The ONLINE software is mainly for the setting up of the system parameters like tuning the receiver to the desired band, focusing the required feed, rotating the GMRT antennas, controlling and monitoring of tracking of the GMRT array etc.
At each antenna there is an antenna base computer (ABC) which controls and receives the information from two subsystems; one does the servo operation (movement and tracking) of the antenna using the servo computer and the other subsystem sets the receiver settings by using monitor and control module (MCM) and focuses the feed. The UNIX workstation in the control room is the central computer which communicates to all the ABCs of the 30 antennas via the communication handler (COMH). The ONLINE software running on this work-station does most of the jobs required for the scheduling and execution of the observing projects by providing the interface which accepts the commands either from the user's desk or from the command file which has the observing schedule.
The figure 2.5 shows the software and hardware components of the ONLINE system.
The ONLINE software also has control over the various observing modes of the correlator, selection of sidebands and channels of the correlator, sampling rate and processing and averaging of the visibility data and recoding of the correlator data. A number of independent group of antennas can be formed to run independent observing runs simultaneously. (Ref : A.P. Rao, "Overview of the GMRT Online Computer System", tech. repo., Dec 1991.)
