VLBI observing notes for the Australia Telescope Compact Array (ATCA) --------------------------------------------------------------------- Steven Tingay, from the originals of Tasso Tzioumis Last modified 05/01/2001 10/01/2001 11/01/2001 12/04/2001 09/03/2003 (AKT) Preliminaries ============= Many of the requirements for VLBI observing at the compact array can be set up well ahead of time, without access to the array: SCHEDULES: Two separate schedules are required for VLBI observing. One schedule runs the telescope from the CAOBS software. Consult the ATCA users manual on how to write a schedule. For typical LBA observations the CAOBS schedule will be provided. For VSOP observations the schedules will need to be made. The second schedule is the field system schedule. Again for most LBA observations this will be provided but for VSOP observations it needs to be made. TAPES: In the screen room, the S-VHS tapes used for VLBI are kept near the VLBI PC table and the S2 recorder (far left-hand corner of room as you walk in the door). Tapes that have not been recorded sit on top of the shelves and recorded tapes sit on the floor in front of the shelves. Tapes are labelled with serial numbers e.g. AT-3-0023118-0, -1, -2, -3, ..., -7 (AT-3-00231 is the serial number, 18 is a checksum, and -0, ..., -7 denotes tapes the eight tapes 0 through 7. Some older tapes are also used, labelled differently e.g. ATNF0123-0, -1, ...., -7. Load a set of tapes into the S2 recorder, located in the far left corner of the room. Load tape 0 into transport 0, tape 1 into transport 1, etc etc. Push the tapes into the transports slowly and gently, let the transport pull the tape in by itself. S2 CABLES: Check that the multicoloured ribbon cable from behind the S2 is plugged into the lower of the two plugs at the rear of the delay units, labelled DAS2. Sometimes a short jumper cable is used to interface the main cable to the DAS. Directions to do this will be in the observing instructions provided on the day in this case. The short jumper cable is not used for VSOP observations. S2 CONTROL: This assumes that you have to start from scratch. Go to the SUN workstation in the control room named orpheus. Look in the virtual workspaces to see if any of the software is running already: v1ca - an xterm running on the PC v1ca cas2 - an xterm (yellow background) running the S2 console oprin - operator input for the PC field system fs - message window for the field system das - a window (green background with 6 horizontal monitor bars which controls the DAS) If the software is not running then follow these steps to get it running. Start a new xterm and telnet to v1ca. The username is 'oper' and the password is the same as for LEON (all lower case; currently the password is 'cycl0ps'). If you can't telnet to v1ca try v1ca.atnf.csiro.au, telnet to kaputar first then v1ca. S2: In the v1ca xterm start the S2 control software by typing s2 cas2 This will start an xterm with a yellow background. If this is already running somewhere else on v1ca it will not start. Check other windows and desktops in that case. Check that the time displayed in the top right hand corner of the S2 display agrees with UT. Check the hour and minute against the control room master clock but check the seconds by dialling the talking clock (0-1194; subtract 10 hours from AEST to get UT). If the time is wrong, you can set it by typing e.g. time s+1 (add one second) time s-3 (subtract three seconds) time 347-16:30:00 (in full: hit CR after the third pip) You can use the command status reset to clear any error messages. Quite often the S2 will not pick up the Info field 3 which is the experiment observation code. If this happens, set the field manually from the S2 window with e.g. user info 3 w094b7 An S2 users manual lives in the document rack just inside the control room door. FIELD SYSTEM: If you can't find the two xterms called oprin and fs, then go back to the v1ca window and type remote_pcfs which should bring them up. In the oprin window, type the following commands: sy=run setcl offset (resynchs the PC clock) schedule=w010fat (for example. The schedule name) or schedule=w010fat,#1 (if less than 10 mins to nominal start) label=at-3-0023118 (tape label) or label=atnf0123,1,lba (if an old style label) Check the message window (fs) to make sure that the schedule name and tape label were accepted. The tapes should start a couple of minutes before the nominal array start time for each schedule. Check the S2 console to see that the tapes have started after the start time has passed. Comments should be entered into oprin as necessary by enclosing them in double quotes. For example comments similar to these are essential to record for each schedule: "tied array 12345 RCP" (tells which antennas are tied and polarisation) "reference antenna ca03 on station w100 (15)" (reference antenna location as described from /gen page in CAMON and on the control room white board) "onsource at approximately 09:00 UT" (onsource at this time) If you need to kill the field system in order to start over use the command terminate in oprin. DAS: If you can't find the DAS control software, go to the v1ca xterm. Type das_env to set up environment variables that need to be set. Then start up the current version of the DAS controller for DAS2. The command to do this is currently das2 Click on 'File' at the left hand end if the command menu and select load. Select the required DAS profile and click ok. For VSOP observations the correct profile is vsop.pro. To set up the profile then click on 'Config Hdw'. Messages will pour out to the v1ca xterm and should end with a message '.....Finished hardware configuration attempt.' If the S2 cabling is set up then click on the 'Start Monitor' and watch to see that the 6 monitor bars go to near their middle ranges and stay there. If not, something is wrong. If all is ok a heart-shaped graphic will blink slowly at the bottom of the xterm. CATIE: On the digital machine next to orpheus, named nemesis, search for a decterm that is logged into the array control computer NOEL and is running CATIE. This has a white background, is sectioned into a table format, and is titled 'TIED ARRAY'. If you cant find such a window, create a new decterm and telnet into NOEL (username observer and password .....). If you cannot login into NOEL, find a noel terminal (e.g. the array consoles), type "set display/create/transp=tcpip/node=nemesis" and then "create /term/det" to send a noel terminal to the nemesis desktop. If the fonts are incorrect, get "options" then "window" and set "Normal font" and "German standard font" to get fonts you can read. Type CATIE to start the tied array software. If you find CATIE already running type 'newlog' to start a new log file. Catie controls how many of the six dishes are added together for the S2 recording, and what polarisation is used: function xx+yy xx-yy xx+yy xx-yy (LCP Check the observing files) function xx-yy xx+yy xx-yy xx+yy (RCP to see which to use) gain 2 antenna 12345 12345 (we normally only tie 1 to 5) Observing ========= CAOBS: Usually a setup file for initial calibration will be provided. In CAOBS type set file w010f_setup (for example, to load the schedule) track 1 (for example, to track the calibration source) When on source and the samplers have settled down, and if the cross spectra are interference free (at 20 cm wavelengths), perform CACAL. CACAL: At a NOEL prompt (usually found underneath the CAOBS window) type cacal and take the first default, a, for automatic calibration. When this has finished, and the results are satisfactory, run CACAL again. This time run it in interactive mode cacal i (for interactive mode) c (for calibrate array) 3 (reference antenna, probably the default) 3 (cycles to average, also the default) p (to calibrate phases) n (to not determine leakage terms) y (for 90 degree XY phase offset for circular) n (not calibrate continously) y (to continue as many times as asked) CACOR: The CACOR gui displayed on nemesis runs the correlator and also produces a log file which is relevant to VLBI. To initiate generation of this log file type the following commands into the command box at the bottom of the gui tda C12345 C12345 (for example, to specify circular polarisation and that 1 to 5 are tied) tdt 6 (to generate a log file entry every 6 correlator cycles, usually 1 minute) CAOBS: Load up the observing schedule. In CAOBS type set file w010f (for example, to load the schedule) start 1 (to start the schedule) CACAL: During the observations the phases will wander with time. If the antennas are tied then this causes the combined signal to be degraded. The phase wander can be monitored in VIS by specifying sel 6cc 6dd (select second frequency, both polarisations, and baselines to antenna 6) If the spread in the phases seen in VIS gets worse than 30 degrees then perhaps some antennas should be removed from the tied array. A better solution is to insert occasional calibrator sources into the schedule so that a CACAL can be performed from time to time to recalibrate the phases and gains. To do this, wait for the calibrator scan and run CACAL at a NOEL prompt cacal i c 3 3 gp (to calibrate gains and phases) y n y TAPE CHANGE: At scheduled tape changes the S2 tapes should eject themselves from the transports automatically. Collect them and replace them with a new set that have been rewound. Upstairs at the oprin prompt type label=AT-3-0023219 (for example) to restart the schedule. The tapes should rewind briefly and then start recording. If the tapes are not rewound then you MUST rewind them BEFORE the label command. You can do this by typing "rewind" in the S2 window but this may generate fs errors. Best is to type into the oprin window i.e. et - stop tapes rw - rewind tapes. WAIT until all are rewound as shown on the S2 window et - stop tapes again (to prevent the fs complaining) and then issue the "label" command as above. SHUTDOWN: Stop CAOBS as normal. Eject the S2 tapes if they are not already ejected and collect them. Exit the various VLBI software CATIE - exit S2 - logout oprin - terminate das - click on 'File' and select 'Exit' Make a CD backup of the RPFITS files from the observations as usual. Miscellany ========== Phone numbers to get help 1801 - Mopra (usually Tasso Tzioumis) 1755 - Parkes (usually John Reynolds) CACAL calibrators 1934-638 19:39:25.026 -63:42:45.63 J2000 0823-500 08:25:26.869 -50:10:38.49 J2000