LFC Commands

Last Updated 23 Dec 2010
by
Kevin Rykoski


LFC commands follow this syntax:

command <argument [optional argument]>


Commands issued without a necessary argument will simply display the current value. Commands may be abbreviated to the shortest length necessary for completion.



Start-up Commands



Setup Exposure Commands

Mcdcom takes exposures and writes data files according to various parameters that you can set. The basic sequence that mcdcom follows is:

(1) Clear the chip
(2) Open the shutter and wait for the predetermined exposure time
(3) Readout the guide chip during the exposure and forward to the guide display at intervals
(4) Close the shutter
(5) Readout the CCDs into memory
(6) Write the contents of memory into FITS format data files
(7) Put the CCDs into idle mode

Not all of these above steps need be taken. The actual sequence followed depends on how the "automatic actions" are set, as described below. There are seven ways to set the basic parameters which govern what mcdcom does:

  1. bias <time [name]>     Setup for a bias exposure. Bias prepares mcdcom to take a bias frame exposure. Bias ignores any exposure time arguments. You can specify a name as the second argument. If you don't specify a name, the previous value for bias is used. Bias sets the automatic actions to:

    Autowipe = ON      Shutter = OFF      Readout = ON      Write = ON      Idle = OFF




  2. comp <time [name]>     Setup for a comparison lamp exposure. Comp prepares mcdcom to take an exposure of a comparison arc for a spectrograph. You can specify the integration time as the first argument. If you don't specify a time, the previous value for comp is used. You can specify a name as the second argument. If you don't specify a name, the previous value for comp is used. Comp sets the automatic actions to:

    Autowipe = ON      Shutter = ON      Readout = ON      Write = ON      Idle = OFF



  3. dark <time [name]>     Setup for a dark field exposure. Dark prepares mcdcom to take an exposure of the dark field. You can specify the integration time as the first argument. If you don't specify a time, the previous exposure time is used. You can specify a name as the second argument. If you don't specify a name, the previous value for dark is used. Dark sets the automatic actions to:

    Autowipe = ON      Shutter = OFF      Readout = ON      Write = ON      Idle = OFF



  4. flat <time [name]>     Setup for a flat field exposure. Flat prepares mcdcom to take an exposure of a flat field. You can specify the integration time as the first argument. If you don't specify a time, the previous exposure time is used. You can specify a name as the second argument. If you don't specify a name, the previous value for flat is used. Flat sets the automatic actions to:

    Autowipe = ON      Shutter = ON      Readout = ON      Write = ON      Idle = OFF



  5. focus <time [name]>     This was a command to set the exposure time for a focus image. The current default exposure time is 5 seconds. If you would like to change the exposure time you may do so by editing the first line of the focus scripts, focus (N) focus_fine.

  6. object <time [name]>     Setup for a general exposure. Object prepares mcdcom to take an exposure of a general target. You can specify the integration time as the first argument. If you don't specify a time, the previous exposure time is used. You can specify an object name as the second argument. If you don't specify a name, the previous value for object is used. Object sets the automatic actions to:

    Autowipe = ON      Shutter = ON      Readout = ON      Write = ON      Idle = OFF



  7. auto     Prompts, and then sets the automatic actions as described above. You can tailor your exposures to suit your needs in this manual way if the preconfigured options above don't meet your needs. The automatic actions are:

    1. Number of times to wipe chip before exposure [1]:
    2. Open shutter for exposure? [yes]:
    3. Read CCD after exposure? [yes]:
    4. Write data to file after read? [yes]:
    5. Turn on continuous wipe after readout? [no]:    "PLEASE DON'T CHANGE THIS OPTION (#5) FOR THE LFC. It can cause problems with the filter wheel as of 2000/03/20."


There are three more commands that you can use to setup your exposures. These do not change any of the automatic actions described above.


Start Exposure Commands


Readout / Write Commands




Shutter Commands

The LFC shutter is operated by two motor controllers. The communication to the motor controllers (plus the filter wheel motor) is via a serial connection. The shutter has two blades which open and close in the same direction, providing a very uniform illumination. The shortest reliable exposure time is 0.6 seconds.

General shutter status and configuration is accomplished via the shutter command. The supported subcommands:

If you receive a "camera not responding" or a shutter error when trying to take an exposure, you will need to start a Cold Boot sequence.


Filter Commands

The LFC has a 4-position filter wheel that holds 6.2 inch square filters in custom holders. The wheel is driven via friction drive, and has Hall effect sensors to read the filter position. There are two sensors that encode which filter is in the beam, and a fine-position sensor to achieve precise alignment. The wheel is controlled by the filter command. Positions are encoded as 0, 1, 2, and 3.

The names for each filter are read from a file, usually /usr/ccd/config/filters.def. If you change filters in the wheel, update this file to correspond. You will need to restart Mcdcom in order to update the filter table.

If the filter wheel fails to locate position 0 (or the filter reports that it is lost when moving to position 0), but it can move to position 1, 2, and 3; you need to issue another filter subcommand, filter bump that will allow you to bump the filter wheel in incremental amounts.

If you receive a "camera not responding" warning when trying to move the filter, you will need to start a Cold Boot sequence.


Guider Commands

The guider maintains the communication to the telescope; LFC issues telescope commands and receives telescope information (headers) through the guider. If LFC is not communicating with the telescope, make sure the guider is running. If the TCS is rebooted, you need to quit and then restart the guider.

The LFC guider runs from a Tek 512x512 CCD in the mosaic focal plane that sits behind the filter and shutter. It is read out periodically during exposures, and the image is sent to the guider GUI. Integration times and other guiding parameters are set with the guider GUI. Corrections are sent from the guider program directly to the telescope. Since the guider runs with the shutter, you can only view the guide field either during an exposure or in a special find mode that opens the shutter and reads the chip.

The guider program is started in one of two ways. When you logged into oasis, you should have logged in with 2 Terminals; one for mcdcom and one for the guider. In the guider Terminal, you can start the guider by typing lfcguide &, in which case all of the guider output is written to the standard output (the Terminal itself). If you want to send the guider output to a file (useful in the early debugging days of the guider), you can use lfcguide >& ~/lfcguide.out &  . This output file will be written to the oasis home directory (/scr6/home/lfc); make sure there is enough free space in this directory to accomodate the long text file that will result.

If you have a question about the operation of the guider, use the help button on the right hand side of the guider GUI.

Most (if not all) of the guider parameters will be set from the guider GUI, but you can issue three guider commands from mcdcom:




Utility Commands

If you receive a "camera not responding" or unreasonable values for a utility status, you will need to start a Cold Boot sequence.




Other LFC Commands

Some other useful LFC commands:




Telescope Commands

There are a number of commands that you can use to control the telescope. Note that the guider must be running for telescope commands to work.


Warm Boot

At some point during the night, you may find it necessary to restart mcdcom. If you accidentally quit the program, if the camera stops "talking", or if there is any other unusual problem; follow the same Start-up Sequence that you used to start mcdcom. If you are not already out of the LFC program, quit mcdcom.

Enter the following commands in this order to re-start the LFC program (the order is crucial):
  1. oasis% mcdcom     This starts the LFC program. Pay attention to the directory that you are in once you quit an Mcdcom session (any directory changes done while in the Mcdcom program are lost).

  2. ccd.001> mosaic <mode>     See mosaic for the current list of available modes. If you are changing your mode, you need to do a cold boot.

  3. ccd.001> shutter startup     This initializes the shutter

  4. ccd.001> shutter home     This sends the shutter to the home position

  5. ccd.001> filter home     This homes the filter wheel; make sure estoff = 0!

  6. ccd.001> utility stat     This displays and tests the current status of the utility board

  7. Charge accumulates on the chips during a cold boot. The only way to fully remove this charge is to readout the chips with either rm or a 0 second bias exposure. Note that all 6 chips are written to disk when you do this.

    Note that the incrementing file number (fn) has been reset to the default value of 001 upon restarting mcdcom. You will want to set fn to your last exposure file number + 1.


    If a Warm Boot has not solved your problem, try a Cold Boot (below).




    Cold Boot

    If a Warm Boot did not solve your problem, then you will need to do a Cold Boot by resetting the power to the electronics in the Prime Focus cage. This is done by having the TO issue commands from the TCS Console. Follow these steps(the order is crucial):
    NOTE: It is recommended to have the telescope at zenith during a cold boot.

    1. lfc_208> quit

    2. Have the TO issue the "ir_off" command to turn off the power to the LFC system. The TO will then wait 30-45 seconds and issue the "ir_on" command to turn the power back on.

    3. oasis% mcdcom

    4. ccd.001> mosaic <mode>     See mosaic for the current list of available modes.

    5. ccd.001> clear

    6. ccd.001> util init     Do this only once for a cold boot; more may lock up the utility board and require another power down.

    7. ccd.001> shut startup

    8. ccd.001> shut home

    9. ccd.001> filter home     You may need to run this more than once. Make sure estoff = 0!

    10. ccd.001> util stat     Make sure that the utility board is alive.

    11. Charge accumulates on the chips during a cold boot. The only way to fully remove this charge is to readout the chips with either rm or a 0 second bias exposure. Note that all 6 chips are written to disk when you do this.

    If your problem isn't fixed or if there are any new problems, cycle the power again and restart the cold boot procedure. Do as many times as necessary to get you back into service. Note that the incrementing file number (fn) has been reset to the default value of 001 upon restarting mcdcom. You will want to set fn to your last exposure file number + 1.