General Principles

• DO NOT use control-c to stop a script, this can leave the instrument in an unsafe state. Use kpfconfig.SCRIPTSTOP to request a stop (also available as a button in the KPF OB GUI).

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Setting SCRIPTSTOP to “Yes” will request that the running script terminate in an orderly fashion. This may take several minutes depending on when the running script reaches a sensible breakpoint. It is important to use SCRIPTSTOP to halt a script (instead of hitting ctrl-c) because cleanup actions will be performed after a SCRIPTSTOP (e.g. turning off laps to preserve their lifetime).

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The agitator can be reenabled by simply setting the keyword to “Yes”. This should only be done by WMKO staff and should only be done if the agitator is fully functional. A broken or misbehaving agitator mechanism presents a significant danger to the science fibers.

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The cal source has likely been disabled for a reason. Reenabling it should only be done by WMKO staff with knowledge of why it was disabled in the first place.

SlewCal or Simultaneous Calibration Source is Wrong

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These two sources are set from the same place and are always kept to the same value using the kpfconfig.SIMULCALSOURCE keyword.

Solution

This value should only be changed by WMKO staff. The choice of calibration source is influenced by our desire to maintain the lifetime of the various lamps and calibration sources and by the need for warmup times on certain sources. This is not something the user should adjust, contact a WMKO Staff Astronomer if you feel it is set incorrectly.

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Then either set FOLDNAM to the destination or set MODE to the desired destination.

Tip Tilt Performance is Poor

Symptom

Tip tilt performance is poor. The star is moving a lot on the guider, perhaps primarily in either the X or Y pixel direction.

Problem

One possibility is that the XY stage is failing. The symptom is that the stage has lost range and can not reach the commanded position. To determine if this is the case, stop observing and stop the tip tilt loops and:

• Watch the kpffiu TTXVAX and TTYVAX keywords (e.g. via an xshow)

• Command one of the axis to someplace near the nominal limit and watch to see if the keyword value reached the location it was commanded to go. The X stage should be able to go from -15 to +15 and the Y stage should be able to go -20 to +20 (they actually can access a bit more, but this is a reasonable amount to test). For example

  • modify -s kpffiu TTXVAX=-15 (note where the keyword actually goes)

  • modify -s kpffiu TTXVAX=15 (note where the keyword actually goes)

  • modify -s kpffiu TTYVAX=-20 (note where the keyword actually goes)

  • modify -s kpffiu TTYVAX=20 (note where the keyword actually goes)

• If one or more of the above tests falls far short of the destination, then we need to tell the software not to use that part of the range.

It is worth repeating the test above to see if you get consistent results. If the results are not consistent, then the procedure below will be of limited utility.

Solution

There are several components to this fix and it is important to understand what each does, so that you can perform the fix properly. The section below explains how the keywords are used, then we will discuss how to set them.

Understanding Tip Tilt Keywords

• The kpffiu service handles commands to the tip tilt stage.

  • TTXVAX and TTYVAX report the position of the stage in arc seconds of tilt. This is tilt of the stage, not movement of the star on the focal plane.

  • TTXRAW and TTYRAW are the position of the stage in raw encoder counts.

  • TTXRON and TTYRON define the home position of the stage for the stage controller in raw encoder counts.

• The kpfguide service handles the control loop used to decide where to command the stage to go.

  • TIPTILT_HOME defines the (x, y) coordinates of the home position in arc seconds of motion of the stage. This is where the stage will be positioned if no tip tilt moves are needed – it is the center of the stage motion.

  • TIPTILT_XRANGE and TIPTILT_YRANGE define the maximum range of motion which the guide system should use during observing (in units of arc seconds of stage motion). This is the half width of the range, so the stage can go from the home position - range to home position + range.

The combination of kpfguide.TIPTILT_HOME and kpffiu.TT{x,y}RON define the center of motion of the stage and we want those to be in agreement. Unfortunately, these are in different units, so we need to keep that in mind and ensure they are consistent when we set new values.

Once the center position is defined, the system uses kpfguide.TIPTILT_{x,y}RANGE to decide how far to push the tip tilt mirror before offloading to the telescope.

Setting Up the Tip Tilt Center Position and Limits

Above we discovered the limits (in TT{x,y}VAX units) where the stage seems to be able to go. Use those values to determine the home position (center point between the limits) and the range (distance from home to one limit). Use those calculated values to set kpfguide.TIPTILT_HOME and kpfguide.TIPTILT_{x,y}RANGE.

Now move the stage to the home position by setting kpffiu.TT{x,y}VAX and read off the kpffiu.TT{x,y}RAW value. Update the kpffiu.TT{x,y}RON strings with that value, maintaining the proper formatting: |{raw value}|0|Home.

There is an experimental script to do the above steps, but you must manually verify that the results look reasonble. Run kpfMeasureTipTiltMirrorRange and it will print out a set of modify commands for you to run (it does not execute them itself). Check the logic and math, the script is experimental! Note that if the script finds a limit which is unexpected (i.e. less range than nominal), it will set up the above keywords to a range 1 arc second smaller than where the limit is. It adds this safety margin to the kpfguide.TIPTILT_{x,y}RANGE keywords, so if you calculate something slightly different than the script, this may be why.

Detectors

kpfexpose.EXPOSE is not Ready

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The detector has likely been disabled for a reason. Reenabling it should only be done by WMKO staff with knowledge of why it was disabled in the first place.

Detector Fails to Trigger Without Error

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