PIMA is software for processing the visibilities data
from VLBI experiments. It performs data inspection,
data calibration, and fringe fitting. PIMA is designed
to process multi-source experiments that are common for
astronomical surveys and geodesy observations. PIMA has output
interface with AIPS, DIFMAP, and VTD/Post-Solve software.

Principles of PIMA
------------------

  PIMA processes visibility data in FITS-IDI format. PIMA
does not transform and does not copy original data. At the 
first step PIMA "loads" the data, i.e. examines the specified
set of visibility data in FITS-IDI format and creates numerous
internal indexing tables that are written in disk. For performing 
all other operations PIMA uses these tables for getting access to
specific fields of input FITS-IDI files.

  PIMA has a flexible command-line interface and it is designed 
for a non-interactive use. PIMA is ideal for being incorporated 
into scripts for shell, python or similar interpreters.

  All control parameters that are needed for processing a given
experiment are gathered in a control file. PIMA does not support
any defaults: all parameters, even those that are not used for 
a specific operation, are to be explicitly defined in that file.

  PIMA supports the following general syntax:

pima control_file operation [qualifier value...] [keyword: value...]

  where  control_file is the name of the control file. The control
         file is a list of pairs keyword: value. Keywords are case
         insensitive, values are case sensitive. The order of keywords
         is irrelevant. If a keyword is defined more than once, the
         last definition overrides all previous definitions.

         operation is the name of the operation performed from 

         the following list:

           acpl -- autocorrelation plotting
           acta -- compute average autocorrelation spectrum
           bmge -- generate bandpass mask for visibility data
           bpas -- compute complex bandpass
           bplt -- plot bandpass
           frib -- baseline fringe fitting
           frip -- fringe-fitting with phase referencing
           gean -- load antenna calibration tables
           load -- load the FITS-IDI files and compute indexing tables
           mkdb -- make output database
           moim -- import interferometric model
           mppl -- plots of multiple tones of phase-cal phases and amplitudes
           onof -- determine on/off time range automatically by investing 
                   visibility data
           opag -- compute slant path delay, atmospheric opacity and 
                   atmosphere brightness temperature on an az/el grid
           opal -- load slant path delay, atmospheric opacity and atmosphere
                   brightness temperature
           pcpl -- make a plot of phase calibration signal
           pdpl -- make a plot of the phase calibration signal at the LL pol
                   with respect to the phase calibration signal at the RR pol
           pmge -- generate bandpass mask for phase-cal data
           pplt -- generate polarization bandpass plot
           prga -- print gain information
           splt -- split the data into sources and write output FITS-files
           tspl -- plotting the system temperature
           tst1 -- reserved for tests
           upgr -- upgrade control file


  Some operations require additional parameters that are defined
for that specific operation. They are specified as a pair qualifier
and value. Some operations require more than one qualifier. The order
of qualifiers is irrelevant.

  A control line may have one or more lines with pairs keyword: value.
These pairs override definitions from the control file. These pairs
can be viewed as an extension of the control file. The latest pair
keyword: value overrides previous definitions

  PIMA supports a number of optional kludge parameters that alter normal
processing in a form of keyword: value. The have a prefix PIMAVAR_.
They can be either defined in the control file or put in the command line.

Minimalistic workflow
---------------------

  The workflow of the minimalistic, simplified analysis:

load         -- parse and load the data. This is always the first operation.
                A user is supposed to prepare control file that defines
                the name of visibility file(s) in FITS-IDI, station
                catalogue, source catalogue, control file for VTD, 
                experiment description file, and parameters that control
                further analysis. Results of parsing the visibility data
                are written in file. For all tasks, except load, pima 
                reads that file.

frib         -- coarse fringe search without bandpass calibration and masking
                bad data. Some results of this fringe search will be used for
                computation of bandpass calibration and automatic flagging.
                Usually, no oversampling is performed.

bpas         -- computation of the complex bandpass calibration and complex
                polarization band-pass (for dual-band data) using results of
                the coarse fringe search.

frib         -- fine fringe search with bandpass calibration applied
                Usually, the data are oversampled with a factor of 4.

mkdb or splt -- results of fringe fitting are used to generate the final 
                product of PIMA: 
                a) the database with total group delays, phase delay rates 
                   and related parameters for consecutive astrometry/geodesy
                   data analysis;
                b) visibilities coherently averaged over frequency and 
                   specified time intervals, with averaged visibilities
                   split into files, one file per source, in a form ready
                   for imaging analysis with DIFMAP.