Screenshots are from VieVS version 2.1.
A Continuous VLBI Campaign CONT11 was scheduled with the NASA sked program to be observed in the second half of September 2011. The plan for the CONT11 campaign was to acquire state-of-the-art VLBI data over a time period of about two weeks to demonstrate the highest accuracy of which the current VLBI system is capable. The stations participated in the CONT11 are shown in the Figure below (WARK12M had to cancel participation due to technical problems).
In our exercise you should make 24-hour schedules for the first two days of the original CONT11 campaign, i.e. September 15 and 16, 2011 starting at 5pm. In the scheduled network following 10 stations should be included (we take fewer stations to speed up the processing):
All baselines (except for baselines with station TIGOCONC) should have a minimum signal-to-noise ratio of 20 in the X-band and 15 for the S-band. For station TIGOCONC, which is a small 6 meter transportable telescope, the desirable SNR is lower, namely 15 for X-band and 12 for S-band. This exception for station TIGOCONC has to be set in an external file: snrmin.txt stored in VieVS/CATALOGS/ .
When the snrmin.txt is changed and stored according to our demands, the VieVS software can be started.
Save + Runbutton.
Here are screenshots of the used GUI menus Scheduling - Parameters and Run - Run options:
Repeat the scheduling for the second session taking place on September 16, 2011. You have to change only the datum in the menu bar Scheduling.
The created schedules and the scheduling protocol can be found in VIEVS/DATA/SCHED/2011/ .
You have now created two schedules - instructions for the radio telescopes which source will be observed at which time. Because there do not exist any real observations which would follow your instructions, we will simulate artificial time delays.
In VieVS the simulated VLBI observables are generated taking into account the three most important stochastic error sources in VLBI, i.e. tropospheric wet delay, station clock, and measurement error.
Save + Run.
Screenshots of the discussed GUI menues (File - Set input files, Simulation and Run - Run options):
The simulated NGS files will be stored in VIEVS/DATA/SIM/2011/ .
The analysis of the artificial observations will be done in the same way as it would be done for the real time delays. It is only recommended not to use any outliers and option directories.
In the analysis of a 24 hour session we usually estimated: clock parameters, zenith wet delays, troposphere gradients, EOP and station coordinates. For the parameterization of these parameters use the default settings of the GUI.
Save + Runbutton.
Below you find the related GUI screenshots (File - Set input files, Estimation and Run - Set input files):
Use the GUI plotting tool and plot the baseline length repeatabilities computed from these two sessions.
In the menu bar Plotting - Session analysis load your subfolder with the results and click on the button
Basel. len. rep.:
With the module VIE_GLOB one can estimate station coordinates from both sessions in a common adjustment.
Before selecting the options in the GUI, an external .txt file with names of the stations which will be used for datum definition (NNT+NNR) has to be created. The recommended stations for datum definition are listed in the Figure below. Save this file in VIEVS/DATA/GLOB/TRF/DATUM/ . (In case you want to estimate the source coordinates, another datum file for the sources has to be created.)
Save + Runbutton.
Below you find screenshots of the discussed setup in the GUI (Global solution - Select parameters, Global solution - TRF/CRF parameterization and Run):
The results are stored in a .txt file in VIEVS/OUT/GLOB/_ESTIMATES/ subfolder and the plots in VIEVS/OUT/GLOB/_PLOTS/subfolder.
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