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KASI Mopra: Setup and Observing


Monitoring and Utility


Connect your local VNC client to the following VNC sessions. Refer to these notes for details on setting up ssh tunneling. If you do not know the current VNC password, refer to these notes

bigrock:1 Main Control
bigrock:10 Pointing
kasi-mark6:3 OCTAD/Mark6

Note the mark6 has a different VNC password as it is a KASI machine.

Schedule Preparation

The first time you login please follow these notes. Note this assumes you have setup a symlink from ~/schedules to ~vlbi/ftp/kasi

A standard .vex file required.

  • mkdir ~/schedules/<exper>
  • Copy .vex file to ~/schedules/<exper>
  • cd ~schedules/<exper>
  • <exper>

This will copy a translated Mopra telescopes schedule ( to the Mopra observing machines.

Note that by default a modulated noisecal will be run for all observations. If ambient temperature noise source is required (at 3mm only), then a scan with intent Mopra:paddle is required. (In the .key file use intent = 'Mopra:paddle'). Allow 60 second for such a scan.

If such paddle scans is included then will also generate a “paddle schedule”

Note currently pointing scans need to be run manually. runs the following commands:

  •, which in turn runs This converts the vex schedule to the local schedule format
  • scp the schedule to bigrock
  • and copies the schedule to bigrock if there are any paddle scans scheduled

Telescope Setup

Connect to bigrock:1 VNC (ssh tunnel via `venice`). Connect to bigrock:10 vnc if pointing corrections will be needed (7 and 3mm).

To further translate the schedule, in a terminal on bigrock:

  cd sched_vlbi

To run the schedule. In a terminal run vlobs:

  file <exper>

The lo_disable step is crucial otherwise the frequency setup will be wrong

To stop a schedule use the vlobs command stop

You will also need to run the following.

In a terminal on bigrock: -hz 0.25 -integration 4
lo_octad <FREQ> <USB|LSB> will set the noisecal cycling with a 4 second period. lo_octad will tune the LO (e.g. lo_octad 92000 LSB). needs to be run after the frequency has been set (and allowing for any receiver change to occur) and will set the focus appropriately. can be left running permanently, or killed (using ^C) once the focus is set.

Finally the “B6” attenuation needs to be adjusted on the KASI MoniCA pageto get the right power level into OCTAD (see below)

For lo_octad, you must use same LO value (in MHz) assumed by OCTAD - this should be listed in the $IF section of the vexfile.

Note actual “central” frequency is offset from LO by +-8004 MHz

Freq lo_setup freq offset Sideband
16-26 GHz -8004 MHz LSB
34-42 GHz -8004 MHz LSB
40-46 GHz +8004 MHz USB
75-97.4 GHz -8004 MHz LSB
97.4-117 GHz +8004 MHz USB

For 3mm (only) observations, if the ambient temperature paddle is to be used, appropriate scans with intent Mopra:paddle must have been added to vexfile, as described above. If this the instructions above were followed there will be a file exper.paddle standard vlbi schedule area. Run the command: exper.paddle


atdrivemon shows the current state of the antenna - tracking, slewing, idle, stowed or drive error. Note if atdrivemon shows “DRIVE_ERROR”, it might be a wind/storm stow. See below.

The KASI C&M Window (from MoniCA) shows the current selected LO, Receiver and attenuator settings. In the lower section you need can set the “B6” attenuators to adjust the OCTAD input power levels. Note the Frequency is that of the synthesiser used to derives the actual receiver LO. For 12mm this is doubled, for 7mm it is tripled and for 3mm quadrupled.

The protection Summary MoniCA windows shows wind levels and if any hardware stows for wind or lightning have been activated. “true” for Lightning or Hardware Stow indicates the antenna has been stowed for its protection.

Octad Power IF setup

The input power for the OCTAD digitizer needs to be adjusted to keep the IF power in the appropriate range. This only needs to be done at the start of the experiment. Use attest (see below at Manual Antenna Control) to move the antenna to an elevation of 30 degrees. Choose the azimuth to either be the current azimuth or the azimuth of the next source observe.

The power level of the octad, viewable on the Mark6 VNC needs to be approximately 1.0:

This corresponds to a “B6” input power (see on the KASI C&M MoniCA window) of around 2.7. The B6 attenuation needs to be adjusted appropriately. This is done on the B6 attenuation input under Controls on the same GUI window.

Only a single value can be entered. This value equals A pol attenuation + B pol attenuation x 16. Note the B6 “B” polarisation corresponds to the first power level on the OCTAD display.

When the OCTAD value is as close to 1.0 as possible, make sure you select the “stop” tab on attest and click “Go”.

Weather Protection

Mopra has robust weather protection and the antenna will automatically stow with high winds or high lighting count (storm stow). If mains power is cut, generators will automatically turn on. When the storm has reduced observing will automatically resume (not until the start of the next scan).

Note this protection is at a very low level, so the antenna control computer registers an error. atdrivemon will show a “Drive Error” message:

While this could indicate a real drive error. It is usually a weather stow. Check the “Lightning Stow Control” and “Hardware Stow Control” on the Protection Summary MoniCA window. Note as the telescope is just leaving a stow event, the telescope may register as “idle” for a few minutes, or “Drive Error” but the above monitor points indicating no stow event. This status is transient and should not last more than a few minutes.

Manual Antenna Control (and Stow)

The attest GUI can be used to stow the antenna or drive it to a given Ra/Dec or Az/El. attest has a range of control functions, click the tab of the function you want to bring those controls to the front. Do not adjust values unless you know what you are doing.

To stow the antenna, click the “Stow” tab, then “Go”.

Note that you should quit `vlobs` (and `tcs` of being used) before you stow the antenna. Stow the antenna at the end of an observing session, or of the weather is particularly bad.

If you wish to send the antenna to a position manually (e.g. for testing), click the goto tab. To track a given Ra/Dec, select RaDecApp from the target and manually enter an Ra/Dec and press <Return>. Note sometimes you need to enter the values twice so check the displayed values. Click “go” to start the telescope slewing.

To send the telesope to a specified Az/El, select AzElApp from target and enter the values you want, press <Return>, then “Go”

When you want to return to vlobs or tcs, you need to select the “Stop” tab in attest and click “Go”.


Pointing needs to be done separately from normal VLBI control, with different LO settings, different control code and from a different VNC.

  • Stop observing in vlobs with the stop command
  • In a terminal window on bigrock, run This will change various timings on the system which have to be restored before VLBI observing restarts
  • Change to the bigrock:10 VNC for the following

Start the TCS program running.

  • run tcs in a bigrock terminal
  • Click “start”
  • Dismiss orange warning message (Click “Dismiss”)

Make sure an appropriate pointing schedule is selected and choose a pointing source from the 7mm or 3mm SiO maser catalogue.

  • Click “Sched file→Standard” then select CALIB and point_7mm or point_3mm if you need to change schedule
  • Click Source name→Browse source catalogues→Standard“ then Select SiO_3mm_maser or SiO_7mm_maser
  • Choose an appropriate maser (double click). Select “Stay up” if you want to try different sources
  • Click “Start sched” button to start pointing

When the antenna is idle, change VNC desktops and run the sio_point program to determine the pointing offset and update the pointing solution if you are happy with the fit.

When you are finished it is important to quit TCS. You will also need to retune the LO (with lo_octad), change the noisecal timing ( and change the “B6” attenuators to the values determined at the start of the experiment. Finally restart vlobs with the start command.

Auto Pointing

This currently does not work


  • Connect to bigrock:10
  • In the directory /nfs/online/local/tcs/sched/2022/VLBI, create a file with SiO maser coordinates:
# Pointing SiO maser
M999, o_Ceti, J2000, 02:19:20.71, -2:58:38.8, /home/atcaobs/sched_tcs/CALIB/point_3mm/ZOOM/point8_zoom.sch, PNT 5 
M999, , , , ,NULL,STOP
# Stop line is essential

Running pointing:

  • Stop vlobs
  • Change B6 attenuation in monica
  • newcain cycle 2.048
  • copy (cp) SiO point file to ~/qm/queue.
  • Type n in queue manager terminal.

Return to vlbi:

  • Wait till telescope idle
  • Change B6 attenuation in monica
  • -hz 0.25 -integration 4
  • lo_octad 92000 LSB (set LO freq and sideband appropriately)
  • start in vlobs
kasi/observing.txt · Last modified: 2023/04/06 18:11 by cormac