 |
Procedure: |
SOFI grism wheel: observational strategy and recovery procedures
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| Keywords: |
SofI - Grism Wheel - Observations - Recovery |
| Prepared/Revised: |
psinclai 2004-10-4 |
Reviewed: |
|
Released: |
epompei 2004-10-19 |
NEWS FLASH!
A software modification (thanks Ismo!) is taking care of the step motion
of the grism wheel so during the operations it is not necessary to move
the wheel by three steps by hand anymore.
Grism wheel recovery
Currently, the grism wheel suffers from a mechanical problem that
prevents a smooth movement in the reverse direction (decreasing encoder
number), which results in lost steps on the stepper motor, and
consequently, loosing the encoder value calibration. In slow speed
(below 1000), the wheel does not move at all in the reverse direction.
A configuration changes have been made by software, making it possible
to use the wheel.
-- One change was to the direction of the anti-backlash compensation which
controls from which side the wheel approaches to the final position. By
reversing that value, the wheel now approaches always into the positive
direction, i.e going from position 1 (wollaston 88611) to position 8
(open, 57627). To check the wheel alignment,you can send it to the
Wollaston position (88611) which will move the wheel in + direction
(from open) and will allow to check the alignment if the JG Mask is
also set.
-- The other change is constrains the grism motion to steps no larger than
three positions: i.e. every three (or two/one in some cases) positions
the wheel pauses before it continues to the final position.
IMPORTANT THINGS TO REMEMBER:
- When the grism wheel is not needed, place it in open,
then put it in simulation following
Procedure B
- When using the spectroscopic mode ALWAYS follow
Procedure A
to take grism wheel out of simulation, then follow the
Observational Strategy
- If the Grism wheel position is lost and you don't know where it
is, do the following:
- Put the JG mask and remove both filters, use LF. Ensure you
have some background light coming in.
- Open the ICS handset and start moving the grism wheel in the
positive (right) direction at a speed of 2000 and look at the
RTD until you see the Wollaston (the JG spots will be
duplicated):
Stop immediately and try to approach the aligned position
slowly. ZOOM. Use low speeds values (down to 1 enc/sec if
required) until you have a perfect vertical alignment of all
spots (use auto cuts in RTD to ensure a good image).
- if you overshoot, you can move the wheel backwards for 1 or 2
seconds in speed 2000, or until you are clearly on the left
side of the required position. Try the alignment again.
- If, by some reason, you cannot position the wheel correctly,
and you need it calibrated CALL IMMEDIATELY LIN (beeper 36),
without attempting anything else.
- if you need to align any slit, check that grism wheel is in
open position and in simulation.
- If you reboot the SOFI LCU, FOLLOW
Procedure C at the end of the page.
By not doing so, the wheels will not be properly initialized
Procedure
to follow if the grism wheel was in simulation and it is needed again
(Procedure A)
- a. Open the ICS Motor Control by clicking the wheel name in ICS Control
- b. Click on the Off button in front of Simulation.
- c. The function will go to Stand-By: Press ONLINE (Init will be issued)
- d. The encoder will be loaded with the position value used last time a FB init
value was entered (it should be:"open" or 57627).
- e. Close the panel and setup the ICS with:
- Slit JG mask
- Filter 1: open
- Filter 2:open
- Grism: Wollaston (one step only is required 8-->1)
- Objective: LF
- f. You should see now in the RTD the image of the JG Mask with all spots
duplicated and perfectly aligned vertically.
If the spots are not perfectly aligned, follow the manual procedure -
RECOVERY!:
- Assume as reference position the wollaston
- Open the ICS tool handset
- Ensure the wheel is some encoder units before the correct position,
i.e., move it backwardws for a few seconds using speed 2000
- Move now the wheel toward positive direction (right arrow) using
as slow speed as required (slow approach, use any value needed, down to 1 enc. step/sec) until
the wheel is perfectly aligned.
- If you overshoot the position, you should go backward again and try once more
- Once the wheel is aligned, do the FB init now with the position of the
Wollaston (88611) and press H/W init. Now the wheel should be aligned
- g. To use the grism wheel please do manually set-it up to the required
position, by taking care of not moving it by more than 3 positions at a time
in the + direction (i.e. from top to bottom in the positions list in
the ICS panel: Wollaston=1, open=8).
Procedure to follow
if the grism wheel is not needed any longer and has to be moved to Simulation
(Procedure B)
- a. Move it to OPEN position (by going in steps of 3 positions maximum
at a time in the + direction or downwards in the list)
- b. Open the ICS Motor Control by clicking the wheel name in ICS Control
- c. Do a FB init at the open position (57627), then press HW init (it loads the open position
in the instrument database).
- d. Click on the On button in front of Simulation
- e. The function will go to Stand-By: Press ONLINE The wheel will not move anymore. Close the panel
- f. Set the Grism wheel to position Open if it is not already there to allow the user to know it is actually there.
- g. When you need to use it again, go to the previous procedure above (Procedure A)
Observational
strategy
The new software modification has made it unnecessary to move the
grism wheel bu hand. HOWEVER, you need to monitor the motion of
the wheel to ensure it follows the "no-more-than-three_steps-at-a-time"
and "no-reverse-motion" rules.
To do thatm start the isiMonitor tool from any xterm on the
wsofi. It will start 2 plots: one for encoder position (left panel)
of the grim wheel and one for speed (right panel) of the grism wheel.
nEhe eoder position plot should always be increasing (expect when
the maximum value is reached; then is jumps all the way down to zero).
The plot is configured to have all circular range of grism wheel, so
line should go down only when upper side of the plot is reached and
then start increasing again.
The speed plot on the right should be always greater or equal than
zero.
In case you detect negative movements, you have to call software
support ASAP to recover old version. And after it is recovered,
you have to manually restrict movements again only max. 3 steps for
the grism wheel (and possible aligning the grism wheel is needed)
The old version of this page that explains how to operate the grism
wheel with the previous version of the software that requires to move
it only in steps of up to three positions is still available
here.
Please, note down starting and target positions, and template name in
case of failure.
Appendix: SOFI LCU reboot (Procedure C)
What to do in case of LCU reboot:
- ICS will stay in OFF, so before going to ONLINE:
- LOAD the database from ICS control panel ---> Configuration tool, for
the "isiInstrumentSOFI.cfg" file. This is needed because the BACKUP OFFSET must
be loaded
- Open "Motor Control Panel" (for example click on the slit wheel)
- To do a toggle: Normal --> Backup --> Normal --> BAckup for both
wheels (slit wheel only)
- ICS to ONLINE
- All wheels SHOULD be initialized
- set Slit_0.6, Ks, Open, Open (and in simulation), LF and check alignment
Appendix: SOFI FB Init (Procedure D)
How to do a FB (fall-back) Init?
- Open the ICS motor controil panel (unless it is already opened)
- Set the motor to OFF (the big upper left button of the group from
six similar buttons)
- Click on the "FALLBACK INIT" button; this will bring up another
window - Fallback Init Launcher
- Write the encoder value corresponding to the current position in
the window; the encoder values for all positions of the current
wheel can be seen from the Positions Tables (it can be opened by
clicking on the button with the same name just above the button
for the FB Init Launcher)
- press on the "F/B Init" button in the F/B Init launcher window;
wait until the window displays "OK"
- press on the "Restore" button in the F/B Init launcher window
- press on "Standby" button in the ICS motor controil panel; the
color on the field above the wheel changes from red to green
- press on "Online" button in the ICS motor controil panel; the
color on the field above the wheel changes from red to gray