3mm ATCA Quick Start
The commands below should get the telescope set up and ready to make observations at 3mm. However they only cover the typical case. After reading this you should discuss with your DA what you will need to do to get set up.
You will need to type in more than one window — check you are typing in the correct one before entering a command.
Stow any unusable antennas and detach them:
caobs> stow ca06 caobs> detach ca06
It is ok to detach antennas while they are stowing.
Ensure the focus on antenna 1 is correct 1 (in
MoniCA, look at the page
caobs> focus ca01 14
Load your observing file:
caobs> set file [your-schedule-file]
Start tracking a bright (> 5 Jy) continuum source from your observing file (n is the source number in your sched file)
caobs> track n
Make sure the
RTprogram is cycling.
VISabout which antennas are in use, so it only plots those:
vis> array 12345
and check the correlator output looks reasonable:
vis> sel aa,bb vis> sel cc,dd
Set the spectral display program
SPD2 to show auto-correlations and cross-correlations, plotting the amplitude on all channels, with averaging turned off:
spd> array 12345 # only show antennae we are using spd> acs # show auto-correlations spd> chan # plot all channels spd> a # plot amplitude on the y-axis spd> noavg # don't average across integration cycles
caobs> track n caobs> set mm ca01 L L caobs> set mm ca02 L L ...repeat for each antenna...
These attenuators set the receiver output power to the 'C26 splitters'. The output power levels are shown on the
Conversion:Freq1_summary. Wait a couple of integration cycles for the readings to settle.
Now let the CABB attenuators adjust themselves:
caobs> corr atts on ...wait a couple of cycles, monitor CACOR and VIS... caobs> corr atts off
After a couple of integration cycles, and check the
CACOR. A level of around 20 units or less is ok.
You must turn the autoadjustment off once it has settled.
Calibrate the interferometer delays3 (and apply them)
caobs> corr dcal a
You can monitor the progress of this in
SPD, by plotting phases for all channels, and by watching the delay plot in
VIS. Check all polarisation products. Sometimes it can help to redo the delay calibration after doing a pointing scan.
If you wish you can do a phase calibration as well:
caobs> corr pcal a
To calibrate amplitudes and Tsys values, you will need to do a paddle scan.
Calibrate your amplitudes by measuring the system temperature with a paddle scan (p is the number of the 'paddle' scan in your sched file):
caobs> stop caobs> start p
When the paddle scan is complete, stop the schedule:
Check your Tsys values as displayed in
CACORlook reasonable (at 3mm, about 300K-400K).
Check atmospheric conditions (
Set up pointing 4 with these commands (x is the number of the pointing scan in your schedule file):
caobs> set point_antennas 12345 caobs> set point_ifflag 1234 caobs> set point_pattern 2 caobs> start x #pointing scan in schedule file
Monitor the progress of the scan in the
CATAGwindow. The pointing type should read
UPDATEduring this scan. (For other scan types it will normally read
When the pointing scan is complete, stop the schedule:
Close the data file to keep the setup data distinct from your source observations.
caobs> corr closefile
Start observations! Don't forget to observe bandpass and flux calibrators at least once during your observation. Also make sure to monitor
VISto ensure no problems develop during the session.
When finished observing, close the data file and stow the antennae:
caobs> corr closefile caobs> stow all
- CA01 Focus
At 3mm, the best focus position for antenna 1 is slightly different to all the other antennae. The cause of this is not yet understood.
- SPD Setup
SPDhas new display commands, you should take the time to become familiar with them.
spd> acs # show auto-correlations spd> noacs # don't show auto-correlations spd> on f1 # show cross-correlations for frequency 1 spd> off f1 # don't show cross-correlations for frequency 1 spd> on f2 # show cross-correlations for frequency 2 spd> off f2 # don't show cross-correlations for frequency 2 spd> sel aa # show the first polarisation product for each displayed frequency spd> sel bb # show the second polarisation product spd> sel aa,bb # show both
Cross-correlations are always shown unless you explicitly turn them off.
When showing auto-correlations as well, the 16-panel PGPLOT display often gets filled by the plots for just one frequency. Make a habit of checking which frequency is being displayed.
The polarisation products for frequency 1 are shown on the plots as
bb, while those for frequency 2 are shown as
The delay errors you should expect are now much smaller (thanks to the larger bandwidth of CABB) — typically well under 1 nanosecond.
The value of the
delavghas an impact here.
delavgis the number of channels the correlator averages together when estimating the delay (by fitting a line to the phase as a function of channel number).
You can find out the value of
CACOR) like this:
You may need to adjust the value of
delavgfrom time to time:
If your delay errors (as viewed in
VIS) are flat but far from zero and the phase spectrum (as viewed in
SPD) is wrapping rapidly, try:
Command: delavg 1
If your delay errors are very noisy, perhaps the source is not bright enough. It may be worth averaging more channels together:
Command: delavg 16
If you do this, once the delays are calibrated you should set
delavgback to the typical value:
Command: delavg 8
While observing with reference pointing you should keep some additional notes. You will need to display the
The PNTCOM value - keep a note of this. If the pointing goes bad, this can be used to backtrack to a good pointing solution, you will need this. To use it,
caobs> stop caobs> ppfix [PNTCOM]
It can be useful to note the Last Azimuth and Last Elevation offsets, so you can see what has changed since the last pointing scan.
Finally, keep an eye on the values of the Global Offsets in Azimuth and Elevation. These should not become too large.
More information about reference pointing are given in the pages.