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VLBI Network Simulator (VNSIM)

The Very Long Baseline Interferometry Network SIMulator (VNSIM), provides an integrated platform assisting radio astronomers to design the Very Long Baseline Interferometry (VLBI) experiments and evaluate the network performance with a user-friendly interface. Though VNSIM is motivated to be designed for the East Asia VLBI Network, it can also be expandable to other VLBI networks and generic interferometers. The software package not only integrates the functionality of plotting $(u,v)$ coverage, scheduling the observation, and displaying the dirty and CLEAN images, but also further extends to add new features such as the sensitivity calculation of a certain network and multiple-satellite space VLBI simulations (still under testing). In addition, VNSIM provides flexible interactions on both command line and graphical user interface and offers friendly support for log report and database management. VNSIM also supports multiprocessing accelerations, enabling to handle large survey data. To facilitate the future development and update, each simulation function is encapsulated in different Python module allowing independently invoking and testing.

As the above figure shows, the framework of VNSIM mainly consists of six function clusters, parameter configuration and other common GUI components such as status bar, menu bar, and logging information. The six cluters answer for four fundamental simulation functions, including (u, v) coverage plotting, imaging, observation survey and simulation of visibility data (clusters 1-4), and two additional functions with parameter evaluation and database management (clusters 5-6). As mentioned before, the programming of these function clusters are mutually independent, so each of them can be directly invoked with appropriate configurations and run separately.

Python Scripts	Functions
Func_uv.py	Basic UV
Func_uv_advanced.py	All-sky, All-year, Multi-srcs UV
Func_obs.py	Az-el, Sky Survey
Func_img.py	Beam, Map, Clean map, Model
Func_radplot.py	radplots, uvplots of read data
Func_survey_all.py	Pipeline to survey Multiple sources
Func_cal.py	Parameter evaluation
Func_db.py	Database Editor
Func_gui.py	A GUI tool

As the Table shows, we implement 8 runnable python scripts corresponding to these above functions. All the scripts are provided with command-line options and arguments, and $(u,v) $ plots and imaging related function require users to specify the observation setting in the configuration file. The Func_survey_all.py scripts provide a simulation routine for survey observation, whic not only provides the image results of $(u,v)$ plots, dirty map and clean map, but also records some quantitative information including the beam size, best observation time range, and dynamic ranges. We highly recommend users to run the packages in command-line mode, especially for evaluate multiple sources, but we also provide a friendly GUI for beginners.