DEIMOS
Manual Grating Change Procedure

Background

This document describes the procedure for changing a DEIMOS grating when the grating system is not able to reach an unload position by itself. The workaround described here involves using keyword-level commands to position the grating select stage and grating tilt independently.

Procedure

  1. Command the grating select stage to the unload position using the command: 
    	modify -s deimot grselord=-3
    for grating 3 unload, or 
    	modify -s deimot grselord=-4
    for grating 4 unload.
  2. Command the grating tilt to the unload position by using any of the following commands:
    Grating 3 Grating 4
    modify -s deimot g3tltraw=-75000 modify -s deimot g4tltraw=-80300
    modify -s deimot g3tltord=-1 modify -s deimot g4tltord=-1
    modify -s deimot g3tltnam=Unload modify -s deimot g4tltnam=Unload
  3. Once you succeed in getting the grating to that position, be sure to turn off servo power to the G3 tilt drive motor via: 
    	modify -s deimot g3tltmod=halt
    This is necessary to prevent damage to the tilt motor!
  4. Remove the old grating.
  5. Insert the new grating and scan the barcode label.
  6. Re-enable the G3 tilt drive motor by: 
    	modify -s deimot g3tltmod=pos
Go to: DEIMOS Home Page - Instruments Home Page - Keck Home Page
Last modified: Fri Jul 21 16:39:10 HST 2006