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Setting up at Hobart for CHI Observations

The instructions below are the same as those written by Simon for remote VLBI observations, but information not relevant to CHI observations has been removed

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 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
    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
    If you want to cancel a timed command

Computer Setup:

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

  • PCFS (hobart)
  • PCFS monitor (hobart)
  • STALM (hobart)
  • cdisko (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 1024×768 :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 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 -name monit2 -e /usr2/fs/bin/monit2 &

To run cdisko

  1. From an xterm on newsmerd (as observer)

To change oscillator frequencies etc

  1. From an xterm on hobart (as oper)


To run STALM

  1. From an xterm on hobart (as oper)

stalm 5000 &

  • It may be useful to run to get remote alarms. See pmSTALM

Recommended VLBI setup for Hobart

Current usage of cables:

  • A1 - 5 MHz from maser.
  • A2 - is connected to receiver tone port.
  • A3 - is faulty, don’t use
  • A4 - has RCP signal from receiver.
  • A5 - has LCP signal from receiver.

Dual Polarization setup (typical for CHI)

  1. Signal from A6 goes to LHS 30 dB amplifier;
  2. LHS 30 dB amplifier connected to input of LHS rotary attenuators;
  3. Output of LHS rotary attenuators connected to RF connector on LHS of frequency translator;
  4. SMY01 (only SMY in Rack 4) goes to input of splitter in panel above coherence CRO in Rack 5 and the two outputs go to the LHS and RHS LO connectors of frequency translator;
  5. IF connector on LHS frequency translator does to LHS 96/16 MHz band-pass filter near the top of Rack 6.
  6. The output of the 96/16 MHz filter goes to the 3A connector in the patch panel at the top of rack 6.
  7. The 6A connector in the patch panel in Rack 3 is connected to the LHS programmable attenuator (doesn’t matter which end)
  8. other end of LHS programmable attenuator is connected to RF IN connector on LHS of square law detector.
  9. DC OUT on LHS of square law detector is connected to VFC #0 input

The setup for the other polarization is the same, except the signal comes from A5, replace 3A and 6A with 3B and 6B for the patch panel connections and replace all occurrences of LHS with RHS and the square law detector DC OUT goes to VFC #1

Single Polarization setup (Rarely used for CHI)

This is very similar to the dual polarization setup, the only differences are:

  1. Take the polarization to be observed and put it in the input to a splitter. So if it is LCP we want to observer, then take the signal from A5 and put it into the input of a splitter near the top of Rack 3.
  2. Take the two splitter outputs and put them into the inputs of the LHS and RHS 30 dB amplifiers
  3. Instead of using one SMY and splitting the signal you will need to use an SMY and the SML not being used for tone generation and put the signal from one directly into the LO connector on the LHS of the frequency translator and the other into the LO connector on the RHS of the frequency translator.

Setting the levels

  1. Make sure the DAS running with an appropriate profile loaded.
  2. Adjust the rotary attenuators until the level on both DAS channels is as close to the centre of the range as possible.
  3. Adjust the programmable attenuators so that the square law detector is within its optimal range (between −5 and −4 dB on the dial meter).
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Page last modified on August 05, 2009, at 04:54 AM