Introduction

Modern radio telescopes are complex assemblies of electronic and electro-mechanical subunits. To allow a successful observation, all of these sub-units have to be ``set'' as per the users requirements. For example, the antennas have to track the selected source, the front-ends have to be tuned to the chosen frequency band, all the amplifiers along the signal path have to be set at the value which would give the optimum signal to noise ratio, the local oscillators have to be tuned to select the desired frequency, the correlator has to be set up to do the appropriate fringe and delay tracking etc. In an interferometer like the GMRT this means that one has to, in a co-ordinated manner, control sub-systems which are several tens of kilometers separated from one another. In addition, it would be highly desirable for the health of the critical sub-systems to be able to be periodically monitored, so that should any subsystem fail, the affected data can be flagged, and also of course remedial action could be taken to fix the faulty unit. Further since it is not humanly possible to remember all the various safety limits of each of the sub-systems, one requires the telescope control system to not permit operations which could endanger the safety of the telescope or the human operators. The GMRT Monitor and control system was designed with all these different requirements in mind.

The GMRT control and monitor system (also referred to as the ``telemetry system'') allows one to

1. Rotate of all the thirty antennas in azimuth and elevation, and/or to track a celestial source.
2. Bringing the required feed in the feed turret to the focus via the Feed Position System(FPS).
3. Select front end system parameters like the observing frequency band, desired noise calibration, etc.
4. Sets the IF sub-systems including the LO frequencies, the IF bandwidths and attenuation, the ALC^24.1 operation etc.
5. Sets the baseband bandwidth and attenuation.
6. Monitor, literally, hundreds of system parameters at all points along the signal flow path.
7. Have a voice link between each antenna shell and the control room in the CEB (Central Electronics Building).

Footnotes

... ALC^24.1

Automatic Level Controller