with the authority to commit the organization to participate in the IVS as an Analysis Center, and agreeing to work closely with the IVS Analysis Coordinator.

  

For the organization:

Name:                                       Date:
  

(see also: ftp://ivscc.gsfc.nasa.gov/pub/forms/opac-form.txt)

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