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Remote VLBI Observing

Setup and instructions

The observing is usually done from a vnc session running from newsmerd:1 (password is the usual one).

Recommended VLBI setup for Hobart

This page contains a full checklist for setting up the Hobart 26m for a remote VLBI observation and it is strongly recommended that you use this.

Receiver selection

The receiver selection is now controlled through a GUI on newsmerd which is described here

Backend configuration

Hobart now has a remotely controllable backend that allows for control of polarisation selection and attenuators. It is described in detail here.

oscillator_gui.sh

This program must be run with the Ceduna PCFS is running.

  • To run oscillator_gui.sh, use ./oscillator_gui.sh in an oper@hobart terminal. It will take ~5 seconds to poll the oscillators and then show their current status in the terminal window. If there are garbled or suspect readings, p-lease try refreshing then display first (by pressing r and then enter). An example of the GUI output is included below

Oscillator Control “GUI”

Index Name Frequency Level (dBm) Ref Osc Output
1 Agilent 11.400 GHz 16.000 EXT ON
2 SML01 508.000 MHz 7.000 EXT ON
3 SML02 508.000 MHz 7.000 EXT ON
5 SMY02 661.500 MHz OFF EXT OFF

Please select the oscillator which you want to adjust, using the index or full name. Press r to refresh the display or q to quit..

  • To set the frequency of an oscillator, first select it using either the corresponding Index or its full name. The script will then prompt you for a new frequency and power level. Note than you can turn an oscillator output on or off with by setting the level to on or off.
  • When you are finished it is best to quit out rather than leave it running. Note that the status is only updated when you enter r, or when one of the outputs is changed.

V255 Methanol parallax setup

This is a combination of the dual and single polarization setups and is required for the v255 (and other methanol maser experiment setups). It is a dual polarization experiment, but uses two SMLs like the single polarization setups.

  1. Set the agilent to 12.2 GHz
  2. Select RCP and LCP as the inputs for channels 1 and 2
  3. SML01 goes to the LHS LO connectors of frequency translator;
  4. Check that the DAS levels are in the acceptable range for LO settings of 468 MHz (7 dBm) and 810 MHz (7dBm). We spend more time in the 810 MHz setting, so centre that as best you can while still keeping the DAS levels in range for 468 MHz.

The setup for the other polarization is the same - use SML02 (set to 810 MHz, 7 dBm) for the RHS frequency translator LO.

To automate frequency changes, you should add two procedures to the experiment’s prc file, and add calls to these procedues at appropriate times in the experiment’s snp file. Template procedures are on hobart in /usr2/proc. as bbc01d.prc and bbc02d.prc and cat be appended to the experiment file with the command cat /usr2/proc/bbc01d.prc >> /usr2/proc/v255xcd.prc.

Setting the levels

  1. With the DAS running and an appropriate profile loaded, make sure that there is no CLOCK error on the DAS. If there is a CLOCK error the DELAY pots on the DAS High-resolution samplers will need to be manually rotated to get the right setting.
  2. Adjust the DAS attenuation in Palfreyman’s Folly until the level on both DAS channels is as close to the centre of the range as possible.
  3. If necessary, adjust the programmable attenuators (in rack 2) so that the square law detector is reading between 05 and −4 dB. This is not generally necessary

Record the setup

For all sorts of reasons it is critically important that you accurately record the setup used for the experiment. This information should be put in two places :

  1. The telescope log information on the experiment wiki
  2. In the PCFS log as a comment.

The information which should be recorded as a minimum is:

  • The agilent/front-end LO frequency and level.
  • The SML/back-end LOs frequency and level.
  • The tone used to check coherence (and where it was observed - bandsplitter port, fine tuner port etc)
  • The DAS profile and the cable connecting the DAS to the vsib box (BG1/straight through or BG3/64 MHz etc).
  • The disk the data is being recorded to (make sure to also update the disk summary table).
  • The approximate clock offset (as reported by clkoff).
  • Which polarization is being sent to which DAS processor.

Timed commands on the PCFS

Its a good idea to make sure that certain information (clock offsets, system temperature, weather etc.) are monitored regularly throughout an experiment. For some experiments some, or all of these checks may be scheduled in (as part of a preob or midob procedure say). Either before the experiment, or soon after it has started look at what checks are being performed regularly by the schedule and add any which are not using a timed command.

  1. To check what is part of the schedule go to the directory /usr2/proc on hobart and look in the .prc file for the experiment (e.g. for the experiment v275c this would be the file /usr2/proc/v275cho.prc). Look at the procedures preob, midob and postob (if they are defined) and see what commands are being issued. These commands will be executed once per scan and so if the experiment has short scans (a few-10 minutes), then you don’t need to worry about those commands.
  2. For commands not in the pre/mid/post ob procedures, or for experiments with long (> 15 minute) scans, you can set the pcfs to issue timed commands using
    clkoff@!,15m
    This will execute clkoff now and every 15 minutes into the future (when you change schedules many of the timed commands get canceled). To see which timed commands are in the system
    ti
    If you want to cancel a timed command
    clkoff@

Computer Setup:

The following process should be running in the newsmerd:1 vnc session during a VLBI session :

  • PCFS (hobart)
  • PCFS monitor (hobart)
  • STALM (hobart) - This can be unreliable. A workaround is to use the pmSTALM.sh script. Details of this script can be found at pmSTALM
  • cdisko2.pl (newsmerd)

This is also the appropriate place to run bruce calibration observations or change oscillator frequencies/test coherence with oscillator_gui.sh

To start/restart the vnc session on newsmerd (if necessary)

  1. Login to newsmerd as observer
  2. Run vncserver -alwaysshared -geometry 1280×720 if it is not currently running. Killing the vncserver process will kill any programs running inside that session.

To access the vnc session

  • On a Linux machine (e.g. newsmerd or cdvsi) vncviewer -shared newsmerd:1 (Usual password)
  • On a graphical VNC client (e.g. Chicken of the VNC on a Mac), just give the machine name as newsmerd.phys.utas.edu.au and the display as 1. Make sure that you allow other users to also connect.

To run the PCFS

  1. As oper@hobart, first check that the NTP time is correct with ntpq -np. The Offset should be <10 (ms) to the servers at 131.217.63.146 and 131.217.63.186. If it isn’t, you should check that the NTP server is working correctly (tac32ho is displayed on the screen in rack 12 and you can use vncviewer timehb and check the tac32 software hasn’t frozen up). Once the tac32 is confirmed as good, issue these commands as root to resynch to the NTP server
    /etc/init.d/ntp stop
    ntpdate tac32cd
    /etc/init.d/ntp start
    Then check the NTP status with ntpq -np
  2. To start the FS, run fs

To start the pcfs status monitor

From an xterm on hobart (as oper)
xterm -geometry 86×6 -e monit2 &

To run the DAS

  1. Connect to the server with vncviewer das:1. If the software is not running, you can start it from the link on the Windows Desktop.
  2. When the DOS window starts it will automatically run the DAS program. When it starts, select vsop.pro as the profile initially (that has the right communications options). After the initial setup, then select the profile you want.

To run cdisko

From an xterm on newsmerd (as observer)
cdisko2.pl &
It’s a good idea to check that the NTP time on hovsi is correct before starting any recordings. To do this, ssh to vlbi@hovsi and run ntpq -np. The Offset should be <10 (ms). If it isn’t, you should check that the NTP server is working correctly (tac32ho is displayed on the screen in rack 12 and you can use vncviewer timehb and check the tac32 software hasn’t frozen up). Once the tac32 is confirmed as good, issue these commands as root to resynch to the NTP server
/etc/init.d/ntp stop
ntpdate tac32cd
/etc/init.d/ntp start
Then check the NTP status with ntpq -np

To change xraid disks

See the detailed instructions here. NOTE: If you are running in a vnc session you may have trouble running the Xraid Admin tools if the DISPLAY environment variable isn’t set correctly (try ssh -X root@hovsi). If its causing problems its usually safe to skip this step. Record the 60 seconds of test data as suggested and if that works OK, the disks are likely to be fine. If not, ask for help from an expert.

To change oscillator frequencies etc

  1. From an xterm on hobart (as oper)
    oscillator_gui.sh

To check coherence

You can use the movable camera to check on the CRO in rack 5.

To run bruce

  1. Start an xterm on newsmerd (as observer)

bruce -f 4

========= Here there be obsolete info ==================

Setup and instructions

For Hobart the intention is not to run sessions completely remotely (in general), but just to make it possible to monitor observations remotely when necessary. To achieve this the observing should be done from a vnc session running from the observer account on newsmerd (password the same as the observer account). Its probably best to make it display 1 so that its easy for everyone to find. If not, let people know what it is, or you can always ps -ef | grep vnc on newsmerd to find it. If you are connecting to the remote VLBI observing VNC session, make sure your client is setup so that it allows others to also connect.

Record the setup

For all sorts of reasons it is critically important that you accurately record the setup used for the experiment. This information should be put in two places :

  1. The telescope log information on the experiment wiki
  2. In the PCFS log as a comment.

The information which should be recorded as a minimum is:

  • The agilent/front-end LO frequency and level.
  • The SMY/back-end LO (or LOs) frequency and level.
  • The tone used to check coherence (and where it was observed - bandsplitter port, fine tuner port etc)
  • The DAS profile and the cable connecting the DAS to the vsib box (BG1/straight through or BG3/64 MHz etc).
  • The disk the data is being recorded to (make sure to also update the disk summary table).
  • The approximate clock offset (as reported by clkoff).
  • Which polarization is being sent to which DAS processor.

Timed commands on the PCFS

Its a good idea to make sure that certain information (clock offsets, system temperature, weather etc.) are monitored regularly throughout an experiment. For some experiments some, or all of these checks may be scheduled in (as part of a preob or midob procedure say). Either before the experiment, or soon after it has started look at what checks are being performed regularly by the schedule and add any which are not using a timed command.

  1. To check what is part of the schedule go to the directory /usr2/proc on hobart and look in the .prc file for the experiment (e.g. for the experiment v275c this would be the file @@/usr2/proc/v275cho.prc). Look at the procedures preob, midob and postob (if they are defined) and see what commands are being issued. These commands will be executed once per scan and so if the experiment has short scans (a few-10 minutes), then you don’t need to worry about those commands.
  2. For commands not in the pre/mid/post ob procedures, or for experiments with long (> 15 minute) scans, you can set the pcfs to issue timed commands using
    clkoff@!,15m
    This will execute clkoff now and every 15 minutes into the future (when you change schedules many of the timed commands get canceled). To see which timed commands are in the system
    ti
    If you want to cancel a timed command
    clkoff@

Computer Setup:

The following process should be running in the newsmerd vnc session during a VLBI session :

  • PCFS (hobart)
  • PCFS monitor (hobart)
  • STALM (hobart)
  • cdisko2 (newsmerd)

You should also run the following process :

  • FS Monitor, this will alert you if either the PCFS or STALM crashes.
  • VSIB Alarm

These could be run from within the vnc session, but probably don’t have to be. They set of the Hobart observatory alarm and if you aren’t there to hear it there isn’t much point setting it off. Both these processes are started by clicking on the appropriately named icons on the desktop on newsmerd.

To start the vnc session on newsmerd (if necessary)

  1. Login to newsmerd as observer
  2. vncserver -geometry 1280×720:1

To access the vnc session

  • On a Linux machine (e.g. newsmerd or cdvsi) vncviewer -shared newsmerd:1 You will need to enter the observer@newsmerd password to see it.
  • On a graphical VNC client (e.g. Chicken of the VNC on a Mac), just give the machine name as newsmerd.phys.utas.edu.au and the display as 1 (assuming that the vncserver has been started on display 1). Make sure that you allow other users to also connect.

To run the PCFS

  1. ssh -X -l oper hobart
  2. fs

To start the pcfs status monitor

  1. From an xterm on hobart (as oper)

xterm -geometry 86×6 -e /usr2/fs/bin/monit2 &

To run cdisko

  1. From an xterm on newsmerd (as observer)

cdisko.pl

To change oscillator frequencies etc

  1. From an xterm on hobart (as oper)

./oscillator_gui.sh This is fully described in http://ra-wiki.phys.utas.edu.au/index.php?n=MtPleasant26m.OscillatorControl

To run STALM

  1. From an xterm on hobart (as oper)

stalm 5000 &

  • It may also be useful to run the pmSTALM.sh script to get audible alarms from your computer. See pmSTALM

To change xraid disks

See the detailed instructions here

Recommended VLBI setup for Hobart

Please go through this checklist to set up the back end system and

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Page last modified on February 26, 2013, at 01:59 AM