Batch Observations

Joachim Köppen Strasbourg 2010

Only when you are well familiar how to do observations manually and when you start systematic observations, perhaps at inconvenient times, then you can turn using batch operating.

The telescope can be operated in batch mode, i.e. without the direct control of the user. For this purpose we prepare a text file which contains all the commands we plan to issue during the observation run. However, we should take care that we do not demand the telescope to go to a source which at that moment happens to be below the horizon ... in this case the telescope will retire to its stow position.

Such a run may be short, and we might simply sit in front of the computer watching the incoming results. This may be useful during tests, such as the ones we need to excute because of the strong interference: All commands are stored in the file and are executed in the prescribed manner ... so that it won't happen that we forget something ;-)

We can also run the telescope for a longer run, such as overnight, or during times we cannot be present. In this case, it is useful to plan ahead, as to ensure that the telescope is not pointed at objects below the horizon. For this purpose, we can use the planning tool or the simulator to check the visibility of your sources.

To run ESA-Haystack in batch mode, you click the CmdFile button, upon which a window opens with a file selection menu. You select your file ... The program then reads and execute one line after the other of the file. The commands are displayed in the lower right hand corner.

In case you want to change something in the file, such as modifying the interation time, having seen the previous results, you may do so: simply open the file with the text editor, apply the changes or add anything, and then save it. Obviously, you can only change lines that have not yet been read by the program!

The rules for the command file text are:

• the program reads one line at a time skipping blank lines, lines which start with * , and lines with past times
• it stops at and executes any line with current or future time
• the time format is
  • hh:mm:ss ... wait until that time [UTC]
  • hh:mm:ss cmd ... at time [UTC] execute the command cmd
  • LST:hh:mm:ss cmd ... executes cmd at that local sideral time
  • LST:hh:mm:ss ... wait idly until that time instant
  • : cmd (note the space after : ) ... executes cmd at the current time
  • :n cmd ... executes cmd n seconds after current time
  • :n ... keep recording data for the next n seconds
  each line MUST start with time or : or * for comment

• azel az_deg el_deg goto this position (az, el)
• beamswitch start beamswitching operation on current source
• freq cent.freq. mode set the frequency grid to the centre frequency and the frequency span indicated by mode:
  

  mode =	1	2	3	4	5	6
  span =	0.5	0.25	0.125	1.2	1.5	2	MHz

• freq cent.freq. 9 num spacing do a frequency scan about the centre frequency, with num points spaced by spacing
• galactic glat_deg glon_deg goto a source at its galactic coordinates
• image start mapping the current source
• map same as image
• offset azoff_deg eloff_deg goto a position offset in Az and El from the current position. Note this will be applied to all subsequent pointings
• pointcorr pazoff_deg peloff_deg apply a pointing correction in Az and El for all subsequent pointings (for the ESA-Haystack we need to do this at the start of every observation: -0.5 -3.5 in order to compensate a small offset of the present configuration!)
• radec hh:mm:ss [sign]dd:mm:ss [epoch] [mode] goto this position (the option 'mode' is not operational at the moment)
• record starts recording data into a file
• roff turns off data recording
• any name given in the catalog file srt.cat goto that source
• stow goto stow position

For example: a solar observation would entail measurement of the solar flux, the background of the empty sky, and the flux from the ISU library wall, which can serve as a flux calibrator source

:  pointcorr -0.5 -3.5	apply the pointing correction
:  freq 1420 1	set centre frequency 1420 MHz and span 500 kHz
:  record	start recording
:  Sun	goto Sun
:600	measure for 10 min
:  offset -90 0	offset 90° east of Sun, same elevation
:600	measure for 10 min
:  ISU	goto ISU wall for flux calibration
:600	measure for 10 min
:  roff	stop record
:  stow	goto stow position

Note that the seconds to wait is right next to the :    but otherwise there is always a space before the command keyword!

It is a good idea to keep an eye on the telescope, during the beginning of each batch run, just to be sure that everything works as it should!

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last update: Apr. 2010 J.Köppen