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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.
|Last modified: Thu Oct 2 08:45:11 EDT 2008||Send comments to Chopo Ma.|