The Data Acquisition System (DAS) software controls, monitors & configures the correlator in various modes of observation. It also performs the acquisition and process the visibility data output from the correlator in real time using various software programs running across the network of computers.
The DAS software initializes, synchronizes and configures the correlator in various modes of
observation. It also loads the instantaneous values of delay tracking, fringe
rotation and fractional delay corrections in the correlator components via the software
modules. The total amount of data produced in the standard mode by each sideband of the
correlator is 4MB/
. The accuracy for time stamping the visibility data is less than 100
, made possible by using the complex algorithm which collects the time information
from the PC clock, GPS pulse and the STA pulse. (Ref : R. K. Singh, "Data Acquisition
System", tech. repo., 2000).
The visibility data is recorded in a locally generated format known as LTA (Long Term Accumulation) format. The data contains information such as, auto-correlation visibilities of all the 30 antennas, cross co-correlation visibilities of all the 435 baselines, co-polar and cross-polar visibilities for specific mode of observations, Real and Imaginary part of the visibility, amplitude and phase of the visibility, IST and LST time, parallactic and the hour angle of the source, antenna elevation and azimuth positions, channel numbers, frequency parameters etc.