2.8 Tidbits of Information

The increased flexibility of the system means that it is more powerful. It also means that there are more interesting ways to go astray. Some commands that are helpful in sorting out what is the status of the system are:

 

SHOW_CURRENT - This command, which is followed by a VERB, shows the current status of the parameters. It also shows you the DEFAULT values. It is very good procedure to always do a show command before starting an observation of type command. This allows you to verify the setup is as you wish!

 

BE_FE - If you just type this command (with no adverbs), it will tell you the current configuration of the backends.

 

DISPL_CHAN - This command (``DISPL_CHAN ?'') tells you what channel is being used by ONLINE CHEF for processing continuum data (i.e. the POINT command). This is important to know if you are using multiple receivers (say the SIS230/SIS490) at the same time.

To change channels, use the command ``DISPL_CHAN X'' where X is either 1 or 2 (for POINT). Channel 2 is used if you want to look at the second receiver's outpu when using two receivers or the second channel of a dual polarization receiver.

   

OBSINP ATN7 gainnumber - sets the gain level for the Filterbanks. Must do some scan (GO, PSWITCH, etc...) for the filterbanks to be updated. It is used for making sure the filterbanks are not saturated (i.e., total power level on hot load between 500 and 750).

 

SET OFFSET - sets the offsets from the SOURCE. If you invoke the SOURCE command, followed by GO or some observation, then any offsets are lost. (This prevents you from mapping some offset position, then moving to a new source only to not see anything because you forgot the offsets!) Note that the OFFSET positions will be used for PSWITCH and similar commands UNLESS you use the /NOOFFSET option. Then the offsets are suppressed.

 

SET REF_POS - sets the reference position from the SOURCE. The observer has considerable control over the distance, the reference coordinate system (AZ, LAM) and whether the reference position is relative to the origin (i.e. the source position of zero offsets) or not.

 

RENAME - The observer's SPECTRA.SMT file can get quite large with time. This will eventually cause Online CHEF to slow down, particularly when processing LPOINT or LWPOINT data. It is therefore convenient to rename the SPECTRA.SMT when it approaches 10000 spectra. For the number of SPECTRA.SMT spectra, look at the ONDIS window on Koenigbacher. A new SPECTRA.SMT file will be created for you after the old one is renamed.

  

SKYDIPs - Both continuum and line observers can do skydips. To reduce the data, one can do the following in one of the FRANKENHEIM windows outside of the OBST program:

To reduce continuum skydips:

 

• skydip - this procedure will do run Kreysa's skydip program. It is used for the bolometer, but can't be used alone for SIS data since it uses load switched data, not total power data.

    Note: If one wishes to reduce continuum data taken with the bolometer receiver, then one should use Kreysa's skydip program.

To reduce spectral line skydips:

   

• plot_skydip - this procedure will take your SKYDIP done with the SIS receiver and process it. It will ask you for a scan number and the desired plot title. The plot is then produced automatically on the laserprinter.

Plot_skydip skydip is a script that consists of some skydip commands, get_skydip and fit_skydip. ``Some skydip'' commands occansionally aborts. In this case, you may be able to manually type them in and run the other two scripts.

 
• skydip - this procedure will do run Kreysa's skydip program. It is used for the bolometer, but can't be used alone for SIS data since it uses load switched data, not total power data.

   

• get_skydip - this procedure will get the skydip data, from Kreysa's skydip program and makes an output file suitable for Jeff Mangum's skydip program.

   

• fit_skydip - fit the skydip (from get_skydip) using Jeff Mangum's skydip program.

Note that the OBST procedure SKYDIP for SIS/HEBOL receivers will ask for a COLD load at the end of the scan!

We ask that observers note down on the logsheets the results of their skydips, the taumeter result, and the frequency observed. This will allow us to build up a table for local use on freq vs taumeter readings.

 

Changing OBST sessions - Sometimes (rarely) the observer will not wish to log out completely when changing a program or changing between two observers. How can one modify the output files and directories so that only one observer area is used?

• OBST> SAVE some_file - save the previous configuration so that the first observer can restore his OBST session.

• OBST> EXIT

• CHANGE_INIT -- FRANKEHEIM will then ask you for a new prompt.

• OBST -- To start new OBST session.

• In the other FRANKENHEIM windows (i.e. GREG, CHEF), type the fix_prompt command if you want to change the prompt to reflect the current observer.

• You will also need to change directories in the FRANKENHEIM windows to the correct directory for your new initials. (Otherwise, you will still be working in the directories you started.) You then can use CHEF offline (or other procedures that you might need) in the correct directory.

 

Changing SPECTRA.SMT files - Sometimes you might wish to use a different SPECTRA.SMT file in your current OBS session, perhaps to put incoming data into a different person's project area.

• OBST> MBC FILE OUT sys$smt:[obs.INI]SPECTRA.SMT /supply

• OBST> MBC FILE IN sys$smt:[obs.INI]SPECTRA.SMT /supply