Purpose
This page is meant for support astronomers only
This document describes the procedure for recovering use of a
NIRSPEC filter wheel which refuses to home. The symptom is that
when the filters are commanded to home via the NIRSPEC startup
script or from the XNIRSPEC/Engineer/Motors/Init menu, XNIRSPEC
returns an error message indicating that one of the filter
wheels failed to home.
Procedure
- Attempt to initialize the stage one more time only
using the XNIRSPEC/Engineer/Motors/Init menu item.
- Check the status of the switches using the
XNIRSPEC/Engineer/Motors/Read Switches menu
item.
- If no switches are set for the filter wheel in question,
this indicates that the stage is not centered on a filter.
Follow these steps to recenter:
- Login to waimea as user nirspec.
- Issue the command cdkw to go to the NIRSPEC
keyword software directory.
- Issue the command
source fil1.csh
(if
filter wheel 1 is failing, else use fil2.csh).
This script will move the stage 10,000 motor steps in
increments of 200 and print out the status of the switches
after each move. The status will be 15 as long as the
wheel is between position. Interrupt the script (using Ctrl-C)
immediately if the value changes from 15 to another value.
If the script completes 10000 motor steps without ever
seeing a switch, then a significant number of motor steps
must have been lost (or the switch is failing). In this
case, repeat the script once more to attempt to find the
switch. If it fails again, then it is unlikely to work
at all --- the wheel is probably stuck and/or the motor
is burned out.
- Check the status of the switches using the
XNIRSPEC/Engineer/Motors/Read Switches menu
item. If the position switch is set, then you were able
to stop the mechanism in a centered position --- proceed
to the next step. If not, you must backtrack to locate
the switch position by typing this command:
source rfil1.csh
(or rfil2.csh as appropriate). Note that
this script prints out both the status of the filter
wheel switches and the status of the slit switches.
Again, hit Ctrl-C if and when the fil1sw
value changes. Re-check the switch settings as
described above and, if needed, run fil1.csh
to go back in the other direction. Repeat as needed
until you are able to catch the position switch 'on'.
- On the Read Switches menu, check whether
the Pri Init or Sec Init light is
'on':
- If Pri Init is on, you are a lucky
soul, because you found the primary initialization
position for this wheel. Consult this table to determine
which filter you are at. Read the corresponding
motor step position, and enter this command to
initialize the wheel manually:
m filMinitloc=N
where M is the filter wheel number (1 or 2)
and N is the number of motor steps from the
table. Example: if you are on filter wheel 1 and
have hit the primary init switch, then you've found
M-wide at 90,000 motor steps.
- If Sec Init is on, you are an equally lucky
soul, because you found the secondary initialization
position for this wheel. Consult this table to determine
which filter you are at. Read the corresponding
motor step position, and enter this command to
initialize the wheel manually:
m filMinitloc=N
where M is the filter wheel number (1 or 2)
and N is the number of motor steps from the
table.
- If neither the Pri Init nor the
Sec Init light is 'on', then we still
can't determine our location unambiguously. In this
case, continue running fil1.csh (or
fil2.csh) until you hit the next position
switch, then again use Read Switches to
check for Pri Init or Sec
Init. Continue as needed until you hit one or
the other.
- Once you've located a primary or secondary initialization
switch and used the filMinitloc keyword
to define position, the XNIRSPEC window should
properly reflect the current position. This means that you
can use the Echelle Format Simulator window to manipulate
the instrument as long as you set the requested filter to
whatever is currently in the flaky wheel.
- If you are brave, you can try moving to an adjacent
filter using the filter selector buttons on
XNIRSPEC. But beware --- if the move fails, you'll
need to start again looking for position switches and
initialization switches!