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We describe here what tools and tool functions could be used in a typical AIPS++ data reduction session. We recommend a GUI based approach. Although a command line approach is possible for using the same tools and tool functions, it will require a lot of typing and ability to remember the various arguments for the required tool function. In GUI based approach, you only need to know how to create the required AIPS++ tool and how to use the tool functions.
To convert the FITS UV data file to an AIPS++ MeasurementSet (MS), use the constructor fitstoms of the tool ms which is in the module ms of the package general. We represent this constructor and the hierarchy it belongs in the format package.module.tool.constructor as:
Similarly, if you want to convert a FITS image to an AIPS++ image use
general.images.image.imagefromfits
If you want to directly `fill' VLA data from the archive, then you could use the global functions:
A summary of the data can be obtained using the File Catalog GUI which, if it is not already active, can be invoked from the Tool Manger (Click on dc in the Tools in Use view and click Show). To obtain the summary select the MS file name by clicking on it and then click on summary. The summary appears in the Logger window.
You can also get the summary using the tool function
Visibility data can be plotted in various ways using the tool
Various columns and sub-Tables of the MeasurementSet can be examined using the Table Browser which can be invoked from the File Catalog GUI by selecting the MS name and then clicking on view.
Currently there are no tools to directly print or type selected portions of the UV data (like LISTR in AIPS). However, if you are adventurous, you can use the tool utilities.table.table and its various tool functions such as colnames, getcol to extract various colums of the MS into Glish arrays (see next section) and use the Glish command print to examine the column values. You can even modify these values and put them back in to the MS using the Table tool function putcol, which can of course be dangerous.
synthesis.msplot is useful for viewing various types of plots of the visibility data, but currently, it has only rudimentary tools for interactive editing of visibility data.
synthesis.flagger contains some simple functions for non-interactive editing.
The tool to use for calibration is:
synthesis.calibrater.calibrater
This is a well developed section of AIPS++. tools are available for a variety of imaging requirements such as 3D, wide-field, multi-field, multi-frequency synthesis and mosaicing. The tools also allow self-calibration to be incorporated into the loop.
Starting from a calibrated MeasurementSet, the main tools for imaging are
In the tool imager, the tool functions to use are:
| setimage | # To set the image size, cellsize, etc. |
| setdata | # To select the require data from the MS |
| uvrange | # Set the UV range |
| setimage | # set the image characterics, size, cell |
| weight | # setting Weighting of UV (robust etc) |
| setbeam | # Specify the convolving beam |
| mask | # Setup a mask to specify ``cleaning'' areas |
| clean | # Make the image and deconvolve |
Some of the steps above are optional, in the sense that sensible defaults will be used. Note that executing each of these tool functions will specify the parameters for the imager tool for that session. In other words you are specifying a state for the Imager tool. Repeated execution of clean, for example, will use this state. This is a general feature of all tools in AIPS++.
A self-calibration loop can be inserted in both imager and dragon tools. In imager the tool function is selfcal which takes as input the name of a calibrater tool which should be setup appropriately before hand.
In dragon, the self-cal loop is built into the tool function image. The relevant parameters to set are amplitudelevel and timescale.
Analysis of images is provided through several tools:
image, imagefitter, imageprofilefitter, imagepol, regionmanager, and coordsys.
The basic Image-related tool is the image tool, in which functions are available for various types of analysis and manipulation. Some of the tool constructors are:
| image | # Construct Image tool from an AIPS++ image file |
| imagefromfits | # Construct Image tool and convert from a FITS file |
| imagemaketestimage | # Construct Image tool from a built-in test image |
Some of the tool functions are
| view | # View image with Viewer |
| summary | # Generate a summary of the image |
| statistics | # Compute and plot various statistics of the image |
| sepconvolve | # Independent convolution off different axes |
| moments | # Compute various moments of images and cubes |
| regrid | # Regrid image |
| subimage | # Make a subimage |
| tofits | # write FITS file of the image |
| calc | # Mathematical combinations of images |
Imagefitter is a comprehensive tool which can perform component fits to selected regions of the image aided by an integrated image display with zoom, pan, region drawing and other options. Similarly, imageprofilefitter is used to fit 1-D models to profiles interactively extracted from an image.
The imagepol tool provides specialized polarimetric image anlaysis.
The regionmanager tool manages image regions of interest.
The coordsys tool manages Coordinate Systems including coordinate conversions.
The main tool for displaying, contour and grey scale plotting of images is viewer
The Viewer is started from File Catalog GUI by choosing the file name and clicking on View. Multiple images can be viewed simultaneously in different display panels. Clicking on View after selecting a file name starts up a new display panel.
Another way of starting the Viewer is to use the tool function image.view.
Grey scale range and contour levels can be controlled using the Adjust button on the display panel.
Once the desired contour or grey scale plot is drawn on the Viewer, the Print button on the display panel can be used to send the plot to a printer.
The suggested method of data archiving is to use the UNIX tar facility. While MeasurementSets and Images can be tarred directly (i.e. in their AIPS++ table format) if they are intended to be read back into AIPS++ directories, we recommend that these be converted to FITS files (using mstofits and image.tofits) and then archived using tar. Use of the FITS format is currently preferred as a long term archive format since the AIPS++ formats may change.