1) The rotation of all the thirty antennas in AZIMUTH and ELEVATION thro' SERVO CONTROL COMPUTER(SCC).
Azimuth --> -270 TO +270 deg
Elevation --> 17 TO 90 deg
--> Using ABC - SERVO RS422 communication link @ 9.6 Kbps.
2) Alignment of the required feed for observation to the focus of the dish thro' Feed Position System(FPS).
0 deg -->
90 deg --> 150 MHz
180 deg --> 1420 MHz
270 deg --> 325 MHz
--> Using ABC - FPS RS485 communication link @ 9.6 Kbps.
3)Selection of FRONT END SYSTEM parameters like observing freq. band,Noise Cal,Channel Swap etc thro' MCM '5' & MCM - FE interface card in the Common Box.
4)Sets the LO Freq. , IF bandwidth (6,16,32 MHz),IF attn.,ALC ON/OFF etc. using MCMs'2','3' & '9' located in LO/IF SYSTEM
5)Sets Baseband bandwidth (62.5 KHz to 16 MHz) using MCMs located in BASEBAND SYSTEM thro' Antcom '0' .
6)Monitors the C & M system parameters at Antenna shell using MCM '0' at NRR and at CEB using 6 MCMs thro' Antcom '31'.
7)Monitors the Temperature at various points in RFI cage in each antenna thro' Temperture Monitor system using MCM '0'.
In addition, it also provides the vital voice communication link between CEB & all the Antennas.ie.You can contact anybody in any antenna using C & M SYSTEM.
The communication medium is a single mode analog optical fibre link operating @ 1310 nm between CEB and all the antennas ie. two fibres are available for each antenna.So,the digital command & control signals are converted to analog form using non-coherent FSK techniques and sent alolng with the LO and IF signals.In the forward link,Telemetry command signals are combined with the LO carriers and transmitted to all the antennas and in the return link,Telemetry monitor signals are combined with the IF signals and brought to CEB.The FORWARD link uses 18 MHz carrier & the RETURN link uses 205.5 MHz .
The ONLINE SOFTWARE running on the UNIX workstation provides the user interface for sending all the USER COMMANDS like antenna postioning,setting various receiver parameters etc to different systems in MRR & all the ANTENNAS and displays the status of the same.
Let us see how the user commands are processed by the ONLINE system.
The user commands are formatted by UNIX workstation and sent to all the antennas thro' COMH at MRR & Antcom located in each of the antenna shell.
More details will be given by Prof.A.P.Rao in his talk on "ONLINE SYSTEM FOR GMRT"
1)Main FSK communication link between COMH
& ANTCOM at 250 Kbits/sec using OF system.
2)Asynchronous data communication link between ANTCOM & SERVO thro' RS 422 link.
3)Asynchronous data communication link between ANTCOM & MCMs thro' RS 485 link.