European Southern Observatory New Technology Telescope

General :
Observations :
Operations :

Long Slit Encoder Calibration Procedure

        ****************************************************************
           Check list to implement a new calibration of the long slit
                          Ph. Gitton - 15/04/98
        ****************************************************************



        This operation is done in 3 distinct steps:
        -------------------------------------------

        1) Physical measurement of the slit width and height
           (2 persons, 3 hours) 

        2) Establish the new conversion formula/table 
           (1 person, 30 minutes) 

        3) Update of the calibration parameters in the EMMI control SW
           (1 person, 3 hours)




        PHYSICAL MEASUREMENT OF THE SLIT WIDTH AND HEIGHT
        ==================================================
        
        This operation will require 2 persons one of them being from the
        optics team in order to operate the electronic microscope they own. 
        One person has to be in the EMMI room in order to make the measurement
        while another will issue command from a terminal (very likely in the 
        NTT control room). The 2 persons will have to communicatethrough the 
        Alcatel phone system during data collection. 


        -1. Make sure the phone link between EMMI room and NTT control 
            room is up and running

        0. Press the EMMI rotator emergency switch

        1. Dismount the long slit unit
           -> verify that all eccentrics are in contact and firmly fixed
           -> disconnect the three control cables (functions 18, 19, 20)
           -> unscrew the 4 bolts and remove the unit taking care not to hit 
              prism unit which is very low down. This operation is quite
              tricky; it is recommended to disconnect the BSLR unit cables 
              as well as the STRL cable in order to ease the operation. 
           -> install the unit on a table close enough to EMMI so that you
              can reconnect the three cables again.

        2. Re-initialize the EMMI functions SLIT and DEKK
           -> call ccseiMsg from an EMMI window
           -> select wemmi environment and emidev process
           -> issue command: init slit
           -> issue command: online slit
           -> issue command: init dekk
           -> issue command: online dekk

        3. Perform the physical mesurement
           -> the optics person should bring the electronic microscope
              in the EMMI room and install it in order to view properly
              the slit. Set the scale of the microscope to 333 microns/div

           * slit width measurement (SLIT function)
           -> move the SLIT using the following command on the terminal
              move SLIT,xxx    where xxx is the encoder position you desire
           -> In order to monitor the motor, open the engineering window
              of motor library from specific SLIT motor typing motei in 
              any wemmi terminal and selecting lemmi environment and SLIT unit.
              Then press status button at the lower part of the motei window.
           -> move the slit via SW until it reaches the minimum width
           -> decouple the SLIT encoder and move it by hand to reach encoder
              position 25 (to be seen on the SLIT motor engineering window)
           -> tight again the encoder carefully
           -> re-initialize SLIT unit 
           -> move the SLIT unit from 25 to 250 by steps of 10 and for each
              of those values, measure the physical width of the slit.
              (the width should vary from 40 microns to 2000 microns)
           
           * slit height measurement (DEKR, DEKL function)
           -> move the DEKK using the following command on the terminal
              move DEKK,xxx    where xxx is the height in arcsec
           -> In order to monitor the motors, open the engineering window
              of motor library from specific DEKR motor typing motei in 
              any wemmi terminal and selecting lemmi environment and DEKR unit.
              Then press status button at the lower part of the motei window.
              Do the same for DEKL unit.
           -> move the dekker via SW until it reaches the minimum height
              write down the encoder values of DEKR and DEKL motors
           -> move the dekker via SW until you reach the maximum height
              write down the encoder values of DEKR and DEKL motors

        4. Remount the long slit unit
           -> disconnect the three cables
           -> install back the unit on EMMI
           -> screw the 4 bolts making sure that the unit is in contact with
              the 4 eccentrics
           -> Reconnect the three cables
           -> Re-intialize the DEKK and SLIT units via SW to make sure that
              everythin is back to normal.
              
        5. Release the EMMI rotator emergency button.



        ESTABLISH THE NEW CONVERSION TABLE/FORMULA
        ===========================================
        
        1. For the slit width (SLIT unit), the conversion is done via a table
           with 2 columns. In the first column the encoder value is given
           while the second column contains the corresponding slit width in i
           ARCSEC. This means that the data previously collected can be used
           directly except that the width has to be expressed in arcsec. The
           conversion factor for the NTT is 187 microns/arcsec

        2. For te slit height (DEKR & DEKL units), the conversion is done
           via a linear formula of the following type:

           enc_DEKL = a_DEKL + b_DEKL * height(arcsec)
           enc_DEKR = a_DEKR + b_DEKR * height(arcsec)

           From the 2 points you measured, compute the 4 unknows a_DEKL,b_DEKL,
           a_DEKR, b_DEKR making sure that you converted the height into arcsec
           (as before the conversion factor is 187 microns/arcsec).

           The units are:
                a_DEKL and a_DEKR : enc
                b_DEKL and b_DEKR : enc/arcsec

           Normally the linear terms (b_DEKL & b_DEKR) should not change
           very much as they are defined by the mechanical system itself.


        UPDATE THE CONVERSION PARAMETERS IN THE EMMI CONTROL SW
        ========================================================

        The conversion parameters are defined in the emidev module:

        ~nttmgr/NTTINSSourceJAN98/EMMI/emidev which must therefore be 
        
        modified by some one who is cmm registered.

        1. Check that the version of emidev currently used is the last one
           archived in cmm. To this end check the header of any emidev file
           (example: emidev/src/Makefile) and the version number is written 
           there. Compare it with the latest version in cmm:
           cmmHistory emidev
           If the version number are different, please contact SW support

        2. Check out from cmm in Garching emidev module for modification
           from your private account on woff:
           cmmModify emidev

        3. Edit and modify the following files:
           -> emidev/dbl/emidevSlitMotor.class
           update the table SERVER:UNIT.unitConversion with the table
           you just established
           IMPORTANT: be careful, parameter xxx should be equal to the
           number of non zero entries + 1
           ("arcsecToEnc", motINTERPOLATION, "", 0, 0.0, 0.0, xxx,
                                                                     -----
           EXAMPLE:
           ("arcsecToEnc",    motINTERPOLATION, "", 0, 0.0, 0.0, 6,
                       0.00,   0,
                       0.17,  25,
                       0.17,  28,
                       0.35,  41,
                       0.47,  46,
                      10.35, 256,
                       0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
                       0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
                       0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
                     motDB_UNIT_INTERP_FILLER),
             -> emidev/dbl/emidevDekrMotor.class 
             update the table SERVER:UNIT.unitConversion as follow:
             ("arcsecToEnc", motLINEAR,"",0,a_DEKR,b_DEKR,motDB_UNIT_LINEAR_FILLER)
                EXAMPLE:
             ("arcsecToEnc", motLINEAR,"",0,3.0,33.3125,motDB_UNIT_LINEAR_FILLER)
             -> emidev/dbl/emidevDeklMotor.class 
             update the table SERVER:UNIT.unitConversion as follow:
                ("arcsecToEnc", motLINEAR,"",0,a_DEKL,b_DEKL,motDB_UNIT_LINEAR_FILLER)
                EXAMPLE:
                ("arcsecToEnc", motLINEAR,"",0,11367.0,-33.3085,motDB_UNIT_LINEAR_FILLER)
             -> emidev/Changelog
                Write down explicitely the changes you have done

        4. Archive the modified emidev module
            mmArchive emidev "New long slit calibration implemented"

        5. Copy back the emidev module in the correct directory saving the 
           old one
           - work in wemmi under nttmgr login
           - mv NTTINSSourceJAN98/EMMI/emidev  NTTINSSourceJAN98/EMMI/emidevOld
           - cd NTTINSSourceJAN98/EMMI
           - cmmCopy emidev
           - emidev/src/make clean all man install

        6. Install new lemmi environment
           - mv /vltdata/ENVIRONMENTS/lemmi /vltdata/ENVIRONMENTS/lemmi.old
           - ~/NTTINSSourceJAN98/nttins/src/nttinsInstallEnvironments lemmi
             [this will take up to 30 minutes as the lemmi DB is recompiled]
           - ~/NTTINSSourceJAN98/nttins/src/nttinsInstallRebootLCUs lemmi

        7. Re-intialize EMMI and check the new slit calibration

        8. Finally do not forget to modify the version number of emidev defined
           in ~/NTTINSSourceJAN98/nttins/src/buildInsFromArchive
           To this end, a similar procedure as 1,2,3,4,5 has to be applied.


          GOOD LUCK !!!

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