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  • October 23, 2008: VTRF2008a_IVS.SSC-1.txt, vtrf2008a.sit, vtrf2008a.vel -- Dear Colleagues,

    After discussion with Axel Nothnagel we decided to use the IVS
    combination TRF for ICRF2 solutions instead of ITRF2005. The IVS
    solution corrects some of the problems in ITRF2005.  The IVS solution
    is VTRF2008a. It is not the final IVS solution but close enough for
    our use now. Sarah Bockmann (at Bonn with Axel) provided the VTRF
    positions and velocities. I have attached 3 files:
    
    1) VTRF2008a_IVS.SSC-1.txt   2) vtrf2008a.sit
    3) vtrf2008a.vel
    
    To make last 2 files, I just converted the IERS SSC format file into
    CALC/SOLVE a priori site and velocity file format. The VTRF file has
    95 sites. This file has all of the sites (sent out by Dave Boboltz)
    that will be used in the NNT/NNR constraints.To be complete, I added a
    priori positions and velocities for the remaining sites using a priori
    files used for our latest quarterly solution.
    
    One issue regarding making solutions is how to handle GILCREEK after
    the Denali earthquake in Nov. 2002. For CALC/SOLVE, there are a couple
    of different ways to handle it: 1) estimate global spline parameters
    for GILCREEK, where the parametrization is specified in the control
    file or 2) apply an a priori model for the post seismic variation in
    the control file.  IF you have any questions about how this works in
    SOLVE, please contact me.
    
    In the solve a priori mod site position file, I only included at most
    2 lines - the positions before and after the episodic event. At
    present SOLVE can't use anything more.  The Bonn group made a
    modification that allows one to use an arbitrary number of positions
    and velocities for a site.  Note that in the VTRF2008a file there is a
    sequence of positions and velocities for GILCREEK corresponding to the
    nonlinear variation following the earthquake. Non SOLVE users might
    use this to model the variation unless they have some other way to do
    it.
    
    Dan MacMillan
    Chopo Ma
    

  • October 23, 2008: -- ICRF2 WG members,

    Some modification needs to be made to the list of no-net-rotation
    sources for the 2 CRF solutions in which Chopo's list of 57 bad
    sources are treated as arc parameters in one solution and global
    parameters in the other. The original plan was to use the 212 ICRF1
    defining sources. However, the list of 57 bad sources contains 11
    ICRF1 defining sources. This would mean that the reference frames
    were defined by 201 sources in one case and 212 in the other case.
    Therefore, the no-net-rotation constraint should use only 201 of
    the ICRF1 defining sources. The 11 ICRF1 sources to remove are:
    
       0007+171, 0014+813, 0235+164, 3C138, 0556+238, 0738+313, 0820+560,
       1038+064, 1308+326, 2052-474, and 2145+067.
    
    Best Regards,
    David Gordon
    Chopo Ma
    

  • October 23, 2008: -- ICRF2 WG members,

    There are 3 known gravitational lenses in the VLBI databases which
    should be excluded from time series and CRF catalog solutions. The
    lenses and their components have the following names in the
    databases:
    
           0218+35A 0218+35B 0218+357
           1422+231
           1830-21A 1830-21B 1830-211
    
    David Gordon
    GSFC VLBI Analysis Center
    

  • October 16, 2008: -- Dear Colleagues,

    Dear Colleagues,
    
    Elena has noted that the reference sources for the two catalogues due by 
    Nov. 1 were not specified.  For simplicity and uniformity I propose to 
    use the ICRF defining sources relative to ICRF.  While these are not 
    ideal, they should be sufficient for the purposes of these catalogues.  
    To easily identify these catalogues, let us use xxx005a.cat for the 
    solution with all sources global and xxx006a.cat for the solution with 
    the selected sources treated with "special handling".  Please let me or 
    the group know if there are other omissions or ambiguities in the 
    catalogue configuration.
    
    Yours,
    
    Chopo
    

  • October 14, 2008: -- Dear Colleagues,

    send you list of the "best" sources (in sense of predictability of their motion):
    0202+149
    0602+673
    0727-115
    1044+719
    1101+384
    1726+455
    2145+067
    2356+385
    Parameters of motion of each sources are very similar for different 
    time series.
    Next sources show predictible motion too but their parameters of
    motion differ for different time series.
    0014+813
    0059+581
    0133+476
    0212+735
    0234+285
    0528+134
    0552+398
    0556+238
    0749+540
    0804+499
    0851+202
    0923+392
    0955+476
    1300+580
    1308+326
    1357+769
    1418+546
    1611+343
    1638+398
    1739+522
    1741-038
    1803+784
    2037+511
    2200+420 
    
    Best regards,
    Vladimir.
    

  • October 14, 2008: eop-format.txt -- Dear Colleagues,

    The action items from the Dresden meeting include the TRF and EOP from 
    the catalogues.  For the TRF Axel has reminded me that the full SINEX is 
    not needed.  The site coordinates should just use the format of the 
    +SOLUTION/ESTIMATE section in the SINEX files together with the +SITE/ID 
    section.  The covariances are not required for this comparison.  For the 
    EOP time series the format should be as in 
    http://vlbi.geod.uni-bonn.de/IVS-AC/data/eop-format.txt .
    
    While the reference sites for the NNT/NNR conditions were distributed by 
    Dave Boboltz, the specific a priori positions and velocities for 
    ITRF2005 were not discussed.  Axel has noted that the ITRF2005 values 
    are not adequate in some respects, particularly for the Russian stations 
    for which the data set then available was weak.  It would be better to 
    use a TRF that includes more recent data, which it is hoped will be 
    available shortly.  In the meantime the catalogue setups should proceed 
    with some interim TRF.
    
    If there are other refinements or clarifications needed for the 
    catalogue specification, please bring them to the attention of the 
    working group.
    
    Yours,
    
    Chopo
    

  • October 13, 2008: -- Dear analysts,

      As decided in Dresden, the observed radio stars have to be
    excluded from the catalogs and time series production. Follow a
    list of identified radio stars, except for the last one (1830+011) where the 
    status of radio star is not clear.
    
    B1950 name   IVS name   Other name
      0236+610    LSI61303   GC236+61
      0459-753    HD32918
      1612+339    SIGCRB
      0334+004    HR1099
      0323+285    UXARI
      1458-083    HD132742
    
      1830+011    LANA              NED information: probably galactic
    
      Best regards
      Anne-Marie
    

  • October 10, 2008: ICRF2_NNR_Stations2.dat -- Dear Colleagues,

    As several colleagues have pointed out, the formal errors on
    the station position depend on the epoch and since a reference epoch
    of 1997.01.01 was used, stations that began observations more
    recently, may not have met the <2mm criteria.  I examined the
    original spool file looking at the "Minimum sigmas" and
    also ran an additional solution with a more recent reference
    epoch as a check.
    
    After doing these checks, two stations TIGOCONC and SVETLOE
    have been added back to the list of stations for the NNR/NNT
    constraints.
    
    Cheers,
    Dave 
    

  • October 8, 2008: ICRF2sub2.doc -- Dear Colleagues,

    Dear Colleagues,
    
    Attached is an updated description of the procedures for submitting
    and retrieving files for the ICRF2 work.  The procedures are the same
    as before but new directories have been added for the TRF and EOP
    results.  Please let me know if there are omissions or ambiguities.  I
    would encourage all the WG members to test the ftp procedures to see
    if they get proper access to the directories.
    
    Yours,
    
    Chopo 
    

  • October 7, 2008: ICRF2_NNR_Stations.dat -- Dear Colleagues,

    Attached is a list of 25 stations to be used in the 
    NNR/NNT constraints for use in producing ICRF 2 catalogs.  
    The criteria for selection of these stations is as follows:
    
    1.  Participated over a time span > 5 years
    2.  >50 sessions used
    3.  >30000 observations used
    4.  Position errors <2mm in X,Y, or Z  (ref. epoch 1997.01.01)
    5.  Participated after 2005.01.01
    6.  No episodic motion
    
    Please let me know if you have any trouble reading the
    file or if there is a problem with the list.
    
    Cheers, 
    Dave Boboltz
    

  • October 6, 2008: badsources.txt -- Dear Colleagues,

    Attached is a list of 57 sources for special handling in making the
    next test catalogues.  The selection is somewhat arbitrary since no
    single objective statistical test has yet been found.  The work was
    done largely by David Gordon using the time series gsf003a with
    additional analysis and suggestions from Zinovy and Alan.  The
    criteria are:
    
    1. systematic trends detected visually by D. Gordon - largest group
    2. velocity >20 microarcsec/yr, sigma <5 microarcsec/yr from Z. Malkin using gsf002a
    3. >1000 points, wrms >0.3 mas in both components
    4. >=50 points, chi-square >3 in either component
    5. chi-square >10 in either component
    
    How each source is to be handled is up to the individual analysis
    center and the options in their software.  For the first ICRF the
    "other" sources were treated as arc parameters.  Since the ICRF2
    solution is to have CRF, TRF and EOP results, some way of constraining
    the position variation is probably desirable, at least for the sources
    with many observations.  Linear motion, splining or some stochastic
    process could be used, depending on the nature of the variation and
    density of data.
    
    The list of NNT/NNR stations for the catalogues has been considered
    and should be distributed tomorrow.  I have received the list of
    "best" and "worst" sources from Vladimir related to the time series
    but need to understand it better.
    
    Yours,
    
    Chopo
    

  • September 26, 2008: gsfc.2008.09.26.arc -- ICRF2 Working Group members, Chopo has asked me to send out GSFC's session list for time series solutions. I've just updated it and attached it to this message. We use all sessions that are not commented out with an asterisk (*) in the first column. - David Gordon
  • March 17, 2008: ts4.arc -- CRF2 Working Group members, At the IVS meeting last week, I was asked to provide GSFC's list of sessions we are using for our source time series solution. I have updated the list and am attaching it. It is in the form of a Solve/Globl arc list. The database name is followed by the version number at GSFC. Your version number may differ. If the line starts with an asterisk (*), then the session is commented out and not used in the solution. Please contact me if you have any questions. - David Gordon
  • October 17, 2007: crf_list_2007Oct17.txt -- the list of all CRF databases (designated XN), including multiple baseline as well as single baseline experiments.
  • August 29, 2007: crossref_USNO_IVS.txt (crossref_USNO_IVS.xls) -- The cross-reference list for the USNO - IVS databases. There are 1091 databases with different names.
  • August 7, 2007: icrf2_f.i -- A draft format format (Version 2) for ICRF-2 time series submissions.
  • June 5, 2007: sourcelisticrf2.txt -- A list of sources compiled by Leonid and checked by Anne-Marie. For the catalogues and time series for the ICRF-2 work the source names should be taken from the third column, labeled B1950-name.
  • May 24, 2007: file_submission_draft.txt -- A draft description of the procedures for submitting and retrieving files for the ICRF-2 work.
  • May 24, 2007: 163unstable_sources.txt -- The list of 163 unstable sources based on time series analysis made by Martine Feissel-Vernier, as requested at the ICRF-2 working group meeting in Vienna. The first colomn is the IERS name (8 caracters) and the second the IVS name (maximum 8 caracters) if different.
  • May 24, 2007: vcs_database_list.txt -- The list of VLBA Calibrator Survey (VCS) databases.