Reprocessing the complete history of VLBI observations with VieVS

1. Reprocessing the complete history of VLBI observations with VieVS Sigrid Böhm

2. Why should one do that? • There are new solution methods/strategies. • There is a new software. • You would like to create a database with the optimal parameterization for each session. • You are interested in time series of special parameters (such as ERP) covering the longest time span available. VieVS User Workshop 2011

3. TS of special parameters - EOP • Which sessions to choose for processing? • Define exclusion/suitability criteria • http://vlbi.geod.uni-bonn.de/IVS-AC/data/exclude.txt • No local or regional networks • No sessions with < 3 stations (except for dUT1 determination from Intensives) • No sessions with < 250 observations VieVS User Workshop 2011

4. Create a process list • Basic list to start: e.g. use mk_list to get a list of intensive sessions, add this int_list to exclude.txt and then use mk_list with the option ‘ALL’ except ‘exclude.txt’. • Use preliminary list and process all sessions with a basic parameterization • Then you can use the data in LEVEL3 to make an extended exclude list according to the previously defined criteria and find sessions which are not working properly VieVS User Workshop 2011

5. Interesting parameters for the criteria and for “not working properly“ • DATA/LEVEL3/SUBDIR/opt_sessname.mat: • opt_.total_obs= numberofobservations • length(opt_.stat) = numberofstations • opt_.mo= errorofunitweight a posteriori • opt_.cond= conditionnumberof N-matrix (a bitdifficulttojudge) • In Matlab: you can use diary(‘thisrun.log’) to store the output from the command window, diary off to stop the function VieVS User Workshop 2011

6. e.g. log-file: search for “RCOND” VieVS User Workshop 2011

7. check “geometry“ • Take the information from the files stored in DATA/LEVEL1 and plot the network Regional network → exclude the session

8. Other log-file “messages“ • Problems with tidal ocean loading at station VLBA85 3 • Problems with tidal atmosphere loading at station VLBA85 3 • Problems with non-tidal atmosphere loading at station VLBA85 3 • Problems with thermal correction at station VLBA85 3 • Problems with VMF1 at station VLBA85 3 VieVS User Workshop 2010

9. For the remaining sessions with high 0 • There is no other way than …  • going through all of them individually • finding clock breaks, bad stations etc. • creating hundreds of OPT files • Most welcome alternative …  • write a module for the automatic detection of clock breaks and creation of OPT files VieVS User Workshop 2011

10. Update process list • Add all sessions you have sorted out to the „exclude“-file and run mk_list again • Create an outlier file for each session with some simple parameterization • Decide about your final parameterization according to your needs VieVS User Workshop 2011

11. Somerulesfor EOP estimation • Basic approachfordailyresolution: • Estimate all five EOP xp,yp,dUT1,dX,dY with 1440 min interval • Estimatestationcoordinatesandapply NNR, NNT conditions • Polar motionwithsubdailyresolution: • Do not estimate but fix nutation!! • Fix stationcoordinates VieVS User Workshop 2011

12. R1 and R4 networks VieVS User Workshop 2011

13. Comment on correlation coefficients • The Matlab function corrcoef works correctly but not for our purpose. • It does not take a covariance matrix as input! (Refer to Matlab Help for further info) • Correlation coefficient: Qxx = inv(atpa_.mat); varii = diag(Qxx); Rxy = Qxx./sqrt(varii*varii'); VieVS User Workshop 2011

14. 5 EOP 24 hours, NNR/NNT VieVS User Workshop 2011

15. 3 ERP 1h, nut 24 h, coord fix VieVS User Workshop 2011

16. 3 ERP 1h, nut fix, NNR/NNT VieVS User Workshop 2011

17. 3 ERP 1h, nut fix, coord fix VieVS User Workshop 2011