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Requirements for Potential Analysis Centres

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

Introductive Information

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

Basic Requirement

The first step is to check if the SINEX files have the right format (in form and content) and can be read by the combination routines and its pre-combination programs. Currently, the agreed data are unconstrained normal equations in the Sinex format. The submitted files have to contain at least the following blocks (besides the Header Line):

A guideline for SINEX files can be found here. The input data have to contain station coordinates, EOP (X- and Y-Pole, UT1-UTC, LOD, X- and Y-Pole-Rate, Nutation dX and dY) as unconstraint normal equation. 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 Centre. For first tests, it is sufficient to submit some test files for about one year, i.e. about 100 sessions (for practical reasons via ftp if possible). These files can be checked at the Combination Centre 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 about the last 10 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 testing-phase, the candidate institution has to formally make an application as an IVS Associate Analysis Centre to the IVS Directing Board (see Approval by the IVS). Within the testing-phase the contribution will be checked for

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

The testing-phase may last from several months up to one year or longer according to occurrence of analysis or software problems, availability of man-power, etc.

Become an IVS operational Analysis Centre

After a successful termination of the testing-phase, the applying institution formally applies to become an IVS operational Analysis Centre and the solution will be taken over fluently into the combined solution without additional tests.

Bid for Analysis Centres

Additional Data

Beside the data which are needed for the combination, the Sinex files should by default contain information (meta data) 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.

Approval by the IVS

After successfully testing within the regular combination process by the IVS Combination Centre, the candidate institution should contact the IVS Analysis Coordinator and make a proposal to the IVS Directing Board in order to be approved as operational Analysis Centre as describes here.
Before the candidate applies for an operational Analysis Centre, it is unavoidable that he has already been IVS Associated Member for some time. The application form to become an IVS Analysis Centre can be found here. A formal description of the definition of IVS components can be found in the IVS Terms of Reference.


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

Appendix I Template for analysis description

Template for analysis description					Version 2.0 (2011-05-26)

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. Authentic 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 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 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 positions' X,Y,Z components 
   and 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 a prioris (state which a prioris)
   b) Select individual sources to be estimated for this session (please state 
   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
on where documentation of your software can be found if software is not in use by 
other IVS Analysis Centers (e.g., publications, Web page)

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

Personnel assigned to Analysis Center functions

How many years is the personnel involved in VLBI data analysis?

Please indicate in sufficient detail which analysis center functions you will

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

This form should be signed by an official committing 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_forms.txt)